2005/12/08 by Nikola Milutinovic, Nikola Milutinović, Jane R. Rigby +7 · 2 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/500314
published as Astrophys.J.641:190-209,2006 · 25 pages, 19 figures, 4 tables
arxiv created 2005/12/08 · openalex publication_date 2006/04/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We consider geometries and physical models for weak low-ionization absorbers based on the relative incidence of low- and high-ionization systems. We present a survey of weak low-ionization systems in 35 high-resolution HST STIS quasar spectra, sometimes supplemented by Keck HIRES and HST FOS data. We found 16 metal-line systems, with low- and/or high-ionization absorption detected. Weak low-ionization absorbers trace an abundant population of metal-enriched regions. Models show that these systems have a ~10 pc region of higher density gas and a ~1 kpc region that represents a lower density, higher ionization phase. The goal of our survey was to compare systems detected in low- and/or high-ionization gas. All but 1 of the 10 weak low-ionization systems have a related high-ionization phase. In three cases the high-ionization gas has only a single component, kinematically centered on the low-ionization absorption, and the other six cases have additional high-ionization components offset in velocity. The high-ionization absorption in weak low-ionization systems has similar kinematic structure to that in high-ionization-only systems. There are just six systems with only a high-ionization phase, as compared to the nine systems with both low- and high-ionization phases. We conclude that filamentary and sheetlike geometries are favored, due to the relatively small observed cross section of high-ionization-only systems. Our statistical arguments suggest that although low-ionization absorbers are not closely associated with luminous galaxies, they arise in their immediate environments within the cosmic web.