The Galactic Environment of the NeVIII Absorber toward HE0226-4110

TL;DR

This study identifies a galaxy system near a NeVIII absorber and suggests that a conductive front between cool clouds and hot gas best explains the observed absorption features, indicating a hot gas reservoir around the galaxy.

Contribution

It presents the discovery of a galaxy system near a NeVIII absorber and proposes a novel explanation involving conductive fronts for the origin of the absorption.

Findings

The galaxy system consists of two 0.25 L* disk galaxies and a 0.05 L* galaxy within 200 h^{-1} kpc.

The conductive front scenario explains the multi-phase gas and absorption profiles.

NeVIII absorption likely traces hot gas in a galaxy halo rather than the intergalactic medium.

Abstract

We report the discovery of a small galaxy system in the vicinity of the NeVIII absorber at z=0.20701 toward HE0226-4110. The galaxy system consists of two 0.25 L* disk galaxies and a 0.05 L* galaxy all within \Delta v < 300 km/s and rho< 200 h^{-1} physical kpc of the absorber. We consider various scenarios for the origin of the NeVIII absorption, including photo-ionized gas from a AGN, a starburst driven wind, a hot intragroup medium, hot gas in a galaxy halo, and a conductive front produced by cool clouds moving at high speed through a hot medium. We argue that the conductive front scenario is most likely responsible for producing the NeVIII feature, because it is consistent with the observed galactic environment around the absorber and because it naturally explains the multi-phase nature of the gas and the kinematic signatures of the absorption profiles. Although our preferred scenario suggests that NeVIII may not be directly probing the warm-hot intergalactic medium, it does imply the existence of an extended hot confining medium around a disk galaxy that may contain a significant reservoir of baryons in the form of hot gas.