Galaxy Interactions in Compact Groups I : The Galactic Winds of HCG16

TL;DR

This study uses integral field spectroscopy to analyze the asymmetric bipolar galactic wind in NGC838, revealing insights into wind structure, excitation mechanisms, and early wind evolution in a compact group environment.

Contribution

First detailed analysis of the galactic wind in NGC838 within Hickson Compact Group 16, highlighting wind asymmetry and early-stage characteristics compared to similar galaxies.

Findings

Wind forms an asymmetric, bipolar, rotating structure.

Photoionization dominates at the wind base, with shock mixing increasing outward.

Wind differs from the symmetric wind in NGC839, indicating intrinsic galaxy properties influence wind characteristics.

Abstract

Using the WiFeS integral field spectrograph, we have undertaken a series of observations of star-forming galaxies in Compact Groups. In this first paper dedicated to the project, we present the analysis of the spiral galaxy NGC838, a member of the Hickson Compact Group 16, and of its galactic wind. Our observations reveal that the wind forms an asymmetric, bipolar, rotating structure, powered by a nuclear starburst. Emission line ratio diagnostics indicate that photoionization is the dominant excitation mechanism at the base of the wind. Mixing from slow shocks (up to 20%) increases further out along the outflow axis. The asymmetry of the wind is most likely caused by one of the two lobes of the wind bubble bursting out of its HI envelope, as indicated by line ratios and radial velocity maps. The characteristics of this galactic wind suggest that it is caught early (a few Myr) in the wind evolution sequence. The wind is also quite different to the galactic wind in the partner galaxy NGC839 which contains a symmetric, shock-excited wind. Assuming that both galaxies have similar interaction histories, the two different winds must be a consequence of the intrinsic properties of NGC838 and NGC839 and their starbursts.