15min:
ABSORPTION LINE SURVEY OF H3+ TOWARD THE GALACTIC CENTER.

MIWA GOTO, Subaru Telescope, 650, North A'ohoku Place, Hilo HI 96720/ Institute for Astronomy, University of Hawaii, 640 North A'ohoku Place, Hilo HI 96720; B. J. MCCALL, Department of Chemistry and Department of Astronomy, University of California, 601, Campbell Hall, Berkeley, CA 94720; T. R. GEBALLE, Gemini Observatory, 670, North A'ohoku Place, Hilo HI 96720; TAKESHI OKA, T. USUDA.

We present high-resolution (R = 20000) spectroscopy of H3+ absorption toward the luminous Galactic center sources GCS~3-2 and GC IRS~3. With the efficient wavelength coverage afforded by a new generation spectrograph available at the 8-m class telescope, six absorption lines of H3+ have been detected in each source, three of which are new. In particular the 3.543~µm absorption line of the R(3, 3)l transition arising from the metastable (J, K) = (3, 3) state has been tentatively detected for the first time in the interstellar medium. The H3+ absorption toward the Galactic center takes place in dense and diffuse clouds along the line of sight as well as the molecular complex close to the Galactic nucleus. At least four kinematic components are found in the H3+ absorption lines. We suggest identifications of the velocity components with those of H i, CO, and H2CO previously reported from radio and infrared observations. Our observation has revealed a striking difference between the absorption profiles of H3+ and CO, demonstrating that the spectroscopy of H3+ provides information complementary to that obtained from CO spectroscopy.