Astronomy and Astrophysics – Astrophysics
Scientific paper
1997-01-13
Astronomy and Astrophysics
Astrophysics
4 page LaTeX requires l-aa.sty and psfig.sty, 1 ps figure. Accepted for publication in A&A Letters
Scientific paper
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 (about 4 sigma) 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 N_D/N_H of 3.9+/-1.0 x 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 (about 24 x 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 about 6 from the primordial abundance.
Braun Robert
Burton William Butler
Chengalur Jayaram N.
No associations
LandOfFree
DI in the outer Galaxy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with DI in the outer Galaxy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and DI in the outer Galaxy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-24542