Two New and Remarkable Sightlines into the GC's Molecular Gas

T. R. Geballe(1), T. Oka(2)

(1) Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720
(2) Department of Astronomy and Astrophysics, Department of Chemistry, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637.

Paper: ApJ, 709, L70

EPrint Server: 09123885


Until now the known sources in the Galactic center with sufficiently smooth spectra and of sufficient brightness to be suitable for high resolution infrared absorption spectroscopy of interstellar gas occupied a narrow range of longitudes, from the central cluster of hot stars to approximately 30 pc east of the center. In order to more fully characterize the gas within the r 180 pc central molecular zone it is necessary to find additional such sources that cover a much wider longitudinal range of sightlines. We are in the process of identifying luminous dust-embedded objects suitable for spectroscopy within 1.2^o in longitude and 0.1^o in latitude of Sgr A* using the Spitzer GLIMPSE and the Two Micron All Sky Survey catalogues. Here we present spectra of H_3+ and CO towards two such objects, one located 140 pc west of Sgr A*, and the other located on a line of sight to the Sgr B molecular cloud complex 85 pc to the east of Sgr A*. The sightline to the west passes through two dense clouds of unusually high negative velocities and also appears to sample a portion of the expanding molecular ring. The spectra toward Sgr B reveal at least ten absorption components covering over 200 km s-1 and by far the largest equivalent width ever observed in an interstellar H_3+ line; they appear to provide the first near-infrared view into that hotbed of star formation.

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