Is there a correlation between the presence of bent radio sources

and the X-ray environment ?

Oozeer NHartRAO

2010 South African SKA Postgraduate Bursary Conference

Content

Galaxy groups/cluster

Multi-wavelength view Methodology

Preliminary sample

Data mining

Statistical tool

Preliminary results

Conclusion

Galaxy groups/clusters

Groups: < 50 members, s ~ 150 km/s, M ~ 2 × 1013 M⊙

Clusters: > 50 members, s ~ 800 km/s, M ~ 1 × 1015 M⊙

Clusters

Rich Poor

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).

Morphology of radio galaxies

Environment of bent radio sources !!! NATs

Bending due to ram pressure stripping

Relatively high sv

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 (sv ~ 100 kms-1)

Poor cluster (Patnaik et al. 1986, Oozeer et al. 2010) and rich cluster (Pinkney et al. 2000 )

FRI & FRII

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 ~ 0.220cm

Xray: rainbowOptical: RGBRadio: red

200kpc

CWAT-01 at z~0.2:Merging of 4+ sub-clusters of galaxies Individual sub-clusters = 5E13 MSOL

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]

99.9Cluster

Virial Size [Mpc]

1.4 GHz Radio power

[Whz-1]

BCG/X-ray separation

[Mpc]

39 17 27 27 26 Xray Lumi [W]

26 27 17BCG/Radio separation

[Mpc]

Mpc)1(

1

km/s100073.1 1

30

200

h

zcl

vR

Lx- sv relation

The best fit is given by

log(Lx)=1.56 log(sv)

+32.24

(Mahdavi et al, 1997.)

Some authors have found that

Lx µ sv4

( Xue & Wu,2000; Ortiz-Gil et al., 2004)

However, Cava et al., 2009

log(Lx)=(4.0±0.3) log(sv)

+(32.6±1.7)

Rband Luminosity v/s velocity dispersion

Virial mass v/s velocity dispersion (sv)

G

RM vv

2

2

3

Lx v/s Lrad at 1.4 GHz

Zhao et al., 1989 found NO correlation between Lx and

P20cm 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 ....

Velocity dispersion v/s BCG radio separation

BCG/radio separation

Virial size distribution

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