Revealing the initial conditions ofstar formation in the Galaxy
and Magellanic Clouds
NAOJ ALMA Scientific Research Grant: 2016-03B
From 2017/2

Toshikazu Onishi
Osaka Prefecture University

Kazuki Tokuda, Sarolta Zahorecz
Specially Appointed Research Staff for the ProjectWith many others + Students
Photo Credit: ALMA (ESO/NAOJ/NRAO), C. PadillaGalaxy evolution→
Individual star formation
kpcAU

ALMA+HSTGas mass concentrations inthe dark lanes at highgravity and at collision area.

Face-on First Core@910GHz(Saigo and Tomisaka 2011)

Formation of stars andthe protostellar envelopeoutflow

Star formation process«Contraction by many orders of magnitude²High spatial resolution + wide spatial range‒⇄ Targets having different distancesHigh spatial resolution at local clouds² Resolving molecular clouds at local galaxies²Object

MolecularCloud

Molecular
Clump

Dense CoreFormation ofProtostar

ProtostarSize(AU)~ 106-7~ 105~ 10４

103 ~ 102

< 10Density(cm-3)~ 102-3

~ 10４

~ 105

~ 1011~ 1016

Star formation Studywith ALMA«High angular resolutions²Envelope structure around protostars
and the fragmentation of dense gas before the formation ofprotostars + feedback from protostars‒ ~10 – 10000AU at local clouds‒²Resolving GMCs in local galaxies‒«~0.01 – 10pc at 50kpc – 5Mpc

Wide spatial frequency coverage: ACA(Morita array)²

From molecular clouds, dense cores to protostars

Our Focus«

Low-mass star formation in nearby clouds²

Dense cores -> Formation of protostars‒«

From 10000AU to 10AU scale

High-mass star formation in Magellanic Clouds²

Molecular clouds -> Dense cores
From kpc to 0.01pc scale‒ Uniform sample of molecular clouds and protostars‒ Stellar feedback‒Low mass star formation«

Higher density -> Shorter time scale -> Rare objects²«

Higher density -> Smaller size -> Higher resolution
²

«

ALMA

Detailed study toward MC27/L1521F in Taurus²«

Large survey

Nagoya 4m -> Large aperture single dish -> ALMA

Search for objects just at protostar formation in nearby SFregions²

Archival studies obtained by SD telescopes and ALMA observations

Nagoya Univ. 4m telescope: 13CO(1-0)
MC27/L1521F

30 ly= 2x106AU
Mizuno et al. (1995), Onishi et al. (1996, 1998)

NRO 45m telescope

10,000AU
Onishi et al. (1999)

ACA

Tokuda et al. (2016)2000 AUALMA

Tokuda et al. (2014)

300 AUMC27/L1521F
The Astrophysical Journal Letters, 789:L4 (6pp), 2014 July 1

HCO+(3-2)

Figure 4. Images of HCO+ (J = 3–2) emission of a red velocity component toward MC27/L1521F. Black contour shows an image of veof HCO+ (J = 3–2) with a velocity range of 6.8–7.0 km s−1 . Both the lowest contour and subsequent contour step are 0.020 Jy beam−1 kintensity-weighted velocity map of the red velocity component with a range of 6.5–14.0 km s−1 is shown in color scale. The magenta conto
dust continuum emission with the same contour levels as Figure 1. The black cross is the position of the Spitzer source. The angular resoluti
is given by the ellipse in the lower right corner, 1.′′ 0 × 0.′′ 8.

MAMBO + ALMA(7m + 12m array)

Tokuda et al. (2014, 2016)

Complex Structure: Fragmentation and interactions
We note that no SiO (J = 6–5) emission was detected, whichmeans that there is no strong shock to excite the line and isturbulence plays an important role in underin the central part of the cloud core, whi

Summary of ALMA Cycle 0 Observations
Outflow
High density dust cores
HCO+(3-2)
H13CO+(3-2)
HCN(3-2), CS(5-4)

1400 AUHigh density core
Spitzer source

AL
MAHigh density coreGas interactingwith outflow
Outflow red shift comp.

Cycle0Outflow blue shift comp.
Gas interactingwith outflow

Arc-like structureHigh density
dust cores

1. Formation site of multiple stars?
2. Initial condition of star formation: Complicated12Tokuda et al. 2014

A Detached Protostellar Diskaround a∼0.2Mo Protostar?
Tokuda et al. (2017)
Contour: Model
Color: Obs.

・Located at the center of a dense core
・Deconvolved size of the disk: ~10AU
・Quite tiny outflow
・Fan-shape scattered light with Siptzer
・Very-low internal luminosity (<0.07 Lo)

Significant mass infall has stopped?
The final stage of protostar formation?

(See also Tokuda’s poster)Dense core survey in Chamaeleon I
Color:
APEX/LABOCA 870 μm(Belloche + 2016)
ALMA field

The 56 starless cores should haveyielded at least two detections,assuming the following:- Turbulent fragmentation- Star formation is continuums, and allof starless cores are collapsing- Timescales are proportional to thefree-fallNone detected in all starless cores(Dunham et al. 2016)

Dense core survey in Chamaeleon I
Color:
APEX/LABOCA 870 μm(Belloche + 2016)
ALMA field

The 56 starless cores should haveyielded at least two detections,assuming the following:- Turbulent fragmentation- Star formation is continuums, and allof starless cores are collapsing- Timescales are proportional to thefree-fallNone detected in all starless cores
ALMA field(Dunham et al. 2016)

Cha-MMS1

The observed point also includes the local peaks of the cores

Large scale observations

Spitzer survey of the LMC
SAGE: Surveying the Agencyof the galaxy’s evolution(Meixner et al. )GMCs, dust, YSOs,
HII regions,
SNRs, AGBs,,…

3.6μm
8.0μm
24μm
1” - 8”

CO: from 1.2 Kkm/s
1.2Kkm/s intervals(Fukui et al. 2008)

Evolution of GMCs andEffect of feedback

What is the mechanism of the formation ofmassive stars in molecular clouds?
What is the lifetime of molecular clouds?
What is the effect of the metallicities to the cloud
structures and star formation.
Statistical studies of variety of clouds in Galaxies byALMA: a view of cloud evolution

Kawamura et al. (2009)

GMCs in the LMC«

Clouds in super star cluster: 30Dor²«

GMCs with different evolutionary stages²«

PI: T. Onishi, N. Naslim

Cold GMC at the edge of the LMC²«

PI: A. Kawamura, T. Wong, R. Chen(see also Takada’s poster)Developed HII regions: N55²«

PI. R. Indebetouw

PI: T. WongHigh mass star formation in an isolated environment²PI: R. Harada (see also Harada’s poster)ALMA 12CO(2-1)

Integrated intensity[K km/s]

N159 E

N159 W

Integrated intensity[Jy/beam km/s]

ASTE 12CO(3-2)

1”.2  0”.8 = 0.29  0.19pc

beam size

22” = 5pc

N159W

Fukui et al. (2015)

12CO(2-1)

N159E

12CO(2-1)

Saigo et al. (2016)

Filament-filament interaction as a possible mechanism of massive star formation

ALMA GMC Observations

Figure by Remy Indebetouw

SFR in NANTEN clouds (est. from Halpha+24µm) vs. CO mass from Fukui+08

ALMA GMC Observations
previous CO & 13CO mapping (Kawamura, Indebetouw, Fukui, Onishi, Wong)previous CO or 13CO mapping (Lebouteiller, Sawada, Fujii, Sano, Sewilo)
Proposal: 2016.1.00193.S

N83C in the SMC Muraoka et al. (2017)
See also Homma’s poster

Density: 104cm-3
Tk: 30-50K
Less filamentary structure

Conclusions• ALMA begins to address many questions– Detecting various “complex” structures from small
scale to galaxy scale• Fragmentation, Density enhancement, CMF, Metallicity
effect– Wide range of scales is essential: 12m + 7m + TP– Case studies -> surveys of carefully selectedsamples• Thank you for the support!

Posters• 18. "Investigating the formation of isolated massive YSOs in theLMC"
Ryohei Harada (Osaka Prefecture Univ.)• 20. "CO, CI observations of N83C in the early stage of star formationin SMC by ALMA"
Aya Homma (Osaka Prefecture Univ.)• 26. "Tracing the evolution of giant molecular clouds in the LMC in
sub-parsec scales by ALMA"
Shota Takada (Osaka Prefecture Univ)• 27. "ALMA view of a protostellar core, MC27/L1521F, with ~20 AUresolution"
Kazuki Tokuda (Osaka Prefecture Univ. / NAOJ)• 30. "High-resolution observations toward G191.51-0.76"
Sarolta Zahorecz (Osaka Prefecture Univ. / NAOJ)

Papers•-[2016-03B]
Tokuda et al. 2017, ApJ, 849, 101, “A Detached Protostellar Disk around a
˜0.2 M ⊙ Protostar in a Possible Site of a Multiple Star Formation in a
Dynamical Environment in Taurus”
Zahorecz et al. 2017, A&A, 602, L3: Gas versus solid-phase deuterated
chemistry: HDCO and D2CO in massive star-forming regions
Muraoka et al. 2017, ApJ, 844, 98, “ALMA Observations of N83C in the
Early Stage of Star Formation in the Small Magellanic Cloud”
Wong et al. 2017, ApJ, 850, 139, “ALMA Observations of a Quiescent
Molecular Cloud in the Large Magellanic Cloud”
Fehér et al. 2017, A&A, 606, 162, “A CO survey on a sample of Herschel
cold clumps,”
Sewilo, M. et al. 2017, ApJ letters, accepted
Naslim et al., submitted to ApJ, “ALMA reveals molecular cloud N55 in theLarge Magellanic Cloud as a site of massive star formation”