4.7 Article

The structure of the local interstellar medium. II. Observations of DI, CII, NI, OI, AlII, and SiII toward stars within 100 parsecs

Journal

ASTROPHYSICAL JOURNAL
Volume 602, Issue 2, Pages 776-802

Publisher

UNIV CHICAGO PRESS
DOI: 10.1086/381083

Keywords

ISM : atoms; ISM : clouds; ISM : structure; line : profiles; ultraviolet : ISM; ultraviolet : stars

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Moderate- and high-resolution measurements (lambda/Deltalambda greater than or similar to 40,000) of interstellar resonance lines of D I, C II, N I, O I, Al II, and Si II (hereafter called light ions) are presented for all available observed targets located within 100 pc that also have high-resolution observations of interstellar Fe II or Mg II (heavy ions) lines. All spectra were obtained with the Goddard High Resolution Spectrograph or the Space Telescope Imaging Spectrograph instrument aboard the Hubble Space Telescope. Currently, there are 41 sight lines to targets within 100 pc with observations that include a heavy ion at high resolution and at least one light ion at moderate or high resolution. We present new measurements of light ions along 33 of these sight lines and collect from the literature results for the remaining sight lines that have already been analyzed. For all of the new observations we provide measurements of the central velocity, Doppler width parameter, and column density for each absorption component. We greatly increase the number of sight lines with useful local interstellar medium (LISM) absorption-line measurements of light ions by using knowledge of the kinematic structure along a line of sight obtained from high-resolution observations of intrinsically narrow absorption lines, such as Fe II and Mg II. We successfully fit the absorption lines with this technique, even with moderate-resolution spectra. Because high-resolution observations of heavy ions are critical for understanding the kinematic structure of local absorbers along the line of sight, we include 18 new measurements of Fe II and Mg II in an Appendix. We present a statistical analysis of the LISM absorption measurements, which provides an overview of some physical characteristics of warm clouds in the LISM, including temperature and turbulent velocity. This complete collection and reduction of all available LISM absorption measurements provides an important database for studying the structure of nearby warm clouds, including ionization, abundances, and depletions. Subsequent papers will present models for the morphology and physical properties of individual structures (clouds) in the LISM.

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