The Homogeneity of Interstellar Krypton in the Galactic Disk
Abstract
We present an analysis of high-resolution Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of Kr I λ1236 absorption in seven sight lines that probe a variety of interstellar environments. In combination with krypton and hydrogen column densities derived from current and archival STIS and Far-Ultraviolet Spectroscopic Explorer data, the number of sight lines with reliable Kr/H ISM abundance ratios has been increased by 50% to 26-including paths that sample a range of nearly 5 orders of magnitude in f(H2) and over 2 orders of magnitude in <nH>, and extend up to 4.8 kpc in length. For sight lines contained entirely within the local spiral arm (the Orion spur), the spread of Kr/H ratios about the mean of log10[N(Kr)/N(H)]ISM=-9.02+/-0.02 is remarkably tight (0.06 dex), less than the typical data-point uncertainty. Intriguingly, the only two sight lines that extend through neighboring structures, in particular gas associated with the Carina/Sagittarius arm, exhibit relatively large, near-solar krypton abundances (log10[N(Kr)/N(H)]combined=-8.75+0.09-0.11). Although these deviations are only measured at the 2 σ level, they suggest the possibility that krypton abundances beyond the Orion spur may differ from the local value.
Based on observations with the NASA/ESA Hubble Space Telescope (HST) and the NASA-CNES-CSA Far-Ultraviolet Spectroscopic Explorer (FUSE). HST spectra were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555 FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS-32985.- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2003
- DOI:
- 10.1086/378323
- arXiv:
- arXiv:astro-ph/0307182
- Bibcode:
- 2003ApJ...597..408C
- Keywords:
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- ISM: Abundances;
- Ultraviolet: ISM;
- Astrophysics
- E-Print:
- 15 page, including 3 figures and 2 tables, accepted for publication in ApJ