(Proposal ID) S12B-043

(PI) Nishiyama, Shogo

(Proposal Title)
Two Modes of Star Formation at the Galactic Center?

(Abstract)
How stars form near the super massive black hole (SMBH) at the Galactic 
center, Sgr A*, has been a long-standing issue for more than two decades. The 
young, massive stars in the central 1pc are strongly concentrated toward the 
SMBH,  with hardly any found at > 0.5 pc from Sgr A*.  The distribution and 
dynamics of these stars combine with simulation  to support the idea that they 
were born in a massive accretion disk.  However, candidates for young, massive 
stars have been found recently  also at distances > 1pc from the SMBH, mainly 
through narrow-band imaging.  We propose spectroscopic observations to confirm 
the nature of  early-type star candidates within 0.5 - 3pc of Sgr A*.  If they 
are indeed young, massive stars, this observation would provide  strong 
evidence for the existence of different modes of star formation  at the 
Galactic center  because the stars at large distances cannot have formed in 
the same way  as the stars in the central 0.5pc.  Radial velocities measured 
in the proposed observations will be combined  with proper motions measured in 
our ongoing project,  to identify the origin of the early-type stars outside 
the central 0.5pc.