Deep Chandra Observations of HCG 16 - II. The Development of the Intra-group Medium in a Spiral-Rich Group

TL;DR

This study uses deep X-ray and radio observations to analyze the origin, composition, and state of the intra-group medium in the spiral-rich HCG 16, revealing a multi-phase, non-virialized environment influenced by galactic winds.

Contribution

It provides new insights into the multi-phase nature and origin of the intra-group medium in a spiral-rich galaxy group, highlighting the role of galactic winds in hot gas enrichment.

Findings

Detected faint, low-temperature intra-group medium extending across the group.

Identified a ridge of hot gas linked to HI tidal filaments.

Estimated that galactic winds contribute 20-40% of the hot gas.

Abstract

We use a combination of deep Chandra X-ray observations and radio continuum imaging to investigate the origin and current state of the intra-group medium in the spiral-rich compact group HCG 16. We confirm the presence of a faint ($L_{X,{\rm bolo}}$=1.87$^{+1.03}_{-0.66}$$\times$10$^{41}$ erg/s), low temperature (0.30$^{+0.07}_{-0.05}$ keV) intra-group medium (IGM) extending throughout the ACIS-S3 field of view, with a ridge linking the four original group members and extending to the southeast, as suggested by previous Rosat and XMM-Newton observations. This ridge contains 6.6$^{+3.9}_{-3.3}$$\times$10$^9$ solar masses of hot gas and is at least partly coincident with a large-scale HI tidal filament, indicating that the IGM in the inner part of the group is highly multi-phase. We present evidence that the group is not yet virialised, and show that gas has probably been transported from the starburst winds of NGC 838 and NGC 839 into the surrounding IGM. Considering the possible origin of the IGM, we argue that material ejected by galactic winds may have played a significant role, contributing 20-40% of the observed hot gas in the system.