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        High radio-frequency properties and variability of brightest cluster galaxies

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        Author
        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.
        Attention
        2299/18854
        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.
        Publication date
        2015-10-21
        Published in
        Monthly Notices of the Royal Astronomical Society
        Published version
        https://doi.org/10.1093/mnras/stv1518
        Other links
        http://hdl.handle.net/2299/18854
        Metadata
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