1 / 15

Early Phases of Massive Star Formation

Early Phases of Massive Star Formation. Qizhou Zhang Harvard-Smithsonian Center for Astrophysics. Motivation How parsec scale clumps  massive cluster? What controls initial fragmentation (thermal, turbulent, magnetic fields)?

alvaro
Download Presentation

Early Phases of Massive Star Formation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Early Phases of Massive Star Formation Qizhou Zhang Harvard-Smithsonian Center for Astrophysics Motivation • How parsec scale clumps  massive cluster? • What controls initial fragmentation (thermal, turbulent, magnetic fields)? • What are the physical/chemical properties? And how do these properies evolve? • Approach: Select massive molecular clumps of 103 Msun with L<103 Lsun, and high column/volume densities Townsville, Australia

  2. OMC Northern Region L~ 103-4 Lsun H2O maser T>30K. Δv > 3.5 km/s More evolved P2 880 Msun 38 Msun 4pc P1 Southern Region L<102 Lsun T<20K Δv < 2 km/s Younger region 1000 Msun 0.1 pc 22 Msun Fragmentation in IRDC G28.34 P1 will evolve into P2 VLA NH3 (Contours) Spitzer 8μm(color) 1.2mm continuum IRDC G28.34 HII region 3’ 4.3pc Zhang, Wang, Pillai, Rathborne 2009; Wang, Zhang, Pillai, Wyrowski, Wu 2008 Wang, Zhang, Rathborne, Jackson, Wu 2006; Rathborne et al. 2006 Townsville, Australia

  3. Li, Goldsmith, Menten 2003 Li, Valusamy, Goldsmith, Langer 2007 T vs. NH3 flux density Early clump (P1) is externally heated! P2: internally heated P1: externally heated Wang, Zhang, Pillai, et al. 2007 Townsville, Australia

  4. 38 Msun 0.1 pc 22 Msun Source Parameters n(H2)=3x105 cm-3, T=16K MJ (thermal) = 1 Msun LJ = 0.05 pc Rms 1 mJy 0.8 Msun For Spatially resolved Cores (res < LJ) Mcore/MJ ~ 10 - 102  ΔV=1.7 km/s MVir ~ 24 Msun Turbulence support or B field stops fragmentation Townsville, Australia

  5. 38 Msun 0.1 pc 22 Msun Further Fragmentation: G28.34 New observations at 870 micron reach an rms of 0.15 Msun, 1/6 of Jeans mass Cores further fragment into condensations at a res ~ 0.5” M(core) = 1.4 – 8.2 Msun. Lower mass cores not detected, possibly due to selection effect CO 3-2 SMA 870μm Well collimated outflows (disk accretion) from intermediate-mass protostars that will likely become high-mass protostellar objects Wang, Zhang et al. in preparation,2010 Townsville, Australia

  6. A ‘Fragmented’ Family Massive molecular clumps of 103 Msun, ~ 1pc in size M(core) = 10 – 100 Msun d(core) <0.1pc in size T = 11-20 K V = 1.5 kms-1 Turbulence support helps the formation of massive cores 870μm NH3 1pc Wang, Zhang et al. in preparation, 2010 Swift 2009 Townsville, Australia

  7. What do these results mean? Competitive AccretionMcore ~ MJ (0.5 Msun) Mcore>> MJ Disk accretion Core Bonnell et al. 2001, 2004 Turbulent Core Collapse Massive cores are connected to molecular clump Don’t find 102 Msun starless cores f * Mcore ~ M* McKee & Tan 2002 Townsville, Australia

  8. SMA, 3”: Warm core spectra 4 pc Chemistry: From Cold to Warm Core 1.2 mm Continuum G28.34+0.06: Warm Core T=40K L~103 Lsun X(CH3OH) = 3 x 10-10 SMA, 3”: Cold core spectra CO depletion > 100 over 0.1 pc Cold Core T=15K L~102 Lsun X(CH3OH) = 10-12- 10-11 2GHz Zhang et al. 2009 Townsville, Australia

  9. Hot Core in G34.43 SMA IRDC G28.53: Depletion IRAM 30m Spectra < 700 Lsun 1200 Msun Rathborne, Jackson, Zhang, Simon 2008. Townsville, Australia

  10. From Cold Core to Hot Cores T, Mass, Luminosity T = 15 K T = 40K T = 200K Hot Core: T=200 K X(CH3OH) = 3 x 10-8 Cold Core: T=15 K Warm Core: T=40 K Townsville, Australia

  11. Chemical Evolution: Cold Core to Hot Core Follow dynamic collapse and chemical evolution (depletion) under a constant T Turn on protostellar heating and follow chemical evolution in gas phase See Viti et al. 2004 Van Dishoeck & Blake 1998 With Jimenez-Sierra, Viti et al. CO CH3OH CH3OH Townsville, Australia

  12. SMA follow up of Herschel Objects M(Clump) > 500-1000 Msun Far IR SEDs show different Tdust 24 m dark to light With Smith, Jimenez-Serra, Molinari, Cesaroni, Beltran, Jackson, Foster, Finn Evolution 4GHz Townsville, Australia

  13. Conclusions • Massive cores after the early fragmentation 10x to 102x more massive than thermal Jeans mass  Important role of turbulence support and/or magnetic fields. • Dense cores harboring massive stars undergo significant increase in temperature (and mass). As a result, they undergo chemical evolution during the early evolution. • These studies will provide more realistic initial conditions to theoretical work. Townsville, Australia

  14. Source Parameters LJ = 0.025 pc (1”) For Spatially resolved condesnation (res < LJ) Mcore/MJ >~ 10 ΔV=?? km/s Require ALMA Townsville, Australia

  15. Density Structures in G28.34(Cores in Equilibrium?) Northern active region b = 1.6+-0.1: SIS? b = 2.1+-0.2: Self-gravitating, hydrostatic core?? Southern quiescent region: SMA4 Zhang, Wang, Pillai, Rathborne 2009 Townsville, Australia

More Related