Probing interstellar silicate dust grain properties in quasar Absorption systems at redshifts z<1.4

Monique C. Aller, Varsha P. Kulkarni, Donald G. York, Daniel E. Welty, Giovanni Vladilo, Debopam Som

Research output: Contribution to journalConference articlepeer-review

Abstract

Absorption lines in the spectra of distant quasars whose sightlines serendipitously pass through foreground galaxies provide a valuable tool to simultaneously probe the dust and gas compositions of the interstellar medium (ISM) in galaxies. In particular, the damped and sub-damped Lymana (DLA/sub-DLA) absorbers trace gas-rich galaxies, independent of the intrinsic luminosities or star-formation rates of the associated galaxy stellar populations. The first evidence of silicate dust in a quasar absorption system was provided through our detection of the 10 mm silicate feature in the z=0.52 DLA absorber toward the quasar AO 0235+164. We present results from 2 follow-up programs using archival Spitzer Space Telescope infrared spectra to study the interstellar silicate dust grain properties in a total of 13 quasar absorption systems at 0.1 < z < 1.4. We find clear detections of the 10 mm silicate feature in the quasar absorption systems studied. In addition, we also detect the 18 mm silicate feature in the sources with adequate spectral coverage. We find variations in the breadth, peak wavelength, and substructure of the 10 mm interstellar silicate absorption features among the absorbers. This suggests that the silicate dust grain properties in these distant galaxiesmay differ relative to one another, and relative to those in the Milky Way. We also find suggestions in several sources, based on comparisons with laboratory-derived profiles from the literature, that the silicate dust grains may be significantly more crystalline than those in the amorphous Milky Way ISM. This is particularly evident in the z=0.89 absorber toward the quasar PKS 1830-211, where substructure near 10 mm is consistent with a crystalline olivine composition. If confirmed, these grain property variations may have implications for both dust and galaxy evolution over the past 9 Gyrs, and for the commonly-made assumption that highredshift dust is similar to local dust. We also discuss indications of trends between silicate dust absorption strength and both carbonaceous dust properties and gas-phase metal properties, such as the gas velocity spread, determined from UV/optical spectra.

Original languageEnglish
JournalProceedings of Science
StatePublished - 2013
EventLife Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments, LCDU 2013 - Taipei, Taiwan, Province of China
Duration: Nov 18 2013Nov 22 2013

Scopus Subject Areas

  • General

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