Presentation on theme: "Is there a correlation between the presence of bent radio sources and the X-ray environment ? Oozeer N HartRAO 2010 South African SKA Postgraduate Bursary."— Presentation transcript:
Is there a correlation between the presence of bent radio sources and the X-ray environment ? Oozeer N HartRAO 2010 South African SKA Postgraduate Bursary Conference
Galaxy groups/clusters Groups: < 50 members, ~ 150 km/s, M ~ 2 × 10 13 M ⊙ Clusters: > 50 members, ~ 800 km/s, M ~ 1 × 10 15 M ⊙ Clusters RichPoor LooseCompact
Galaxy clusters are the largest gravitationally bound system ~ 50 to 1000's of galaxies, diffuse hot gas dark matter Most galaxies exist in groups/clusters, Clusters are in super-clusters Clusters and super-clusters of galaxies have been studied extensively both for their intrinsic properties and to investigate the dark matter in the universe, the baryon content of the universe, large-scale structure, evolution, and cosmology. Galaxy clusters
Our views of clusters of galaxies have changed dramatically over the past decade. Clusters are no longer seen as simple, spherical, isolated structures in virial or hydrostatic equilibrium. Dynamic, evolving and young, strongly influenced by large scale strutctures, Chambers et al 2000. The general process of galaxy cluster formation through hierarchical merging is well understood, but many details, such as the impact of feedback sources on the cluster environment and radiative cooling in the cluster core, are not. How can we find clusters ? X-ray surveys Optical/IR surveys Radio surveys Sunyaev-Zel’dovich (SZ) effect Gravitational lensing
X-ray view (direct detection) X-ray studies of groups of galaxies provides information about the environment (hot gas of the ICM) and the process occurring therein. Presence of diffuse X-ray emission in a group would indicate the group is likely to be gravitationally bound temperature, luminosity and surface brightness profile provide information concerning the depth of the potential well and the distribution of mass in the system. Bachall et al, 2008.
Optical view Typical Properties of Clusters and Groups Distribution of Clusters with Richness and Distance Number Density of Clusters Fraction of Galaxies in Clusters Galaxy Overdensity in Rich Clusters Density Profile Central Density and Core Size Galactic Content in Rich Clusters Velocity Dispersion
Radio surveys (in-direct detection) Importance of radio sources and radio surveys Classes of objects - Bent radio sources !!! The existence of bent radio sources implies close interactions between the radio structure and the surrounding environment of these sources. Therefore it is by studying the characteristics and properties of a source and its medium that we can explain the shape of the radio source. Bent radio sources show various morphologies, from Wide Angle Tail radio galaxies (WATs) to Head Tail sources (HTs) and Narrow Angle Tail radio galaxies (NATs).
Environment of bent radio sources !!! NATs Bending due to ram pressure stripping Relatively high v Exist in both poor (Venkatesan et al, 1994) and rich clusters (Sarazin, 1988 – for review) WATs C or V - radio morphology FRI/FRII break Associated with cD or D optical host galaxy cDs and Ds giant elliptical at rest in the potential well of the cluster ( v ~ 100 kms -1 ) Poor cluster (Patnaik et al. 1986, Oozeer et al. 2010) and rich cluster (Pinkney et al. 2000 )
FIRST - Blanton et al, 2001. 384 sources visually selected from the VLA FIRST survey Optically followed up (imaging and spectroscopy) Low-z complete sample showed that 50% of BDs are found in clusters, as revealed in the optical and X-ray
COSMOS field z ~ 0.2 20cm Xray: rainbow Optical: RGB Radio: red 200kpc CWAT-01 at z~0.2: Merging of 4+ sub-clusters of galaxies Individual sub-clusters = 5E13 M SOL Smolcic et al., 2007, Oklopcic et al., 2010
MRC 1925-296 & MRC 1928-266 MRC B1925-296 – Note the similarity shape of the X-ray blob and the radio jets MRC B1925-296 – ROSAT PSPC pointing
HST & Chandra image of MRC B1928-266 MRC B1928-266 – The cluster environment as revealed by the NAT south of the X-ray plasma MRC B1928-266 – HST image with radio overlay. This new cluster is at z=0.352
Methodology - sample Popesso+, 2007 and Yoon+, 2008, Owen, 1997 Galaxy clusters in SDSS-DR5 137 spectroscopically confirmed Abell systems 924 records of BCG – Our sample: 45 Abell clusters 0.04 < z <0.15 Median z = 0.08 WAT=17, NAT=11, Gal ? =17 Vizier NVSS (1.4 GHz radio survey) counterparts Optical counterparts – Soan Digital sky survey (SDSS) X-ray environment - Rosat All Sky Survey (RASS, X-ray clusters) R-statistics tool
Correlation matrix Linear – BCG to Radio peak RadPow – radio luminosity at 1.4 GHz Sigma – velocity dispersion R_band – Rband Luminosity XLinear – separation between BCG and X-ray peak Lx - X-ray luminosity Mass – Virial mass Virial – virial size NHI – neutral hydrogen density Morphological Type – (WAT, NAT or G)
Correlation coefficients Velocity dispersion [km/s] R band luminosity [Lsol] 99.9 Cluster Virial Size [Mpc] 1.4 GHz Radio power [Whz-1] BCG/X-ray separation [Mpc] 391727 26 Xray Lumi [W] 262717 BCG/Radio separation [Mpc]
L x - v relation The best fit is given by log(L x )=1.56 log( v )+32.24 (Mahdavi et al, 1997.) Some authors have found that L x v 4 ( Xue & Wu,2000; Ortiz-Gil et al., 2004) However, Cava et al., 2009 log(L x )=(4.0±0.3) log( v )+(32.6±1.7)
L x v/s L rad at 1.4 GHz Zhao et al., 1989 found NO correlation between L x and P 20cm from an X-ray selected sample of 71 Abell clusters. However, we know X-ray luminosity/ radio correlation exist for various classes of objects, e.g: for AGN, Seyferts, halos, etc....
Conclusion Since the appearance of radio sources is affected by interaction with the ICM (confinement, distortion), we can use bent radio sources to locate distant clusters of galaxies that would be difficult to find in optical (b.c. of projection effects) or X-ray (b.c. of flux limits) surveys. Data mining – need to get a good platform to query maximum data (~ 55 000 new BCGs, Tago et al, 2010) Demonstrate a statistical tool which can be used to analyse huge data set Most of the physical parameters investigated here seems to correlate to X- ray luminosity