Detection of Low Metallicity Warm Plasma in a Galaxy Overdensity Environment at z ~ 0.2

Abstract

We present results from the analysis of a multiphase O VI - broad Ly-alpha absorber at z = 0.19236 in the HST/COS spectrum of PG 1121+422. The low and intermediate ionization metal lines in this absorber have a single narrow component, whereas the Ly-alpha has a possible broad component with b(HI) $\sim 71$ km/s. Ionization models favor the low and intermediate ions coming from a $T\sim 8,500$ K, moderately dense photoionized gas with near solar metallicities. The weak O VI requires a separate gas phase that is collisionally ionized. The O VI coupled with BLA suggests $T\sim 3.2\times 10^5$ K, with significantly lower metal abundance and $\sim 1.8$ orders of magnitude higher total hydrogen column density compared to the photoionized phase. SDSS shows 12 luminous ($>L^{\ast }$) galaxies in the $\rho \le 5$ Mpc, $|\Delta v|\le 800$ km/s region surrounding the absorber, with the absorber outside the virial bounds of the nearest galaxy. The warm phase of this absorber is consistent with being transition temperature plasma either at the interface regions between the hot intragroup gas and cooler photoionized clouds within the group, or associated with high velocity gas in the halo of a $\lesssim L^{\ast }$ galaxy. The absorber highlights the advantage of O VI-BLA absorbers as ionization model independent probes of warm baryon reserves.

MNRAS Accepted, 16 pages, 8 figures

References in corpus (17)

• The 1% Concordance Hubble Constant
• Time-Dependent Ionization in Radiatively Cooling Gas
• The Search for the Missing Baryons at Low Redshift
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• Halo Gas Cross Sections And Covering Fractions of MgII Absorption Selected Galaxies
• HST-COS Observations of AGN. II. Extended Survey of Ultraviolet Composite Spectra from 159 Active Galactic Nuclei
• The Nature and Origin of Low-Redshift O VI Absorbers
• The Properties of Low Redshift Intergalactic O VI Absorbers Determined from High S/N Observations of 14 QSOs with the Cosmic Origins Spectrograph
• The Photon Underproduction Crisis
• On the HI content, dust-to-gas ratio and nature of MgII absorbers
• Absorption signatures of warm-hot gas at low redshift: OVI
• The Chemical and Ionization Conditions in Weak Mg II Absorbers
• HST/COS detection of a Ne VIII absorber towards PG 1407+265: An unambiguous tracer of collisionally ionized hot gas?
• The Warm Circum-Galactic Medium: 10^5-6 K Gas Associated with a Single Galaxy Halo or with an Entire Group of Galaxies?
• Super-Solar Metallicity in Weak Mg II Absorption Systems at z ~ 1.7
• A hot gaseous galaxy halo candidate with Mg X absorption

Cited by in corpus (3)

• Physical Conditions of Five O VI Absorption Systems Towards PG $1522+101$
• Detection of a Multiphase Intragroup Medium: Results from the COS-IGrM Survey
• Pair Lines of Sight Observations of Multiphase Gas Bearing O VI in a Galaxy Environment