Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21930204r&link_type=abstract
American Astronomical Society, AAS Meeting #219, #302.04
Astronomy and Astrophysics
Astronomy
Scientific paper
We present the results of an archival survey of neutron-capture elements in diffuse interstellar clouds from HST/STIS observations of over 50 Galactic sight lines. Existing measurements of the interstellar abundances of Kr, Rb, Cd, and Sn have indicated deficiencies in our understanding of the production of elements beyond the iron peak via slow and rapid neutron-capture processes. The elements Kr and Rb, which are primarily synthesized by massive stars through the weak s-process and the r-process, are found to be underabundant in interstellar gas compared to expectations based on current knowledge of dust depletion. At the same time, Cd and Sn, which are produced in larger part by the main s-process in low-mass AGB stars, exhibit less depletion than expected. By combining new abundance determinations for As, Cd, Sn, and Pb with recent surveys of Ga, Ge, Kr, and Rb, our study seeks to reveal the causes of the inferred deficit in the contribution from massive stars to the abundances of neutron-capture elements in the current epoch. We find that while Ga, Ge, and Pb follow normal depletion patterns, As is significantly overabundant, with an overall depletion level similar to Sn. Yet, unlike Sn, As is almost entirely a product of massive-star nucleosynthesis. The ultimate resolution of these discrepancies will likely involve a deeper understanding of dust grain depletion than presently exists.
This research was funded by the Space Telescope Science Institute through grant HST-AR-12123.
Federman Steven Robert
Lambert David L.
Ritchey Adam M.
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