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arXiv · 1507.03022

High Radio Frequency Properties and Variability of Brightest Cluster Galaxies

M. T. Hogan·A. C. Edge·J. E. Geach·K. J. B. Grainge·J. Hlavacek-Larrondo·T. Hovatta·A. Karim·B. R. McNamara·C. Rumsey·H. R. Russell·P. Salomé·H. D. Aller·M. F. Aller·D. J. Benford·A. C. Fabian·A. C. S. Readhead·E. M. Sadler·R. D. E. Saunders
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Abstract

We consider the high radio frequency (15 GHz - 353 GHz) properties and variability of 35 Brightest Cluster Galaxies (BCGs). These are the most core-dominated sources drawn from a parent sample of more than 700 X-ray selected clusters, thus allowing us to relate our results to the general population. We find that >6.0% of our parent sample (>15.1% if only cool-core clusters are considered) contain a radio-source at 150 GHz of at least 3mJy (~1x10^23 W/Hz at our median redshift of z~0.13). Furthermore, >3.4% of the BCGs in our parent sample contain a peaked component (Gigahertz Peaked Spectrum, GPS) in their spectra that peaks above 2 GHz, increasing to >8.5% if only cool-core clusters are considered. We see little evidence for strong variability at 15 GHz on short (week-month) time-scales although we see variations greater than 20% at 150 GHz over 6-month times-frames for 4 of the 23 sources with multi-epoch observations. Much more prevalent is long-term (year-decade time-scale) variability, with average annual amplitude variations greater than 1% at 15 GHz being commonplace. There is a weak trend towards higher variability as the peak of the GPS-like component occurs at higher frequency. We demonstrate the complexity that is seen in the radio spectra of BCGs and discuss the potentially significant implications of these high-peaking components for Sunyaev-Zel'dovich cluster searches.

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M. T. Hogan, A. C. Edge, J. E. Geach, K. J. B. Grainge, J. Hlavacek-Larrondo, T. Hovatta, A. Karim, B. R. McNamara, C. Rumsey, H. R. Russell, P. Salomé, H. D. Aller, M. F. Aller, D. J. Benford, A. C. Fabian, A. C. S. Readhead, E. M. Sadler, R. D. E. Saunders. 2015-07-10. High Radio Frequency Properties and Variability of Brightest Cluster Galaxies. https://doi.org/10.1093/mnras%2Fstv1518

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