Astronomy & Astrophysics manuscript no. 7235-astroph c© ESO 2018
December 8, 2018
Near- and Far-Infrared Counterparts of Millimeter Dust Cores
in the Vela Molecular Ridge Cloud D ⋆
M. De Luca1,2, T. Giannini1, D. Lorenzetti1, F. Massi3, D. Elia4, and B. Nisini1
1 INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone (Roma), Italy
e-mail: deluca, giannini, lorenzetti, nisini@oa-roma.inaf.it
2 Dipartimento di Fisica - Università di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00033 Roma, Italy
3 INAF - Osservatorio Astrofisico di Arcetri, Largo E.Fermi 5, 50125 Firenze, Italy
e-mail: fmassi@arcetri.astro.it
4 Dipartimento di Fisica - Università di Lecce, CP 193, 73100 Lecce, Italy
Preprint online version: December 8, 2018
ABSTRACT
Aims. Identify the young protostellar counterparts associated to dust millimeter cores of the Vela Molecular Ridge Cloud D
through new IR observations (H2 narrow-band at 2.12 µm and N broad band at 10.4 µm) along with an investigation performed
on the existing IR catalogues.
Methods. The association of mm continuum emission with infrared sources from catalogues (IRAS, MSX, 2MASS), JHK data
from the literature and new observations, has been established according to spatial coincidence, infrared colours and spectral
energy distributions.
Results. Only 7 out of 29 resolved mm cores (and 16 out of the 26 unresolved ones) do not exhibit signposts of star formation
activity. The other ones are clearly associated with: far-IR sources, H2 jets pointing back to embedded objects not (yet) detected
or near-IR objects showing a high intrinsic colour excess. The distribution of the spectral indices pertaining to the associated
sources is peaked at values typical of Class I objects, while three objects are signalled as candidates Class 0 sources. Objects
with far-IR colours similar to those of T-Tauri and Herbig Ae/Be stars seem to be very few. An additional population of young
objects exists associated not with the mm-cores, but with both the diffuse warm dust emission and the gas filaments. We remark
the high detection rate (30%) of H2 jets driven by sources located inside the mm-cores. They appear not driven by the most
luminous objects in the field, but rather by less luminous objects in young clusters, testifying the co-existence of both low- and
intermediate-mass star formation.
Conclusions. The presented results reliably describe the young population of VMR-D. However, the statistical evaluation of
activity vs inactivity of the investigated cores, even in good agreement with results found for other star forming regions, seems
to reflect the limiting sensitivity of the available facilities rather than any property intrinsic to the mm-condensations.
Key words. Stars: formation – Infrared: stars – ISM: individual objects: Vela Molecular Ridge – ISM: clouds – ISM: jets and
outflows – Catalogs
1. Introduction
The association of far-infrared (FIR) sources with the
gas and dust emission cores in Giant Molecular Clouds
(GMCs) is the starting point of any effort aimed to obser-
vationally study high- and intermediate-mass star forma-
tion modalities. Indeed the Galactic matter is distributed
in such a way that prevents to have a significant num-
ber of GMCs located near our Sun. Also low-mass star
formation occurs in GMCs, but GMCs are usually found
Send offprint requests to: M. De Luca
⋆ Based on observations collected at NTT and 3.6m telescope
(ESO - La Silla, Chile).
at distances greater than 1-2Kpc, where the sensitivity of
the current fore-front instrumentation makes it possible
to sample only the most luminous (i.e. the most massive)
objects. As a consequence, studying low-mass star forma-
tion is limited to nearby dark clouds, leaving GMCs as
the privileged targets for high-mass studies. Exceptions
exist, which are represented by the Orion and Vela GMCs
(usually named Vela Molecular Ridge - VMR) and by the
OB association in Scorpius-Centaurus and Perseus, whose
distances range between 300 and 700 pc. Orion GMC is by
far the most studied star formation site at all wavelengths
and both modalities (high- and low-mass) are observation-
ally documented to take place in it (e.g. Chen & Tokunaga
http://arxiv.org/abs/0704.1228v1
2 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
1994). Its location outside the plane of the Galaxy (b≈ -
20◦) has originally sanctioned its leading rôle in star for-
mation studies, when extinction and crowding represented
insurmountable observational barriers. Also Sco-Cen and
Per OB associations are located at about +20◦ and -20◦,
respectively. The rapid growth of multi-frequency facil-
ities at an increasing spatial resolution, makes it possi-
ble now to study, with enough accuracy, even extincted
and crowded regions, as the VMR, in the plane of the
Galaxy. Thanks to the forthcoming facilities, investigat-
ing the plane will be easier and easier and the properties
derivable from the VMR will be the most suitable for ob-
taining a direct comparison with those of the other galax-
ies, whose planes represent the main volume we are able
to sample.
The VMR is a complex of four GMCs (Murphy & May
1991; Yamaguchi et al. 1999) and it is probably one of the
best regions for studying the processes involved in star
formation (clustering, isolation, matter outflows). It is lo-
cated in the galactic plane (b = ± 3◦) outside the solar cir-
cle (ℓ ∼ 260◦ − 275◦) and most of the gas is at a distance
of ∼ 700 pc (Liseau et al. 1992). So far we have accumu-
lated a large data-base on VMR clouds through ground-
based observations from near-IR (NIR) to mm wave-
lengths. In particular, our analysis, based on the IRAS
point source catalog (IRAS-PSC 1988), unveiled a re-
markable concentration of red FIR sources with bolomet-
ric luminosities < 104L⊙ (Liseau et al. 1992, Lorenzetti et
al. 1993). These are very young intermediate-mass stars
and we found (Massi et al. 2000, 2003) that FIR sources
with Lbol > 10
3L⊙ coincide with young embedded clus-
ters (size ∼ 0.1 pc, ∼ 50-100 members). In particular, we
find that the region of the VMR named cloud D (here-
inafter VMR-D) hosts a large number of these, revealing
a high efficiency in this mode of star formation. At the
same time, the presence of IRAS sources having bolomet-
ric luminosities of only few solar luminosities, shows that
the formation of isolated, low-mass stars is also active in
this region.
We have searched the region around a complete sample of
IRAS sources in VMR-D for protostellar jets, using NIR
imaging and spectroscopy (Lorenzetti et al. 2002), and we
have discovered a significant number of shock tracers (H2
and [FeII] line emission knots), which signal the pres-
ence of protostellar jets in VMR-D. We have also clarified
the details of the interactions between jets and circumstel-
lar environment as well as the properties of the exciting
sources (Caratti o Garatti et al. 2004, Giannini et al. 2001,
2005).
Recently we mapped a ∼ 1 deg2 area of the VMR-D in
the 1.2mm continuum of dust emission, along with the
12CO(1–0) and 13CO(2–1) transitions (see Fig. 1 in Massi
et al. 2007 and Figs. 3-4 in Elia et al. 2007). The aim
of the present paper is to correlate dust map and avail-
able FIR and NIR catalogues to have a complete census
of the VMR-D young population that allows us to assess
the pre-main sequence evolutionary stage properties. The
correspondence between dust cores and molecular clumps
has been already presented in Elia et al. (2007).
An increasing number of millimeter surveys towards star
formation regions along with a comparison with existing
FIR catalogues is now available. For the VMR complex, in
particular, an investigation of the Vela-C cloud has been
carried out by Moriguchi et al. (2003) and by Baba et al.
(2006), and mm-studies of few individual sources belong-
ing to VMR-D are reported by Faundez et al. (2004) and
Fontani et al. (2005).
In the following, we give in Sect. 2 a short summary of
the results on the mm-maps (both dust and gas) we have
presented elsewhere. The criteria for associating IR coun-
terparts to the dust emission cores are discussed in Sect. 3,
along with the analysis of a particular selected area, as an
example. New IR observations are also presented in this
section. The results are then summarized in Sect. 4 and
discussed in Sect. 5. In appendix A, the associations for
all the regions of dust emission are discussed separately.
2. The investigated region
Our observations of the VMR-D carried out in the mil-
limeter range with the SEST (ESO - La Silla) telescope
are described elsewhere and consist of three maps of
about 1 deg2, both in the dust continuum emission at
1.2mm (Massi et al. 2007) and in the molecular transi-
tions 12CO(1-0), at 2.6mm, and 13CO(2-1), at 1.3mm
(Elia et al. 2007).
The 12CO data (resolution: 43”, sampling: 50”) out-
line a filamentary distribution of diffuse molecular emis-
sion connecting regions of enhanced intensity where there
is evidence of clustered, intermediate-mass, star forma-
tion in progress (Elia et al. 2007, Massi et al. 2007).
The map of 13CO emission, because of its lower abun-
dance with respect to 12CO, traces denser regions of the
molecular cloud, which present a quite clumpy structure.
Summarizing the results from the 13CO map, we have
found 49 clumps with mass, size and mean velocity rang-
ing from 2 to 140M⊙, from 0.15 to 0.67pc and from 1 to
13 km s−1, respectively (see Tab. 3 in Elia et al. 2007).
The dust map (resolution: 24”, corresponding to about
0.1 pc, in fast scanning mode of 80 arcsec s−1) also shows
a clumpy structure and we have individuated 29 cores of
mass and size in the ranges 0.2 - 80M⊙ and 0.03 - 0.3 pc
respectively (see Tab. 1 in Massi et al. 2007), almost all of
them nearly coincident with the brightest regions of the
velocity integrated CO maps. In addition, other 26 cores,
whose size is under the spatial resolution, have been iden-
tified, even if their genuine nature remains uncertain.
3. Association with point-sources
In this work we aim to correlate the millimeter emis-
sion with objects from both new IR images (1-10µm)
carried out on selected areas (see Sect. 3.1) and the
infrared existing catalogs of point sources in order to
find out the sources that dominate the dust cores heat-
ing. In particular, the considered catalogs are: (i) the
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 3
IRAS point source catalog (IRAS-PSC 1988), that pro-
vides flux densities at 12, 25, 60 and 100µm; (ii) the
MSX (Midcourse Space Experiment) point source cata-
log (Price et al. 2001) at 8.28, 12.13, 14.65 and 21.3µm;
(iii) the 2MASS point source catalog (Cutri et al. 2003),
based on J , H , Ks bands, complemented with litera-
ture data (Massi et al. 1999) of deeper IRAC2 images
(Moorwood et al. 1992).
3.1. Observations
An observational campaign has been carried out by using
NIR (narrow-band H2 1-0S(1) at λ=2.13µm) and mid-
IR (MIR) (N broad-band) imaging facilities to observe
fields selected from the mm-emission maps. All the rec-
ognized dust cores (except one) have been imaged in H2,
with the aim of searching for protostellar jet evidences.
The 10.4µm survey covered those cores associated to the
presence of a young embedded cluster (Massi et al. 2003,
2006), aiming, thanks to an adequate spatial resolution,
to pick-up those source(s) (if any) that dominate(s) the
detected fluxes at FIR wavelengths.
3.1.1. NIR imaging
Broadband J , H , Ks and narrow-band images in the
H2 1-0S(1) (λ=2.13µm, ∆λ=0.03µm) were obtained
in January 2006 with SofI1 (Lidman et al. 2000) at
ESO-NTT (La Silla, Chile). The total field of view is
4.9×4.9 arcmin2, which corresponds to a plate scale of
0.29 arcsec/pixel. All the observations were obtained by
dithering the telescope around the pointed position and
the raw imaging data were reduced by using standard
procedures for bad pixel removal, flat fielding, and sky
subtraction.
3.1.2. N-band imaging
Imaging in the N10.4 broadband filter was carried out in
January 2006 with Timmi2 (Saviane & Doublier 2005) at
the 3.6m ESO telescope (La Silla, Chile). The adopted
plate scale is 0.3 arcsec/pxl, corresponding to a 96′′ × 72′′
field of view. The observations were obtained by chop-
ping the signal and by nodding and jittering the tele-
scope around the pointed position in the usual ABB′A′
mode. The raw data were reduced by using standard
procedures for bad pixel removal and the observed field
was flux calibrated by using photometric standard stars
(HD29291, HD32887, HD123139). The photometric re-
sults are given in Tab. 1, together with the IRAS/MSX
results. Although these latter refer to different effective
wavelengths and different epochs, ground-based values
are significantly lower than IRAS/MSX determinations.
These discrepancies have been remarked several times in
the literature concerning YSO’s (e.g. Walsh et al. 2001)
1 J and H images were obtained only for those fields con-
taining the young clusters.
and may be due to the higher environmental contamina-
tion suffered by the larger IRAS/MSX beams.
3.2. FIR associations
Within molecular clouds the correlation between the po-
sitions of dust emission cores and FIR point-like sources
represents an important method to obtain a census of both
the young stellar population and the different modalities
of the star formation. To search the catalogs for sources
associated to the dust cores listed in Tab. 1 of Massi et al.
(2007), a working definition of the core size has to be firstly
provided. Indeed, in that Table the core size is given (col-
umn 4), which results from the geometrical mean of the
quantities ∆x and ∆y. These latter (see Tab. 2, column
2) are directly provided by the adopted search algorithm
(Clumpfind), and indicate the FWHM of the linear profile
of the core itself, along its x (right ascension) and y (decli-
nation) axes, respectively (Williams et al. 1994). The area
covered by a dust core up to the (bidimensional) FWHM
flux level can thus be roughly individuated by the ellipse
centered at the peak coordinates and having axes ∆x and
∆y. For simplicity, we will call hereinafter this ellipse as
dust FWHM-ellipse (see e.g. Fig. 1, where it is represented
by the red, inner curve). Analogously, we operatively de-
fine as dust 2FWHM-ellipse that with axes 2∆x and 2∆y
(red, outer ellipse in Fig. 1).
Searching for catalogued sources we use this FWHM value
by adopting the following criterion: an IRAS or MSX
point source is considered associated to the core if its po-
sitional uncertainty ellipse overlaps (or is tangent to) the
dust 2FWHM-ellipse. However, to evidence the most com-
pelling cases, the association within one FWHM-ellipse
are boldfaced in Tab. 1. With respect to the criterion
adopted in similar works (e.g. Mookerjea et al. 2004,
Beltrán et al. 2006), for which an IRAS/MSX source is
associated to a core if it lies inside 90′′/40′′, our criterion
both takes into account the dust emission morphology and
compensates for the large IRAS/MSX beam.
3.3. NIR associations
Both the 2MASS catalog and the IRAC2 catalog reported
in Massi et al. (1999) were searched for NIR associations,
i.e. the sources that dominates the cores heating. Since
the NIR sources positional accuracy is by far larger than
the deconvolved core size, there is no need of defining a
specific criterion for the association: we simply consider
all the NIR sources falling within the FWHM-ellipse of
each core that present a valid flux (not an upper limit) at
least in a single band (J , H , K). Furthermore, we have
tentatively selected the most probable NIR counterpart of
the dust core according to the following criteria:
1. Closeness to the peak of dust emission and to the FIR
source possibly associated, if any.
2. Intrinsic excess in the two colours (J-H vs H-K) dia-
gram (hereafter colour-colour diagram). This criterion
4 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
makes it possible to pick up the NIR objects whose
spectral energy distribution (SED) is typical of a young
stellar object (YSO), and does not appear as stellar
photosphere reddened by the intervening dust along
the line of sight. In this context, to point out their
intrinsic colour excess, we will define two loci in the
colour-colour diagram (e.g. shaded regions in panel
a of Fig. 2): the locus of the red objects (mainly T-
Tauri), immediately to the right of the main sequence
(reddened) stars and the locus of the very red sources
(mainly Class I and Herbig Ae/Be protostars), to the
right of the T-Tauri (reddened) stars.
3. Largest spectral index α = d log(λFλ)/d log(λ) among
those with α≥ 0. Sources with α < 0, in fact, are gen-
erally visible in the optical plates, thus this item cut
off at least bright visible stars.
3.4. The core MMS1
Here we describe a typical example of the approach
adopted to detect the FIR/NIR counterparts of the mm-
core MMS1. Similar considerations have been done for any
individual mm-core, and all the results are provided in the
Appendix A.
As a first step, we overlay the contour map of dust
emission (green contours, from 3 σ=3× 15mJy/beam in
steps of 3σ) and the H2 narrow-band (gray-scale) image
(Fig. 1). The red ellipses centered on the mm-peak repre-
sent the FWHM- and the 2FWHM-ellipses within which
the association with the IR sources has been searched (see
Sections 3.2 and 3.3). The magenta and green ellipses in
Fig. 1 individuate the 3σ positional uncertainties of the
IRAS2 and MSX point sources, respectively, while the
blue asterisks signal the position of the 10.4µm sources
observed by Timmi2 in the field of view delimited in fig-
ure by the blue line. The 2MASS and IRAC2 NIR sources
are labelled 2M ♯ (following an internal numbering) and
MGL99 ♯ (following Massi et al. 1999), respectively. The
IRAC2 field of view does not cover the whole image and
is depicted as the orange rectangle.
Both IRS16 (08438 − 4340, corresponding to MSX
G263.6200-00.5308 and DGL 4) and G263.5925-00.5364
are located outside the FWHM-ellipse and do not appear
directly associated to the core, while the association is
more compelling with the sources DGL 1, DGL 2 and
G263.5994-00.5236.
The IRAS source coincides with a NIR young cluster and
an HII region located at the center of the region bordered
by the cores MMS1-2-3, almost equidistant from all of
them. The NIR cluster has been already investigated in
detail by Massi et al. (2003) and we complement those
data with the new N -band observation that points out
the presence of a very diffuse emission, indicated as DGL
2 Hereinafter we will adopt for the IRAS sources, when avail-
able, the shorter names IRS♯ defined in Liseau et al. (1992).
Both the original names and these ones, however, are listed in
Tab. 1.
4, corroborating the hypothesis that the FIR source can be
originated by warm circumstellar matter associated with
the most luminous (in the NIR) cluster member, MGL99
Also the MSX source G263.5295-00.5364, that falls at the
western border of the 2FWHM-ellipse, does not seem to
be related to the dust peak. It has been detected at 8µm
only and, presumably, such flux arises from diffuse emis-
sion, as an inspection of the MSX image suggests3.
To feature the NIR stellar content close to the peak po-
sition we give in Fig. 2-a the colour-colour diagram of all
the detected sources within the FWHM-ellipse. Here are
also drawn: the locus of the main sequence, class V stars
(Tokunaga 2000) (dark curve), the locus of the T-Tauri
stars (Meyer et al. 1997) (red line) and three reddening
lines (blue) (Rieke & Lebofsky 1985), starting from three
significant points, with four crosses indicating values of 0,
1, 5 and 10 mag of visual extinction. The separation of the
sources in the two regions red and very red (see Sect. 3.3)
is also evidenced by a different shading. The arrows on
the data points denote constraints on colours derived from
upper limits on the NIR photometry. This diagram allows
us to select the most interesting objects: in particular, the
sources labelled as MGL99 156, MGL99 179 and MGL99
155 show the highest colour excess.
We report in Fig. 2-b the Spectral Energy Distribution
(SED) of the very red stars within the FWHM-ellipse, to-
gether with the Timmi2 measured fluxes and the SED of
the MSX object G263.5994-00.5236. The arrows denote
again the upper limits.
From the SEDs, we see that MGL99 179 and MGL99
156, considering the upper limits, are the sources with
the steepest spectral indexes. Moreover, (see Fig. 1), while
MGL99 179 has been identified as the counterpart of the
Timmi2 source DGL 1, MGL99 156 has lack of detection
in N , although its K magnitude is comparable to that of
MGL99 179.
This allows us to suggest that the main contributor to the
millimeter flux should be the object MGL99 179=DGL
1. However, considering the richness of very red sources
in the field (Tab. 2), a contribution to the millimeter flux
from multiple sources or from objects too much embed-
ded to be investigated with the described tools, cannot be
ruled out. Moreover, the HII region at the southern border
of the core could provide an additional external heating
by means of UV photons.
3 It lacks of any NIR suitable counterpart (unfortunately, at
that position we have no IRAC2 data) although the nearest
NIR significant object, MGL99 156, 27 arcseconds apart, may
contribute to the measured flux.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 5
Fig. 1. MMS1 field of view (center [J2000]: 08:45:32.8, -43:50:12.3). Grayscale image: H2 emission; green contours:
dust continuum (from 3σ, in steps of 3 σ). See text for other details.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
2M-25930
MGL99-155
MGL99-179
MGL99-156
red very red
1 2 5 10 2
-20.5
-20.0
-19.5
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-25930
MGL99-123
MGL99-155
MGL99-179
MGL99-156
G263.5994-00.5236
DGL-2
DGL-1
Fig. 2. a - Colour-colour diagram of the sources falling within the FWHM-ellipse around MMS1. b - Spectral energy
distribution of the very red sources within the FWHM-ellipse. See text for more details.
6 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
4. Results
All the results derived from the association to dust emis-
sion cores of sources from both FIR/NIR catalogs and our
ground-based new observations are given in three different
Tables organized as follows:
- Table 1 - Here all the dust cores detected in the mm
map (column 1) having an association with a MIR
and/or FIR object are listed. The core identification
follows that of the dust map (Massi et al. 2007), where
the naming MMS# refers to the resolved cores while
umms# (second part of the Table) are under-resolved
(i.e. size smaller than the SIMBA beam4, see Tab. 2
of Massi et al. 2007). Then, for those cores associ-
ated with a FIR source, IRAS and MSX names, flux
densities and distances from the peak (d) are given,
along with an indicator (CC = correlation coefficient
for each band, see IRAS manual) of the point-like na-
ture of the IRAS source. For the IRAS objects is also
indicated the 1.2mm flux at the IRAS coordinates ob-
tained by integrating the dust map within 24 arcsec
(= SIMBAHPBW) aperture. Finally, for comparison
purposes with IRAS (12µm) and MSX (8.28 and
12.13µm) fluxes, the results of the Timmi2 observa-
tions (at 10.4µm, objects coded as DGL ♯) are also
reported in the last columns of this Table (again with
the distances from the peak). As anticipated, the bold-
faced lines correspond to FIR/MIR associations within
the corresponding FWHM-ellipse, and, consequently,
have to be considered as more robust cases.
We remark here that all the cores reported in Tab. 1 are
also associated with CO clumps, with the exception of
MMS29, umms1-23-24 and 25, which are outside the
CO map coverage5 (Elia et al. 2007).
- Table 2 - This Table lists the NIR counterparts of all
the cores. In column 2 the core size is identified through
the FWHM-ellipse axes ∆x and ∆y (see Sect. 3.2). In
column 3 the numbers of NIR red or very red sources
that are located within the FWHM-ellipse are given.
The census of the NIR population is based, whenever
it is possible, on the IRAC2 images (Massi et al. 1999,
objects coded as MGL99 ♯) that are deeper than the
2MASS frames (K band limit magnitude 18 instead
of 14). Otherwise 2MASS images have been exploited
(objects coded as 2M ♯). In columns 4 to 6 the loca-
tion of the most probable candidate counterpart to the
mm emission or to the FIR associated object is given,
while the 7th column signals the morphology of the H2
emission as detected in our ground-based observations.
4 The circumstance of having an associated FIR source
makes some of the under-resolved cores suitable targets in the
next future for high spatial resolution southern facilities in the
mm-range (e.g. ALMA).
5 The integrated 12CO and 13CO maps show a noticeable
enhancement of the integrated emission towards umms1, al-
though this enhancement is not fully mapped.
- Table 3 - This table lists all the IRAS sources, falling
within the dust map, but not associated to any core,
that present at least two valid detections (not upper
limits) between 12 and 60µm and a flux increasing
with the wavelength, namely F12µm < F25µm < F60µm,
or upper limits at 12 and 25µm compatible with this
condition. Studying the VMR-D young population,
these sources have some relevance. Indeed these red
and cold sources are not randomly distributed, as the
not-red sources do, but tend to be located along the
gas filaments. As in Tab. 3, we also report the 1.2mm
flux derived at the IRAS position.
Table 1. Dust cores with associated FIR and/or MIR point sources.
mm IRAS associated sources a MSX associated sourcesa Timmi2 observationsa
core id F12 F25 F60 F100 F1.2mm CC
d id F8.3 F12.1 F14.7 F21.3 d id RA Dec F10.4 d
(Jy) (”) (Jy) (”) (J2000) (J2000) (Jy) (”)
MMS1 08438-4340 13.4 56.0 638.3 1576 0.203 ECDB 49 G263.5994-00.5236 1.6 2.2 2.0 4.1 29 DGL 1 8:45:33 -43:50:04 0.05 17
(IRS16) G263.6200-00.5308 1.8 5.1 6.9 15.6 51 DGL 2 8:45:33 -43:49:48 1.8 33
G263.5925-00.5364 0.5 <0.7 <0.5 <1.6 56 DGL 4 8:45:36 -43:51:02 diffuse ∼49
MMS2 G263.6338-00.5497 0.4 <6.9 <5.4 1.6 25 DGL 3 8:45:34 -43:52:26 0.25 26
MMS3 08438-4340 13.4 56.0 638.3 1576 0.203 ECDB 55 G263.6385-00.5217 0.9 1.3 0.8 1.4 20 DGL 5 8:45:38 -43:51:14 0.08 26
(IRS16) G263.6366-00.5148 0.3 <0.9 <0.7 <1.9 39 DGL 4 8:45:36 -43:51:02 diffuse ∼55
G263.6329-00.5127 0.4 0.7 <0.9 <2.7 46
G263.6200-00.5308 1.8 5.1 6.9 15.6 54
MMS4c 08448-4343 8.7 88.1 326.6 1005 0.984 AABB 7 G263.7759-00.4281 7.5 10.1 13.8 65.5 5 MGL99 57d 8:46:35 -43:54:31 8.79 7
(IRS17) G263.7733-00.4151 1.2 1.3 0.5 2.6 53 MGL99 25d 8:46:34 -43:54:50 0.21 15
G263.7867-00.4437 0.3 0.8 <0.4 <1.2 63 MGL99 40d 8:46:33 -43:54:39 0.14 17
MMS12 08470-4321 44.9 130.1 342.6 406.9 0.331 AAAA 11 G263.7434+00.1161 30.8 52.6 70.3 93.5 3 DGL 7 8:48:49 -43:32:29 18.3 5
(IRS19)
MMS18 08472-4326A 0.9 0.9 10.6 <406.9 0.044 BABF 28 G263.8432+00.0945 0.3 <0.7 <0.5 <1.3 16 DGL 8 8:49:03 -43:37:55 0.07 19
MMS20 08474-4323 1.5 1.1 <106.4 125.9 <0.005 BCAD 39 G263.8221+00.1494 0.1 <0.9 <0.6 <1.9 37 DGL 9 8:49:12 -43:35:52 0.08 28
MMS21 08474-4325 <0.3 1.0 <16.4 57.5 0.207 DAHD 7 DGL 9 8:49:12 -43:35:52 0.08 39
MMS22 08476-4306 5.7 44.0 216.3 503.7 0.337 AAAB 10 G263.6177+00.3652 3.9 6.0 7.6 27.7 12 DGL 11 8:49:26 -43:17:12 2.01 12
(IRS20) DGL 10 8:49:26 -43:17:21 0.02 19
MMS24 08476-4306 5.7 44.0 216.3 503.7 0.337 AAAB 48 G263.6280+00.3847 0.3 <0.6 <0.5 <1.3 28 <0.03
(IRS20)
MMS25 08477-4359 9.0 26.3 317.0 580.8 0.174 BAAA 20 G264.3225-00.1857 4.7 5.0 2.3 8.0 19 DGL 12 8:49:33 -44:10:60 0.21 30
(IRS21)
MMS26 08477-4359 9.0 26.3 317.0 580.8 0.174 BAAA 16 G264.3225-00.1857 4.7 5.0 2.3 8.0 16 DGL 12 8:49:33 -44:10:60 0.21 6
(IRS21)
MMS27 DGL 13 8:49:36 -44:11:46 0.03 16
MMS28 08483-4305 1.5 2.5 <39.0 189.2 0.049 EEFD 14 G263.6909+00.4713 0.1 0.6 <0.7 <2.0 11 not obs.
MMS29 08483-4305 1.5 2.5 <39.0 189.2 0.049 EEFD 45 not obs.
umms1 08446-4331 <1.1 0.5 7.4 42.8 0.160 GBBB 2 not obs.
umms8 08458-4332 1.1 2.7 17.8 52.7 0.017 CABA 24 <0.03
umms9 08458-4332 1.1 2.7 17.8 52.7 0.017 CABA 29 <0.03
umms11 G263.7651-00.1572 0.2 <0.5 0.5 <1.2 11 DGL 6 8:47:43 -43:43:48 0.07 10
umms16 08464-4335 <0.3 <0.3 6.6 <47.2 0.160 -JB- 19 <0.03
umms23 G263.5672+00.4036 0.1 <0.9 <0.7 <1.9 17 not obs.
umms24 G263.5622+00.4185 0.2 <0.7 <0.5 <1.5 13 not obs.
umms25 G263.5622+00.4185 0.2 <0.7 <0.5 <1.5 19 not obs.
Notes to the table: the mm sources labeled as umms♯ are not resolved by the SIMBA HPBW (see text and Massi et al. 2007).
aBold faced sources are more compelling associations (within the FWHM-ellipse of the core, see text).
bPoint source correlation coefficient encoded as alphabetic characters (A=100%, B=99%, ..., N=87%) according to the IRAS Catalogs and Atlases Explanatory Supplement (IRAS-PSC 1988).
cThis core has been divided into two components by Giannini et al. (2005).
dNames following the numbering convention used in Massi et al. (1999). A description of the Timmi2 observations of these objects is given in Giannini et al. (2005).
8 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
Table 2. NIR sources and H2 emission associated with dust cores.
mm core FWHM ♯ of NIRa Counterparts candidates H2 emission
name ∆x-∆y red / very red sourcesb name RA Dec morphologyc
(”) within the FWHM-ellipse (J2000) (J2000)
MMS1d 59-64 5 / 8 e MGL99 179 08:45:32.86 -43:50:03.80 diffuse, knots
MMS2d 59-55 1 / 3 e MGL99 25 08:45:35.93 -43:51:45.60 diffuse, jet-like
MMS3d 61-58 0 / 1 e MGL99 36 08:45:39.21 -43:51:34.70 diffuse
MMS4d 82-71 19 / 43 f MGL99 57 08:46:34.77 -43:54:30.63 diffuse, jet-like, knots
MMS5 40-31 0 / 0 diffuse
MMS6 27-23 0 / 0 diffuse
MMS7 29-37 1 / 4 -
MMS8 24-26 0 / 1 2M 9671 08:48:39.13 -43:31:31.36 -
MMS9 32-36 0 / 0 -
MMS10 25-28 0 / 0 -
MMS11 36-24 0 / 1 2M 14732 08:48:46.54 -43:37:44.02 -
MMS12d 57-37 8 / 20 f MGL99 49 08:48:48.51 -43:32:29.08 diffuse, knots
MMS13 41-20 2 / 0 f MGL99 2 08:48:50.04 -43:33:19.47 -
MMS14 29-38 0 / 0 -
MMS15 33-20 0 / 0 -
MMS16 23-36 0 / 0 diffuse, jet-like
MMS17 67-37 0 / 2 jet-like
MMS18d 36-36 1 / 0 diffuse
MMS19 26-60 3 / 2 2M 36076 08:49:08.49 -43:35:37.79 -
MMS20d 38-32 0 / 0 knots
MMS21d 54-57 0 / 3 2M 29953 08:49:13.39 -43:36:29.20 knots
MMS22d 35-37 9 / 13 f MGL99 98 08:49:26.23 -43:17:11.11 diffuse, jet-like, knots
MMS23 39-22 0 / 0 diffuse
MMS24d 35-25 0 / 3 f MGL99 90 08:49:32.27 -43:17:14.43 -
MMS25d 52-86 3 / 5 diffuse
MMS26d 60-67 1 / 8 diffuse
MMS27d 67-48 1 / 2 knots
MMS28d 30-31 0 / 0 -
MMS29d 40-36 1 / 1 2M 36339 08:50:11.04 -43:17:10.74 knots
umms1d <24-24 0 / 0 not observed
umms2 <24-24 0 / 0 -
umms3 <24-24 0 / 0 -
umms4 <24-24 0 / 1 -
umms5 <24-24 1 / 0 -
umms6 <24-24 1 / 0 -
umms7 <24-24 0 / 0 -
umms8d <24-24 1 / 1 2M 16128 08:47:37.87 -43:43:42.41 -
umms9d <24-24 0 / 0 -
umms10 <24-24 0 / 0 -
umms11d <24-24 0 / 2 2M 9173 08:47:42.93 -43:43:48.05 -
umms12 <24-24 0 / 0 -
umms13 <24-24 0 / 0 -
umms14 <24-24 0 / 0 -
umms15 <24-24 0 / 0 -
umms16d <24-24 0 / 0 jet-like
umms17 <24-24 0 / 0 jet-like
umms18 <24-24 0 / 0 jet-like
umms19 <24-24 1 / 0 2M 10742 08:48:33.95 -43:30:47.20 knot
umms20 <24-24 0 / 0 knot
umms21 <24-24 0 / 3 2M 16489 08:48:37.03 -43:13:53.63 -
umms22 <24-24 0 / 0 -
umms23d <24-24 0 / 1 2M 11799 08:49:24.56 -43:13:15.49 -
umms24d <24-24 0 / 0 -
umms25d <24-24 0 / 0 -
umms26 <24-24 0 / 0 -
aWhere not specified, the reported numbers refer to 2MASS data.
bThe terms red and very red refer to different regions of the colour-colour diagram (see text and e.g. Fig. 2-a).
cBold-faced if inside the FWHM-ellipse.
dCores presenting a MIR or FIR association (see Tab. 1).
eCore only partially covered by IRAC2 observations.
fCore fully covered by IRAC2 observations.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 9
5. Discussion
5.1. IR counterparts of dust cores
The starting information is the sample of 29 well re-
solved and 26 unresolved dust cores (Massi et al. 2007).
As illustrated in the AppendixA, some of them are
not isolated, but belong to more complex structures of
dust emission that present different cores (e.g. the one
composed by MMS7, umms13-14-15, Fig.A.6); other are
elongated structures formed by aligned knots (e.g. both
MMS5, MMS6, umms6 of Fig.A.5 and umms23-24-25 of
Fig.A.38). These multiple core structures often present as-
sociated FIR counterpart(s) that tend(s) to be located in
a position intermediate between the individual cores. This
is the reason why in Tab. 1 the same IRAS/MSX source
is sometimes assigned to two different cores. Conversely,
the NIR counterparts distribution is more clearly defined
because of the increased spatial resolution at such wave-
lengths. In Appendix A all the observational details per-
taining to each individual dust core are presented; however
we can draw here some general remarks. Firstly, all the in-
formation given in Tabs. 1 and 2 are statistically summa-
rized in Tab. 4, where, among the 29 resolved cores (MMS)
only 8 are clearly associable to a MIR/FIR source (with
or without a near-IR counterpart); 7 have some MIR/FIR
source in their neighbourhood, but additional evidences
(i.e. the presence of H2 jets) point back to an embedded
object not (yet) detected; 7 additional cores seem to be
associated with very red NIR objects; the 7 remaining
cores do not present any sign of star formation activity
at the current instrumental sensitivity. If the same ap-
proach is applied to the sample of the 26 unresolved cores
(umms), we obtain that 4 are associable to a MIR/FIR
source, 3 to a NIR counterpart, 3 to jet-like structures,
and 16 appear as inactive sites. Substantially, both MMS
and umms present a similar statistics of associated cat-
egories, although the latter sample is more widely dom-
inated by objects that could be artifacts, caused by the
searching algorithm, or sites harbouring weak IR counter-
parts. The total number of resolved cores associable to an
IR object (irrespective of being NIR or FIR sources) is 15
(column 6 of Tab. 4) with respect to the 14 unassociated
cores (column 7): such percentages are in full agreement
with those found in other galactic surveys of star forming
regions (e.g. Yonekura et al. 2005, Mookerjea et al. 2004,
Beltrán et al. 2006).
Such categorization, however, does not necessarily reflect
a property intrinsic to the cores themselves, but is likely
the product of the limiting instrumental sensitivities of the
considered facilities. In fact, recent results of SPITZER
MIR surveys have substantially modified the percentage
of active vs inactive cores in favour of the first ones (e.g.
Young et al. 2004). Such a caveat should be taken into
account when drawing general conclusions from our anal-
ysis.
5.2. Star formation modalities and evolutionary stages
Different modalities of star formation are simultaneously
active in VMR-D. Such a co-existence is confirmed by
the presence of 8 clusters (see last column of Tab. 4) and
by the remaining cases of isolated star formation. This
twofold modality, already recognized in Orion (e.g. Chen
& Tokunaga 1994) and now in VMR-D as well, seems to be
a feature of all the regions where intermediate and high-
mass stars form. Indeed, it is likely that the lacking detec-
tion of the isolated mode in far and massive star forming
regions is only due to limitations on sensitivity and spatial
resolution.
To investigate whether or not the different cores of VMR-
D harbour protostellar objects in different evolutionary
stages we have constructed the distribution of the spec-
tral slope of the sources associated to the cores (see Fig. 3).
For each source the slope α is calculated through the re-
lationship α = ∆ log(λiFλi)/∆ log(λi), between the wave-
lengths λ1 and λ2, corresponding to about 2 and 10µm,
respectively. A certain degree of inhomogeneity is intro-
duced by the fact that the flux attributed to the 10µm
band corresponds to that detected by different instru-
ments (MSX, Timmi2, IRAS) operating at different ef-
fective wavelengths (8.28, 10.4 and 12µm, respectively).
These differences affect only the details of the slope dis-
tribution, but do not alter its significance, as proved by the
five sources having a multiple detection. Fig. 3 illustrates
how the sample of the sources associated to the dust cores
presents a distribution highly peaked at values 0 < α < 3,
typical of Class I sources. It is worthwhile noting that the
NIR contribution to the slope generally relies on 2MASS
data, that provide a K band limiting magnitude of about
14mag; deeper NIR surveys (see e.g. Giannini et al. 2005),
could make it possible to find weaker NIR counterparts,
increasing the number of sources with high α values. As a
result, the presented bar graph (Fig.3) could be shifted to-
wards larger α values. As expected, the sources associated
to the dust cores are essentially Class I objects, although
the distribution presents a significant tail toward the less
evolved objects, whose slope is greater than 3.
In Tab. 3 we also list all the IRAS sources lying inside the
region mapped in the 1.2mm continuum and showing a
flux increasing with wavelength but not directly associ-
ated to any dust core (see Sect. 4). These sources, with
only few exceptions, tend to be distributed all along both
the diffuse emission detected by MSX at 8.3µm and the
gas filaments.
To evaluate the intrinsic nature of all the IRAS sources
discussed so far (both associated or not), we present, in
Fig. 4, an IRAS two colours diagram, [12-25] vs [25-60],
with all those sources. As expected, the objects not asso-
ciated to the cores have a greater number of upper limits
(especially at 12µm), but tend to occupy the same re-
gion of the plot where the associated sources are located.
This common region pertains to sources that can be de-
scribed as a two dust components system, one at 1000K
and the other in between 50 and 100K, with variable rela-
10 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
Table 3. IRAS point sources with increasing fluxes not associated with any core.
id F12 F25 F60 F100 F1.2mm CC
08440-4253 <0.3 0.2 1.2 <30.5 <0.005 -BBD
08461-4314 0.7 0.8 5.9 <48.5 0.003 BCDB
08475-4255 <0.4 0.4 3.3 45.6 0.020 EDDB
08475-4311 <0.5 0.5 9.4 <37.8 0.020 DEC-
08481-4258 <0.4 1.1 7.6 <34.8 0.008 BDC-
08459-4338 <0.2 0.6 6.5 38.3 0.005 -DCB
08442-4328 <1.4 2.2 41.3 113.9 0.020 HDCA
08448-4341 1.3 6.6 <327 <1005 <0.005 DAC-
08468-4330 <0.3 0.4 3.4 <31.6 0.010 FDD-
08491-4310 0.5 0.6 7.6 38.6 <0.005 EBCC
08496-4320 0.6 0.7 7.6 <37.1 <0.005 BCBH
08463-4343 <0.3 0.5 7.4 <43.5 <0.005 NBDG
08478-4403 0.5 0.5 <5.4 <580.8 <0.005 CCJG
aSee note b in Tab. 1.
Table 4. Statistics about the dust cores population.
Cores Associated with
MIR/FIR only very red H2 jet no source NIR or no source or embedded
NIR object FIR object H2 only cluster
29 resolved 8 7 7 7 15 14 6
26 unresolved 4 3 3 16 7 19 2
tive contributions. The IRAS selected sources have colours
definitely redder and colder than those pertaining to pre-
main sequence stars (T-Tauri and Herbig Ae/Be; see, e.g.,
Berrilli et al. 1992), apart from few cases. While the ab-
sence of IRAS sources with the colours of T-Tauri stars
in our sample is probably due to an observational bias (in
fact the IRAS detectability limit is > 0.5L⊙ in Taurus,
corresponding to > 10L⊙ in VMR-D), the doubtful pres-
ence of Herbig Ae/Be appears to be an intrinsic property
of VMR-D. Indeed, Herbig Ae/Be located inside dust cores
having masses comparable to those belonging to the VMR-
D ones have been already found at distances of 1Kpc or
less (e.g. Henning et al. 1998). This difference likely re-
flects different star formation histories, being in VMR-D a
shorter time (≈ 106 yr) elapsed from the earliest collapse
events (Massi et al. 2000) with respect to other studied
massive clouds.
We have calculated the bolometric luminosity, Lbol, for all
the IRAS sources from 12µm to 1.2mm. The bar graph in
Fig. 5 shows our result: the sources associated to the dust
cores (both resolved and not) are, on average, objects of
intermediate luminosity (Lbol ∼ 10
3L⊙), while the unas-
sociated FIR sources, even showing similar SEDs, tend to
be lower luminosity objects (Lbol ∼ 10
2L⊙). Therefore, we
can firmly conclude that massive star formation (Lbol >
104L⊙) does not occur in VMR-D, and that our sample of
Class I sources is not contaminated by ultracompact HII
regions, which would be indistinguishable based on their
FIR colours alone (Wood & Churchwell 1989).
An attempt to search for Class 0 objects within our sam-
ple of IRAS sources has also been done by applying the
criterion proposed by André et al. (1993) for low-mass
protostars: Lbol/L1.3mm . 2 × 10
4. None of the selected
IRAS sources (Tabs. 1 and 3) strictly satisfies this crite-
rion6. It should be said, however, that overestimates of the
IRAS fluxes result in overestimates of the Lbol/L1.3mm ra-
tio. Thus, leaving any quantitative approach, we point out
that three sources of our sample (08446-4331, 08474-4325
and 08464-4335) show a ratio Lbol/L1.3mm one order of
magnitude less than the others and thus they are likely the
youngest objects in the field. This hypothesis is strongly
supported by (i) the tight association of these sources with
the mm cores umms1, MMS21 and umms16, respectively;
(ii) by the lack of a measured flux at 12µm7, and, but only
for the last case, (iii) by the presence of H2 jet-like emis-
sion crossing the dust peak (no H2 images are available
for the core umms1).
5.3. H2 survey
A powerful approach to indirectly probe ongoing star for-
mation activity is to investigate over the presence and
characteristics of collimated flows, which commonly ex-
6 Hatchell et al. (2007) reduces such limiting ratio to
Lbol/L1.3mm . 3×10
3 and underlines how this indicator should
vary with envelope mass.
7 For the core MMS21 with the associated source 08474-4325
we report in Tab. 2 a candidate NIR counterpart, but such as-
sociation is quite questionable (see Appendix A and Fig. A.18).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 11
tend far from the most embedded regions where the
young protostars are located. For this reason, we have
complemented our search for infrared counterparts of
mm cores with a survey in the narrow-band filter cen-
tered at the H2 2.12µm line, which represents the main
NIR cooling channel of shock-excited gas at thousands of
Kelvin (e.g. Gredel 1994). Our observations have been also
aimed to define the occurrence of the jet phenomenon in
intermediate-mass star forming regions and to understand
whether jets in clusters are associated with the massive
cores or with some closeby low-mass component. A de-
tailed description of the H2 emission detected in the var-
ious fields is given in Appendix A, while here we briefly
comment on some general aspects. Out of 54 investigated
fields, we find a positive detection (in the form of jet-
like morphologies, knots and diffuse emission) in 23 fields,
the large majority (18) being related to resolved cores. We
note that the occurrence of jets in proximity of umms cores
testifies in favour of the genuine nature of some of these
latter. The H2 emission seems to be directly connected
with the mm cores in about one third of the investigated
fields (namely MMS2-19-22-29, umms16-19 and possibly
MMS16), but we are able to identify a possible (NIR) driv-
ing source in only two cases (MMS22 and MMS29, see
Tab. 2, last column). Given the poor sensitivity of MSX
and IRAS observations, Class 0 protostars might already
be embedded in the other dust cores, which represent
interesting cases to be investigated with SPITZER. All
the fields of young clusters (those associated with cores
MMS2-4-12-22 and 25) show H2 emission and close to
three peaks (MMS2-4-22), all associated with an IRAS
source, we have found a sub − parsec scale jet (with ex-
tension 0.30, 0.30 and 0.68 pc, respectively). Only in one
case the jet seems to be emitted by the most luminous
object in the field (i.e. the one that contributes the most
to the FIR flux in the IRAS bands), in all the other cases
the driving source is a less luminous (and less massive)
object in the cluster. A similar result was pointed out by
Lorenzetti et al. (2002), who, having surveyed a sample of
12 IRAS protostellar candidates in VMR, have detected
H2 emission in 5 fields, clearly coming from low-mass ob-
jects clustered around the IRAS source, and not from the
IRAS source itself. This feature is likely related to a dif-
ferent duration of the jet phase in low and high luminosity
(mass) sources: this topic will be discussed in depth in a
forthcoming paper (Giannini et al. 2007, in preparation).
6. Conclusions
A southern sky area of 1×1deg2 belonging to the
star forming region VMR-D, previously surveyed at
mmwavelengths to identify the dust cores, has been stud-
ied by means of both IR catalogues (IRAS/MSX/2MASS)
and a set of new dedicated observations, to identify the
young protostellar counterparts associated to dust cores.
The motivation for the new IR observations is twofold: (i)
to perform a complete survey of all the recognized dust
cores in the H2 narrow-band filter (2.12µm) to search ev-
idence of protostellar jets; and (ii) to obtain a broad band
N (10.4µm) survey of those cores associated to embedded
clusters, aiming to pick up the source(s) that mainly con-
tribute(s) in the far-IR regime.
The main conclusions of this work are summarized here:
- In the majority of cases, MIR and/or FIR sources as-
sociated with dust cores do not coincide with the mm
peaks, although they are located in their vicinity. In
those cases of close-by cores, often the IR source is
located in between them.
- The resolved mm cores (i.e. those larger than the in-
strumental beam) are more frequently associated to
a NIR or FIR counterpart than the unresolved ones
(smaller than the instrumental beam). The existence
of signs of star formation activity around these latter
in the form of H2 jets, however, attests the genuine
nature of lots of them.
- The statistics of active vs inactive cores is in good
agreement with that found in other star forming re-
gions, but should be critically revised in the light of
more sensitive observations that will become available
in near future (e.g. SPITZER MIPS and IRAC maps).
- The SEDs of the associated sources present a slope
α = d log(λFλ)/d log(λ) between 2 and 10µm whose
distribution is strongly peaked at values typical of
Class I sources (0 < α < 3), in some cases even larger.
- An attempt has been done to search for Class 0 sources.
Ten IRAS sources (with upper limits at 12µm) do not
present any NIR reliable counterpart, but no one of
them satisfies the criterion Lbol/L1.3mm . 2×10
4 pro-
posed by André et al. (1993). However, considered the
probable overestimates of the IRAS fluxes (and bolo-
metric luminosities), we indicate the three objects with
the lowest Lbol/L1.3mm ratios as the youngest IRAS
sources of the region.
- The sources associated to the dust cores, both resolved
and unresolved, have all the same FIR colours, typical
of a black-body stratification between 50 and 1000K,
with a stronger contribution of the former component.
In other words, sources with FIR colours typical of
pre-main sequence T-Tauri and Herbig Ae/Be stars
seem to be absent, indicating VMR-D as a young (∼
106 years) region.
- Sources associated with unresolved cores are system-
atically less luminous (average Lbol ≃ 1.5 × 10
than those related to the resolved ones (average Lbol ≃
1.5 × 103L⊙), providing evidence that two modalities
of star formation, namely low- and intermediate-mass,
are simultaneously present in VMR-D.
- This occurrence is also confirmed by the existence of
a further (low luminosity) population of young objects
that have the same colours as the sources associated
to the dust cores (resolved or unresolved), but are lo-
cated, on the contrary, in the diffuse warm dust and
along the gas filaments.
- Observing the dust cores in the H2 1-0S(1) line ev-
idences a high detection rate (30%) of jets driven
12 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
by sources located inside the cores. They appear not
driven by the most luminous objects in the field,
but rather by less luminous (and less massive) ob-
jects in surrounding star clusters, testifying the co-
existence of both low and intermediate-mass star for-
mation, being the former more likely associated to
molecular jet activity. Moreover the jet compactness
(at sub − arcsecond scales) is a further indication for
the prevalence of very young objects.
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M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 13
< -1.5 -1.5 < < 0 0 < < 1.5 1.5 < < 3 > 3
Spectral Index
Class III Class II Class I
Fig. 3. Spectral index (α2−10) distribution of core counterparts. In cases of multiple estimates of the 10µm flux
(Timmi2, MSX, IRAS) the value obtained with better spatial resolution has been used to determine α.
130 K
150 K
200 K
100 K
T-Tauri
Herbig Ae/Be
-0.5 0.0 0.5 1.0 1.5 2.0 2.5
[25-60]
↑ ↑ ↑
Associated with:
MMS (1FWHM-ellipse)
MMS (2FWHM-ellipse)
umms (1FWHM-ellipse)
Not associated
Fig. 4. Two colours diagram for all the IRAS sources listed in Tabs. 1 and 3. The mean error bars, the extinction
vector corresponding to 5mag of visual extinction and the locus of blackbodies (leftmost line) are indicated (see text
for more details).
14 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
<1.5 1.5-2 2-2.5 2.5-3 3-3.5 3.5-4 >4
Log(Lbol / L )
s Associated
Not associated
Fig. 5. Luminosity distribution of both associated and not associated IRAS sources (Tabs. 1 and 3).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 1
Online Material
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 2
Appendix A: Counterparts of the dust cores
In the following we present a brief discussion of the NIR
to FIR associations found for each dust core. Other signs
of star formation activity (e.g. H2 knots and jets or young
embedded clusters) will be also evidenced. For each core
(or group of cores) we will show the SofI H2 (or 2MASS
H band) gray scale image supplied with: dust emission
contours, position of the most interesting sources, cov-
erage of IRAC2 and Timmi2 fields of view and arrows
indicating the occurrence of H2 knots (see Sect. 3.4 for
more details). Whenever needed for the analysis, the cor-
responding colour-colour diagrams and SED plots will be
shown as well.
– MMS2 (Figs. A.1, A.2): one MSX associated ob-
ject inside the FWHM-ellipse, G263.6338-00.5497,
with a N band counterpart, DGL 3, having a flux
(F10.4µm = 0.25 Jy) smaller than that measured by
MSX (F8.3µm = 0.4 Jy).
Inside the FWHM-ellipse, many NIR stars (recogniz-
able in the SofI H2 image) have not been detected
by 2MASS and are only upper limits for IRAC2 in
both J and H bands. The object showing the highest
colour excess (MGL99 25) and steepest spectral index
(Fig. A.2) is not visible in the N band (at 30mJy
sensitivity level). We have tentatively indicated
that one in Tab. 2 as candidate NIR counterpart.
However, an intense H2 line emission is present
all over the core, both diffuse and in knots and,
remarkably, a well collimated H2 jet crosses the
very center of the core. No reliable exciting source
has been detected along the jet. Likely, it is heavily
embedded near the peak position and contributes
significantly (or mainly) to the observed dust emission.
– MMS3 (Figs. A.3, A.4): an IRAS source (IRS16) is
marginally associated to the peak (see Sect. 3.4). Three
MSX detections (one of them inside the FWHM-
ellipse) fall in a region of enhanced and diffuse 8µm
emission and don’t seem to be point-like (as suggested
by the MSX image and by the failed detection in N).
A Timmi2 source (DGL 5, identified with MGL99 65)
is instead observed in the direction of the IRAS source
and NIR cluster.
A steep decrease in the number of NIR detections
towards the peak suggests a high extinction level.
Moreover, the majority of the IRAC2 sources within
the FWHM-ellipse presents very red colours. MGL99
36, the one closest to the peak position, could be the
main source associated to the millimeter core.
– MMS4: a detailed analysis of this core has
been already presented in a dedicated paper
(Giannini et al. 2005), which the reader is referred to.
– MMS5-6, umms6 (Fig. A.5): a dust elongated struc-
ture of connected cores pointing towards south-west in
the direction of MMS4, the brightest core of the whole
dust map; a dust filament which is likely undergoing
fragmentation. Neither MIR-FIR associations, nor
interesting NIR sources are present (although no
IRAC2 data are available); signs of star formation
activity are quite hidden and can be only recognized
as a faint H2 emission around MMS5 and MMS6.
– MMS7, umms13-14-15 (Fig. A.6): resolved core
(MMS7) surrounded by three unresolved cores
(umms13-14-15). The J , H and Ks photometry of the
cluster of about 20 members around the central core
will be analyzed in a forthcoming paper. Neither FIR
emission nor H2 features are present (no 10µm image
has been collected). We just remark here the colour
excess of 4 very red stars within the FWHM-ellipse of
MMS7.
– MMS8-9 (Fig. A.7): these cores are part of a long
tail of connected cores (extending for about 1 pc),
going from the bright core MMS12 to umms19, whose
dynamical behaviour is not clear (Massi et al. 2007).
No FIR point sources or clues of H2 emission have
been observed. Timmi2 observations, although not
covering the whole dust emission, gave negative results
as well. Only one very red NIR object, 2M 9671 (no
IRAC2 data available), lies within the FWHM-ellipse
of MMS8.
– MMS10-11 (Fig. A.8): without any MIR-FIR coun-
terpart, these are the only two resolved cores included
in the 13CO map that lack of an associated CO clump
(Elia et al. 2007). The colour-colour diagram of the
2MASS sources (no IRAC2 data available) within
the FWHM-ellipse gives only one reddened candidate
(2M-14732) for MMS11.
– MMS12 (Figs.A.9, A.10): one of the brightest
cores, MMS12 (∼ 18M⊙) coincides with a young
embedded cluster having in its center the IRAS source
08470-4321 (IRS19), the MSX G263.7434+00.1161
and the Timmi2 DGL 7 object. The new observed
flux at 10µm (F10.4µm = 18.3 Jy) is less than a half of
the IRAS/MSX measurements at 8-12µm. We ascribe
this discrepancy to the presence of a strong diffuse
contribution to the flux at these wavelengths.
The correspondence of these sources with the NIR
object MGL99 49 has been already discussed in Massi
et al. (1999) and is confirmed here.
Complex and intense H2 emission is also present,
especially at the peak position, and at the eastern
part of the core; it cannot be clearly distinguished as
a single jet-like structure.
– MMS13 (Fig.A.11): no MIR-FIR association and no
significant H2 emission for this core at the south of
MMS12. The two possible NIR counterparts have red
colours (MGL99 2, MGL99 7).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 3
– MMS14-15-16 (Fig. A.12): neither MIR-FIR associ-
ations nor NIR red sources detected by 2MASS (no
IRAC2 data). We note a faint H2 emission aligned
with both the peak MMS16 and the H2 knot visible
at the east of MMS12 (see also Fig.A.9). We cannot
exclude the existence of an embedded exciting source
near the MMS16 peak position.
– MMS17 (Fig. A.13): a double H2 knot (probably jet-
like) in proximity of the peak suggests the existence
of star forming activity, but no MIR-FIR objects have
been detected and the 2MASS data do not point out
any interesting source within the FWHM-ellipse.
– MMS18 (Figs.A.14, A.15): one IRAS source (08472-
4326A) is associated within 2FWHM-ellipse, while one
MSX source (G263.8432+00.0945) and one Timmi2
object (DGL 8) are inside the FWHM-ellipse. The
positional uncertainties of these three objects seem
to exclude their coincidence, although the IRAS and
MSX fluxes (due to their beam sizes) are surely con-
taminated by the Timmi2 source (whose counterpart,
2M 29896, peaks in the H band) and probably by
diffuse emission, visible in the H2 filter as well.
– MMS19 (Fig. A.16): core connected to MMS20 and
MMS21. Neither MIR-FIR sources associated nor H2
emission detected. We signal two very red 2MASS ob-
jects (2M-36076, 2M 36192) within the FWHM-ellipse.
– MMS20 (Fig. A.17): one IRAS (08474-4323, corre-
sponding to MSX G263.8221+00.1494) source turns
out to be very marginally associated (positional uncer-
tainty tangent to the 2FWHM-ellipse), but the dust
emission around its position seems to be negligible.
One Timmi2 source (DGL 9) has been detected within
2FWHM-ellipse, in the middle between this core and
MMS21 not signalled by IRAS/MSX (SofI images
points out at least three objects, partially resolved by
2MASS in two very red sources, 2M 27831 and 2M
37241).
– MMS21 (Figs. A.18, A.19): one IRAS source, 08474-
4325, whose fluxes indicate this one as one of the
youngest objects of VMR-D, coincides with the peak
position. The Timmi2 observation has given no results
(for the source DGL 9 see MMS20 description) and
no MSX sources are reported in the catalogs. Three
2MASS sources fall close to the IRAS uncertainty
ellipse center, two of which (2M-29953, 2M 37193)
have very red colours. The SofI H2 image, however,
points out the presence of a complex morphology,
which cannot be resolved in individual sources with
the SofI spatial resolution.
– MMS22 (Figs. A.20, A.21): characterized by a power-
ful bipolar jet (0.7 pc long, discussed in a forthcoming
paper) arising from the IRAS source 08476-4306
(IRS20), located 10′′ at the west of the peak. In cor-
respondence with the IRAS source there are a young
cluster, a MSX point source (G263.6177+00.3652)
and two 10µm objects: DGL 11 (main counterpart
of the IRAS/MSX object) and DGL 10 (2σ de-
tection, outside the FWHM-ellipse). The DGL 11
flux, F10.4µm = 2.01 Jy, is significantly smaller than
those measured by MSX and IRAS: F8.3µm = 3.9 Jy,
F12µm = 5.7 Jy, F12.1µm = 6.0 Jy, but the Timmi2 ob-
servation points out a diffuse emission which can have
contributed to the MIR fluxes measured by IRAS and
MSX. The presence of nebular NIR and H2 emission
completes the picture of this crowded region. The NIR
cluster characteristics have been discussed in detail
by Massi et al. (1999) and the conclusions reported
in that paper about the candidate NIR counterpart
(MGL99 98) of IRS20 are confirmed by our Timmi2
observation. MGL99 98 is also the best candidate as
exciting source of the jet, although the complexity of
the jet morphology and the difficulty to discriminate
between nebular and point-like unresolved emission
makes this identification questionable. We also remark
one dark strip clearly visible in the H2 image, likely
due to an obscuring dust lane crossing the cluster
center.
– MMS23 (Fig. A.22): isolated, small core with no
IR detected sources near the peak (not observed at
10µm). H2 multiple knots are visible to the north
of the peak together with a faint emission near
the center. We cannot exclude the presence of an
embedded, young, low-mass stellar object producing
that emission, but more sensitive observations are
required to confirm this possibility.
– MMS24 (Fig.A.23): this core is connected with the
brighter MMS22 and is characterized by diffuse K
emission close to a MSX source (within 2FWHM-
ellipse) not detected by Timmi2. The NIR source
MGL99 90, at the border of the FWHM-ellipse, shows
the highest colour excess.
– MMS25-26 (Figs. A.24, A.25): this complex re-
gion is constituted by two not well resolved cores
(also linked to the brighter MMS27) and, between
them, in correspondence with a young NIR cluster
(Massi et al. 2006), there are the IRAS source 08477-
3459 (IRS21), the MSX source G264.3225-00.1857
and the Timmi2 object DGL 12 (corresponding to
the NIR MGL99 27). Moreover, the 10µm emission
observed by Timmi2 shows a diffuse emission (in the
surroundings of the source MGL99 35) and, probably,
another point source corresponding to MGL99 32,
although an artifact in the Timmi2 image prevented
us to give a reliable estimate of its flux. Remarkable is
also a shell-like K emission (clearly visible also in the
H2 image) approximately centered near MGL99 63.
The colour-colour diagram (Fig. A.25) points out the
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 4
existence of many red and very red sources within the
FWHM-ellipse of both the cores, lots of which having
upper limits in the J and H bands. The SEDs of the
MIR-FIR objects and of the NIR stars with larger
colour excess show significant discrepancies among the
fluxes of the MIR-FIR detections. No clear evidence
has been found for NIR stars (if any) that can be
most likely associated to the mm core8.
– MMS27 (Fig. A.26): although this is one of the bright-
est cores of the whole dust map, no IRAS-MSX point
sources have been detected. Only one faint object
(DGL 13), counterpart of the NIR very red 2M 53071
(we lack of IRAC2 data for this source), can be seen at
10 µm, inside the FWHM-ellipse, together with three
more very red sources.
Interesting is the case of 2M 47136, the closest one to
the peak: no point-like source can be extracted from
the K image which shows instead a very diffuse emis-
sion well observable also in the H2 image of Fig.A.26.
It is crossed by a dark horizontal strip (quite likely
due to obscuring dust). A knot of H2 emission is also
visible above this strip and one more on the other
side of the core, in the south-west direction, making
this core of a peculiar interest for future investigations.
– MMS28-29 (Fig. A.27): inside the FWHM of
MMS28 there are the IRAS 08483-4305 and MSX
G263.6909+00.4713 sources and, remarkably, H2
aligned knots are visible between the two peaks. We
lack of both Timmi2 and IRAC2 observations, but the
2MASS data reveal one very red source, 2M 36339,
incompatible with the position of the FIR sources, but
aligned with the knots, which could be their exciting
source.
In the following we present the unresolved cores not
previously discussed.
– umms1 (Fig. A.28): despite the high noise level of
the dust map in this position, this unresolved core is
one of the most interesting cases: (i) it is by far the
most intense core among the unresolved ones, (ii) its
coordinates coincide with an IRAS source showing
fluxes increasing with wavelength and (iii) the 12CO
integrated emission map presents an increase towards
this peak, altough it falls immediately outside that
map (see note 5). Unfortunately we lack of both
IRAC2 and SofI images at this position and only
one 2MASS (red) object falls inside the FWHM-ellipse.
8 The lack of any Timmi2 detectable flux in correspondence
of MGL99 50, the previously hypothesized NIR counterpart
of the IRAS source (Massi et al. 1999), makes that association
questionable. Observing its SED, indeed, it is quite unlikely
that it could be missed, if point-like, at 10µm.
– umms2-3-4-5 (Fig. A.29): region of high noise level
of the dust map. These cores are probably artifacts of
the reconstruction algorithm and do not present any
feature suggesting star formation activity.
– umms7-10-12 (Fig. A.30): a small cluster within
2FWHM-ellipse of umms10 (forthcoming dedicated
paper) is the only noticeably feature of this field.
– umms8-9-11 (Figs. A.31, A.32): dust emission as-
sociated with an IRAS source (08458-4332, having
flux increasing with λ, associated to umms8-9) and
a MSX-Timmi2 object (G263.7651-00.1572-DGL 6,
associated with umms11 and the 2MASS objects
2M 9173 and 2M 11131). One very red and one red
NIR object (2M-116128 and 2M 18032, respectively)
within the FWHM-ellipse of umms8.
– umms16 (Fig. A.33): core remarkably crossed by H2
jet-like emission and with an IRAS source (08464-
4335), although the Timmi2 observation gave no
results and no red or very red NIR stars have been
observed by 2MASS as possible jet exciting source.
– umms17-18 (Fig. A.34): also this couple of cores
presents an intense H2 jet-like emission, but without
any NIR-MIR interesting source.
– umms19-20 (Fig. A.35): these cores are part of a
chain of connected cores (see description of MMS8-9).
No FIR-MIR point sources have been observed and
only a knot of H2 emission is visible in the FWHM-
ellipse of umms19, close to a red 2MASS source
(2M-10742).
– umms21 (Figs.A.36): connected to the previous
cores. No FIR-MIR point sources or clues of H2
emission have been observed. One very red NIR object
(2M-16489) within the FWHM-ellipse.
– umms22 (Figs.A.37): No FIR point source or clues
of H2 emission have been observed (no Timmi2 data
available). Absence also of NIR red objects within the
FWHM-ellipse.
– umms23-24-25 (Figs.A.38): thin, elongated dust
structure with three cores coinciding with a sim-
ilar shaped K emission. Two MSX sources,
G263.5672+00.4036 and G263.5622+00.4185, are
tightly associated to umms23 and umms24, respec-
tively. Two very red sources fall within the FWHM of
umms23, but they seem to be incompatible with the
position of the MSX sources (for which we suspect a
high contamination from diffuse emission).
– umms26 (Figs. A.39): a small cluster outside
2FWHM-ellipse (forthcoming paper) is the only
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 5
noticeably feature of this field.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 6
Fig.A.1. MMS2 field of view (center [J2000]: 08:45:34.200, -43:51:54.40). Grayscale image: H2 emission; green con-
tours: dust continuum (from 3 σ, in steps of 3σ); red ellipses: FWHM-ellipse and 2FWHM-ellipse of the core (see
Sect. 3.2 for an explanation); green and magenta ellipses: MSX and IRAS 3σ positional uncertainty; orange line:
IRAC2 field of view.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
MGL99-4
MGL99-25
MGL99-14
MGL99-9,
MGL99-15
1 2 3
-20.0
-19.5
-19.0
-18.5
-18.0
-17.5
2M-26276
MGL99-25
MGL99-4
MGL99-14
MGL99-9
MGL99-15
Fig.A.2. a) Colour-colour diagram (see text for more details) of the NIR sources within the FWHM-ellipse of MMS2.
The Spectral Energy Distributions of the very red ones are shown in panel b). To reduce confusion the wavelength
range is limited to the J , H , K bands and the main objects are in red colour. Dashed lines refer to 2MASS sources
and arrows denote upper limits.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 7
Fig.A.3. MMS3 field of view (center [J2000]: 08:45:39.5, -43:51:25.0).
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
MGL99-65
MGL99-36
1 2 3
-20.2
-20.0
-19.8
-19.6
-19.4
-19.2
-19.0
-18.8
MGL99-36
MGL99-65
Fig.A.4. MMS3: colour-colour and SED diagrams.
Fig.A.5. MMS5-6 and umms6 field of view (center [J2000]: 08:46:52.0, -43:53:01.3).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 8
0.0 0.5 1.0 1.5 2.0
[H-K]
2M-16616
2M-10095
2M-18266
2M-8124
Fig.A.6. MMS7 and umms13-14-15 field of view (center [J2000]: 08:47:58.9, -43:39:22.9) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 9
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
2M-9671
Fig.A.7. MMS8-9 field of view (center [J2000]: 08:48:41.3, -43:31:36.2) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 10
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-14732
Fig.A.8. MMS10-11 field of view (center [J2000]: 08:48:44.2, -43:37:19.1) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 11
Fig.A.9. MMS12 field of view (center [J2000]: 08:48:48.5, -43:32:20.8).
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
MGL99-49
1 2 5 10 2 5 10
MGL99-49
DGL-7
IRS19
G263.7434+00.1161
Fig.A.10. MMS12 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 12
0.0 0.5 1.0 1.5
[H-K]
MGL99-2
MGL99-7
Fig.A.11. MMS13 field of view (center [J2000]: 08:48:49.4, -43:33:11.2) and colour-colour diagram.
Fig.A.12. MMS14-15-16 field of view (center [J2000]: 08:48:51.6, -43:31:09.9).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 13
Fig.A.13. MMS17 field of view (center [J2000]: 08:48:57.2, -43:38:23.1).
Fig.A.14. MMS18 field of view (center [J2000]: 08:49:03.2, -43:38:05.2).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 14
0.0 0.5 1.0 1.5
[H-K]
2M-29896
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
-15.5
-15.0
2M-29896
DGL-8
08472-4326A
G263.8432+00.0945
Fig.A.15. MMS18 colour-colour and SED diagrams.
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-36192
2M-36076
Fig.A.16. MMS19 field of view (center [J2000]: 08:49:08.5, -43:35:43.7) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 15
0.0 0.5 1.0 1.5 2.0
[H-K]
2M-37241
2M-27831
Fig.A.17. MMS20 field of view (center [J2000]: 08:49:11.2, -43:35:25.9) and colour-colour diagram.
Fig.A.18. MMS21 field of view (center [J2000]: 08:49:13.0, -43:36:21.8).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 16
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-37193
2M-29953
2M-34100
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-29953
2M-37193
2M-34100
08474-4325
Fig.A.19. MMS21 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 17
Fig.A.20. MMS22 field of view (center [J2000]: 08:49:26.0, -43:17:13.0).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 18
0 1 2 3 4 5
[H-K]
MGL99-98
1 2 5 10 2 5 10
MGL99-98
DGL-10
DGL-11
IRS20
G263.7434+00.1161
Fig.A.21. MMS22 colour-colour and SED diagrams.
Fig.A.22. MMS23 field of view (center [J2000]: 08:49:30.2, -44:04:10.0).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 19
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
MGL99-90
Fig.A.23. MMS24 field of view (center [J2000]: 08:49:30.1, -43:17:00.2) and colour-colour diagram.
Fig.A.24. MMS25-26 field of view (center [J2000]: 08:49:33.5, -44:10:34.5).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 20
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
[H-K]
1 2 5 10 2 5 10
DGL-12
IRS21
G263.7434+00.1161
Fig.A.25. MMS25-26 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 21
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
] 2M-47136
2M-53071
Fig.A.26. MMS27 field of view (center [J2000]: 08:49:35.2, -44:11:52.8) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 22
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-36339
Fig.A.27. MMS28-29 field of view (center [J2000]: 08:50:10.0, -43:16:41.3) and colour-colour diagram.
Fig.A.28. umms1 field of view (center [J2000]: 08:46:25.7, -43:42:28.3) (2MASS H band image).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 23
Fig.A.29. umms2-3-4-5 field of view (center [J2000]: 08:46:44.0, -43:19:48.2).
Fig.A.30. umms7-10-12 field of view (center [J2000]: 08:47:37.4, -43:26:21.7).
Fig.A.31. umms8-9-11 field of view (center [J2000]: 08:47:39.6, -43:43:36.1).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 24
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-9173
2M-11131
2M-18032
2M-16128
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-9173
2M-11131
2M-16128
DGL-6
08458-4332
G263.7651-00.1572
Fig.A.32. umms8-9-11 colour-colour and SED diagrams.
Fig.A.33. umms16 field of view (center [J2000]: 08:48:15.3, -43:47:06.5).
Fig.A.34. umms17-18 field of view (center [J2000]: 08:48:24.6, -43:31:36.7).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 25
Fig.A.35. umms19-20 field of view (center [J2000]: 08:48:33.9, -43:30:46.0).
Fig.A.36. umms21 field of view (center [J2000]: 08:48:36.4, -43:31:11.5).
Fig.A.37. umms22 field of view (center [J2000]: 08:48:36.3, -43:16:45.9).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 26
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-15995
2M-11799
Fig.A.38. umms23-24-25 field of view (center [J2000]: 08:49:25.9, -43:12:39.2) and colour-colour diagram.
Fig.A.39. umms26 field of view (center [J2000]: 08:49:58.9, -43:22:55.1).
	Introduction
	The investigated region
	Association with point-sources
	Observations
	NIR imaging
	N-band imaging
	FIR associations
	NIR associations
	The core MMS1
	Results
	Discussion
	IR counterparts of dust cores
	Star formation modalities and evolutionary stages
	H2 survey 
	Conclusions
	Counterparts of the dust cores

  The aim of this paper is to identify the young protostellar counterparts
associated to dust millimeter cores of the Vela Molecular Ridge Cloud D through
new IR observations (H_2 narrow-band at 2.12 micron and N broad band at 10.4
micron) along with an investigation performed on the existing IR catalogues.
The association of mm continuum emission with infrared sources from catalogues
(IRAS, MSX, 2MASS), JHK data from the literature and new observations, has been
established according to spatial coincidence, infrared colours and spectral
energy distributions. Only 7 out of 29 resolved mm cores (and 16 out of the 26
unresolved ones) do not exhibit signposts of star formation activity. The other
ones are clearly associated with: far-IR sources, H_2 jets or near-IR objects
showing a high intrinsic colour excess. The distribution of the spectral
indices pertaining to the associated sources is peaked at values typical of
Class I objects, while three objects are signalled as candidates Class 0
sources. We remark the high detection rate (30%) of H_2 jets driven by sources
located inside the mm-cores. They appear not driven by the most luminous
objects in the field, but rather by less luminous objects in young clusters,
testifying the co-existence of both low- and intermediate-mass star formation.
The presented results reliably describe the young population of VMR-D. However,
the statistical evaluation of activity vs inactivity of the investigated cores,
even in good agreement with results found for other star forming regions, seems
to reflect the limiting sensitivity of the available facilities rather than any
property intrinsic to the mm-condensations.

Introduction
The association of far-infrared (FIR) sources with the
gas and dust emission cores in Giant Molecular Clouds
(GMCs) is the starting point of any effort aimed to obser-
vationally study high- and intermediate-mass star forma-
tion modalities. Indeed the Galactic matter is distributed
in such a way that prevents to have a significant num-
ber of GMCs located near our Sun. Also low-mass star
formation occurs in GMCs, but GMCs are usually found
Send offprint requests to: M. De Luca
⋆ Based on observations collected at NTT and 3.6m telescope
(ESO - La Silla, Chile).
at distances greater than 1-2Kpc, where the sensitivity of
the current fore-front instrumentation makes it possible
to sample only the most luminous (i.e. the most massive)
objects. As a consequence, studying low-mass star forma-
tion is limited to nearby dark clouds, leaving GMCs as
the privileged targets for high-mass studies. Exceptions
exist, which are represented by the Orion and Vela GMCs
(usually named Vela Molecular Ridge - VMR) and by the
OB association in Scorpius-Centaurus and Perseus, whose
distances range between 300 and 700 pc. Orion GMC is by
far the most studied star formation site at all wavelengths
and both modalities (high- and low-mass) are observation-
ally documented to take place in it (e.g. Chen & Tokunaga
http://arxiv.org/abs/0704.1228v1
2 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
1994). Its location outside the plane of the Galaxy (b≈ -
20◦) has originally sanctioned its leading rôle in star for-
mation studies, when extinction and crowding represented
insurmountable observational barriers. Also Sco-Cen and
Per OB associations are located at about +20◦ and -20◦,
respectively. The rapid growth of multi-frequency facil-
ities at an increasing spatial resolution, makes it possi-
ble now to study, with enough accuracy, even extincted
and crowded regions, as the VMR, in the plane of the
Galaxy. Thanks to the forthcoming facilities, investigat-
ing the plane will be easier and easier and the properties
derivable from the VMR will be the most suitable for ob-
taining a direct comparison with those of the other galax-
ies, whose planes represent the main volume we are able
to sample.
The VMR is a complex of four GMCs (Murphy & May
1991; Yamaguchi et al. 1999) and it is probably one of the
best regions for studying the processes involved in star
formation (clustering, isolation, matter outflows). It is lo-
cated in the galactic plane (b = ± 3◦) outside the solar cir-
cle (ℓ ∼ 260◦ − 275◦) and most of the gas is at a distance
of ∼ 700 pc (Liseau et al. 1992). So far we have accumu-
lated a large data-base on VMR clouds through ground-
based observations from near-IR (NIR) to mm wave-
lengths. In particular, our analysis, based on the IRAS
point source catalog (IRAS-PSC 1988), unveiled a re-
markable concentration of red FIR sources with bolomet-
ric luminosities < 104L⊙ (Liseau et al. 1992, Lorenzetti et
al. 1993). These are very young intermediate-mass stars
and we found (Massi et al. 2000, 2003) that FIR sources
with Lbol > 10
3L⊙ coincide with young embedded clus-
ters (size ∼ 0.1 pc, ∼ 50-100 members). In particular, we
find that the region of the VMR named cloud D (here-
inafter VMR-D) hosts a large number of these, revealing
a high efficiency in this mode of star formation. At the
same time, the presence of IRAS sources having bolomet-
ric luminosities of only few solar luminosities, shows that
the formation of isolated, low-mass stars is also active in
this region.
We have searched the region around a complete sample of
IRAS sources in VMR-D for protostellar jets, using NIR
imaging and spectroscopy (Lorenzetti et al. 2002), and we
have discovered a significant number of shock tracers (H2
and [FeII] line emission knots), which signal the pres-
ence of protostellar jets in VMR-D. We have also clarified
the details of the interactions between jets and circumstel-
lar environment as well as the properties of the exciting
sources (Caratti o Garatti et al. 2004, Giannini et al. 2001,
2005).
Recently we mapped a ∼ 1 deg2 area of the VMR-D in
the 1.2mm continuum of dust emission, along with the
12CO(1–0) and 13CO(2–1) transitions (see Fig. 1 in Massi
et al. 2007 and Figs. 3-4 in Elia et al. 2007). The aim
of the present paper is to correlate dust map and avail-
able FIR and NIR catalogues to have a complete census
of the VMR-D young population that allows us to assess
the pre-main sequence evolutionary stage properties. The
correspondence between dust cores and molecular clumps
has been already presented in Elia et al. (2007).
An increasing number of millimeter surveys towards star
formation regions along with a comparison with existing
FIR catalogues is now available. For the VMR complex, in
particular, an investigation of the Vela-C cloud has been
carried out by Moriguchi et al. (2003) and by Baba et al.
(2006), and mm-studies of few individual sources belong-
ing to VMR-D are reported by Faundez et al. (2004) and
Fontani et al. (2005).
In the following, we give in Sect. 2 a short summary of
the results on the mm-maps (both dust and gas) we have
presented elsewhere. The criteria for associating IR coun-
terparts to the dust emission cores are discussed in Sect. 3,
along with the analysis of a particular selected area, as an
example. New IR observations are also presented in this
section. The results are then summarized in Sect. 4 and
discussed in Sect. 5. In appendix A, the associations for
all the regions of dust emission are discussed separately.
2. The investigated region
Our observations of the VMR-D carried out in the mil-
limeter range with the SEST (ESO - La Silla) telescope
are described elsewhere and consist of three maps of
about 1 deg2, both in the dust continuum emission at
1.2mm (Massi et al. 2007) and in the molecular transi-
tions 12CO(1-0), at 2.6mm, and 13CO(2-1), at 1.3mm
(Elia et al. 2007).
The 12CO data (resolution: 43”, sampling: 50”) out-
line a filamentary distribution of diffuse molecular emis-
sion connecting regions of enhanced intensity where there
is evidence of clustered, intermediate-mass, star forma-
tion in progress (Elia et al. 2007, Massi et al. 2007).
The map of 13CO emission, because of its lower abun-
dance with respect to 12CO, traces denser regions of the
molecular cloud, which present a quite clumpy structure.
Summarizing the results from the 13CO map, we have
found 49 clumps with mass, size and mean velocity rang-
ing from 2 to 140M⊙, from 0.15 to 0.67pc and from 1 to
13 km s−1, respectively (see Tab. 3 in Elia et al. 2007).
The dust map (resolution: 24”, corresponding to about
0.1 pc, in fast scanning mode of 80 arcsec s−1) also shows
a clumpy structure and we have individuated 29 cores of
mass and size in the ranges 0.2 - 80M⊙ and 0.03 - 0.3 pc
respectively (see Tab. 1 in Massi et al. 2007), almost all of
them nearly coincident with the brightest regions of the
velocity integrated CO maps. In addition, other 26 cores,
whose size is under the spatial resolution, have been iden-
tified, even if their genuine nature remains uncertain.
3. Association with point-sources
In this work we aim to correlate the millimeter emis-
sion with objects from both new IR images (1-10µm)
carried out on selected areas (see Sect. 3.1) and the
infrared existing catalogs of point sources in order to
find out the sources that dominate the dust cores heat-
ing. In particular, the considered catalogs are: (i) the
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 3
IRAS point source catalog (IRAS-PSC 1988), that pro-
vides flux densities at 12, 25, 60 and 100µm; (ii) the
MSX (Midcourse Space Experiment) point source cata-
log (Price et al. 2001) at 8.28, 12.13, 14.65 and 21.3µm;
(iii) the 2MASS point source catalog (Cutri et al. 2003),
based on J , H , Ks bands, complemented with litera-
ture data (Massi et al. 1999) of deeper IRAC2 images
(Moorwood et al. 1992).
3.1. Observations
An observational campaign has been carried out by using
NIR (narrow-band H2 1-0S(1) at λ=2.13µm) and mid-
IR (MIR) (N broad-band) imaging facilities to observe
fields selected from the mm-emission maps. All the rec-
ognized dust cores (except one) have been imaged in H2,
with the aim of searching for protostellar jet evidences.
The 10.4µm survey covered those cores associated to the
presence of a young embedded cluster (Massi et al. 2003,
2006), aiming, thanks to an adequate spatial resolution,
to pick-up those source(s) (if any) that dominate(s) the
detected fluxes at FIR wavelengths.
3.1.1. NIR imaging
Broadband J , H , Ks and narrow-band images in the
H2 1-0S(1) (λ=2.13µm, ∆λ=0.03µm) were obtained
in January 2006 with SofI1 (Lidman et al. 2000) at
ESO-NTT (La Silla, Chile). The total field of view is
4.9×4.9 arcmin2, which corresponds to a plate scale of
0.29 arcsec/pixel. All the observations were obtained by
dithering the telescope around the pointed position and
the raw imaging data were reduced by using standard
procedures for bad pixel removal, flat fielding, and sky
subtraction.
3.1.2. N-band imaging
Imaging in the N10.4 broadband filter was carried out in
January 2006 with Timmi2 (Saviane & Doublier 2005) at
the 3.6m ESO telescope (La Silla, Chile). The adopted
plate scale is 0.3 arcsec/pxl, corresponding to a 96′′ × 72′′
field of view. The observations were obtained by chop-
ping the signal and by nodding and jittering the tele-
scope around the pointed position in the usual ABB′A′
mode. The raw data were reduced by using standard
procedures for bad pixel removal and the observed field
was flux calibrated by using photometric standard stars
(HD29291, HD32887, HD123139). The photometric re-
sults are given in Tab. 1, together with the IRAS/MSX
results. Although these latter refer to different effective
wavelengths and different epochs, ground-based values
are significantly lower than IRAS/MSX determinations.
These discrepancies have been remarked several times in
the literature concerning YSO’s (e.g. Walsh et al. 2001)
1 J and H images were obtained only for those fields con-
taining the young clusters.
and may be due to the higher environmental contamina-
tion suffered by the larger IRAS/MSX beams.
3.2. FIR associations
Within molecular clouds the correlation between the po-
sitions of dust emission cores and FIR point-like sources
represents an important method to obtain a census of both
the young stellar population and the different modalities
of the star formation. To search the catalogs for sources
associated to the dust cores listed in Tab. 1 of Massi et al.
(2007), a working definition of the core size has to be firstly
provided. Indeed, in that Table the core size is given (col-
umn 4), which results from the geometrical mean of the
quantities ∆x and ∆y. These latter (see Tab. 2, column
2) are directly provided by the adopted search algorithm
(Clumpfind), and indicate the FWHM of the linear profile
of the core itself, along its x (right ascension) and y (decli-
nation) axes, respectively (Williams et al. 1994). The area
covered by a dust core up to the (bidimensional) FWHM
flux level can thus be roughly individuated by the ellipse
centered at the peak coordinates and having axes ∆x and
∆y. For simplicity, we will call hereinafter this ellipse as
dust FWHM-ellipse (see e.g. Fig. 1, where it is represented
by the red, inner curve). Analogously, we operatively de-
fine as dust 2FWHM-ellipse that with axes 2∆x and 2∆y
(red, outer ellipse in Fig. 1).
Searching for catalogued sources we use this FWHM value
by adopting the following criterion: an IRAS or MSX
point source is considered associated to the core if its po-
sitional uncertainty ellipse overlaps (or is tangent to) the
dust 2FWHM-ellipse. However, to evidence the most com-
pelling cases, the association within one FWHM-ellipse
are boldfaced in Tab. 1. With respect to the criterion
adopted in similar works (e.g. Mookerjea et al. 2004,
Beltrán et al. 2006), for which an IRAS/MSX source is
associated to a core if it lies inside 90′′/40′′, our criterion
both takes into account the dust emission morphology and
compensates for the large IRAS/MSX beam.
3.3. NIR associations
Both the 2MASS catalog and the IRAC2 catalog reported
in Massi et al. (1999) were searched for NIR associations,
i.e. the sources that dominates the cores heating. Since
the NIR sources positional accuracy is by far larger than
the deconvolved core size, there is no need of defining a
specific criterion for the association: we simply consider
all the NIR sources falling within the FWHM-ellipse of
each core that present a valid flux (not an upper limit) at
least in a single band (J , H , K). Furthermore, we have
tentatively selected the most probable NIR counterpart of
the dust core according to the following criteria:
1. Closeness to the peak of dust emission and to the FIR
source possibly associated, if any.
2. Intrinsic excess in the two colours (J-H vs H-K) dia-
gram (hereafter colour-colour diagram). This criterion
4 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
makes it possible to pick up the NIR objects whose
spectral energy distribution (SED) is typical of a young
stellar object (YSO), and does not appear as stellar
photosphere reddened by the intervening dust along
the line of sight. In this context, to point out their
intrinsic colour excess, we will define two loci in the
colour-colour diagram (e.g. shaded regions in panel
a of Fig. 2): the locus of the red objects (mainly T-
Tauri), immediately to the right of the main sequence
(reddened) stars and the locus of the very red sources
(mainly Class I and Herbig Ae/Be protostars), to the
right of the T-Tauri (reddened) stars.
3. Largest spectral index α = d log(λFλ)/d log(λ) among
those with α≥ 0. Sources with α < 0, in fact, are gen-
erally visible in the optical plates, thus this item cut
off at least bright visible stars.
3.4. The core MMS1
Here we describe a typical example of the approach
adopted to detect the FIR/NIR counterparts of the mm-
core MMS1. Similar considerations have been done for any
individual mm-core, and all the results are provided in the
Appendix A.
As a first step, we overlay the contour map of dust
emission (green contours, from 3 σ=3× 15mJy/beam in
steps of 3σ) and the H2 narrow-band (gray-scale) image
(Fig. 1). The red ellipses centered on the mm-peak repre-
sent the FWHM- and the 2FWHM-ellipses within which
the association with the IR sources has been searched (see
Sections 3.2 and 3.3). The magenta and green ellipses in
Fig. 1 individuate the 3σ positional uncertainties of the
IRAS2 and MSX point sources, respectively, while the
blue asterisks signal the position of the 10.4µm sources
observed by Timmi2 in the field of view delimited in fig-
ure by the blue line. The 2MASS and IRAC2 NIR sources
are labelled 2M ♯ (following an internal numbering) and
MGL99 ♯ (following Massi et al. 1999), respectively. The
IRAC2 field of view does not cover the whole image and
is depicted as the orange rectangle.
Both IRS16 (08438 − 4340, corresponding to MSX
G263.6200-00.5308 and DGL 4) and G263.5925-00.5364
are located outside the FWHM-ellipse and do not appear
directly associated to the core, while the association is
more compelling with the sources DGL 1, DGL 2 and
G263.5994-00.5236.
The IRAS source coincides with a NIR young cluster and
an HII region located at the center of the region bordered
by the cores MMS1-2-3, almost equidistant from all of
them. The NIR cluster has been already investigated in
detail by Massi et al. (2003) and we complement those
data with the new N -band observation that points out
the presence of a very diffuse emission, indicated as DGL
2 Hereinafter we will adopt for the IRAS sources, when avail-
able, the shorter names IRS♯ defined in Liseau et al. (1992).
Both the original names and these ones, however, are listed in
Tab. 1.
4, corroborating the hypothesis that the FIR source can be
originated by warm circumstellar matter associated with
the most luminous (in the NIR) cluster member, MGL99
Also the MSX source G263.5295-00.5364, that falls at the
western border of the 2FWHM-ellipse, does not seem to
be related to the dust peak. It has been detected at 8µm
only and, presumably, such flux arises from diffuse emis-
sion, as an inspection of the MSX image suggests3.
To feature the NIR stellar content close to the peak po-
sition we give in Fig. 2-a the colour-colour diagram of all
the detected sources within the FWHM-ellipse. Here are
also drawn: the locus of the main sequence, class V stars
(Tokunaga 2000) (dark curve), the locus of the T-Tauri
stars (Meyer et al. 1997) (red line) and three reddening
lines (blue) (Rieke & Lebofsky 1985), starting from three
significant points, with four crosses indicating values of 0,
1, 5 and 10 mag of visual extinction. The separation of the
sources in the two regions red and very red (see Sect. 3.3)
is also evidenced by a different shading. The arrows on
the data points denote constraints on colours derived from
upper limits on the NIR photometry. This diagram allows
us to select the most interesting objects: in particular, the
sources labelled as MGL99 156, MGL99 179 and MGL99
155 show the highest colour excess.
We report in Fig. 2-b the Spectral Energy Distribution
(SED) of the very red stars within the FWHM-ellipse, to-
gether with the Timmi2 measured fluxes and the SED of
the MSX object G263.5994-00.5236. The arrows denote
again the upper limits.
From the SEDs, we see that MGL99 179 and MGL99
156, considering the upper limits, are the sources with
the steepest spectral indexes. Moreover, (see Fig. 1), while
MGL99 179 has been identified as the counterpart of the
Timmi2 source DGL 1, MGL99 156 has lack of detection
in N , although its K magnitude is comparable to that of
MGL99 179.
This allows us to suggest that the main contributor to the
millimeter flux should be the object MGL99 179=DGL
1. However, considering the richness of very red sources
in the field (Tab. 2), a contribution to the millimeter flux
from multiple sources or from objects too much embed-
ded to be investigated with the described tools, cannot be
ruled out. Moreover, the HII region at the southern border
of the core could provide an additional external heating
by means of UV photons.
3 It lacks of any NIR suitable counterpart (unfortunately, at
that position we have no IRAC2 data) although the nearest
NIR significant object, MGL99 156, 27 arcseconds apart, may
contribute to the measured flux.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 5
Fig. 1. MMS1 field of view (center [J2000]: 08:45:32.8, -43:50:12.3). Grayscale image: H2 emission; green contours:
dust continuum (from 3σ, in steps of 3 σ). See text for other details.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
2M-25930
MGL99-155
MGL99-179
MGL99-156
red very red
1 2 5 10 2
-20.5
-20.0
-19.5
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-25930
MGL99-123
MGL99-155
MGL99-179
MGL99-156
G263.5994-00.5236
DGL-2
DGL-1
Fig. 2. a - Colour-colour diagram of the sources falling within the FWHM-ellipse around MMS1. b - Spectral energy
distribution of the very red sources within the FWHM-ellipse. See text for more details.
6 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
4. Results
All the results derived from the association to dust emis-
sion cores of sources from both FIR/NIR catalogs and our
ground-based new observations are given in three different
Tables organized as follows:
- Table 1 - Here all the dust cores detected in the mm
map (column 1) having an association with a MIR
and/or FIR object are listed. The core identification
follows that of the dust map (Massi et al. 2007), where
the naming MMS# refers to the resolved cores while
umms# (second part of the Table) are under-resolved
(i.e. size smaller than the SIMBA beam4, see Tab. 2
of Massi et al. 2007). Then, for those cores associ-
ated with a FIR source, IRAS and MSX names, flux
densities and distances from the peak (d) are given,
along with an indicator (CC = correlation coefficient
for each band, see IRAS manual) of the point-like na-
ture of the IRAS source. For the IRAS objects is also
indicated the 1.2mm flux at the IRAS coordinates ob-
tained by integrating the dust map within 24 arcsec
(= SIMBAHPBW) aperture. Finally, for comparison
purposes with IRAS (12µm) and MSX (8.28 and
12.13µm) fluxes, the results of the Timmi2 observa-
tions (at 10.4µm, objects coded as DGL ♯) are also
reported in the last columns of this Table (again with
the distances from the peak). As anticipated, the bold-
faced lines correspond to FIR/MIR associations within
the corresponding FWHM-ellipse, and, consequently,
have to be considered as more robust cases.
We remark here that all the cores reported in Tab. 1 are
also associated with CO clumps, with the exception of
MMS29, umms1-23-24 and 25, which are outside the
CO map coverage5 (Elia et al. 2007).
- Table 2 - This Table lists the NIR counterparts of all
the cores. In column 2 the core size is identified through
the FWHM-ellipse axes ∆x and ∆y (see Sect. 3.2). In
column 3 the numbers of NIR red or very red sources
that are located within the FWHM-ellipse are given.
The census of the NIR population is based, whenever
it is possible, on the IRAC2 images (Massi et al. 1999,
objects coded as MGL99 ♯) that are deeper than the
2MASS frames (K band limit magnitude 18 instead
of 14). Otherwise 2MASS images have been exploited
(objects coded as 2M ♯). In columns 4 to 6 the loca-
tion of the most probable candidate counterpart to the
mm emission or to the FIR associated object is given,
while the 7th column signals the morphology of the H2
emission as detected in our ground-based observations.
4 The circumstance of having an associated FIR source
makes some of the under-resolved cores suitable targets in the
next future for high spatial resolution southern facilities in the
mm-range (e.g. ALMA).
5 The integrated 12CO and 13CO maps show a noticeable
enhancement of the integrated emission towards umms1, al-
though this enhancement is not fully mapped.
- Table 3 - This table lists all the IRAS sources, falling
within the dust map, but not associated to any core,
that present at least two valid detections (not upper
limits) between 12 and 60µm and a flux increasing
with the wavelength, namely F12µm < F25µm < F60µm,
or upper limits at 12 and 25µm compatible with this
condition. Studying the VMR-D young population,
these sources have some relevance. Indeed these red
and cold sources are not randomly distributed, as the
not-red sources do, but tend to be located along the
gas filaments. As in Tab. 3, we also report the 1.2mm
flux derived at the IRAS position.
Table 1. Dust cores with associated FIR and/or MIR point sources.
mm IRAS associated sources a MSX associated sourcesa Timmi2 observationsa
core id F12 F25 F60 F100 F1.2mm CC
d id F8.3 F12.1 F14.7 F21.3 d id RA Dec F10.4 d
(Jy) (”) (Jy) (”) (J2000) (J2000) (Jy) (”)
MMS1 08438-4340 13.4 56.0 638.3 1576 0.203 ECDB 49 G263.5994-00.5236 1.6 2.2 2.0 4.1 29 DGL 1 8:45:33 -43:50:04 0.05 17
(IRS16) G263.6200-00.5308 1.8 5.1 6.9 15.6 51 DGL 2 8:45:33 -43:49:48 1.8 33
G263.5925-00.5364 0.5 <0.7 <0.5 <1.6 56 DGL 4 8:45:36 -43:51:02 diffuse ∼49
MMS2 G263.6338-00.5497 0.4 <6.9 <5.4 1.6 25 DGL 3 8:45:34 -43:52:26 0.25 26
MMS3 08438-4340 13.4 56.0 638.3 1576 0.203 ECDB 55 G263.6385-00.5217 0.9 1.3 0.8 1.4 20 DGL 5 8:45:38 -43:51:14 0.08 26
(IRS16) G263.6366-00.5148 0.3 <0.9 <0.7 <1.9 39 DGL 4 8:45:36 -43:51:02 diffuse ∼55
G263.6329-00.5127 0.4 0.7 <0.9 <2.7 46
G263.6200-00.5308 1.8 5.1 6.9 15.6 54
MMS4c 08448-4343 8.7 88.1 326.6 1005 0.984 AABB 7 G263.7759-00.4281 7.5 10.1 13.8 65.5 5 MGL99 57d 8:46:35 -43:54:31 8.79 7
(IRS17) G263.7733-00.4151 1.2 1.3 0.5 2.6 53 MGL99 25d 8:46:34 -43:54:50 0.21 15
G263.7867-00.4437 0.3 0.8 <0.4 <1.2 63 MGL99 40d 8:46:33 -43:54:39 0.14 17
MMS12 08470-4321 44.9 130.1 342.6 406.9 0.331 AAAA 11 G263.7434+00.1161 30.8 52.6 70.3 93.5 3 DGL 7 8:48:49 -43:32:29 18.3 5
(IRS19)
MMS18 08472-4326A 0.9 0.9 10.6 <406.9 0.044 BABF 28 G263.8432+00.0945 0.3 <0.7 <0.5 <1.3 16 DGL 8 8:49:03 -43:37:55 0.07 19
MMS20 08474-4323 1.5 1.1 <106.4 125.9 <0.005 BCAD 39 G263.8221+00.1494 0.1 <0.9 <0.6 <1.9 37 DGL 9 8:49:12 -43:35:52 0.08 28
MMS21 08474-4325 <0.3 1.0 <16.4 57.5 0.207 DAHD 7 DGL 9 8:49:12 -43:35:52 0.08 39
MMS22 08476-4306 5.7 44.0 216.3 503.7 0.337 AAAB 10 G263.6177+00.3652 3.9 6.0 7.6 27.7 12 DGL 11 8:49:26 -43:17:12 2.01 12
(IRS20) DGL 10 8:49:26 -43:17:21 0.02 19
MMS24 08476-4306 5.7 44.0 216.3 503.7 0.337 AAAB 48 G263.6280+00.3847 0.3 <0.6 <0.5 <1.3 28 <0.03
(IRS20)
MMS25 08477-4359 9.0 26.3 317.0 580.8 0.174 BAAA 20 G264.3225-00.1857 4.7 5.0 2.3 8.0 19 DGL 12 8:49:33 -44:10:60 0.21 30
(IRS21)
MMS26 08477-4359 9.0 26.3 317.0 580.8 0.174 BAAA 16 G264.3225-00.1857 4.7 5.0 2.3 8.0 16 DGL 12 8:49:33 -44:10:60 0.21 6
(IRS21)
MMS27 DGL 13 8:49:36 -44:11:46 0.03 16
MMS28 08483-4305 1.5 2.5 <39.0 189.2 0.049 EEFD 14 G263.6909+00.4713 0.1 0.6 <0.7 <2.0 11 not obs.
MMS29 08483-4305 1.5 2.5 <39.0 189.2 0.049 EEFD 45 not obs.
umms1 08446-4331 <1.1 0.5 7.4 42.8 0.160 GBBB 2 not obs.
umms8 08458-4332 1.1 2.7 17.8 52.7 0.017 CABA 24 <0.03
umms9 08458-4332 1.1 2.7 17.8 52.7 0.017 CABA 29 <0.03
umms11 G263.7651-00.1572 0.2 <0.5 0.5 <1.2 11 DGL 6 8:47:43 -43:43:48 0.07 10
umms16 08464-4335 <0.3 <0.3 6.6 <47.2 0.160 -JB- 19 <0.03
umms23 G263.5672+00.4036 0.1 <0.9 <0.7 <1.9 17 not obs.
umms24 G263.5622+00.4185 0.2 <0.7 <0.5 <1.5 13 not obs.
umms25 G263.5622+00.4185 0.2 <0.7 <0.5 <1.5 19 not obs.
Notes to the table: the mm sources labeled as umms♯ are not resolved by the SIMBA HPBW (see text and Massi et al. 2007).
aBold faced sources are more compelling associations (within the FWHM-ellipse of the core, see text).
bPoint source correlation coefficient encoded as alphabetic characters (A=100%, B=99%, ..., N=87%) according to the IRAS Catalogs and Atlases Explanatory Supplement (IRAS-PSC 1988).
cThis core has been divided into two components by Giannini et al. (2005).
dNames following the numbering convention used in Massi et al. (1999). A description of the Timmi2 observations of these objects is given in Giannini et al. (2005).
8 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
Table 2. NIR sources and H2 emission associated with dust cores.
mm core FWHM ♯ of NIRa Counterparts candidates H2 emission
name ∆x-∆y red / very red sourcesb name RA Dec morphologyc
(”) within the FWHM-ellipse (J2000) (J2000)
MMS1d 59-64 5 / 8 e MGL99 179 08:45:32.86 -43:50:03.80 diffuse, knots
MMS2d 59-55 1 / 3 e MGL99 25 08:45:35.93 -43:51:45.60 diffuse, jet-like
MMS3d 61-58 0 / 1 e MGL99 36 08:45:39.21 -43:51:34.70 diffuse
MMS4d 82-71 19 / 43 f MGL99 57 08:46:34.77 -43:54:30.63 diffuse, jet-like, knots
MMS5 40-31 0 / 0 diffuse
MMS6 27-23 0 / 0 diffuse
MMS7 29-37 1 / 4 -
MMS8 24-26 0 / 1 2M 9671 08:48:39.13 -43:31:31.36 -
MMS9 32-36 0 / 0 -
MMS10 25-28 0 / 0 -
MMS11 36-24 0 / 1 2M 14732 08:48:46.54 -43:37:44.02 -
MMS12d 57-37 8 / 20 f MGL99 49 08:48:48.51 -43:32:29.08 diffuse, knots
MMS13 41-20 2 / 0 f MGL99 2 08:48:50.04 -43:33:19.47 -
MMS14 29-38 0 / 0 -
MMS15 33-20 0 / 0 -
MMS16 23-36 0 / 0 diffuse, jet-like
MMS17 67-37 0 / 2 jet-like
MMS18d 36-36 1 / 0 diffuse
MMS19 26-60 3 / 2 2M 36076 08:49:08.49 -43:35:37.79 -
MMS20d 38-32 0 / 0 knots
MMS21d 54-57 0 / 3 2M 29953 08:49:13.39 -43:36:29.20 knots
MMS22d 35-37 9 / 13 f MGL99 98 08:49:26.23 -43:17:11.11 diffuse, jet-like, knots
MMS23 39-22 0 / 0 diffuse
MMS24d 35-25 0 / 3 f MGL99 90 08:49:32.27 -43:17:14.43 -
MMS25d 52-86 3 / 5 diffuse
MMS26d 60-67 1 / 8 diffuse
MMS27d 67-48 1 / 2 knots
MMS28d 30-31 0 / 0 -
MMS29d 40-36 1 / 1 2M 36339 08:50:11.04 -43:17:10.74 knots
umms1d <24-24 0 / 0 not observed
umms2 <24-24 0 / 0 -
umms3 <24-24 0 / 0 -
umms4 <24-24 0 / 1 -
umms5 <24-24 1 / 0 -
umms6 <24-24 1 / 0 -
umms7 <24-24 0 / 0 -
umms8d <24-24 1 / 1 2M 16128 08:47:37.87 -43:43:42.41 -
umms9d <24-24 0 / 0 -
umms10 <24-24 0 / 0 -
umms11d <24-24 0 / 2 2M 9173 08:47:42.93 -43:43:48.05 -
umms12 <24-24 0 / 0 -
umms13 <24-24 0 / 0 -
umms14 <24-24 0 / 0 -
umms15 <24-24 0 / 0 -
umms16d <24-24 0 / 0 jet-like
umms17 <24-24 0 / 0 jet-like
umms18 <24-24 0 / 0 jet-like
umms19 <24-24 1 / 0 2M 10742 08:48:33.95 -43:30:47.20 knot
umms20 <24-24 0 / 0 knot
umms21 <24-24 0 / 3 2M 16489 08:48:37.03 -43:13:53.63 -
umms22 <24-24 0 / 0 -
umms23d <24-24 0 / 1 2M 11799 08:49:24.56 -43:13:15.49 -
umms24d <24-24 0 / 0 -
umms25d <24-24 0 / 0 -
umms26 <24-24 0 / 0 -
aWhere not specified, the reported numbers refer to 2MASS data.
bThe terms red and very red refer to different regions of the colour-colour diagram (see text and e.g. Fig. 2-a).
cBold-faced if inside the FWHM-ellipse.
dCores presenting a MIR or FIR association (see Tab. 1).
eCore only partially covered by IRAC2 observations.
fCore fully covered by IRAC2 observations.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 9
5. Discussion
5.1. IR counterparts of dust cores
The starting information is the sample of 29 well re-
solved and 26 unresolved dust cores (Massi et al. 2007).
As illustrated in the AppendixA, some of them are
not isolated, but belong to more complex structures of
dust emission that present different cores (e.g. the one
composed by MMS7, umms13-14-15, Fig.A.6); other are
elongated structures formed by aligned knots (e.g. both
MMS5, MMS6, umms6 of Fig.A.5 and umms23-24-25 of
Fig.A.38). These multiple core structures often present as-
sociated FIR counterpart(s) that tend(s) to be located in
a position intermediate between the individual cores. This
is the reason why in Tab. 1 the same IRAS/MSX source
is sometimes assigned to two different cores. Conversely,
the NIR counterparts distribution is more clearly defined
because of the increased spatial resolution at such wave-
lengths. In Appendix A all the observational details per-
taining to each individual dust core are presented; however
we can draw here some general remarks. Firstly, all the in-
formation given in Tabs. 1 and 2 are statistically summa-
rized in Tab. 4, where, among the 29 resolved cores (MMS)
only 8 are clearly associable to a MIR/FIR source (with
or without a near-IR counterpart); 7 have some MIR/FIR
source in their neighbourhood, but additional evidences
(i.e. the presence of H2 jets) point back to an embedded
object not (yet) detected; 7 additional cores seem to be
associated with very red NIR objects; the 7 remaining
cores do not present any sign of star formation activity
at the current instrumental sensitivity. If the same ap-
proach is applied to the sample of the 26 unresolved cores
(umms), we obtain that 4 are associable to a MIR/FIR
source, 3 to a NIR counterpart, 3 to jet-like structures,
and 16 appear as inactive sites. Substantially, both MMS
and umms present a similar statistics of associated cat-
egories, although the latter sample is more widely dom-
inated by objects that could be artifacts, caused by the
searching algorithm, or sites harbouring weak IR counter-
parts. The total number of resolved cores associable to an
IR object (irrespective of being NIR or FIR sources) is 15
(column 6 of Tab. 4) with respect to the 14 unassociated
cores (column 7): such percentages are in full agreement
with those found in other galactic surveys of star forming
regions (e.g. Yonekura et al. 2005, Mookerjea et al. 2004,
Beltrán et al. 2006).
Such categorization, however, does not necessarily reflect
a property intrinsic to the cores themselves, but is likely
the product of the limiting instrumental sensitivities of the
considered facilities. In fact, recent results of SPITZER
MIR surveys have substantially modified the percentage
of active vs inactive cores in favour of the first ones (e.g.
Young et al. 2004). Such a caveat should be taken into
account when drawing general conclusions from our anal-
ysis.
5.2. Star formation modalities and evolutionary stages
Different modalities of star formation are simultaneously
active in VMR-D. Such a co-existence is confirmed by
the presence of 8 clusters (see last column of Tab. 4) and
by the remaining cases of isolated star formation. This
twofold modality, already recognized in Orion (e.g. Chen
& Tokunaga 1994) and now in VMR-D as well, seems to be
a feature of all the regions where intermediate and high-
mass stars form. Indeed, it is likely that the lacking detec-
tion of the isolated mode in far and massive star forming
regions is only due to limitations on sensitivity and spatial
resolution.
To investigate whether or not the different cores of VMR-
D harbour protostellar objects in different evolutionary
stages we have constructed the distribution of the spec-
tral slope of the sources associated to the cores (see Fig. 3).
For each source the slope α is calculated through the re-
lationship α = ∆ log(λiFλi)/∆ log(λi), between the wave-
lengths λ1 and λ2, corresponding to about 2 and 10µm,
respectively. A certain degree of inhomogeneity is intro-
duced by the fact that the flux attributed to the 10µm
band corresponds to that detected by different instru-
ments (MSX, Timmi2, IRAS) operating at different ef-
fective wavelengths (8.28, 10.4 and 12µm, respectively).
These differences affect only the details of the slope dis-
tribution, but do not alter its significance, as proved by the
five sources having a multiple detection. Fig. 3 illustrates
how the sample of the sources associated to the dust cores
presents a distribution highly peaked at values 0 < α < 3,
typical of Class I sources. It is worthwhile noting that the
NIR contribution to the slope generally relies on 2MASS
data, that provide a K band limiting magnitude of about
14mag; deeper NIR surveys (see e.g. Giannini et al. 2005),
could make it possible to find weaker NIR counterparts,
increasing the number of sources with high α values. As a
result, the presented bar graph (Fig.3) could be shifted to-
wards larger α values. As expected, the sources associated
to the dust cores are essentially Class I objects, although
the distribution presents a significant tail toward the less
evolved objects, whose slope is greater than 3.
In Tab. 3 we also list all the IRAS sources lying inside the
region mapped in the 1.2mm continuum and showing a
flux increasing with wavelength but not directly associ-
ated to any dust core (see Sect. 4). These sources, with
only few exceptions, tend to be distributed all along both
the diffuse emission detected by MSX at 8.3µm and the
gas filaments.
To evaluate the intrinsic nature of all the IRAS sources
discussed so far (both associated or not), we present, in
Fig. 4, an IRAS two colours diagram, [12-25] vs [25-60],
with all those sources. As expected, the objects not asso-
ciated to the cores have a greater number of upper limits
(especially at 12µm), but tend to occupy the same re-
gion of the plot where the associated sources are located.
This common region pertains to sources that can be de-
scribed as a two dust components system, one at 1000K
and the other in between 50 and 100K, with variable rela-
10 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
Table 3. IRAS point sources with increasing fluxes not associated with any core.
id F12 F25 F60 F100 F1.2mm CC
08440-4253 <0.3 0.2 1.2 <30.5 <0.005 -BBD
08461-4314 0.7 0.8 5.9 <48.5 0.003 BCDB
08475-4255 <0.4 0.4 3.3 45.6 0.020 EDDB
08475-4311 <0.5 0.5 9.4 <37.8 0.020 DEC-
08481-4258 <0.4 1.1 7.6 <34.8 0.008 BDC-
08459-4338 <0.2 0.6 6.5 38.3 0.005 -DCB
08442-4328 <1.4 2.2 41.3 113.9 0.020 HDCA
08448-4341 1.3 6.6 <327 <1005 <0.005 DAC-
08468-4330 <0.3 0.4 3.4 <31.6 0.010 FDD-
08491-4310 0.5 0.6 7.6 38.6 <0.005 EBCC
08496-4320 0.6 0.7 7.6 <37.1 <0.005 BCBH
08463-4343 <0.3 0.5 7.4 <43.5 <0.005 NBDG
08478-4403 0.5 0.5 <5.4 <580.8 <0.005 CCJG
aSee note b in Tab. 1.
Table 4. Statistics about the dust cores population.
Cores Associated with
MIR/FIR only very red H2 jet no source NIR or no source or embedded
NIR object FIR object H2 only cluster
29 resolved 8 7 7 7 15 14 6
26 unresolved 4 3 3 16 7 19 2
tive contributions. The IRAS selected sources have colours
definitely redder and colder than those pertaining to pre-
main sequence stars (T-Tauri and Herbig Ae/Be; see, e.g.,
Berrilli et al. 1992), apart from few cases. While the ab-
sence of IRAS sources with the colours of T-Tauri stars
in our sample is probably due to an observational bias (in
fact the IRAS detectability limit is > 0.5L⊙ in Taurus,
corresponding to > 10L⊙ in VMR-D), the doubtful pres-
ence of Herbig Ae/Be appears to be an intrinsic property
of VMR-D. Indeed, Herbig Ae/Be located inside dust cores
having masses comparable to those belonging to the VMR-
D ones have been already found at distances of 1Kpc or
less (e.g. Henning et al. 1998). This difference likely re-
flects different star formation histories, being in VMR-D a
shorter time (≈ 106 yr) elapsed from the earliest collapse
events (Massi et al. 2000) with respect to other studied
massive clouds.
We have calculated the bolometric luminosity, Lbol, for all
the IRAS sources from 12µm to 1.2mm. The bar graph in
Fig. 5 shows our result: the sources associated to the dust
cores (both resolved and not) are, on average, objects of
intermediate luminosity (Lbol ∼ 10
3L⊙), while the unas-
sociated FIR sources, even showing similar SEDs, tend to
be lower luminosity objects (Lbol ∼ 10
2L⊙). Therefore, we
can firmly conclude that massive star formation (Lbol >
104L⊙) does not occur in VMR-D, and that our sample of
Class I sources is not contaminated by ultracompact HII
regions, which would be indistinguishable based on their
FIR colours alone (Wood & Churchwell 1989).
An attempt to search for Class 0 objects within our sam-
ple of IRAS sources has also been done by applying the
criterion proposed by André et al. (1993) for low-mass
protostars: Lbol/L1.3mm . 2 × 10
4. None of the selected
IRAS sources (Tabs. 1 and 3) strictly satisfies this crite-
rion6. It should be said, however, that overestimates of the
IRAS fluxes result in overestimates of the Lbol/L1.3mm ra-
tio. Thus, leaving any quantitative approach, we point out
that three sources of our sample (08446-4331, 08474-4325
and 08464-4335) show a ratio Lbol/L1.3mm one order of
magnitude less than the others and thus they are likely the
youngest objects in the field. This hypothesis is strongly
supported by (i) the tight association of these sources with
the mm cores umms1, MMS21 and umms16, respectively;
(ii) by the lack of a measured flux at 12µm7, and, but only
for the last case, (iii) by the presence of H2 jet-like emis-
sion crossing the dust peak (no H2 images are available
for the core umms1).
5.3. H2 survey
A powerful approach to indirectly probe ongoing star for-
mation activity is to investigate over the presence and
characteristics of collimated flows, which commonly ex-
6 Hatchell et al. (2007) reduces such limiting ratio to
Lbol/L1.3mm . 3×10
3 and underlines how this indicator should
vary with envelope mass.
7 For the core MMS21 with the associated source 08474-4325
we report in Tab. 2 a candidate NIR counterpart, but such as-
sociation is quite questionable (see Appendix A and Fig. A.18).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 11
tend far from the most embedded regions where the
young protostars are located. For this reason, we have
complemented our search for infrared counterparts of
mm cores with a survey in the narrow-band filter cen-
tered at the H2 2.12µm line, which represents the main
NIR cooling channel of shock-excited gas at thousands of
Kelvin (e.g. Gredel 1994). Our observations have been also
aimed to define the occurrence of the jet phenomenon in
intermediate-mass star forming regions and to understand
whether jets in clusters are associated with the massive
cores or with some closeby low-mass component. A de-
tailed description of the H2 emission detected in the var-
ious fields is given in Appendix A, while here we briefly
comment on some general aspects. Out of 54 investigated
fields, we find a positive detection (in the form of jet-
like morphologies, knots and diffuse emission) in 23 fields,
the large majority (18) being related to resolved cores. We
note that the occurrence of jets in proximity of umms cores
testifies in favour of the genuine nature of some of these
latter. The H2 emission seems to be directly connected
with the mm cores in about one third of the investigated
fields (namely MMS2-19-22-29, umms16-19 and possibly
MMS16), but we are able to identify a possible (NIR) driv-
ing source in only two cases (MMS22 and MMS29, see
Tab. 2, last column). Given the poor sensitivity of MSX
and IRAS observations, Class 0 protostars might already
be embedded in the other dust cores, which represent
interesting cases to be investigated with SPITZER. All
the fields of young clusters (those associated with cores
MMS2-4-12-22 and 25) show H2 emission and close to
three peaks (MMS2-4-22), all associated with an IRAS
source, we have found a sub − parsec scale jet (with ex-
tension 0.30, 0.30 and 0.68 pc, respectively). Only in one
case the jet seems to be emitted by the most luminous
object in the field (i.e. the one that contributes the most
to the FIR flux in the IRAS bands), in all the other cases
the driving source is a less luminous (and less massive)
object in the cluster. A similar result was pointed out by
Lorenzetti et al. (2002), who, having surveyed a sample of
12 IRAS protostellar candidates in VMR, have detected
H2 emission in 5 fields, clearly coming from low-mass ob-
jects clustered around the IRAS source, and not from the
IRAS source itself. This feature is likely related to a dif-
ferent duration of the jet phase in low and high luminosity
(mass) sources: this topic will be discussed in depth in a
forthcoming paper (Giannini et al. 2007, in preparation).
6. Conclusions
A southern sky area of 1×1deg2 belonging to the
star forming region VMR-D, previously surveyed at
mmwavelengths to identify the dust cores, has been stud-
ied by means of both IR catalogues (IRAS/MSX/2MASS)
and a set of new dedicated observations, to identify the
young protostellar counterparts associated to dust cores.
The motivation for the new IR observations is twofold: (i)
to perform a complete survey of all the recognized dust
cores in the H2 narrow-band filter (2.12µm) to search ev-
idence of protostellar jets; and (ii) to obtain a broad band
N (10.4µm) survey of those cores associated to embedded
clusters, aiming to pick up the source(s) that mainly con-
tribute(s) in the far-IR regime.
The main conclusions of this work are summarized here:
- In the majority of cases, MIR and/or FIR sources as-
sociated with dust cores do not coincide with the mm
peaks, although they are located in their vicinity. In
those cases of close-by cores, often the IR source is
located in between them.
- The resolved mm cores (i.e. those larger than the in-
strumental beam) are more frequently associated to
a NIR or FIR counterpart than the unresolved ones
(smaller than the instrumental beam). The existence
of signs of star formation activity around these latter
in the form of H2 jets, however, attests the genuine
nature of lots of them.
- The statistics of active vs inactive cores is in good
agreement with that found in other star forming re-
gions, but should be critically revised in the light of
more sensitive observations that will become available
in near future (e.g. SPITZER MIPS and IRAC maps).
- The SEDs of the associated sources present a slope
α = d log(λFλ)/d log(λ) between 2 and 10µm whose
distribution is strongly peaked at values typical of
Class I sources (0 < α < 3), in some cases even larger.
- An attempt has been done to search for Class 0 sources.
Ten IRAS sources (with upper limits at 12µm) do not
present any NIR reliable counterpart, but no one of
them satisfies the criterion Lbol/L1.3mm . 2×10
4 pro-
posed by André et al. (1993). However, considered the
probable overestimates of the IRAS fluxes (and bolo-
metric luminosities), we indicate the three objects with
the lowest Lbol/L1.3mm ratios as the youngest IRAS
sources of the region.
- The sources associated to the dust cores, both resolved
and unresolved, have all the same FIR colours, typical
of a black-body stratification between 50 and 1000K,
with a stronger contribution of the former component.
In other words, sources with FIR colours typical of
pre-main sequence T-Tauri and Herbig Ae/Be stars
seem to be absent, indicating VMR-D as a young (∼
106 years) region.
- Sources associated with unresolved cores are system-
atically less luminous (average Lbol ≃ 1.5 × 10
than those related to the resolved ones (average Lbol ≃
1.5 × 103L⊙), providing evidence that two modalities
of star formation, namely low- and intermediate-mass,
are simultaneously present in VMR-D.
- This occurrence is also confirmed by the existence of
a further (low luminosity) population of young objects
that have the same colours as the sources associated
to the dust cores (resolved or unresolved), but are lo-
cated, on the contrary, in the diffuse warm dust and
along the gas filaments.
- Observing the dust cores in the H2 1-0S(1) line ev-
idences a high detection rate (30%) of jets driven
12 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
by sources located inside the cores. They appear not
driven by the most luminous objects in the field,
but rather by less luminous (and less massive) ob-
jects in surrounding star clusters, testifying the co-
existence of both low and intermediate-mass star for-
mation, being the former more likely associated to
molecular jet activity. Moreover the jet compactness
(at sub − arcsecond scales) is a further indication for
the prevalence of very young objects.
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M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D 13
< -1.5 -1.5 < < 0 0 < < 1.5 1.5 < < 3 > 3
Spectral Index
Class III Class II Class I
Fig. 3. Spectral index (α2−10) distribution of core counterparts. In cases of multiple estimates of the 10µm flux
(Timmi2, MSX, IRAS) the value obtained with better spatial resolution has been used to determine α.
130 K
150 K
200 K
100 K
T-Tauri
Herbig Ae/Be
-0.5 0.0 0.5 1.0 1.5 2.0 2.5
[25-60]
↑ ↑ ↑
Associated with:
MMS (1FWHM-ellipse)
MMS (2FWHM-ellipse)
umms (1FWHM-ellipse)
Not associated
Fig. 4. Two colours diagram for all the IRAS sources listed in Tabs. 1 and 3. The mean error bars, the extinction
vector corresponding to 5mag of visual extinction and the locus of blackbodies (leftmost line) are indicated (see text
for more details).
14 M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D
<1.5 1.5-2 2-2.5 2.5-3 3-3.5 3.5-4 >4
Log(Lbol / L )
s Associated
Not associated
Fig. 5. Luminosity distribution of both associated and not associated IRAS sources (Tabs. 1 and 3).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 1
Online Material
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 2
Appendix A: Counterparts of the dust cores
In the following we present a brief discussion of the NIR
to FIR associations found for each dust core. Other signs
of star formation activity (e.g. H2 knots and jets or young
embedded clusters) will be also evidenced. For each core
(or group of cores) we will show the SofI H2 (or 2MASS
H band) gray scale image supplied with: dust emission
contours, position of the most interesting sources, cov-
erage of IRAC2 and Timmi2 fields of view and arrows
indicating the occurrence of H2 knots (see Sect. 3.4 for
more details). Whenever needed for the analysis, the cor-
responding colour-colour diagrams and SED plots will be
shown as well.
– MMS2 (Figs. A.1, A.2): one MSX associated ob-
ject inside the FWHM-ellipse, G263.6338-00.5497,
with a N band counterpart, DGL 3, having a flux
(F10.4µm = 0.25 Jy) smaller than that measured by
MSX (F8.3µm = 0.4 Jy).
Inside the FWHM-ellipse, many NIR stars (recogniz-
able in the SofI H2 image) have not been detected
by 2MASS and are only upper limits for IRAC2 in
both J and H bands. The object showing the highest
colour excess (MGL99 25) and steepest spectral index
(Fig. A.2) is not visible in the N band (at 30mJy
sensitivity level). We have tentatively indicated
that one in Tab. 2 as candidate NIR counterpart.
However, an intense H2 line emission is present
all over the core, both diffuse and in knots and,
remarkably, a well collimated H2 jet crosses the
very center of the core. No reliable exciting source
has been detected along the jet. Likely, it is heavily
embedded near the peak position and contributes
significantly (or mainly) to the observed dust emission.
– MMS3 (Figs. A.3, A.4): an IRAS source (IRS16) is
marginally associated to the peak (see Sect. 3.4). Three
MSX detections (one of them inside the FWHM-
ellipse) fall in a region of enhanced and diffuse 8µm
emission and don’t seem to be point-like (as suggested
by the MSX image and by the failed detection in N).
A Timmi2 source (DGL 5, identified with MGL99 65)
is instead observed in the direction of the IRAS source
and NIR cluster.
A steep decrease in the number of NIR detections
towards the peak suggests a high extinction level.
Moreover, the majority of the IRAC2 sources within
the FWHM-ellipse presents very red colours. MGL99
36, the one closest to the peak position, could be the
main source associated to the millimeter core.
– MMS4: a detailed analysis of this core has
been already presented in a dedicated paper
(Giannini et al. 2005), which the reader is referred to.
– MMS5-6, umms6 (Fig. A.5): a dust elongated struc-
ture of connected cores pointing towards south-west in
the direction of MMS4, the brightest core of the whole
dust map; a dust filament which is likely undergoing
fragmentation. Neither MIR-FIR associations, nor
interesting NIR sources are present (although no
IRAC2 data are available); signs of star formation
activity are quite hidden and can be only recognized
as a faint H2 emission around MMS5 and MMS6.
– MMS7, umms13-14-15 (Fig. A.6): resolved core
(MMS7) surrounded by three unresolved cores
(umms13-14-15). The J , H and Ks photometry of the
cluster of about 20 members around the central core
will be analyzed in a forthcoming paper. Neither FIR
emission nor H2 features are present (no 10µm image
has been collected). We just remark here the colour
excess of 4 very red stars within the FWHM-ellipse of
MMS7.
– MMS8-9 (Fig. A.7): these cores are part of a long
tail of connected cores (extending for about 1 pc),
going from the bright core MMS12 to umms19, whose
dynamical behaviour is not clear (Massi et al. 2007).
No FIR point sources or clues of H2 emission have
been observed. Timmi2 observations, although not
covering the whole dust emission, gave negative results
as well. Only one very red NIR object, 2M 9671 (no
IRAC2 data available), lies within the FWHM-ellipse
of MMS8.
– MMS10-11 (Fig. A.8): without any MIR-FIR coun-
terpart, these are the only two resolved cores included
in the 13CO map that lack of an associated CO clump
(Elia et al. 2007). The colour-colour diagram of the
2MASS sources (no IRAC2 data available) within
the FWHM-ellipse gives only one reddened candidate
(2M-14732) for MMS11.
– MMS12 (Figs.A.9, A.10): one of the brightest
cores, MMS12 (∼ 18M⊙) coincides with a young
embedded cluster having in its center the IRAS source
08470-4321 (IRS19), the MSX G263.7434+00.1161
and the Timmi2 DGL 7 object. The new observed
flux at 10µm (F10.4µm = 18.3 Jy) is less than a half of
the IRAS/MSX measurements at 8-12µm. We ascribe
this discrepancy to the presence of a strong diffuse
contribution to the flux at these wavelengths.
The correspondence of these sources with the NIR
object MGL99 49 has been already discussed in Massi
et al. (1999) and is confirmed here.
Complex and intense H2 emission is also present,
especially at the peak position, and at the eastern
part of the core; it cannot be clearly distinguished as
a single jet-like structure.
– MMS13 (Fig.A.11): no MIR-FIR association and no
significant H2 emission for this core at the south of
MMS12. The two possible NIR counterparts have red
colours (MGL99 2, MGL99 7).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 3
– MMS14-15-16 (Fig. A.12): neither MIR-FIR associ-
ations nor NIR red sources detected by 2MASS (no
IRAC2 data). We note a faint H2 emission aligned
with both the peak MMS16 and the H2 knot visible
at the east of MMS12 (see also Fig.A.9). We cannot
exclude the existence of an embedded exciting source
near the MMS16 peak position.
– MMS17 (Fig. A.13): a double H2 knot (probably jet-
like) in proximity of the peak suggests the existence
of star forming activity, but no MIR-FIR objects have
been detected and the 2MASS data do not point out
any interesting source within the FWHM-ellipse.
– MMS18 (Figs.A.14, A.15): one IRAS source (08472-
4326A) is associated within 2FWHM-ellipse, while one
MSX source (G263.8432+00.0945) and one Timmi2
object (DGL 8) are inside the FWHM-ellipse. The
positional uncertainties of these three objects seem
to exclude their coincidence, although the IRAS and
MSX fluxes (due to their beam sizes) are surely con-
taminated by the Timmi2 source (whose counterpart,
2M 29896, peaks in the H band) and probably by
diffuse emission, visible in the H2 filter as well.
– MMS19 (Fig. A.16): core connected to MMS20 and
MMS21. Neither MIR-FIR sources associated nor H2
emission detected. We signal two very red 2MASS ob-
jects (2M-36076, 2M 36192) within the FWHM-ellipse.
– MMS20 (Fig. A.17): one IRAS (08474-4323, corre-
sponding to MSX G263.8221+00.1494) source turns
out to be very marginally associated (positional uncer-
tainty tangent to the 2FWHM-ellipse), but the dust
emission around its position seems to be negligible.
One Timmi2 source (DGL 9) has been detected within
2FWHM-ellipse, in the middle between this core and
MMS21 not signalled by IRAS/MSX (SofI images
points out at least three objects, partially resolved by
2MASS in two very red sources, 2M 27831 and 2M
37241).
– MMS21 (Figs. A.18, A.19): one IRAS source, 08474-
4325, whose fluxes indicate this one as one of the
youngest objects of VMR-D, coincides with the peak
position. The Timmi2 observation has given no results
(for the source DGL 9 see MMS20 description) and
no MSX sources are reported in the catalogs. Three
2MASS sources fall close to the IRAS uncertainty
ellipse center, two of which (2M-29953, 2M 37193)
have very red colours. The SofI H2 image, however,
points out the presence of a complex morphology,
which cannot be resolved in individual sources with
the SofI spatial resolution.
– MMS22 (Figs. A.20, A.21): characterized by a power-
ful bipolar jet (0.7 pc long, discussed in a forthcoming
paper) arising from the IRAS source 08476-4306
(IRS20), located 10′′ at the west of the peak. In cor-
respondence with the IRAS source there are a young
cluster, a MSX point source (G263.6177+00.3652)
and two 10µm objects: DGL 11 (main counterpart
of the IRAS/MSX object) and DGL 10 (2σ de-
tection, outside the FWHM-ellipse). The DGL 11
flux, F10.4µm = 2.01 Jy, is significantly smaller than
those measured by MSX and IRAS: F8.3µm = 3.9 Jy,
F12µm = 5.7 Jy, F12.1µm = 6.0 Jy, but the Timmi2 ob-
servation points out a diffuse emission which can have
contributed to the MIR fluxes measured by IRAS and
MSX. The presence of nebular NIR and H2 emission
completes the picture of this crowded region. The NIR
cluster characteristics have been discussed in detail
by Massi et al. (1999) and the conclusions reported
in that paper about the candidate NIR counterpart
(MGL99 98) of IRS20 are confirmed by our Timmi2
observation. MGL99 98 is also the best candidate as
exciting source of the jet, although the complexity of
the jet morphology and the difficulty to discriminate
between nebular and point-like unresolved emission
makes this identification questionable. We also remark
one dark strip clearly visible in the H2 image, likely
due to an obscuring dust lane crossing the cluster
center.
– MMS23 (Fig. A.22): isolated, small core with no
IR detected sources near the peak (not observed at
10µm). H2 multiple knots are visible to the north
of the peak together with a faint emission near
the center. We cannot exclude the presence of an
embedded, young, low-mass stellar object producing
that emission, but more sensitive observations are
required to confirm this possibility.
– MMS24 (Fig.A.23): this core is connected with the
brighter MMS22 and is characterized by diffuse K
emission close to a MSX source (within 2FWHM-
ellipse) not detected by Timmi2. The NIR source
MGL99 90, at the border of the FWHM-ellipse, shows
the highest colour excess.
– MMS25-26 (Figs. A.24, A.25): this complex re-
gion is constituted by two not well resolved cores
(also linked to the brighter MMS27) and, between
them, in correspondence with a young NIR cluster
(Massi et al. 2006), there are the IRAS source 08477-
3459 (IRS21), the MSX source G264.3225-00.1857
and the Timmi2 object DGL 12 (corresponding to
the NIR MGL99 27). Moreover, the 10µm emission
observed by Timmi2 shows a diffuse emission (in the
surroundings of the source MGL99 35) and, probably,
another point source corresponding to MGL99 32,
although an artifact in the Timmi2 image prevented
us to give a reliable estimate of its flux. Remarkable is
also a shell-like K emission (clearly visible also in the
H2 image) approximately centered near MGL99 63.
The colour-colour diagram (Fig. A.25) points out the
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 4
existence of many red and very red sources within the
FWHM-ellipse of both the cores, lots of which having
upper limits in the J and H bands. The SEDs of the
MIR-FIR objects and of the NIR stars with larger
colour excess show significant discrepancies among the
fluxes of the MIR-FIR detections. No clear evidence
has been found for NIR stars (if any) that can be
most likely associated to the mm core8.
– MMS27 (Fig. A.26): although this is one of the bright-
est cores of the whole dust map, no IRAS-MSX point
sources have been detected. Only one faint object
(DGL 13), counterpart of the NIR very red 2M 53071
(we lack of IRAC2 data for this source), can be seen at
10 µm, inside the FWHM-ellipse, together with three
more very red sources.
Interesting is the case of 2M 47136, the closest one to
the peak: no point-like source can be extracted from
the K image which shows instead a very diffuse emis-
sion well observable also in the H2 image of Fig.A.26.
It is crossed by a dark horizontal strip (quite likely
due to obscuring dust). A knot of H2 emission is also
visible above this strip and one more on the other
side of the core, in the south-west direction, making
this core of a peculiar interest for future investigations.
– MMS28-29 (Fig. A.27): inside the FWHM of
MMS28 there are the IRAS 08483-4305 and MSX
G263.6909+00.4713 sources and, remarkably, H2
aligned knots are visible between the two peaks. We
lack of both Timmi2 and IRAC2 observations, but the
2MASS data reveal one very red source, 2M 36339,
incompatible with the position of the FIR sources, but
aligned with the knots, which could be their exciting
source.
In the following we present the unresolved cores not
previously discussed.
– umms1 (Fig. A.28): despite the high noise level of
the dust map in this position, this unresolved core is
one of the most interesting cases: (i) it is by far the
most intense core among the unresolved ones, (ii) its
coordinates coincide with an IRAS source showing
fluxes increasing with wavelength and (iii) the 12CO
integrated emission map presents an increase towards
this peak, altough it falls immediately outside that
map (see note 5). Unfortunately we lack of both
IRAC2 and SofI images at this position and only
one 2MASS (red) object falls inside the FWHM-ellipse.
8 The lack of any Timmi2 detectable flux in correspondence
of MGL99 50, the previously hypothesized NIR counterpart
of the IRAS source (Massi et al. 1999), makes that association
questionable. Observing its SED, indeed, it is quite unlikely
that it could be missed, if point-like, at 10µm.
– umms2-3-4-5 (Fig. A.29): region of high noise level
of the dust map. These cores are probably artifacts of
the reconstruction algorithm and do not present any
feature suggesting star formation activity.
– umms7-10-12 (Fig. A.30): a small cluster within
2FWHM-ellipse of umms10 (forthcoming dedicated
paper) is the only noticeably feature of this field.
– umms8-9-11 (Figs. A.31, A.32): dust emission as-
sociated with an IRAS source (08458-4332, having
flux increasing with λ, associated to umms8-9) and
a MSX-Timmi2 object (G263.7651-00.1572-DGL 6,
associated with umms11 and the 2MASS objects
2M 9173 and 2M 11131). One very red and one red
NIR object (2M-116128 and 2M 18032, respectively)
within the FWHM-ellipse of umms8.
– umms16 (Fig. A.33): core remarkably crossed by H2
jet-like emission and with an IRAS source (08464-
4335), although the Timmi2 observation gave no
results and no red or very red NIR stars have been
observed by 2MASS as possible jet exciting source.
– umms17-18 (Fig. A.34): also this couple of cores
presents an intense H2 jet-like emission, but without
any NIR-MIR interesting source.
– umms19-20 (Fig. A.35): these cores are part of a
chain of connected cores (see description of MMS8-9).
No FIR-MIR point sources have been observed and
only a knot of H2 emission is visible in the FWHM-
ellipse of umms19, close to a red 2MASS source
(2M-10742).
– umms21 (Figs.A.36): connected to the previous
cores. No FIR-MIR point sources or clues of H2
emission have been observed. One very red NIR object
(2M-16489) within the FWHM-ellipse.
– umms22 (Figs.A.37): No FIR point source or clues
of H2 emission have been observed (no Timmi2 data
available). Absence also of NIR red objects within the
FWHM-ellipse.
– umms23-24-25 (Figs.A.38): thin, elongated dust
structure with three cores coinciding with a sim-
ilar shaped K emission. Two MSX sources,
G263.5672+00.4036 and G263.5622+00.4185, are
tightly associated to umms23 and umms24, respec-
tively. Two very red sources fall within the FWHM of
umms23, but they seem to be incompatible with the
position of the MSX sources (for which we suspect a
high contamination from diffuse emission).
– umms26 (Figs. A.39): a small cluster outside
2FWHM-ellipse (forthcoming paper) is the only
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 5
noticeably feature of this field.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 6
Fig.A.1. MMS2 field of view (center [J2000]: 08:45:34.200, -43:51:54.40). Grayscale image: H2 emission; green con-
tours: dust continuum (from 3 σ, in steps of 3σ); red ellipses: FWHM-ellipse and 2FWHM-ellipse of the core (see
Sect. 3.2 for an explanation); green and magenta ellipses: MSX and IRAS 3σ positional uncertainty; orange line:
IRAC2 field of view.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
MGL99-4
MGL99-25
MGL99-14
MGL99-9,
MGL99-15
1 2 3
-20.0
-19.5
-19.0
-18.5
-18.0
-17.5
2M-26276
MGL99-25
MGL99-4
MGL99-14
MGL99-9
MGL99-15
Fig.A.2. a) Colour-colour diagram (see text for more details) of the NIR sources within the FWHM-ellipse of MMS2.
The Spectral Energy Distributions of the very red ones are shown in panel b). To reduce confusion the wavelength
range is limited to the J , H , K bands and the main objects are in red colour. Dashed lines refer to 2MASS sources
and arrows denote upper limits.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 7
Fig.A.3. MMS3 field of view (center [J2000]: 08:45:39.5, -43:51:25.0).
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
MGL99-65
MGL99-36
1 2 3
-20.2
-20.0
-19.8
-19.6
-19.4
-19.2
-19.0
-18.8
MGL99-36
MGL99-65
Fig.A.4. MMS3: colour-colour and SED diagrams.
Fig.A.5. MMS5-6 and umms6 field of view (center [J2000]: 08:46:52.0, -43:53:01.3).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 8
0.0 0.5 1.0 1.5 2.0
[H-K]
2M-16616
2M-10095
2M-18266
2M-8124
Fig.A.6. MMS7 and umms13-14-15 field of view (center [J2000]: 08:47:58.9, -43:39:22.9) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 9
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
2M-9671
Fig.A.7. MMS8-9 field of view (center [J2000]: 08:48:41.3, -43:31:36.2) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 10
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-14732
Fig.A.8. MMS10-11 field of view (center [J2000]: 08:48:44.2, -43:37:19.1) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 11
Fig.A.9. MMS12 field of view (center [J2000]: 08:48:48.5, -43:32:20.8).
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[H-K]
MGL99-49
1 2 5 10 2 5 10
MGL99-49
DGL-7
IRS19
G263.7434+00.1161
Fig.A.10. MMS12 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 12
0.0 0.5 1.0 1.5
[H-K]
MGL99-2
MGL99-7
Fig.A.11. MMS13 field of view (center [J2000]: 08:48:49.4, -43:33:11.2) and colour-colour diagram.
Fig.A.12. MMS14-15-16 field of view (center [J2000]: 08:48:51.6, -43:31:09.9).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 13
Fig.A.13. MMS17 field of view (center [J2000]: 08:48:57.2, -43:38:23.1).
Fig.A.14. MMS18 field of view (center [J2000]: 08:49:03.2, -43:38:05.2).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 14
0.0 0.5 1.0 1.5
[H-K]
2M-29896
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
-15.5
-15.0
2M-29896
DGL-8
08472-4326A
G263.8432+00.0945
Fig.A.15. MMS18 colour-colour and SED diagrams.
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-36192
2M-36076
Fig.A.16. MMS19 field of view (center [J2000]: 08:49:08.5, -43:35:43.7) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 15
0.0 0.5 1.0 1.5 2.0
[H-K]
2M-37241
2M-27831
Fig.A.17. MMS20 field of view (center [J2000]: 08:49:11.2, -43:35:25.9) and colour-colour diagram.
Fig.A.18. MMS21 field of view (center [J2000]: 08:49:13.0, -43:36:21.8).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 16
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-37193
2M-29953
2M-34100
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-29953
2M-37193
2M-34100
08474-4325
Fig.A.19. MMS21 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 17
Fig.A.20. MMS22 field of view (center [J2000]: 08:49:26.0, -43:17:13.0).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 18
0 1 2 3 4 5
[H-K]
MGL99-98
1 2 5 10 2 5 10
MGL99-98
DGL-10
DGL-11
IRS20
G263.7434+00.1161
Fig.A.21. MMS22 colour-colour and SED diagrams.
Fig.A.22. MMS23 field of view (center [J2000]: 08:49:30.2, -44:04:10.0).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 19
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
MGL99-90
Fig.A.23. MMS24 field of view (center [J2000]: 08:49:30.1, -43:17:00.2) and colour-colour diagram.
Fig.A.24. MMS25-26 field of view (center [J2000]: 08:49:33.5, -44:10:34.5).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 20
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
[H-K]
1 2 5 10 2 5 10
DGL-12
IRS21
G263.7434+00.1161
Fig.A.25. MMS25-26 colour-colour and SED diagrams.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 21
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H-K]
] 2M-47136
2M-53071
Fig.A.26. MMS27 field of view (center [J2000]: 08:49:35.2, -44:11:52.8) and colour-colour diagram.
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 22
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-36339
Fig.A.27. MMS28-29 field of view (center [J2000]: 08:50:10.0, -43:16:41.3) and colour-colour diagram.
Fig.A.28. umms1 field of view (center [J2000]: 08:46:25.7, -43:42:28.3) (2MASS H band image).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 23
Fig.A.29. umms2-3-4-5 field of view (center [J2000]: 08:46:44.0, -43:19:48.2).
Fig.A.30. umms7-10-12 field of view (center [J2000]: 08:47:37.4, -43:26:21.7).
Fig.A.31. umms8-9-11 field of view (center [J2000]: 08:47:39.6, -43:43:36.1).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 24
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-9173
2M-11131
2M-18032
2M-16128
1 2 5 10 2 5 10
-19.0
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
2M-9173
2M-11131
2M-16128
DGL-6
08458-4332
G263.7651-00.1572
Fig.A.32. umms8-9-11 colour-colour and SED diagrams.
Fig.A.33. umms16 field of view (center [J2000]: 08:48:15.3, -43:47:06.5).
Fig.A.34. umms17-18 field of view (center [J2000]: 08:48:24.6, -43:31:36.7).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 25
Fig.A.35. umms19-20 field of view (center [J2000]: 08:48:33.9, -43:30:46.0).
Fig.A.36. umms21 field of view (center [J2000]: 08:48:36.4, -43:31:11.5).
Fig.A.37. umms22 field of view (center [J2000]: 08:48:36.3, -43:16:45.9).
M. De Luca et al.: IR Counterparts of mm Dust Cores in the VMR-D, Online Material p 26
0.0 0.5 1.0 1.5 2.0 2.5
[H-K]
2M-15995
2M-11799
Fig.A.38. umms23-24-25 field of view (center [J2000]: 08:49:25.9, -43:12:39.2) and colour-colour diagram.
Fig.A.39. umms26 field of view (center [J2000]: 08:49:58.9, -43:22:55.1).
	Introduction
	The investigated region
	Association with point-sources
	Observations
	NIR imaging
	N-band imaging
	FIR associations
	NIR associations
	The core MMS1
	Results
	Discussion
	IR counterparts of dust cores
	Star formation modalities and evolutionary stages
	H2 survey 
	Conclusions
	Counterparts of the dust cores
