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The Homogeneity of Interstellar Krypton in the Galactic Disk

Stefan I. B. Cartledge·David M. Meyer·J. T. Lauroesch
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Abstract

We present an analysis of high resolution HST Space Telescope Imaging Spectrograph (STIS) observations of Kr I 1236 Angstrom 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(H_2), over 2 orders of magnitude in , and extending 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 log_10[N(Kr)/N(H)]_ISM = -9.02+/-0.02 is remarkably tight (0.06 dex), less than the typical datapoint 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 (log_10[N(Kr)/N(H)]_combined = -8.75+0.09_-0.11). Although these deviations are only measured at the 2 sigma level, they suggest the possibility that krypton abundances beyond the Orion Spur may differ from the local value.

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Stefan I. B. Cartledge, David M. Meyer, J. T. Lauroesch. 2003-07-09. The Homogeneity of Interstellar Krypton in the Galactic Disk. https://doi.org/10.1086/378323

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