2003/02/14 by Jie Ding, J. Ding, J. C. Charlton +5 · 2 citations
Chemistry · Physics and Astronomy · #Absorption spectroscopy #Analytical Chemistry (journal) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble space telescope #Intergalactic medium #Ion #Ionization #Lyman limit #Optics #Photoionization #Physics #Quasar #Redshift #Resolution (logic) #Space Telescope Imaging Spectrograph #Spectral line #Spectrograph #Telescope #astro-ph
paper · pdf · doi:10.1086/368250
published as Astrophys.J. 587 (2003) 551-561 · 25 pages, 4 figures; to appear in ApJ, April 20, 2003
arxiv created 2003/02/14 · openalex publication_date 2003/04/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The z = 0.9902 system along the quasar PG 1634+706 line of sight is a strong Mg II absorber [ W r (λ2796) > 0.3 Å] with only weak C IV absorption (it is "C IV-deficient"). To study this system, we used high-resolution spectra from both the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) and the Keck I telescope High Resolution Echelle Spectrometer (HIRES). The STIS spectrum has a resolution of R = 30,000 and covers key transitions such as Si II, C II, Si III, C III, Si IV, and C IV. The HIRES spectrum, with a resolution of R = 45,000, covers the Mg I, Mg II, and Fe II transitions. Assuming a Haardt & Madau extragalactic background spectrum, we modeled the system with a combination of photoionization and collisional ionization. Based on a comparison of synthetic spectra with the data profiles, we infer the existence of the following four phases of gas: