High radio-frequency properties and variability of brightest cluster galaxies

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

Abstract

We consider the high radio-frequency (15–353 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 per cent of our parent sample (≥15.1 per cent if only cool-core clusters are considered) contain a radio source at 150 GHz of at least 3 mJy (≈1×1023 W Hz−1 at our median redshift of z ≈ 0.13). Furthermore, ≥3.4 per cent 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 per cent 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 per cent at 150 GHz over six-month time 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 per cent 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.

Citation

Hogan, M., Edge, A., Geach, J., Grainge, K., Hlavacek-Larrondo, J., Hovatta, T., …Saunders, R. (2015). High radio-frequency properties and variability of brightest cluster galaxies. Monthly Notices of the Royal Astronomical Society, 453(2), 1223-1240. https://doi.org/10.1093/mnras/stv1518

• Journal Article Type: Article
• Acceptance Date: Jul 7, 2015
• Publication Date: Oct 21, 2015
• Deposit Date: Oct 28, 2015
• Publicly Available Date: Nov 5, 2015
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 453
• Issue: 2
• Pages: 1223-1240
• DOI: https://doi.org/10.1093/mnras/stv1518
• Keywords: Galaxies: active, Galaxies: clusters: general, Galaxies: jets, Radio continuum: galaxies.
• Public URL: https://durham-repository.worktribe.com/output/1427773
• Related Public URLs: http://ukads.nottingham.ac.uk/abs/2015MNRAS.453.1223H