Origin of high-mass protostars in Cygnus-X

Transcription

1 T. Csengeri Service d Astrophysique, CEA-Saclay Supervisor: Co-advisor: Collaborators: S. Bontemps N. Schneider F. Motte F. Gueth P. Hennebelle S. Dib Ph. André 7. April From stars to Galaxies, Gainesville, Florida

2 Massive protostars: fundamental open issues Precursors of OB stars: How to collect such large mass? How to transform it into a star? slow (quasi-static) versus fast (dynamic) process Additional support needed to prevent fragmentation into M J objects (McKee & Tan 2003) high level of (isotropic) turbulence seeds for star-formation by gravo-turbulent fragmentation of the gas+competitive accretion (Bonnell & Bate 2006) dm/dt ~ c s 3 eff / G ~ M Sun /yr These processes can only be caught in the earliest phases of massive star and cluster formation Cygnus-X: Motte et al. (2007) revealed a complete sample of cores and clumps, many of them massive and young

3 Cygnus-X massive dense cores DR21 filament 6 IR-quiet massive dense cores (MDC) ten times more massive than in nearby regions M Sun ~ 0.1 pc prototypes of turbulence regulated cores We expect them to form massive stars, but how? turbulent line-widths tend to be small monolithic collapse to form a single massive star fragmentation into many M J objects Spitzer 8 micron image (Hora et al.) (McKee & Tan 2003) (Dobbs et al. 2005) PdBI follow-up at 1 and 3mm fragmentation + kinematics 1 ~ 1700 AU Bontemps, Motte, Csengeri and Schneider, 2009, arxiv:

4 Fragmentation of massive dense cores N3 N3 N12 N12 3mm continuum 1mm continuum N40 N M 10 M ~ AU N53 N pc N63 N63 ~0.2 pc N48 N48 Bontemps, Motte, Csengeri and Schneider, 2009, arxiv:

5 Fragmentation of massive dense cores CygX-N3 CygX-N48 84 M PdBI continuum 3.5 mm 3 arcsec res. (5000 AU) 8.1 M 6.3 M 197 M 10 M 7.0 M 0.1 pc 5000 AU CygX-N12 CygX-N53 86 M 85 M 22 M 11 M 13 M 14 M CygX-N40 CygX-N M 58 M 55 M ~0.2 pc PdBI - 3.5mm 0.2 pc PdBI - 1.3mm Bontemps 0.06 et pc al. (2009.) 5

6 Fragmentation of massive dense cores 84 M 8.1 M 6.3 M 197 M 10 M 7.0 M Fragments within MDCs masses: M SUN density: cm -3 self-gravitating objects 17 % 8.6 % 86 M 85 M 11 M 13 M 14 M 28 % 42 % 22 M a population of individual massive protostars IMF/SFE 30%: M max = 3.3 M (80 stars) In 3 cores: more than ~30% in 2 protostars not clear whether turbulent-core or gravoturbulent fragmentation + competitive accretion plays a role 106 M 58 M 55 M Kinematics at protostellar scales is essential! 1.) level of support 2.) level of dynamics (competitive accretion?) 95 % molecular line studies

7 Level of micro-turbulence Infall Rotation 3mm continuum overlay 0.2 pc 0.2 pc Red: HCO + Black: H 13 CO + Line position of H13 CO+ Large-scale global motions: contribution to the line-width Disentangle from large scale motions the get line-width due to microturbulence

8 Dense gas at high-resolution PdBI 3mm cont. SD+PdBI H13CO+ 3mm continuum + integrated intensity of H13CO Csengeri et al. (in prep.)

9 Turbulent support? We searched for support mechanism to stabilize MDCs line-width size relation ~0.03 pc turbulent support not enough on ~0.1 pc scales at smaller scales (~0.03 pc) even smaller line-widths...

10 Velocity field in MDCs reveal rich kinematics SD+PdBI H 13 CO + Velocity field map N3 Contribution from different spectral components reveal high level of dynamics Dynamic origin of the DR21 filament: Schneider, Csengeri et al arxiv: Diversity in fragmentation properties A large fraction of mass already in protostars MDCs in N63 high-density gas tracers seem to be very dynamic

11 Witnessing the birth of massive protostars Example: N53 Scale of protostars ~ 5000 AU (diameter) 1mm continuum 5000 AU Bontemps et al. (in prep.)

12 Summary Isolated massive dense cores MDCs are fragmented and show a diversity MDCs are biased towards massive fragments origin? Bontemps, Motte, Csengeri and Schneider (arxiv: ) Complex kinematics of dense gas at highresolution no evidence for turbulent support at smallscales indications for high level of dynamics Csengeri, Bontemps, Motte, and Schneider (in prep) Perspectives further investigations in Cygnus-X: magnetic field, deuterated lines and H 2 O lines with HIFI/Herschel (in progress) need to extend the sample to galactic scales ALMA will provide similar physical scales at larger distances DR21(OH)-clump Filament interacting with a subfilament The whole filament is in a global (large-scale) collapse Dynamical origin of the filament A cluster in formation with objects at different evolutionary state Velocity dispersion of individual protostars relative to the cluster? Line-widths of protostellar envelopes? progress Schneider, Csengeri et al. (arxiv: )...work in Thank you for your attention!