2003/10/16 by Barry McKernan, B. McKernan, Tahir Yaqoob +5 · 30 citations
Physics and Astronomy · #Absorption (acoustics) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Baryon #Cold dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intergalactic medium #Intergalactic travel #Line (geometry) #Line-of-sight #Lyman-alpha forest #Optics #Physics #Quasar #Redshift #astro-ph
paper · pdf · doi:10.1086/380775
published in The Astrophysical Journal 598(2), L83-L86 (IOP Publishing) · 4 pages, uses emulateapj.cls, ApJL (accepted)
arxiv created 2003/10/16 · openalex publication_date 2003/11/12 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We observed the Seyfert I active/broad-line radio galaxy 3C 120 with the Chandra high-energy transmission gratings and present an analysis of the soft X-ray spectrum. We identify the strongest absorption feature (detected at >99.9% confidence) with O VIII Lyα (FWHM = 1010 km s -1 ), blueshifted by -5500 ± 140 km s -1 from systemic velocity. The absorption may be due to missing baryons in a warm/hot intergalactic medium (WHIGM) along the line of sight to 3C 120 at z = 0.0147 ± 0.0005, or it could be intrinsic to the jet of 3C 120. Assuming metallicities of ~0.1 Z ☉ , we estimate an ionic column density of N O VIII > 3.4 × 10 16 cm - 2 for the WHIGM and a filament depth of less than 19 h Mpc. We find a baryon overdensity greater than 56 relative to the critical density of a Λ-dominated cold dark matter universe, which is in reasonable agreement with WHIGM simulations. We detect, at marginal significance, absorption of O VIII Lyα at z ~ 0 due to a hot medium in the Local Group. We also detect an unidentified absorption feature at ~0.71 keV. Absorption features that might be expected along with O VIII Lyα were not significant statistically. Relative abundances of metals in the WHIGM and local absorbers may therefore be considerably different from solar.