(Proposal ID) S11A-035

(PI) Oka, Takeshi

(Proposal Title)
Studies of Gas near the Galactic Center using Infrared Spectrum of H_3^+

(Abstract)
Following up our inspiring observations at the Subaru Telescope using IRCS 
this May (S10A-113) of high column densities of H_3^+ in (1,0), (1,1), (2,2) 
and (3,3) rotational levels toward the two newly found hot and bright dust 
embedded stars, we propose to observe the H_3^+ spectrum for a dozen stars 
widely distributed in the Central Molecular Zone from 140 pc West to 120 pc 
East of Sgr A*. The wide wavelength coverage of the IRCS with its cross 
dispersing grating is ideal for this purpose and will allow us to observe the 
needed spectral lines simultaneously. The new stars qualified for the H_3^+ 
spectroscopy have been selected from stars catalogued by the Spitzer Telescope 
by our parallel project of their low resolution CO spectroscopy. This project 
will extend our previous discovery of warm (T ~ 250 K) and diffuse (n ~ 
100 cm^-3) environment with a large volume filling factor from the center to 
30 pc East to wider regions of the CMZ.