FUGINが見た分子雲衝突;
Cloud-cloud collisions with the FUGIN data
Kazufumi Torii（NAOJ/NRO）• Fujita, S, Kohno, M., Nishimura, A., Fukui, Y. (NagoyaUniv.), Kuno, N.(Univ. of Tsukuba), Matsuo, M.,
Umemoto,T., Minamidani, T. (NRO), and other FUGIN
members

Nobeyama 45m telescope and FOREST receiver
Nobeyama 45m telescope• Diameter: 45m• Beam size@115GHz: ~15”
FOREST (FOur-beam REceiver System on
the 45-m Telescope)• Minamidani et al. 2016, Proc. SPIE
• 80–116GHz• 4 beams x 2 pols. x 2 SBs = 16 IFs• Tsys ~ 150K@110GHz, ~250K@115GHz• IF 4–11GHz → simultaneous 12CO,13CO, C18O observation• SPW mode (2016–): CO three isotopes
can be obtained at 0.1 km/s resolution atminimum
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FUGIN project
FOREST Unbiased Galactic plane Imaging survey
with Nobeyama 45-m telescope
Large-scale 12CO, 13CO, C18O J=1-0
observations in the Galactic Plane• 1st quad.: l ~ 10° – 50°, b < |1°|
• 3rd quad: l ~ 198° – 236°, b< |1°|
• effective beam sizes: 20”• ch resolution: ~0.65km/s(effective: 1.3km/s)• Trms(Tmb): 0.7K@13CO & C18O,
1.5K@12CO• Data (fits cube) will be public in 2018
Aims
• Understanding ISM and star formation in the MW.
• Understanding the galactic structures in the MW.
• Constructing a bridge between the MW and galaxies.

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Observed regions• Observed: 130 deg2 (84% of the plan)• 1st quad.: 80deg2 (Complete)• 3rd quad.: 50deg2

magenta: planned, red: observed

Studies on GMCs with the FUGIN datab < |0.7º|

1. W33 (Kohno et al. accepted to PASJ, arXiv:1706.07964)
2. M17 (Nishimura et al. accepted to PASJ, arXiv:1706.06956;
Yamagishi et al. 2016)

3. Spitzer bubble N18 (Torii et al., arXiv:1706.07164)
4. Spitzer bubble N35 + α (Torii et al., arXiv:1710.08564)
5. W51 (Fujita et al., arXiv: 1711.01695)

4Studies on GMCs with the FUGIN datab < |0.7º|

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5

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3

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1. W33 (Kohno et al. accepted to PASJ, arXiv:1706.07964)
2. M17 (Nishimura et al. accepted to PASJ, arXiv:1706.06956;
Yamagishi et al. 2016)

3. Spitzer bubble N18 (Torii et al., arXiv:1706.07164)
4. Spitzer bubble N35 + α (Torii et al., arXiv:1710.08564)
5. W51 (Fujita et al., arXiv: 1711.01695)

5Cloud-cloud collisions• Trigger of (massive) star formation– NGC1333 (Loren 1976); SgrB2 (Hasegawa+1994)– Galactic super star clusters (Furukawa+2010, Fukui+2014, 2016)– HII regions (Torii+2011, 2015, 2017, Ohama+2017a, 2017b, etc.)– Colliding velocities: ~10–30 km/s
– CCC-driven star formation is dominated by massive GMCs having
masses > 105.5 M⊙, which accounts for a few 10% of the total starformation in the MW (Kobayashi et al. 2017)• Merger/coagulation of clouds– Frequency o collisions in MW-like galaxies ~ 7–10 Myr (Tasker & Tan 11;
Dobbs+15).

– Collision cooling to form giant clumps in gas-rich galaxy disk (Li 2017).
– Little impact on the evolution of ISMs (Dobbs+15).
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Cloud-cloud collision (CCC) model
before collision

during collision

p-v diagram••

Takahira+14: Simulations of CCC between two dissimilar clouds.
Haworth+15a, 15b: Synthetic CO J=1-0 observations with aradiative transfer code using the Takahira et al.’s data, in which theobserver viewing angle is set to parallel to the colliding axis.
• When a smaller cloud drives into a larger cloud, a cavity is createdon the larger cloud.
• In a position-velocity diagram, two velocity peaks separated byemissions with intermediate intensities (= broad bridge features)are observed.
• Bridge features are observable as long as the collision continues.
7Cloud-cloud collision (CCC) model

Spatial distributions of the twocolliding clouds and bridge
features with the synthetic COJ=1-0 data.
• The larger cloud with acavity shows a ring-like gas
distribution.
• The inner radiuscorresponds to the radius of
the smaller cloud, showing acomplementary distribution
between the two velocity
clouds.

Torii+2017a8

MHD numerical calculations (Inoue+2017)• Formation of filaments
within the colliding layer.
• Dense clumps with highMdot are formed.

W33 (Kohno et al. arXiv:1706.07964)•Image (Spitzer):
Red: 24 um
Green: 8um
Blue: 3.6um•••

Massive star forming
region complex with a totalbolometric luminosity of~8x105 Lo.
Dust clumps/cores, which
include hot cores, compact
HII regions, and massive
outflows.
HII regions and O stars.
Parallaxial distance: 2.4kpc(Immer et al. 2013)

Contours:
White: VLA 90cm
Pink: ATLASGAL 870um•Multiple velocity molecular
gas components between
30–60 km/s.
10W33 (Kohno et al. arXiv:1706.07964)

Image: 8um
35km/s vs 58km/s

Image: 24um

Two velocity clouds
35 km/s cloud• ~5x104 Mo• Spatially correlated withalmost all of the dustclumps and HII regions inW33• High CO 3-2/1-0 ratios58 km/s cloud• ~2x104 Mo• Arch-like structure whichsurrounds W33• dense gas clump in W33B
• High CO 3-2/1-0 ratios<– heating by W33
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W33 (Kohno et al. arXiv:1706.07964)
Two velocity clouds
35 km/s cloud• ~5x104 Mo• Spatially correlated withalmost all of the dust
clumps and HII regions inW33• High CO 3-2/1-0 ratios
58 km/s cloud• ~2x104 Mo• Arch-like structure whichsurrounds W33• dense gas clump in W33B
• High CO 3-2/1-0 ratios<– heating by W33
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CCC in W33•••

Collision between two molecular clouds with different sizes at a
relative velocity of ~23 km/s.
As the smaller cloud is much dense than the larger cloud, thesmaller cloud has punched the larger cloud.
Collisional timescale ~ 1 Myr.
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CCCs with the FUGIN data
• Roles of CCCs on evolution of ISM as well as starformation in the MW.
– GMC formation?
– Contribution to the global star formation rate.

• Variation depending on the location in the MW.
• Driving source of the cloud-cloud velocity dispersions.
– Related to the galactic structures?
– or stellar feedbacks?

• FUGIN provides– Large area coverage at high spatial resolution.
– Diagnostics of the high- and low-density structures.

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Barred spiral galaxies
CO

NGC3627
1kpc

HaBar-end:• mini-starburst at kpc scale• Site of CCCs
M83
Ha

NGC4303 2kpc

Ha2kpcGalactic mini-starbursts at the bar-end

W43main
W51B

W43south

W51A

W51

W43

D：～5.4kpc (parallax)
Lbol: ~ 106.7 L¤
GMC
size：～100pc
mass：～106 M¤

D：～5.5kpc (parallax)
Lbol: ~ 105.9 L¤
GMC
size: >100pc
mass：～107 M¤
c.f., Lgalaxy ~ 0.76x108 Lo (Urquhart+2014)

High-mass star forming regions in the bar-end
N34+N35 complex
W43
G45.12+0.13
G45.45+0.06
W51

Candidate tangental
point of the 3kpcarm

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W51 and two GMCs
W51B

W51Akm/s
uTwo large components ~45 – 65
5~7.0×10 MSUN
W51 GMC &(Carpenter & Sanders 1998)
High Velocity Stream(HVS)

W51 GMC

W51B

W51 GMCeocity StrHigh Vel)am (HVS~1.1×105 MSUN

65 – 75 km/s

45 – 65 km/s

W51A~68 km/s, ~100 pc

W51A

W51B

HVSJCMT 13CO (3–2) (Parsons+ 2012)

GMC in W51A
Spitzer 8 & 24 um
コントア 21cm連続波

Fujita+2017 submitted

GMC in W51A

GMC in W51A

GMC in W51A

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GMC in W51A

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GMC in W51A••

Four dense clumps having different velocities over ~15km/s areconcentrated within the central 2-3 pc.
Triggering star formation via multiple collisions?

High-mass star forming regions in the bar-end
N34+N35 complex
W43
G45.12+0.13
G45.45+0.06
W51

Possible tangental
point of the 3kpcarm

25Spitzer bubbles N34 & N35, etc.
G24.47+00.49

N35N3426

N35 and nearby HII regions (Torii+, arXiv:1710.08564)
Contours: 90cm
Image: 8um (green)
24um (red)

••

•
•

Distance: ~6–8kpc
N35: Ring-like 8um structure
which surrounds an HIIregion
Total infrared luminosity of
N35: ~106 Lo (Hattori+17)
Spectral types of theexciting stars estimatedfrom Nly (assuming singleobject):– N35: O4V– HII region A: O6– HII region B: O727

Spitzer bubble N35 and nearby HII regions

Contours: 8um

GMC associated with the three
HII regions• Size: 30pc x 40pc
• Mass: ~106 Mo
The HII regions are located at
the eastern rim of the GMC.

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Two velocity components in the GMC
moment1 [km/s]

Galactic Latitude [degree]

10pc

108

114

moment2 [km/s]
10pc

120

0.4

0.4

0.3

0.3

0.2

0.2

0.1

0.1

0.0

0.0

-0.1

(a)

-0.1
24.6

24.5
24.4
24.3
Galactic Longitude [degree]

24.2

02

4

24.5
24.4
24.3
Galactic Longitude [degree]

24.2

(b)
24.6

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Two velocity components in the GMC•••

Lower velocity component (LVC):- includes the majority of gas in the GMC (~106 Mo, order of 1022 cm-2)
Higher velocity components (HVCs):- three distinct components with masses 104–105 Mo at order of 1022 cm-2
Velocity separations: ~ 10km/s
30Two velocity components in the GMC•

Complementary distributions between LVC and HVCs
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N35

HII region A

HII region B

Position-velocity diagrams:• Intermediate velocity emissions• Steep velocity gradients in N35 andHII region A.

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CCCs between LVC and HVCs••Collisions between a large GMC with 106Mo with smaller clouds.
Timescales: ~2–3 Myr for N35, 0.2–0.3 Myr for HII regions A & B.
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Future prospects (W43)12CO2-1

13CO2-1•

Multiple velocity components at~80km/s and ~100km/s.
• Broad velocity emission toward
W43 main and W43 south(Kiridoshi, Master thesis 2016,
Osaka Pref. Univ.)
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Future prospects (Bar-end region??)35

Future prospects (Bar-end region??)36

Future prospects• Identify molecular clouds, including distances, and checkassociations of signs of star formation• Global properties of gas– Intensity ratio variations, e.g., CO J=3-2/J-1-0, 12CO/13CO.
– PDF, Brightness distribution index (BDI, Sawada+12)• Diagnose physical properties of the individual clouds– Dynamics of the clouds– Cloud evolution based on a statistical study, e.g., cloudmass function, fraction of dense gas, etc.
– Frequency of cloud-cloud collision• Comparisons with the numerical calculations

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FUGIN data release••••2018.6.1: open to the public
3D fits, 2D fits (Integrated intensities), r.m.s 2D map
JVO operated by ADC, NAOJSome useful catalogs, e.g., clouds, clumps, filaments, etc.

Preliminary

Special thanks: Shirasaki, Y., Zapart C., M. Oishi (ADC/NAOJ)

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