63

Dynamics of a massive binary at birth・大質量星の形成はなぜ難しいか？
球対称の仮定では、Mstar>20Msunで、輻射圧>重力になって降着が止まる。
解決案1：そもそも降着率が大きければいい→観測的にも高い降着率が示唆される(10^4Msun/yearとか)Show affiliations• Zhang, Yichen; Tan, Jonathan C.; Tanaka, Kei E. I.; De Buizer, JamesM.; Liu, Mengyao; Beltrán, Maria T.; Kratter, Kaitlin;Mardones, Diego; Garay,
Guido
Abstract*解決案2：円盤を通した非軸対称降着ならもうちょい小さな
Almost all massive stars have bound stellar companions, existing in binaries orhigher-order multiples1-5. While binarity is theorized to be an essential feature
降着率でもいいof how massive stars form6, essentially all information about such properties isderived from observations of already formed stars, whose orbital properties may
have evolved since birth. Little is known about binarity during formation stages. ・高降着率だと何が起こるか？
Here we report high-angular-resolution observations of 1.3 mm continuum and円盤が分裂してバイナリーを作るだろう
H30α recombination line emission, which reveal a massive protobinary with
→高分解能で大質量原始星周りの円盤を観測しapparent separation of 180 au at the centre of the massive star-forming regionて確かめたいIRAS 07299-1651. From the line-of-sight velocity diﬀerence of 9.5 km s-1 of thetwo protostars, the binary is estimated to have a minimum total mass of 18 solar
masses, consistent with several other metrics, and maximum period of 570 yr,
・これまでの観測
assuming a circular orbit. The H30α line from the primary protostar shows
kinematics consistent with rotation along a ring of radius of 12 au. The
赤外線観測、赤外干渉計、センチ波などでバイナ
observations indicate that disk fragmentation at several hundred astronomical
リーの距離を調べてた。
units may have formed the binary, and much smaller disks are feeding the
IRAS 20126+4104: 850 au, G35.20-0.74: 800 au,
individual protostars.
NGC 7538IRS1: 430 au, IRAS 17216-3801: 170 au

見た目の軌道間隔だけではなくて、軌道の運動なども知りたい。
https://ui.adsabs.harvard.edu/abs/2019NatAs...3..517Z/abstractLETTERS

NATURE ASTRONOMYaA

・とにかく質量を知りたい
1.3 mm 電波連続波からの見積もり→周り(>500 au)がoptically thinだと思って見積もると周りのガスはだいたい 3.8­8M⊙ くらい。
*ただし、干渉計観測なので広がった成分は見えていない。これは下限値

H30α観測からの見積もり
Zero-Age主系列星(ZAMS)の星のモデルを仮定し、制動放射の強さから星の質量を見積もる。
連続波を引き去って、free-free成分が39mJy and 4mJy だとわかった。そこから→12.5M⊙ (A) and 10M⊙ (B)

LETTERS

NATURE ASa*ZAMSじゃないと思うと、8­19M⊙(A) , 7­17M⊙ (B)A

LETTERS

NATURE ASTRONOMY

or different HRLs of same source have central velocities different26 by ~5 km s−1,
while some studies show that multiple HRLs have same central velocities which
are consistent with the source velocity based on modelling13. However, there wasno mm HRL observation with a spatial resolution <100 au previously. With suchby the approximately Gaussian profiles of the observed H30α spectra), the ratio
between H30α peak intensity and free-free continuum intensity is derived to be29
TH30α

6 ⎛ Te ⎞−1−1⎛ Δv ⎞ ⎡⎛ Te ⎞−1⎤ ⎡N (He+) ⎤−1

64

Physical Properties of Large-scale Galactic Filaments
Show affiliations• Zucker, Catherine; Battersby, Cara; Goodman, Alyssa
Abstract
The characterization of our Galaxy’s longest filamentary gas features has been the subjectof several studies in recent years, producing not only a sizable sample of large-scalefilaments, but also confusion as to whether all these features (e.g., “Bones,” “Giant
Molecular Filaments”) are the same. They are not. We undertake the first standardized
analysis of the physical properties (H2 column densities, dust temperatures,morphologies, radial column density profiles) and kinematics of large-scale filaments inthe literature. We expand and improve upon prior analyses by using the same data sets,techniques, and spiral arm models to disentangle the filaments’ inherent properties fromselection criteria and methodology. Our results suggest that the myriad filament-finding
techniques are uncovering diﬀerent physical structures, with length (11-269 pc), width(1-40 pc), mass (3× {10}3 {M}☉ {--}1.1× {10}6 {M}☉ ), aspect ratio (3:1-117:1), and highcolumn density fraction (0.2%-100%) varying by over an order of magnitude across the
sample of 45 filaments. We develop a radial profile-fitting code, RadFil, which is publicly
available. We also perform a position-position-velocity (p-p-v) analysis on a subsample
and find that while 60%-70% lie spatially in the plane of the Galaxy, only 30%-45%
concurrently exhibit spatial and kinematic proximity to spiral arms. In a parameter space
defined by aspect ratio, dust temperature, and column density, we broadly distinguishthree filament categories, which could indicate diﬀerent formation mechanisms or
histories. Highly elongated “Bone-like” filaments show the most potential for tracing grossspiral structure (e.g., arms, spurs), while other categories could be large concentrations ofmolecular gas (giant molecular clouds, core complexes).

https://ui.adsabs.harvard.edu/abs/2018ApJ...864..153Z/abstract

・銀河系の大スケールフィラ
メント
銀河系スケールに、大きなスケールで細いのフィラメント構造が見つかってきている。
文献によって調べ方はまちまちなので、統一的な手法で系統的に調べたいThe Astrophysical Journal, 797:53 (13pp), 2014 December 10

Goodman et al.

The Astrophysical Journal, 864:153 (34pp), 2018 September 10

Zucker, Battersby, & Goodman

Figure 13. Top: l–v diagram of the spiral arm models and large-scale ﬁlaments in a section of the ﬁrst Galactic quadrant. The MST “Bones” based on the catalog data
are shown, but the tracks for the MST “Bones” based on the continuum data are functionally equivalent. Background grayscale shows 12CO emission from the Dameet al. (2001) survey, integrated between −1°<b<1°. Spiral arm traces are taken from Reid et al. (2016) and include the Local Spur (LoS), the Aquila Rift (AqR),
the Aquila Spur (AqS), the Sagittarius Near arm (SgN), the Sagittarius Far arm (SgF), the Scutum Near arm (ScN), and the Norma arm (Nor). The colored dots
correspond to the four different large-scale ﬁlament catalogs included in this study, derived through Gaussian ﬁtting of the ﬁlament’s CO emission in 0°. 1 longitudeintervals (see Section 3.6). Bottom: plane-of-the-sky map of the same section of the ﬁrst Galactic quadrant. Background grayscale also shows the 12CO emission fromthe Dame et al. (2001) survey, now integrated between 0 and 110 km s−1. The ﬁlament masks are overlaid to scale and color-coded according to ﬁlament catalog. The
same spiral arm models are shown as in the top panel.

determine the central velocities of our ﬁlaments at evenly spaced

plane-of-the-sky map over an identical longitude range (weanalyses—including a jupyter notebook that users can run
themselves—is publicly available online as part of the RadFil
package.17 The RadFil package and its functionality is
described in Zucker & Chen 2018 and more information isprovided in Appendix A.8.
Our ﬁrst estimate of the width involves taking perpendicular
cuts across the spine, determining where the cut touches the edgeof the mask on either side of the spine, and taking the medianlength of these cuts as the mask-based ﬁlament width (see the thin
red cuts across the spine in the bottom panel of Figure 9(a)). This
mask-based width was determined for every ﬁlament in the sample
and is given in Column (6) of Table 3. For our second estimate of
the width, we ﬁt a Gaussian function to the radial column density
proﬁles of a subset of ﬁlaments whose quantitative boundaries aredeﬁned via the Hi-GAL column density maps (the Zucker
et al. 2015 Bones and Wang et al. 2015 Large-scale Herschelﬁlaments). The Gaussian-based width was not determined for the
GMF and MST “Bone” samples. Speciﬁcally, we determine thepixel with the maximum column density value along each of theperpendicular cuts and build a radial column density proﬁle alongeach cut with respect to this pixel. We then ﬁt a Gaussian to theentire ensemble of radial column density proﬁles given by these setof cuts. Our Gaussian model has two free parameters (amplitude,-r 2
standard deviation) and is given by N (r ) = aexp 2s 2 , where ais the amplitude, and σ is the standard deviation. We ﬁrst subtract a( )Several studies (Juvela et al. 2012b; Smith et al. 2014b) haveshown that the best-ﬁt radial column density proﬁle values are
intimately dependent on background subtraction and ﬁtting radius.
As such, we provide alternative Gaussian-based widths for ourﬁlaments using different background subtraction and ﬁtting radiiin Table 4. The impact of ﬁtting parameter variation is discussed
at length in Appendix A.8, but the average FWHM typicallychanges by a few tenths of a parsec for a reasonable range ofﬁtting parameters. The process of building and ﬁtting a radialcolumn density proﬁle for Filament 2 is shown in Figure 9 andoutlined in more detail in Appendix A.8.
Box-and-whisker plots for the length, linear mass, width, andaspect ratio distributions are shown as side-by-side panels in
Figure 10. As seen in the leftmost panel of Figure 10, themedian lengths of the four different ﬁlament classes span
approximately a factor of 3, with the GMFs having the highest
median length (94 pc), followed by the Large-scale Herschelﬁlaments (50 pc), the Milky Way Bones (36 pc), and the MST“Bone” ﬁlaments (31 pc for the catalog-based method, 27 pc
for the continuum-based method).
In the middle-left panel of Figure 10, we see that the medianlinear masses for the four classes vary by a factor of 4: theGMFs have the highest linear mass (≈1500 Me pc−1), with theaverage MST “Bone” linear mass about half that value(≈700–800 Me pc−1). The Milky Way Bones and the Largescale Herschel ﬁlaments have the lowest linear masses, with

CO-dark gas in the Milky Wa

議論- GMF？aspect比は他に比べて低いが(8:1)、
普通のGMC(例えば1.5:1)よりは高い。GMF
はただのkinny subset of GMCか？

- MST Bone?円柱のソーセージ不安定？あるいは、GMC内でﬁlamentaryな構造が暴走的に成長した？

- Bone candidates? large-scale gravityが必要？最も長くて密なBone-likeなフィラメントは銀河系の重力によって作られ維持されている？

COのデータのある22/45 のフィラメントについて、position-position-velocityの解析をした。近場のスパイラル構造と同じところにいるか調べた。
->35%のフィラメントがスパイラルと同じ場
所(<20 pc,<10 km/s)だとわかったが、残り65%はそうじゃない

The Astrophysical Journal, 864:153 (34pp), 2018 September 10

Zucker, Battersby, & Goodman

were then derived via the morphology of the low-density
tracing 13CO emission enveloping these dense ﬁlamentarycomplexes. Ragan et al. (2014) and Abreu-Vicente et al. (2016)
conﬁrmed velocity contiguity by collapsing the 13CO cubes inlatitude bounds around the ﬁlament and ensuring that the p –v
diagram exhibits unbroken emission. Together, Ragan et al.
(2014) and Abreu-Vicente et al. (2016) identiﬁed 16 GMFs
(9 claimed to be associated with spiral arms), all of which areincluded in this study.
Wang et al. (2015) undertook a search for the coldest anddensest ﬁlaments (“Large-scale Herschel ﬁlaments”) by visuallyinspecting Herschel Hi-GAL images of the inner galaxy (Molinari
et al. 2010) and conﬁrming velocity contiguity via a custom 13CO
p –v slice taken along the ﬁlament. Wang et al. (2015) uncovered
nine ﬁlaments with typical lengths on the order of 40–100 pc,
column densities ≈1×1021–2×1022 cm−2, and dust temperatures 17–21 K. Seven of these are claimed to be associated withspiral arms, and all nine ﬁlaments listed in Table 2 from Wanget al. (2015) are included in this study.
Next, Zucker et al. (2015) carried out a by-eye search of themid-IR GLIMPSE and MIPSGAL surveys (Carey et al. 2009;
Churchwell et al. 2009) speciﬁcally for Nessie analogs—the“Bones of the Milky Way.” Zucker et al. (2015) cataloged
Figure 2. Top-down artist’s conception view of the Milky Way Galaxy
highly elongated extinction features (typical lengths 20–60 pc)(courtesy of Robert Hurt, NASA). The longitude range of the full sample isthat lie parallel and in close proximity to the plane-of-the-sky
shown as a yellow arc (with the radius of the arc set by the farthest ﬁlamentdistance, ≈10 kpc; see Table 1). Every ﬁlament we consider lies in this area. In
projections of known spiral arms. Zucker et al. (2015)13
orange we show the range of longitudes covered by the GRS survey of CO in
identiﬁed 10 candidates and developed a set of Bone criteria
the ﬁrst quadrant (Jackson et al. 2006), which we use to perform a kinematic(with prescriptions for aspect ratio, spatial and kinematic
analysis on a subset of the ﬁlaments as discussed in Section 3.6 and Figure 13.
proximity to spiral arms, and velocity contiguity) intended todifferentiate features most likely to form due to the Milky
Way’s global spiral potential. To conﬁrm velocity contiguity,
2. Sample Selection
Zucker et al. (2015) took a custom 13CO p –v slice along theWe draw our selection of large-scale ﬁlaments from several
ﬁlament and ensured that dense gas catalog sources tracing theexisting catalogs. To be included in Figure
this analysis,ﬁlamenta gradient<3thekmhighlys−1 per
10 pc. section
Six of tenof disc in the Milky Way simulati
2. Mapa of
total columnﬁlamentdensity exhibitof hydrogen
nucleioffor
resolvedof themust be at least 10 pc long, stated to becontiguous
inthese
met arms,
all Bone
criteria (withthe otherfour failinggasvelocity
has a rangeof morphologies,
fromﬁlaments
dense spiralto filamentary
spurs,
to diﬀuse
inter-arm regions.
3the original paper presenting it, and be part of a catalog whose
the aspect ratio criterion ), and we include all 10 listed in Table
members are purported to lie near or be associated with some2 from Zucker et al. (2015), plus Nessie (Goodman et al. 2014),
aspect of spiral structure. Filaments that satisfy these criteria
in this study (hereafter the “Milky Way Bone” catalog).
3 (GMFs)RESULTS
MILKY
WAY
include the Giant Molecular Filamentsfrom FROM
Ragan THEFinally,Wang
et al. (2016) produced a population of MST
SIMULATION
et al. (2014) and Abreu-Vicente et al. (2016),
the Large-scaleﬁlaments by applying an MST algorithm to dense molecular
Herschel ﬁlaments from Wang et al. (2015), the Milky Way

65

Mapping Distances across the Perseus Molecular Cloud Using CO
Observations, Stellar Photometry, and Gaia DR2 Parallax Measurements
Show affiliations• Zucker, Catherine; Schlafly, Edward F.; Speagle, Joshua S.; Green, Gregory M.; Portillo, Stephen K.
N.; Finkbeiner, Douglas P.;Goodman, Alyssa A.
Abstract
We present a new technique to determine distances to major star-forming regions across the Perseus
Molecular Cloud, using a combination of stellar photometry, astrometric data, and 12CO spectral-line
maps. Incorporating the Gaia DR2 parallax measurements when available, we start by inferring the distanceand reddening to stars from their Pan-STARRS1 and Two Micron All Sky Survey photometry, based on atechnique presented by Green et al. and implemented in their 3D “Bayestar” dust map of three-quarters of
the sky. We then refine their technique by using the velocity slices of a CO spectral cube as dust templates
and modeling the cumulative distribution of dust along the line of sight toward these stars as a linear
combination of the emission in the slices. Using a nested sampling algorithm, we fit these per-star distancereddening measurements to find the distances to the CO velocity slices toward each star-forming region.
This results in distance estimates explicitly tied to the velocity structure of the molecular gas. We determine
distances to the B5, IC 348, B1, NGC 1333, L1448, and L1451 star-forming regions and find that
individual clouds are located between ≈275 and 300 pc, with typical combined uncertainties of ≈5%.
We find that the velocity gradient across Perseus corresponds to a distance gradient of about 25 pc, withthe eastern portion of the cloud farther away than the western portion. We determine an average distance tothe complex of 294 ± 17 pc, about 60 pc further than the distance derived to the western portion of thecloud using parallax measurements of water masers associated with young stellar objects. The method we
present is not limited to the Perseus Complex, but may be applied anywhere on the sky with adequate COdata in the pursuit of more accurate 3D maps of molecular clouds in the solar neighborhood and beyond.
https://ui.adsabs.harvard.edu/abs/2018ApJ...869...83Z/abstracthttps://ui.adsabs.harvard.edu/abs/2018ApJ...864..152Z/abstract

1

A sensitive λ 3 mm line survey of L483. A broad view of
the chemical composition of a core around a Class 0
objectShow affiliations• Agúndez, M.; Marcelino, N.; Cernicharo, J.; Roueﬀ, E.; Tafalla, M.
Abstract
An exhaustive chemical characterization of dense cores is mandatory to our understanding of chemical compositionchanges from a starless to a protostellar stage. However, only a few sources have had their molecular composition
characterized in detail. Here we present a λ 3 mm line survey of L483, a dense core around a Class 0 protostar, which
was observed with the IRAM 30 m telescope in the 80-116 GHz frequency range. We detected 71 molecules (140including diﬀerent isotopologs), most of which are present in the cold and quiescent ambient cloud according to theirnarrow lines (FWHM 0.5 km s-1) and low rotational temperatures (≲10 K). Of particular interest among the detected
molecules are the cis isomer of HCOOH, the complex organic molecules HCOOCH3, CH3OCH3, and C2H5OH, awide variety of carbon chains, nitrogen oxides like N2O, and saturated molecules like CH3SH, in addition to eight newinterstellar molecules (HCCO, HCS, HSC, NCCNH+, CNCN, NCO, H2NCO+, and NS+) whose detection has alreadybeen reported. In general, fractional molecular abundances in L483 are systematically lower than in TMC-1 (especiallyfor carbon chains), tend to be higher than in L1544 and B1-b, and are similar to those in L1527. Apart from theoverabundance of carbon chains in TMC-1, we find that L483 does not have a marked chemical diﬀerentiation withrespect to starless/prestellar cores like TMC-1 and L1544, although it does chemically diﬀerentiate from Class 0 hot
corino sources like IRAS 16293-2422. This fact suggests that the chemical composition of the ambient cloud of someClass 0 sources could be largely inherited from the dark cloud starless/prestellar phase. We explore the use of
potential chemical evolutionary indicators, such as the HNCO/C3S, SO2/C2S, and CH3SH/C2S ratios, to trace theprestellar/protostellar transition. We also derived isotopic ratios for a variety of molecules, many of which show
isotopic ratios close to the values for the local interstellar medium (remarkably all those involving 34S and 33S), while
there are also several isotopic anomalies like an extreme depletion in 13C for one of the two isotopologs of c-C3H2, adrastic enrichment in 18O for SO and HNCO (SO being also largely enriched in 17O), and diﬀerent abundances for thetwo 13C substituted species of C2H and the two 15N substituted species of N2H+. We report the first detection in
space of some minor isotopologs like c-C3D. The exhaustive chemical characterization of L483 presented here,
together with similar studies of other prestellar and protostellar sources, should allow us to identify the main factorsthat regulate the chemical composition of cores along the process of formation of low-mass protostars. A copy of the
reduced spectrum (FITS file) is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A147Based on observations carried out with
the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

https://ui.adsabs.harvard.edu/abs/2019A%26A...625A.147A/abstractM. Agúndez et al.: A 3 mm line survey of L483

(a few 104 yr; André et al. 2000) evolutionary stage like theClass 0 one remains unclear. This may be related to the way theswitch on of the protostar affects the ambient cloud. In somesources the cloud would preserve much of the characteristics of
A&A 625, A147 (2019)the starless/prestellar phase, displaying high C4 H/CH3 OH ratios
and being rich in carbon chains, while in others the chemical
content of the ambient cloud would be strongly processed by
the injection of energy from the protostar, thus showing low
C4 H/CH3 OH ratios and abundant COMs (hot corinos). However,a deeper understanding of why this would happen is still lacking.
A possible explanation of the chemical differentiation between
Class 0 sources rich in carbon chains and rich in COMs (hot corinos) has been suggested by Sakai et al. (2008a). These authors
proposed that sources rich in carbon chains would have had ashort lifetime of the prestellar collapse, in which case ices would
be rich in CH4 and the evaporation of these during the switch onof the protostar would lead to the formation of carbon chains by
gas phase chemistry. On the other hand, hot corinos would result
from a longer prestellar collapse phase, meaning that ices would
be rich in CO, which upon hydrogenation and further processing driven by protostar heating would lead to abundant COMs
in the gas phase. Chemical models following this idea have been
carried out (Aikawa et al. 2008, 2012; Hassel et al. 2008, 2011)
but still a definitive theoretical validation of the chemical differentiation between Class 0 sources rich in carbon chains and hot
corinos is lacking. More recently, a survey of the C2 H/CH3 OH
in 36 Class 0/I protostars by Higuchi et al. (2018) pointed tothe environmental effect of the dense core being located ina more inner or outer region of the molecular cloud comFig. 6. Column density of C4 H represented as a function of the column density of CH3 OH (leftpanel), HCOOCH (middle panel), and CH OCH3
plex as a possible driver3 of the diversity of C2 H/CH33OH ratios(right panel) in various starless/prestellar cores, Class 0 sources, and hot corinos. All column
densities are beam-averaged values obtained withobserved.
single-dish telescopes. See references in the caption of Fig. 5 for the column densities of C4 H We
andalsoCHinvestigatedL1527.
whetherL1544,
the use B1-b,of moreandspecific
prox3 OH in TMC-1,
of COMs
likelimits),
HCOOCH, ratherthan
Column densities of HCOOCH3 and CH3 OCH3 are taken from Marcelino et al. (in prep.) for ies
TMC-1(upperJiménez-Serra
et3al.
(2016)
forthe3 and CH3 OCH
generic
CH3 OH,
could provide
insightfor
into
L1544, Cernicharo et al. (2012) for B1-b, and Yoshida et al. (2019) for L1527 (upper limits). more
For thethreeone
hotofcorino
sources,columnsome
densities
the chemicaldifferentiation
between starless/prestellar and proC4 H are from Sakai et al. (2009a), for CH3 OH from Maret et al. (2005), and for HCOOCH3 andCH3 OCH
3 from Cazaux et al. (2003) (values havetostellar sources. Therefore, in the middle and right panels of
been averaged for a 1000 source size) and from Bottinelli et al. (2007).
Fig. 6 we show the column density of C4 H versus that of
HCOOCH3 and CH3 OCH3 , respectively, for the same sources
considered before. We see that the Class 0 sources B1-b, L1527,
at the Class 0 stage. We however warn that this interpretation is other type of chemicalthat is,movingfromanyasoftheand L483family;
cluster aroundthewhensame region
in thediagramstarless/prestellar
sources,
they canbe clearly differennot sufficiently robust because of the low statistics of sources these two sourcesto L483, there
is nowhileobviousdifferentiation
inFig. 7. Some column density ratios which are potentially good chemical evolutionary indicators of the prestellar/protostellar transition. The
upper limit to the column density of CH3 SH in TMC-1 is taken fromMarcelino et al. (in prep.).

4.5. Isotopic ratios

The high sensitivity of the line survey permitted us to detect agood number of isotopologs substituted with rare isotopes (D,13
C, 15 N, 18 O, 17 O, 34 S, and 33 S), and even some doubly substituted species. Isotopolog abundance ratios have been obtained
from the column densities derived and are presented in Tables 2
and 3. The uncertainties in these ratios are estimated to be 30%.
We note that although the estimated uncertainties in the column
densities are of the order of 50% (see above in Sect. 4.2), we
can reasonably expect lower uncertainties for isotopic ratios. An
important part of the uncertainty that affects the determinationof a column density is dominated by the error in the rotationaltemperature, which becomes less important when computing
column density ratios between different isotopologs of a given
molecule because these are expected to have similar excitation
conditions. This latter statement has been verified in the few
cases in which we have enough lines to estimate the rotationaltemperature for different isotopologs of the same molecule. For
example, for c-HCC13 CH and c-C3 HD we derive rotational temperatures of 4.1 ± 0.3 and 4.1 ± 0.2, respectively (see Table 1).

58

Fates of hydrous materials during planetesimal collisions
Wakita, Shigeru; Genda, Hidenori
Abstract
Hydrous minerals are found on the surfaces of asteroids, but their origin is notclear. If their origin is endogenic, the hydrous minerals that were formed in the
inner part of a planetesimal (or parent body) should come out on to the surface
without dehydration. If their origin is exogenic, the source of hydrous minerals
accreting onto asteroids is needed. Collisions in the asteroid belt would be related
to both origins because collisions excavate the surface and eject the materials.
However, the fate of hydrous minerals in large planetesimals during the collisional
process has not been well investigated. Here, we explore planetesimal collisions
by using the iSALE-2D code, and investigate the eﬀect of an impact for the target
planetesimal containing hydrous minerals. Our numerical results for the fiducial
case (5 km/s of the impact velocity) show that hydrous minerals are slightly
heated during the collisions. This moderate heating indicates that they can avoid
the dehydration reaction and keep their original composition. Some hydrous
minerals have larger velocity than the escape velocity of the collision system. Thismeans that hydrous minerals can escape from the planetesimal and support thetheory of exogenic origin for the hydrous minerals on asteroids. Meanwhile, thevelocity of other hydrous minerals is smaller than the escape velocity of thesystem. This also indicates the possibility of an endogenic origin for the hydrous
minerals on asteroids. Our results suggest that hydrous minerals on asteroids canbe provided by planetesimal collisions.

https://ui.adsabs.harvard.edu/abs/2019Icar..328...58W/abstract

・含水鉱物の起源
小惑星の表面に水を含んだ鉱物が見つかっている。
表面にあるためには
母天体内側で作って、水と反応せずに表面に出てくる？
表層にあとから降り積もる？
→２つの微惑星の衝突計算で調べる→若干加熱されるだけなのでdehydrationを回避できて、original compositionを維持できる。

once the S of hydrous materials exceeds Sdehyd, we deﬁne it as a dehydrated part. We do not switch the EOS from serpentine to dunite in
the collisional simulations. This is because we focus on the occurrenceof the dehydration reaction and what occurs after the dehydration reaction is irrelevant to this study.
Fig. 1 shows the Hugoniot curve for serpentine derived from ANEOStable in iSALE code which is based on Brookshaw (1998). When theimpact velocity exceeds 6 km/s, S also exceeds Sdehyd. Therefore, for apurely hydrodynamic case, the typical impact velocity (∼5 km/s) of
asteroids in the current main asteroid belt (Bottke et al., 1994; Farinella
and Davis, 1992) cannot cause a signiﬁcant dehydration reaction.
However, a recent study considering material strength (Kurosawa andGenda, 2018) reports that frictional heating during an impact increases
enormously S. Numerical simulations with the strength model areneeded for precise evaluation of the dehydration reaction during planetesimal collisions. Note that the dehydration reaction would be an
endothermic reaction (Wakita and Sekiya, 2011). The main purpose ofthis study is to understand whether or not planetesimal collision would
trigger the dehydration reaction. Thus, we do not take into account theheat consumption in this work due to the dehydration reaction.

3. Results

59

The Astrophysical Journal, 875:153 (10pp), 2019 April 20

Walther & Geballe

New Near-infrared Imaging and Spectroscopy of NGC 2071-IR
Show affiliations• Walther, D. M.; Geballe, T. R.
Abstract
We present high-resolution images of NGC 2071-IR in the J, H, and K bands and in theemission at 2.12 μm of the v = 1─0 S(1) line of molecular hydrogen. We also present
moderate-resolution K-band spectra of two young stellar objects, IRS 1 and IRS 3, within
NGC 2071-IR, that are candidate sources of one or more of the outflows observed in theregion. Two of the eight originally identified infrared point sources in NGC 2071-IR are
binaries, and we identify two new sources, one coincident with the radio source Very
Large Array-1 and highly reddened. The H2 Q(3)/S(1) line intensity ratios at IRS 1 and IRS
3 yield high and very high extinctions, respectively, to them, as is implied by their nearinfrared colors and K-band continuum slopes. The spectra also reveal the presence ofhot, dense circumstellar molecular gas in each, suggesting that both are strong
candidates for having energetic molecular outflows. We agree with a previous suggestionthat IRS 1 is the likely source of an east─west-oriented outflow and conclude that thisoutflow is probably largely out of the plane of the sky. We also conclude that if IRS 3 isthe source of the large-scale northeast─southwest outflow, as has been previously
suggested, its jet/wind must precess in order to explain the angular width of that outflow.
We discuss the nature of the point sources and their possible contributions, if any, to thecomplex morphology of the H2 line emission.

https://ui.adsabs.harvard.edu/abs/2019ApJ...875..153W/abstract

Figure 3. Continuum-subtracted image of NGC 2071-IR in the 1−0 S(1) line of H2. The positions of most of the known (proto)stars are marked, along with theoutﬂow regions IA-III designated by E00. The arrows denote the directions of the E- and NNE-pointing ionized jets from IRS 1 and IRS 3, respectively, as determinedfrom radio continuum measurements by T98, S02, TRR09, and CG12.

remarkably great. Both IRS 1 and IRS 3 lie between these twoemission lobes, and as noted by several previous investigators,
are possible sources of this wind. Source VLA-1 also is locatedbetween the lobes.
Walther & Geballe
Considerable H2line emission is present in Figure 3 outsideof IA and IB. Much of this was described by E00, but thepresent higher-resolution images reveal additional detail. In
particular, the morphology between those two lobes is highly
complex, especially to the east. Knots of bright H2line
emission are present to the east of IRS 1, VLA-1, and IRS3,extending as far as 40″ from them, and are collectively called
Outﬂow IIA by E00. Approximately 15″ to the west of thesesources a bright arc of emission is present within a larger regionof lower surface brightness, which E00 labeled IIB. Lying

3.2. Molecular Hydrogen Image
Figure 3 is a continuum-subtracted image of the H21−0 S(1) line at 0 35 resolution, covering ∼60%of the full extent ofThe
Astrophysical Journal,
875:153 (10pp),
2019 April
NE–SW-oriented
line emission(designated
IA 20
and IB in theﬁgure, following E00) detected by earlier observers at lower
angular resolution and imaged in full by E00 using a camera
with 0 81 pixels in unspeciﬁed seeing conditions. Figure 4 is amore detailed view, in contours of intensity, of the central 45″.
Outside of the central 30″ many of the brightest emitting
regions are located on the outer edges of the NE and SW lobes,
suggesting that they are regions where an outﬂowing windfrom a star is colliding with and shocking the surrounding
cloud. Although these edges appear to be sharp, especially in
the NE lobe (IA), the non-uniformity in surface brightness is
4

Figure 4. Contour map of H21–0 S(1) line emission in the central region of Figure 3. The locations of point sources are denoted by yellow stars. Also shown are theorientations of the disks of IRS 1 and IRS 3 (orange rectangles), as determined from observations of H2O maser spots by T98, and TRR09, and their ionized jets (bluearrows), as determined from radio continuum measurements by T98, S02, TRR09, and CG12.

60

Sheets, filaments, and clumps - high-resolution simulationsof how the thermal instability can form molecular clouds

Name
Paper IV HD(Wareing et al. 2018)
Model 1Model 2Model 3Model 4Clump

Domainpc on a sideG0
# of cells

Levelsof AMR

tstart(Myr)

Resolution
(pc)

HD
/MHD?

Cooling? Heating? G

300

8×8×8

8

0.0

0.29

HD

Y

Y

100
100
100
100
10

10 × 10 × 10
10 × 10 × 10
10 × 10 × 10
10 × 10 × 10
10 × 10 × 10

6
7
8
9
7

16.2
21.7
21.7
22.8
44

0.3125
0.156
0.078
0.039
0.0156

HD
HD
HD
HD
HD

Y
Y
Y
Y
Y

Y
Y
Y
Y
Y

Show affiliations• Wareing, C. J.; Falle, S. A. E. G.; Pittard, J. M.
Abstract
This paper describes 3D simulations of the formation of collapsing cold clumps via
thermal instability inside a larger cloud complex. The initial condition was a diﬀuse
atomic, stationary, thermally unstable, 200 pc diameter spherical cloud in pressure
equilibrium with low-density surroundings. This was seeded with 10 per cent density
perturbations at the finest initial grid level (0.29 pc) around nH= 1.1 cm-3 and evolved
with self-gravity included. No magnetic field was imposed. Resimulations at a higher
resolution of a region extracted from this simulation (down to 0.039 pc) show that thethermal instability forms sheets, then filaments, and finally clumps. The width of
the filaments increases overtime, in one particular case from 0.26 to 0.56 pc.
Thereafter, clumps with sizes of around 5 pc grow at the intersections of filaments. 21
3. Evolution of the diffuse cloud into a complex of clumps shrinking through gravitational collapse. Six time snapshots from Model 3 are
distinct clumps, with properties similar to those observed in molecular clouds, are Figure
in a box with sides of length 50 pc. Each snapshot shows a 3D isosurface rendering of density, with 10 isosurfaces shown at density levels ranging ln = 100 cm . Isosurface opacity increases with density, reaching high opacity by n = 10 cm , sharper and coloured green (digital-ofound using the FellWalker algorithm to find minima in the gravitational potential. Not upthe tofigure.
Lower density more translucent isosurfaces are diffuse and bluer in colour (digital-only), indicating the extent of unstable material (1< 10 cm ). The isosurfaces have been created from Silo datafiles using thetoolkit. Movie and Silo format raw data files are available
https://doi.org/10.5518/483.
all of these are gravitationally bound, but the convergent nature of the flow andincreasing central density suggest they are likely to form stars. Further simulation of the mass and volume filling fractions of cold gas, are relatively
to the choice of cooling function. On the other hand,
the most massive clump shows the gravitational collapse to a density >106 cm-3. insensitive
the cloud morphology and the l e-sc e velocity distribution ofg do stronly depen on the coolin funtion They sotime-variation of properties and derived statistics as well ti
These results provide realistic initial conditions that can be used to study feedback inthe
investig ed the properties of the dene clumps formed within theirsnapshots of slices, projections, and isosurface plots reveal
cloud. They found that the majority of these clumps are not selfproperties. Plotting mechanisms within the MG code areindividual clumps, interacting clumps, and the entire molecular cloud complex.
gravitating, suggesting that some form of lare-scale collapse of the(VisIt Collabo
H

−3

−3

H

−3

VISIT

VISIT

cloud m y be required in order to produce grvit ion ly untble2012).
clumps hence stars. It remains to be explored in future work theextent to which different heting and cooling prescriptions ffectthis work. The prescriptions used--175(herein,--175(which)-176(study--174(precisely)-176(such)TJ] ETqQ 1.571509001.5715091097.721-

Fig. 3 provides an overview of the evolution of the cloud, fromthe first condensations cause steep density increases at t = 2

https://ui.adsabs.harvard.edu/abs/2019MNRAS.485.4686W/abstract
MNRAS 485, 4686–4702 (2019)

61

The Gaia-ESO Survey: asymmetric expansion of the Lagoon
Nebula cluster NGC 6530 from GES and Gaia DR2

Show affiliations Show all authors• Wright, Nicholas J.; Jeﬀries, R. D.; Jackson, R. J.; Bayo, A.; Bonito, R.; Damiani,F.; Kalari, V.; Lanzafame, A. C.; Pancino, E.;Parker, R. J.; Prisinzano, L.; Randich,S.; Vink, J. S.; Alfaro, E. J.; Bergemann, M.; Franciosini, E.; Gilmore, G.; Gonneau,
A.;Hourihane, A.; Jofré, P. ; ...
Abstract
2488
N. J. Wright et al.
The combination of precise radial velocities from multi-object spectroscopy and highly
Table 3. Central velocities and velocity dispersions for the entire Lagoon Nebula population and the subsets of NGC 6530, M8E, and thesubgroup.
Velocity dispersions are not calculated for the latter two as they are not sufficiently well sampled. The north-western
accurate proper motions from Gaia DR2 opens up the possibility fornorth-westerndetailed
3D
subgroup lacks any sources with spectroscopy and so its RV is not known.
kinematic studies of young star-forming regions and clusters. Here, we perform such
SampleRVσµσµ
σ
an analysis by combining Gaia-ESO Survey spectroscopy with Gaia astrometry for(km s )(km s )
(mas yr )(mas yr )(mas yr )(mas yr )Lagoon Nebula
members)
0.08
2.12
1.19 ± 0.05
0.644
−1.94 ± 0.04
0.443
̃900 members of the Lagoon Nebula cluster, NGC 6530. We measurethe(all3D
velocity
NGC 6530 (r < 2.5 arcmin)
0.82
1.80
1.21 ± 0.04
0.251
−2.00 ± 0.03
0.216
dispersion of the region to be 5.35^{+0.39}_{-0.34} km s-1, which isM8E
large
enough to 0.75 ± 0.72
(r < 2 arcmin)–
1.78 ± 0.23–
−2.14 ± 0.34–
North-western group (r < 1––
1.77 ± 0.20–
−1.50 ± 0.17–
suggest the region is gravitationally unbound. The velocity ellipsoid arcmin)is anisotropic,
implying that the region is not suﬃciently dynamically evolved to achieve isotropy,
use the luminosity-weighted average of the two as the photocentre
though the central part of NGC 6530 does exhibit velocity isotropy
that suggests
RV, which is then added to the modelled RV.
we add measurement
uncertainties for the RVs and PMs
suﬃcient mixing has occurred in this denser part. We find strong Finallyevidencethat thefor each star, randomly sampling these from the observed uncerdistributions andstellar population is expanding, though this is preferentially tainty
occurringininclude
the the correlated PM uncertainties
quoted in Gaia DR2 (random sampling of uncertainties is necessary
declination direction and there is very little evidence for expansion
in therightbecause the modelled
population
is significantly larger than theobserved population). This model has 6 free parameters, the velocity
ascension direction. This argues against a simple radial expansion
pattern, as
dispersion and central velocity in each dimension. Wide and uniform
priorswere used for eachofthese context
parameters covering 0–100 km s
predicted by models of residual gas expulsion. We discuss thesefindings
inthefor the velocity dispersions and −100 to +100 km s for the central
velocities.
of cluster formation, evolution, and disruption theories.
0
−1

RV
−1

+0.34
−0.30
+0.34
−0.34

+0.24
−0.22
+0.40
−0.37

12

−1

−1

https://ui.adsabs.harvard.edu/abs/2019MNRAS.486.2477W/abstract

To sample the posterior distribution function we use the affineinvariant MCMC ensemble sampler (Goodman & Weare 2010)
EMCEE (Foreman-Mackey et al. 2013) and compared the model tothe observations using an unbinned maximum-likelihood test, which
is made efficient by the smooth velocity distributions modelled. For
the MCMC sampler we used 1000 walkers and 2000 iterations,discarding the first half as a burn-in. The six parameters were

α0

−1

µα

−1

+0.044−0.045+0.045−0.043

δ0

−1

µδ

−1

+0.036−0.038+0.038−0.036

62

Parallaxes for Star-forming Regions in the Inner
Perseus Spiral Arm
Show affiliations• Zhang, Bo; Reid, Mark J.; Zhang, Lian; Wu, Yuanwei; Hu,
Bo; Sakai, Nobuyuki; Menten, Karl M.; Zheng, Xingwu;Brunthaler,
Andreas; Dame, Thomas M.; Xu, Ye
Abstract
We report trigonometric parallax and proper motion measurementsof 6.7 GHz CH3OH and 22 GHz H2O masers in eight high-massstar-forming regions (HMSFRs) based on Very Long Baseline Array(VLBA) observations as part of the Bar and Spiral Structure Legacy(BeSSeL) Survey. The distances of these HMSFRs combined with
their Galactic coordinates, radial velocities, and proper motions,allow us to assign them to a segment of the Perseus arm with ℓ ≲70°. These HMSFRs are clustered in Galactic longitude from ≈30°
to ≈50° neighboring a dearth of such sources between longitudes≈50° to ≈90°.

https://ui.adsabs.harvard.edu/abs/2019AJ....157..200Z/abstract

８個の大質量形成領域で6.7 GHzメタノールメーザーと22GHz
水メーザーを用いて、parallaxとproper motionを決めた。