(Proposal ID) S10A-113

(PI) Oka, Takeshi

(Proposal Title)
H_3^+ studies of sightlines toward new YSOs near the Galactic center

(Abstract)
Following up our exciting discovery at the Gemini South Observatory this summer
 of large column densities of H_3^+ with extremely rich velocity profiles 
toward newly found YSOs, we propose to use IRCS on the Subaru Telescope to 
obtain high resolution spectra of H_3^+ and CO toward the YSOs. So far our 
discovery is limited to H_3^+ in the lowest (J, K) =(1, 1) rotational level, 
and we will extend observations to other rotational levels (1, 0), (2, 2), 
and (3, 3) to determine temperature and density of the gas toward the new 
stars. We will also attempt to discover H_3^+ in higher metastable levels 
(4, 4), (5, 5), (6, 6), and also observe CO and CH. The wide wavelength 
coverage of the IRCS with the cross dispersing grating is singularly suited 
for this purpose and will allow us to observe many spectral lines 
simultaneously. So far our understanding of the physical and chemical nature 
of the gas in the Central Molecular Zone (CMZ) has been limited to the central 
region from the center to 30 pc to the East, but the proposed observation 
using YSOs which spans a wide region of the CMZ from 100 pc East to 140 West 
of Sgr A* will give us much more general picture of the gas in the region.