(Proposal ID) S12A-563

(PI) Matsunaga, Noriyuki

(Proposal Title)
Trajectories of Cepheid variable stars in the Galactic nuclear bulge

(Abstract)
The central region of our Galaxy provides us with a good opportunity to study 
the evolution of galactic nuclei and bulges because we can observe various 
phenomena in detail at the proximity of 8 kpc. There is a hierarchical 
alignment of stellar systems with different sizes; from the extended bulge, 
the nuclear bulge, down to the compact cluster around the central supermassive 
blackhole. The nuclear bulge contains stars as young as a few Myr, and even 
hosts the ongoing star formation. These are in contrast to the more extended 
bulge which are dominated by old stars, ~10Gyr. It is considered that the star 
formation in the nuclear bulge is caused by fresh gas provided from the inner 
disk. In this picture, the nuclear bulge plays an important role as the 
interface between the gas supplier, the inner disk, and the galactic nucleus. 
Kinematics of young stars in the nuclear bulge is important to discuss the 
star forming process and the gas circulation in the Galactic Center. We here 
propose spectroscopic observations of Cepheid variable stars, ~25 Myr, which 
we recently discovered in the nuclear bulge. The spectra taken in this 
proposal will allow timely estimates of the systemic velocities of the 
variable stars.