The XXL Survey XLV. Linking the ages of optically selected groups to their X-ray emission
J. P. Crossett, S. L. McGee, T. J. Ponman, M. E. Ramos-Ceja, M. J. I., Brown, B. J. Maughan, A. S. G. Robotham, J. P. Willis, C. Wood, J., Bland-Hawthorn, S. Brough, S. P. Driver, B. W. Holwerda, A. M. Hopkins, J., Loveday, M. S. Owers, S. Phillipps, M. Pierre, K. A. Pimbblet

TL;DR
This study links optical group properties with X-ray emission, revealing that X-ray luminous groups are more evolved, with fewer star-forming galaxies and more dominant central galaxies, indicating different evolutionary stages.
Contribution
It provides the largest combined optical and X-ray dataset for galaxy groups, analyzing their properties to understand the connection between X-ray emission and group evolution.
Findings
X-ray overluminous groups have fewer blue and star-forming galaxies.
Overluminous groups possess more dominant central galaxies with larger magnitude gaps.
Some underluminous groups are dynamically mature despite weak X-ray emission.
Abstract
We investigate the properties of 232 optical spectroscopically selected groups from the Galaxy And Mass Assembly (GAMA) survey that overlap the XXL X-ray cluster survey. X-ray aperture flux measurements combined with GAMA group data provides the largest available sample of optical groups with detailed galaxy membership information and consistently measured X-ray fluxes and upper limits. 142 of these groups are divided into three subsets based on the relative strength of X-ray and optical emission, and we see a trend in galaxy properties between these subsets: X-ray overluminous groups contain a lower fraction of both blue and star forming galaxies compared with X-ray underluminous systems. X-ray overluminous groups also have a more dominant central galaxy, with a magnitude gap between first and second ranked galaxies on average 0.22 mag larger than in underluminous groups. The central…
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Taxonomy
TopicsAstrophysical Phenomena and Observations · Galaxies: Formation, Evolution, Phenomena · Gamma-ray bursts and supernovae
