Fresh Activity in Old Systems: Radio AGN in Fossil Groups of Galaxies

Type Conference Paper
Names Kelley M. Hess, E. M. Wilcots, V. L. Hartwick
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #219, #403.08
Volume 219
Date January 1, 2012
Short Title Fresh Activity in Old Systems
Library Catalog NASA ADS
Abstract We present the first systematic VLA 1.4 GHz radio survey of candidate fossil galaxy groups: systems believed to have formed over a gigayear in the past through the merger of group members into a single, massive elliptical galaxy. We find that 3 of the candidates are clearly not fossil groups based on new photometry from SDSS DR7. Of the remaining 30 fossil groups, we find that 67% contain a radio-loud (L1.4GHz > 1023 W Hz-1) active galactic nucleus (AGN) at the center of the dominant elliptical galaxy. We compare the radio observations with optical photometry and X-ray luminosities in order to connect the properties of the AGN with the properties of the group environment, or the properties of the remnant elliptical galaxy. The radio luminosity may be weakly correlated to the X-ray luminosity of the halo, however there is no correlation between the radio and optical luminosities of the central galaxy. This suggests that the AGN frequency in fossil groups is independent of their formation history. We compare the AGN frequency with that of other galaxy populations. Finally, we discuss the possibilities for fueling an AGN in the present day, long after the fossil group has undergone its last major merger.
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