We present an analysis of the energetics and particle content of the lobes of 24 radio galaxies at the cores of cooling clusters. The radio lobes in these systems have created visible cavities in the surrounding hot, X-ray-emitting gas, which allow direct measurement of the mechanical jet power of radio sources over six decades of radio luminosity, independently of the radio properties themselves. We find that jet (cavity) power increases with radio synchrotron power approximately as P_jet_~L^{beta}^_radio_, where 0.35<={beta}<=0.70 depending on the bandpass of measurement and state of the source. Furthermore, we place limits on the magnetic field strengths and particle content of the radio lobes using a variety of X-ray constraints. We find that the lobe magnetic field strengths vary between a few to several tens of microgauss depending on the age and dynamical state of the lobes.
The Abell clusters 2125 and 2645 have different radio source populations, despite being very similar in richness (Abell class 4) and redshift (0.25). The number density of radio sources in Abell 2125 is almost an order of magnitude more than that in Abell 2645, based on observations to the same optical and radio luminosities of the two clusters. About 30% of the radio sources in Abell 2125 shows signs of star formation, with the largest concentration of them in the southwest clump 2Mpc from the cluster center.
We present a VLA C-configuration imaging survey of 14 rich Abell clusters. The observations were undertaken with the intent of characterizing the galaxy orbits within the cluster by combining galaxy redshifts with indicators of orbital shape. We present maps of the observed clusters, detailed maps of resolved sources detected in the survey, comparisons with optical images of the clusters, and tables of source parameters for all detected sources with measured flux values.
Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields.
The Australia Telescope Compact Array (ATCA) has been used at 1.38 and 2.38GHz to survey seven southern Abell clusters of galaxies with high X-ray luminosities: A2746, A2837, A3126, A3216, A3230, A3827 and A3836. The clusters have also been surveyed at 0.843GHz with the Molonglo Observatory Synthesis Telescope (MOST). We have listed a complete 1.38-GHz sample of 149 radio sources within the Abell circles centred on their X-ray centroids. We compare their identification fractions, emitted 1.38-GHz and optical powers, radio spectral indices and radial variation in projected source density with those of the radio-selected samples of Slee et al. (1998AuJPh..51..971S). We compare our fractional radio luminosity function with that of the radio-selected samples of Ledlow and Owen (1996AJ....112....9L) and Slee et al. (1998AuJPh..51..971S). Three significant differences are noted between X-ray and radio-selected samples of clusters; (1) the X-ray sample has an excess of flat-spectrum radio sources; (2) the fractional radio luminosity function for the FR I sources in the X-ray selected sample is much steeper, implying that fewer of their cluster galaxies become hosts for the stronger FR I radio galaxies; (3) a complete absence of FR II radio galaxies in the X-ray selected sample. The average excess projected density of radio sources near our cluster centres is approx. 5 times the background source density.
MUSE observations of the cluster of galaxies CGr32 (M200~2x10^14^M_{sun}_) at z=0.73 reveal the presence of two massive star forming galaxies with extended tails of diffuse gas detected in the [OII]3727-3729{AA} emission- line doublet. The tails, which have a cometary shape with a typical surface brightness of a few 10^-18^erg/s/cm^2^/arcsec^2^, extend up to ~100kpc (projected distance) from the galaxy discs and are not associated to any stellar component. All this observational evidence suggests that the gas has been removed during a ram-pressure stripping event. This observation is thus the first evidence that dynamical interactions with the intracluster medium were active when the Universe had only half of its present age. The density of the gas derived using the observed [OII]3729/[OII]3726 line ratio implies a very short recombination time, suggesting that a source of ionisation is necessary to keep the gas ionised within the tail.
We describe the ROSAT All-Sky Survey Center for Astrophysics Loose Systems (RASSCALS), the largest X-ray and optical survey of low-mass galaxy groups to date. We draw 260 groups from the combined Center for Astrophysics and Southern Sky Redshift Surveys, covering one-quarter of the sky to a limiting Zwicky magnitude of m_z_=15.5.
A field of 1.013sr in the ROSAT All-Sky Survey (RASS), centered on the south Galactic pole (SGP), has been searched in a systematic, objective manner for clusters of galaxies. The procedure relied on a correlation of the X-ray positions and properties of ROSAT sources in the field with the distribution of galaxies in the COSMOS digitized database, which was obtained from scanning the plates of the UK Schmidt IIIa-J optical survey of the southern sky. The study used the second ROSAT survey database (RASS-2) and included several optical observing campaigns to measure cluster redshifts. The search, which is a precursor to the larger REFLEX survey encompassing the whole southern sky, reached the detection limits of both the RASS and the COSMOS data and yielded a catalog of 186 clusters in which the lowest flux is 1.5x10-12ergs/cm^2^/s in the 0.1-2.4keV band. Of these 157 have measured redshifts. Using a flux limit of 3.0x10-12ergs/cm^2^/s a complete subset of 112 clusters was obtained, of which 110 have measured redshifts. The spatial distribution of the X-ray clusters out to a redshift of 0.15 shows an extension of the Local Supercluster to the Pisces-Cetus supercluster (z<0.07), and an orthogonal structure at higher redshift (0.07<z<0.15). This result is consistent with large-scale structure suggested by optical surveys.
The tables list the optical and X-rays properties of the RASS-SDSS galaxy clusters catalog. The catalog contains 114 X-ray selected systems in the area observed by the Sloan Digital Sky Survey (SDSS). The X-ray data are taken from the ROSAT All Sky Survey (RASS, <IX/10>) while the optical data are taken from the SDSS (<J/AJ/123/567>) archive.
