Colloq Abstract - Zhang

May 6, 2016

11am Mountain

 

Qizhou Zhang

CfA

 

How to Make Massive Stars

Massive stars dominate the appearance and the evolution of galaxies.  Despite their prominent role in shaping on the dynamics and chemistry of the interstellar medium, their birth is still poorly understood.  In the Milky Way, most young massive stars are found in parsec-scale molecular clumps with a cluster of companion stars. Therefore, massive star birth is linked to the collapse and fragmentation of molecular clouds and clustered star formation. The physical conditions (temperature and density) in a molecular clump limit the Jeans mass to about 1 Msun. This creates the first barrier for massive star formation since dense cores much larger than 1 Msun tend to further fragment into lower mass cores. Once protostars
reach 8-10 Msun, the radiation pressure may halt the infall and prohibit stars from further mass growth. As protostars reach more than 15 Msun, significant ionization may disrupt mass accretion as HII regions develop and expand.

In this talk, I will focus on the early stages of massive star formation:  the formation of massive cores. I will review recent studies that begin to shed light on how molecular clumps may collapse and fragment. I will discuss the implication of the findings to current theoretical ideas of massive star and cluster formation.

 

 

 

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