Triggered Massive Star Formation Induced by Galaxy Interaction and Cloud Collision

Triggered massive star formation induced by galaxy interaction and cloud collision

Kengo Tachihara, Kisetsu Tsuge, Yasuo Fukui (Nagoya University) Super-star cluster RMC 136 (R136)

R144 binary

- Yung cluster : ~ 1.5 Myr 5 - The most massive in the local group: ~10 M☉ - Super-massive stars

265 M☉, 195 M☉, 175 M☉, 135 M☉ (Crowther et al. 2010) The most massive stars and binaries

• The most massive star R136a1 (SpT=WN5h): 265 MД at

present and 320 MД at birth

• The most massive binary R144 (SpT=WN6h): total 200-300 MД

at present, 400 MД at birth • Both are in 30 Dor in the LMC

• in R136 10 stars with M > 50 MД

• Galactic analog: NGC3603-A1 eclipsing binary (116+86 MД) • They are all Black Hole progenitors • Period of R144 ≲ 1 year => orbital semi-major axis ≲ 10 AU • Black hole binary progenitor Formation of (Galactic) super-star clusters

• Westerlund 2 cloud • Clusters of ~300 YSOs, 5000 Mo

• Mcloud ~ 105 Mo • 2 molecular clouds with different V by ~ 16 km/s • Triggered formation by Cloud-cloud collision

(Furukawa+ 2009; Ohama+ 2010) Super-star cluster R136

The Large Magellanic Cloud (LMC) distance : ~ 50 kpc Inclination : ~ 30 deg. 5 Atomic gas HI 21 cm Molecular gas 12CO (J = 1-0)

2 velocity components separated by ~ 50 km/s L-component D-component (Low velocity) (Disk)

R136 +

200 250 300

Vlsr [km/s] Separation of L- & D-components The bridge feature connecting P-V diagram image: HI, contour: CO the 2 velocity components Complementary distribution of the 2 components

complementary distribution with displacement ~ 200 to 300 pc Collision time scale ~ 2.4 to 3.6 Myr Variation in gas/dust ratio

Planck dust opacity map HI intensity [K km/s]

Dust optical depth (�353) Large gas/dust ration in the region with the L-component => possible contamination of low-metal gas from the SMC The Magellanic bridge (LMC - SMC tidal interaction)

The HI Parkes All-Sky Survey (HIPASS) ave. beam size: 15.5 arcmin. SMC

NGC 602 +

LMC

Magellanic bridge + R136

Putman et al. (1998) Image: HI 21 cm The Small Magellanic Cloud: SMC

NGC 602 in N90 N71

N80 N76 N66

NGC 346 in N66 N50

N36

N84

N90 Atomic hydrogen HI 21 cm line (L. Staveley-Smith et al. 1997) Molecular cloud 12CO(J = 1-0) (NANTEN)

The HI 21 cm line typical spectrum Scatter plot between τ353 and W(HI) L-component D-component

NGC NGC 602 602

Extended L-component distribution The Small Magellanic Cloud (SMC): NGC 602

15 The Small Magellanic Cloud (SMC): NGC 602

Collision timescale ~ 300 pc / 40 km s−1 ~ 8 Myr The Small Magellanic Cloud (SMC): NGC 602 Dec.-velocity diagram L D

17 Mixture of the gas Gas/dust ratio variation M33 and a supermassive cluster NGC 604 The M31-M33 stream

M31

65 kpc

M33

NGC 604 by HST WFPC

2nd largest HII region in the local group ~ 200 OB stars 360 pc x 450 pc in size ~ 3 Myr old M33 spiral galaxy at 794 kpc in analogous to R136 in LMC a member of the local group (Tachihara et al. 2018) Numerical simulation of colliding gas ﬂow

10kms−1 1.5 5.0

5.0

4.5 ]) )] 4.5 −3 1.0 −3 [cm n 4.0 (cm H2 n log( 4.0 (pc) z y 3.5 0.5

3.5 log [mean x y

0.0 3.0 −1.5 −1.0 −0.5 0.0 Simulation by Inoue & Fukui (2013) x (pc)

10kms−1 1.2 (a) (b)

1.1 (pc) y

1.0 1pc −1.0 −0.9 −0.8 −0.7 −0.6 x (pc) z y x V-ﬁeld

Cores identiﬁed by CLUMPFIND (Fukui et al. 2019 submitted) Filaments and cores

toward massive cores (×10) (1) (2) 3 z (1) 10 102 14 10 y 1

12 (3) (2) 103 2 ) 1pc (4) 10 −2 Number of pixels

m N =5 10 c massive core

22 10 1

(10 3 (3) Nmassive core =7 10 8 102 (5) 10 1 6 (4) N =4 103 column density massive core 2 2

H 10 Number of pixels 4 10 (8) 1 (7) (6) (5) 103 2 102 10 1

N =1 3 (6) Nmassive core =9 (7) (8) massive core 10 102 10 Number of pixels 1 1020 1021 1022 1023 1020 1021 1022 1023 1020 1021 1022 1023 −2 −2 −2 NH2 (cm ) NH2 (cm ) NH2 (cm )

4 Histograms3 of column density Fig. 11. Column density map of H2 (low density gas with < 10 cm is excluded) in the y-z plane at t =0.7 Myr (top-left panel) and column density histogram in the 8 regions of 1.5 pc 1.5 pc (panels (1) – (8)). The crosses in the top-left panel show the positions of massive cores with Mcore > 10 M ⇥ eff and Mcore > 10M , and the dots show intermediate mass cores with Mcore =5– 10M . j

32 Identiﬁed dense cores

Core Mass Function eff Mcore >10M⊙ and Mcore >Mj 8

3 10 0.8 Axial ratio ±

Mcore >Mj eff 1.9

Mcore >Mj =

6 ) b ) / ⊙ W43 cores a

M 2

/ 10 (Motte et al. 2018) RCW38 cores (Torii et al. 2019) core c mean( /

M 4 b log( d

/ mean(b/c)=2.5±0.9 10

dN Kroupa (2001) IMF 2

Chabrier (2005) IMF

1 0 10−2 10−1 1 10 102 0 2 4 6 8 a/b Mcore (M⊙)

Massive cores are tend to be in oblate shape Angular momentum of the massive cores

L vs major-axis

Massive cores tend to be oblate, nd L vs 2 -major-axis and spinning around the minor axis

formation of massive binaries(?)

L vs minor-axis L vs B Conclusion • Super star clusters and very massive stars are likely to form by cloud-cloud collision • Galaxy interaction induces HI gas collision • Tidal interaction between the Magellanic clouds induced the cloud collision via HI gas exchange • Numerical simulation successfully reproduce dense cores from ﬁlaments • Collision of high column density clouds is preferable for massive cluster formation • The simulated massive cores tend to be in oblate shape spinning around the minor axis, and may evolve into BH binaries