The composition of interstellar grains toward ζ ophiuchi: Constraining the elemental budget near the diffuse-dense cloud transition

Charles A. Poteet, Douglas C.B. Whittet, Bruce T. Draine

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

We investigate the composition of interstellar grains along the line of sight toward ζ Ophiuchi, a well-studied environment near the diffuse-dense cloud transition. A spectral decomposition analysis of the solid-state absorbers is performed using archival spectroscopic observations from the Spitzer Space Telescope and Infrared Space Observatory. We find strong evidence for the presence of sub-micron-sized amorphous silicate grains, principally comprised of olivine-like composition, with no convincing evidence of H2O ice mantles. However, tentative evidence for thick H2O ice mantles on large (a 2.8 μm) grains is presented. Solid-state abundances of elemental Mg, Si, Fe, and O are inferred from our analysis and compared to standard reference abundances. We find that nearly all of the Mg and Si atoms along the line of sight reside in amorphous silicate grains, while a substantial fraction of the elemental Fe resides in compounds other than silicates. Moreover, we find that the total abundance of elemental O is largely inconsistent with the adopted reference abundances, indicating that as much as 156 ppm of interstellar O is missing along the line of sight. After taking into account additional limits on the abundance of elemental O in other O-bearing solids, we conclude that any missing reservoir of elemental O must reside on large grains that are nearly opaque to infrared radiation.

Original languageEnglish (US)
Article number110
JournalAstrophysical Journal
Volume801
Issue number2
DOIs
StatePublished - Mar 10 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • ISM: abundances
  • ISM: molecules
  • dust, extinction
  • infrared: ISM
  • local interstellar matter
  • stars: individual (ζ Oph, HD 149757)

Fingerprint Dive into the research topics of 'The composition of interstellar grains toward ζ ophiuchi: Constraining the elemental budget near the diffuse-dense cloud transition'. Together they form a unique fingerprint.

  • Cite this