Science Review ofNearby Galaxy and Star Formation

Toshikazu Onishi
Osaka Prefecture University

Photo Credit: ALMA (ESO/NAOJ/NRAO), C. PadillaGalaxy evolution→
Individual star formation
kpc

AU

ALMA+HST
Gas 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 envelope
outflow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 galaxies²

ObjectMolecularCloud

MolecularClump

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 resolutions²

Envelope structure around protostars
and the fragmentation of dense gas before the formation ofprotostars + feedback from protostars‒ ~100 – 1000AU at local clouds‒²

Resolving GMCs in local galaxies‒«

Wide spatial frequency range: ACA(Morita array)²«~0.1 – 10pc at 50kpc – 5Mpc

From molecular clouds, dense cores to protostars

Polarization/Magnetic fieldStar formation Studywith ALMA«

Wide range and high resolution in frequency²Chemistryin low-mass and high-mass star forming regions‒ as a probe of the evolution‒«

In this talk²

Molecular clouds -> formation of protostars‒

stellar feedback, chemistry

Low mass star formation

Tobin et al. (2016)
VLA observationsin 9mm.
Outcome of star formation processFormation of multiple stars
ALMA and VLA images of the disk and triple protostar system
L1448 IRS3B

0.27″

ALMA 1.3mm
0.16″ (62 AU 37 AU)
Tobin et al., Nature, 2016

VLA 8mm

a wide-separation quadruple system

JE Pineda et al. Nature 518, 213-215 (2015) doi:10.1038/nature14166

What about starless cores«

Complex structures seen in MC27/L1521F²«Tokuda et al. (2014, 2016)

No continuum source detected toward 56
starless cores in Cha with ALMA 12m array.
²

Dunham et al. (2016)

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
intensity-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 resolut
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 undein the central part of the cloud core, wh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

What about starless cores• Source selection is important– Some hints in single dish observations• Column density peak, detection of high excitation lines– ACA: efficient tool to disentangle the evolution• Statistical studies– Fragmentation: How? Time scale?

Core Mass Function -> IMF
1000 AU~0.0045 pc

Oph A Ridge
A-MM6• CMF appears tofollow the same
power law as Salpeter
IMF down to 0.1M8.
The turn over mass isabout 0.1M8.

Contour = 4s, 8s, 12s,…
(blue~10s, green~30s,red > 50s)
A-MM1
1s ~ 0.25 mJy/beam

SM1N
SM1

A-MM2

VLA1623(Class 0)
A-MM3

SM2

beam size =1.2” x 0.7”

1.3-mm continuum (7-m +12-m)

Nakamura et al.

Massive star formation• Initial condition of massive stars– Fragmentation, collapse, magnetic field• Disk envelope– G31.41+0.31, HH80-81, AFGL 4176, G35.02• Strong feedback• ChemistryGlobal collapse and spiral structures
Massive protocluster G33.93+0.11
L~2.5x105Lo, M=3000Mo, <1pc

Liu et al. (2015)

Massive star forming clump
W43-MM1
ALMA Band 6 Continuum

Highly fragmented filament with source masses ranging from 14Mo to 312Mo.
Magnetic field strength from 0.2 to 9mG
All the fragments are in a super-critical state.

Protocluster hub: G03.39-00.33

A network of narrow, 0.028pc wide, filamentary structures.
Much narrower than “quasi-universal” ~0.1pc width.
Henshaw et al. (2016)

Stellar feedback
Explosive outflows in OMC1CO(2-1)
Bally 2016
Blue-shifted emission(-110 to 0 km/s) in blue,
red-shifted emission (+20 to 130 km/s) in red

The flow is nearly isotropic with over
100-arcsec-wide CO streamers

Nearby Galaxy• Angular resolution of 1 arcsec– 0.24pc at 50kpc, 5pc at 1Mpc
– Cloud-scale studies tracing gas properties and starformation– Gas dynamics in a whole galaxy• Influence of spiral arms, bars, and so on.

– Scaling relations of molecular clouds with a wide
range of environmental parameters• Conditions of massive star formation, effect of metallicity

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

NGC 1068
CO(3-2) 0.3 – 0.5” (25-30pc)

ALMA reveals how galaxy
dynamics (re-)arrange gas

Inward flow in ring and bar
Gas dynamics
García-Burillo et al 2014

Salak et al. 2016 (NGC 1808), Pereira-Santaella et al. 2016 (ESO 320-G030), ...

NGC 1068
CO(3-2) 0.3 – 0.5” (25-30pc)

ALMA reveals how galaxy
dynamics (re-)arrange gas

Inward flow in ring and bar
Gas dynamics
García-Burillo et al 2014

Salak et al. 2016 (NGC 1808), Pereira-Santaella et al. 2016 (ESO 320-G030), ...

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 by
ALMA: a view of cloud evolution

Kawamura et al. (2009)

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)

ALMA 12CO(2-1)

Integrated intensity[K km/s]

N159 E

N159 W

Integrated intensity[Jy/beam km/s]

ASTE 12CO(3-2)

1”.20”.8 = 0.29

0.19pcbeam 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

Total N(H2)

I(CO J=1-0)

Glover & Clark 2012

Comparison with Galactic molecular clouds※H2 column density calculated from 13CO(2-1)

Column densities of LMC clouds (N159W/E) areOrion-A
N159W-S
N159EW43-Mainhigher than the that of the Galactic clouds.
Papillion
Osaka 1.85-m
ALMA
IRAM 30-m

CO in the low metallicity
dwarf galaxy WLM
Tiny CO clouds in WLM.

Molecular cloud at 13% metallicity
Photo-dissociation region is 5x larger than CO cores
Follows galactic scaling relations
Marginally self-bound by gravity

Rubio et al. (2015)

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 selected samples– Polarization observations would be a key toinvestigate the evolution of molecular clouds toprotostars