Using head-tail galaxies to constrain the intracluster magnetic field: an in-depth study of PKS J0334−3900

• Published in: Monthly notices of the Royal Astronomical Society 2013-06, Vol.432 (1), p.243-257
• Main Authors: Pratley, Luke, Johnston-Hollitt, Melanie, Dehghan, Siamak, Sun, Ming
• Format: Article
• Language: English
• Subjects: Magnetic fields; Morphology; Simulation; Space telescopes; Star & galaxy formation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stt448

We present an in-depth, multiwavelength study of the radio galaxy PKS J0334−3900, which resides at the centre of Abell 3135. The spectro-polarimetric radio observations are combined with spectroscopic optical and X-ray data to illustrate the use of head-tail radio galaxies in revealing properties of the intracluster medium (ICM). Australia Telescope Compact Array (ATCA) observations at 1.4, 2.5, 4.6 and 8.6 GHz are presented with a detailed analysis of the morphology and spectral indices which give physical parameters to constrain the dynamical history of the galaxy. Using these constraints we produce a simulation of PKS J0334−3900. We find that this particular head-tail morphology can be induced via a combination of orbital motion due to a binary companion and the relative motion through the ICM. New Chandra images of A3135 are presented from which we obtain a cluster electron density of , a global temperature of 2.4 keV and a lower limit to the radio jet power of PKS J0334−3900 of 1.6 × 1044 erg s−1. A new redshift analysis of the cluster from available spectroscopic data demonstrates A3135 to be comprised of galaxies with 0.058 ≤ z < 0.066 and gives a new mean cluster redshift of 0.06228 ± 0.00015. We also uncovered a background subgroup within the range 0.066 ≤ z < 0.070. Additionally, ATCA Stokes Q and U data of Abell 3135 were used to obtain rotation measure values along the line of sight to PKS J0334−3900. Using our simulation, we are able to infer the distance between the jets along the line of sight to be 154 ± 16 kpc, which when combined with the difference in rotation measure between the jets provides a novel new way to estimate the average magnetic field within a cluster. A lower limit to the cluster magnetic field was calculated to be 0.09 ± 0.03 μG. From these results, we have shown that different techniques can be combined from the observations of head-tail galaxies to infer information on the cluster environment, showing them to be an important class of objects in next generation all sky surveys.