Massive compact galaxies with high-velocity outflows: morphological analysis and constraints on AGN activity

Type Journal Article
Names P. H. Sell, C. A. Tremonti, R. C. Hickox, A. M. Diamond-Stanic, J. Moustakas, A. Coil, A. Williams, G. Rudnick, A. Robaina, J. E. Geach, S. Heinz, E. M. Wilcots
Publication Monthly Notices of the Royal Astronomical Society
Volume 441
Issue 4
Pages 3417-3443
Journal Abbreviation Monthly Notices of the Royal Astronomical Society
Date July 1, 2014
DOI 10.1093/mnras/stu636
ISSN 0035-8711
Short Title Massive compact galaxies with high-velocity outflows
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Abstract We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z ˜ 0.6) that host high-velocity ionized gas outflows (v > 1000 km s-1). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGNs). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their stellar mass, even when compared with galaxies at z ˜ 2-3. For 9/12 galaxies, we rule out an AGN contribution to the nuclear light and hypothesize that the unresolved core comes from a compact central starburst triggered by the dissipative collapse of very gas-rich progenitor merging discs. We find evidence of AGN activity in half the sample but we argue that it accounts for only a small fraction (≲10 per cent) of the total bolometric luminosity. We find no correlation between AGN activity and outflow velocity and we conclude that the fast outflows in our galaxies are not powered by ongoing AGN activity, but rather by recent, extremely compact starbursts.
Tags GALAXIES: EVOLUTION, GALAXIES: INTERACTIONS, galaxies: active, galaxies: starburst
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