2006/11/30 by Rik J. Williams, Smita Mathur, Fabrizio Nicastro +1 · 42 citations
Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intergalactic travel #Line (geometry) #Line-of-sight #Quasar #Redshift #Spectral line #astro-ph
paper · pdf · doi:10.1086/518818
published in The Astrophysical Journal 665(1), 247-256 (IOP Publishing) · 11 pages, 9 figures; minor changes, accepted to ApJ
arxiv created 2007/04/16 · openalex publication_date 2007/08/03 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The X-ray-bright z = 0.116 quasar PKS 2155-304 is frequently observed as a Chandra calibration source, with a total of 483 ks of Low Energy Transmission Grating (LETG) exposure time accumulated through May 2006. Highly ionized metal absorption lines, including numerous lines at z = 0 and a putative O VIII Kα line at z = 0.055, have been reported in past Chandra studies of this source. Using all available Chandra LETG spectra and analysis techniques developed for such z = 0 X-ray absorption along other sight lines, we revisit these previous detections. We detect four absorption lines at >3 σ significance (O VII Kα/β, O VIII Kα, and Ne IX Kα), with O VII Kα being a 7.3 σ detection. The 1 σ range of z = 0 O VII column density and Doppler parameter are consistent with that derived for Mrk 421 and within 2 σ of the Mrk 279 absorption. Temperatures and densities inferred from the relative O VII and other ionic column densities are found to be consistent with either the local warm-hot intergalactic medium or a Galactic corona. Unlike the local X-ray absorbers seen in other sight lines, a link with the low- or high-velocity far-ultraviolet O VI absorption lines cannot be ruled out. The z = 0.055 O VIII absorption reported by Fang et al. is seen with 3.5 σ confidence in the ACIS/LETG spectrum, but no other absorption lines are found at the same redshift.