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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 607395.0, MPI für Astronomie / Publikationen_mpia
Absorption-line survey of H3+ toward the Galactic center sources. III. Extent of warm and diffuse clouds
Authors:Goto, M.; Usuda, T.; Geballe, T. R.; Indriolo, N.; McCall, B. J.; Henning, T.; Oka, T.
Date of Publication (YYYY-MM-DD):2011
Journal Abbrev.:Publications of the Astronomical Society of Japan
Volume:63
Issue / Number:2
Start Page:L13
End Page:L17
Audience:Not Specified
Abstract / Description:We present a follow-up observation on Geballe and Oka (2010, ApJ, 709, L70), who found high column densities of H3+ Ëœ 100 pc apart from the Galactic center on the lines of sight to 2MASS J17432173-2951430 (J1743) and 2MASS J17470898-2829561 (J1747). The wavelength coverages on these sightlines have been extended in order to observe two key transitions of H3+ - R(3, 3)l and R(2, 2)l - which constrain the temperature and density of the environment. The profiles of the H3+ R(3, 3)l line, which is due only to gas in the Galactic center, closely match the differences between the H3+ R(1, 1)l and CO line profiles, just as they do for previously studied sightlines in the Galactic center. Absorption in the R(2, 2)l line of H3+ is present in J1747 at velocities of between -60 and +100 km s-1. This is the second clear detection of this line in the interstellar medium after GC IRS 3 in the Central cluster. The temperature of the absorbing gas in this velocity range is 350 K, significantly warmer than that of diffuse clouds in other parts of the Central Molecular Zone. This indicates that the absorbing gas localizes on the Sgr B molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005, ApJ, 632, 882) apparently extends to Ëœ100 pc, but there is a hint that its temperature is somewhat lower in the line of sight to J1743 than elsewhere in the Galactic center. The observation of H3+ toward J1747 is compared with the recent Herschel observation of H2O+ toward Sgr B2, and their chemical relation and remarkably similar velocity profiles are discussed.
Free Keywords:Galaxy: center; ISM: clouds; ISM: lines and bands; ISM: molecules
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://cdsads.u-strasbg.fr/abs/2011PASJ...63L..13G
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