A High‐Abundance Arc in the Compact Group of Galaxies HCG 62: An AGN‐ or Merger‐Induced Metal Outflow?

Abstract

We present a Chandra study of the metal distribution in the X-ray bright compact group of galaxies HCG 62. We find that the diffuse X-ray emission is peaked at the core of the central galaxy NGC 4778 and is dominated by the contribution of the hot gas. The diffuse emission is roughly symmetric within ≃0.25′, which is straddled by doublesided X-ray cavities aligned in the northeast-southwest direction. By mapping the emission hardness ratio distributions and by performing a two-dimensional spectral analysis, we identify a remarkable high-abundance arc region at about 2′ (33.6 h 70 -1 kpc) from the X-ray peak that spans over a vast region from south to northwest, a part of which roughly coincides with the outer edge of the southwest X-ray cavity. The measured average abundance in this arc is higher than that in its neighboring regions by a factor of about 2, and the abundance ratios therein are nicely consistent with the dominance of the SN la yields. We estimate that the mass of iron contained in the arc is > 3 × 10 6 h 70 -2.5 M⊙, which accounts for > 3% of the iron synthesized in the galaxy. The high-abundance arc could have been formed by AGN activity. However, it is also possible that the arc was formed in a recent merger, as implied by the recent optical kinematic study by Spavone and colleagues, which suggests that mergers may be as important as AGN activity in metal redistributions in early-type galaxies and their associated groups or clusters. © 2007. The American Astronomical Society. All rights reserved.