THE STAR FORMATION NEWSLETTER No February /5/29

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1 THE STAR FORMATION NEWSLETTER No February /5/ Understanding star formation in molecular clouds II. Signatures of gravitational collapse of IRDCs to Cloud-cloud collision as a trigger of the highmass star formation; a molecular line study in RCW120 (D3)

2 Understanding star formation in molecular clouds II. Signatures of gravitational collapse of IRDCs! N.Schneider et al. Accepted by A&A IRDCs (infrared dark clouds) IRDCs - Dark, cold (< 25 K) absorption features, with high column density (N > cm -2 ) - GMC (not isolated features) - Span a large of mass and size, with and without star formation activity Massive and largest IRDCs: 1. The earliest stage of massive star formation (e.g. Rathborne et al. 2006) 2. Active and ongoing (massive) star formation (e.g. Carey et al. 2000)? Sample: 4 prominent, massive IRDCs

3 Data (全てarchive data) : 70, 170, 250, 350, 500 µm - Herschel Infrared GALactic plane survey - Galactic Ring Survey (by FCRAO) : 13CO(1-0) - CO High-Resolution Survey (by JCMT) : 12CO(3-2) - APEX Telescope Large Area Survey of the Galaxy : 870 µm Results

4 Results - Massive IRDCs are embedded in more extended molecular clouds - Similar physical properties (peak and average molecular clouds, surface density) as ridges (high column density regions with N > cm -2 over small areas) - Probability distribution function (PDF) of column density 4 IRDCs (3 (proto) stars 1 ) power-law power-law Large scale gravitational collapse Free-fall collapse of pre- and protostellar cores for the highest column densities log-normal power-law

5 An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud: I. Physical Properties of Filaments and Dense cores! Young Min Seo et al. Accepted by ApJ The formation filaments and the evolution from filaments to dense core Target : L1495-B218 filament - Prominent in the Taurus molecular cloud extending over 3 degrees on the sky - Contain cores that range from chemically young starless cores (e.g. L1521B, L1521E) to more evolved protostellar cores (in B7/L1495) - (e.g. dust extinction, dust continuum emission, 12 CO, 13 CO, C 18 O, N2H + ) Observation - Telescope : 100 m Green Bank Telescope - Frequency : NH3(1,1) ( GHz), NH3(2,2) ( GHz) - Angular resolution : 31, velocity resolution : km s -1

6 Results - 55 NH3 structures 39 leaves, 16 branches Gravitationally bound : 9 7/9, Gravitationally unbound : 30 12/30 pressure-confined Dense core pressure-confirmed structure gravitationally bound core collapse to form a protostar 500 μm dust continuum NH3 (1,1)

7 The properties of discs around planets and brown dwarfs as evidence for disc fragmentation! Dimitris Stamatellos and Gregory J. Herczeg Accepted by MNRAS Predictions of the disc fragmentation model regarding the properties of the discs around low-mass objects (planets, brown dwarfs) Method : Simulation - Stamatellos & Whitworth, Initial condition : M* = 0.7 M, MD = 0.7 M, RD = 400 AU!!! - Numerical method : SPH code DRAGON (Treats the radiation transport within the disc with the diffusion approximation of Stamatellos et al. 2007) The code uses time dependent viscosity with parameters α = 0.1, β = 2α

8 Results - Disk fragmentation low-mass objects disk mass, accretion rate Mdisk - M* relation, M* - M* relation! - scaling relation high-mass, low-mass

9 A Sub-arcsecond Survey Toward Class 0 Protostars in Perseus: Searching for Signatures of Protostellar Disks! John J. Tobin et al Accepted by ApJ CARMA 1.3 mm continuum survey toward 9 Class 0 protostars in the Perseus molecular cloud Observation - Telescope: CALMA - Frequency: GHz (1.3 mm), 12 CO(2-1), 13 CO(2-1), C 18 O(2-1) - Resolution: ~0.3 (~70 AU) - Follow-up observation: 12 CO(2-1), 13 CO(2-1), C 18 O(2-1), H 13 CO +, HCO + (4-3) by SMA Sample: 9 Class 0, 2 Class I

10 Results AU disk 2 L1448 IRS2, Per-emb-14 - Outflow marginally resolved structure 3 (L1448 IRS3C, IRAS , L1448C) disk - 2 Resolved structure (L1448 IRS3B, IRAS ) massive inner envelopes or disks - L1448 IRAS3B companion (separeted by 0.9 (~ 210 AU))

11 Cloud-cloud collision as a trigger of the high-mass star formation; a molecular line study in RCW 120! K.Trii et al Accepted by ApJ The present cloud-cloud collision scenario explains the observed signatures of RCW 120 Target : RCW Galactic HII region - Beautiful ring-like structure - O8V, O9V star Observation - Telescope : NANTEN, Mopra, ASTE - Emission : 12 CO(1-0), 13 CO(1-0) (by NANTEN, Mopra), C 18 O(1-0) (by Mopra), 12 CO(3-2) (by ASTE) - Resolution : 200 (NANTEN), 33 (Mopra), 22 (ASTE) - Velocity resolution : 0.17 km s -1 (NANTEN), km s -1 (Mopra), 0.43 km s -1 (ASTE)

12 Results - Blue cloud (-28 km s ), red cloud (-8 km s ) を検出 両cloudsのkinetic temperatures > ~ 30 K heated by O star and/or HII region - Expansion model を示す特徴見られない - Blue cloud, red cloudの衝突によって O star が形成されたと考えられる short timescale Myr

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