A new method for finding and characterizing galaxy groups via low-frequency radio surveys

J. H. Croston, J. Ineson, M. J. Hardcastle, B. Mingo

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We describe a new method for identifying and characterizing the thermodynamic state of large samples of evolved galaxy groups at high redshifts using high-resolution, low-frequency radio surveys, such as those that will be carried out with LOFAR and the SquareKilometreArray.We identify a sub-population of morphologically regular powerful [Fanaroff-Riley type II (FR II)] radio galaxies and demonstrate that, for this sub-population, the internal pressure of the radio lobes is a reliable tracer of the external intragroup/intracluster medium (ICM) pressure, and that the assumption of a universal pressure profile for relaxed groups enables the total mass and X-ray luminosity to be estimated. Using a sample of well-studied FR II radio galaxies, we demonstrate that our method enables the estimation of group/cluster X-ray luminosities over three orders of magnitude in luminosity to within a factor of ~2 from low-frequency radio properties alone. Our method could provide a powerful new tool for building samples of thousands of evolved galaxy groups at z > 1 and characterizing their ICM.

Original languageEnglish
Article numberstx1347
Pages (from-to)1943-1949
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date31 May 2017
Publication statusPublished - 11 Sept 2017


  • Galaxies: active
  • X-rays: galaxies: clusters


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