Detection of metal-rich, cool-warm gas in the outskirts of galaxy clusters

Jayadev Pradeep, Anand Narayanan, Sowgat Muzahid, Daisuke Nagai, Jane C. Charlton, Raghunathan Srianand

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Abstract

We present an ultraviolet quasar absorption line analysis of metal lines associated with three strong intervening H I absorbers (with N(H I) > 1016.5 cm−2) detected in the outskirts of Sunyaev-Zel'dovich (SZ) effect-selected galaxy clusters (zcl ∼ 0.4-0.5), within clustocentric impact parameters of ρcl ∼ (1.6-4.7)r500. Discovered in a recent set of targeted far-UV HST/COS spectroscopic observations, these absorbers have among the highest H I column densities ever observed in the outskirts of galaxy clusters, and are also rich in metal absorption lines. Photoionization models yield single phase solutions for the three absorbers with gas densities of nH ∼ 10−3-10−4 cm−3 and metallicities of [X/H] > −1.0 (from one-tenth solar to near-solar). The widths of detected absorption lines suggest gas temperatures of T ∼ 104 K. The inferred densities (temperatures) are significantly higher (lower) compared to the X-ray emitting intracluster medium in cluster cores. The absorbers are tracing a cool phase of the intracluster gas in the cluster outskirts, either associated with gas stripped from cluster galaxies via outflows, tidal streams or ram-pressure forces, or denser regions within the intracluster medium that were uniformly chemically enriched from an earlier epoch of enhanced supernova and Active Galactic Nucleus (AGN) feedback.

Original languageEnglish (US)
Pages (from-to)5327-5339
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume488
Issue number4
DOIs
StatePublished - Jan 1 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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