DI in the outer galaxy

Chengalur, Jayaram N. ; Braun, Robert ; Butler Burton, W. (1997) DI in the outer galaxy Astronomy & Astrophysics, 318 . L35-L38. ISSN 0004-6361

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Official URL: http://arxiv.org/PS_cache/astro-ph/pdf/9701/970105...


We report on a deep search with the Westerbork Synthesis Radio Telescope towards the galactic anticenter for the 327 MHz hyperfine transition of DI. This is a favorable direction for a search because: (i) the HI optical depth is high due to velocity crowding; (ii) the observed molecular column density is low (implying that most of the deuterium would probably be in atomic form, rather than in HD); and (iii) the stellar reprocessing should be minimal. Our observations are about a factor of two more sensitive than previous searches for DI in this direction. We detect a low significance (~ 4 σ) feature, consistent in both amplitude and center frequency with an emission feature reported previously (Blitz & Heiles 1987). If this is the DI line, then the implied ND/NH of 3.9±1.0×10−5 is comparable to the inferred pre-solar deuterium abundance. Our observation is consistent with the recent low measurements of D/H towards high-redshift Lyman-limit systems. On the other hand, if the reports of high DI abundance (˜ 24 × 10−5) in such systems are confirmed, then our observations imply that even in regions of reduced star formation within the outer Galaxy, the DI abundance has been reduced by a factor of ~ 6 from the primordial abundance.

Item Type:Article
Source:Copyright of this article belongs to EDP Sciences.
Keywords:Cosmology: Observations; ISM: Abundances; Galaxy: Abundances; Radio Lines: ISM
ID Code:63524
Deposited On:29 Sep 2011 04:02
Last Modified:29 Sep 2011 04:02

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