Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

X-ray constraints on cluster-scale emission around high-redshift radio galaxies

Elena Belsole

in collaboration with

D. Worrall & M. Hardcastle

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Outline

•Introduction

Theory for jet confinement

Environment expected from radio observations and minimum energy condition

What was the situation with ROSAT

•Observational situation:

An example: Two sources observed with XMM

The new picture from Chandra and XMM

•Conclusions

•Future prospects

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Introduction

• Powerful (P178 Mhz > 1027 W Hz-1 sr-1) radio sources are visible at high redshift

• Sources classified as FRII have a double sided jet which terminates in hotspots sometimes at distances of ~ 1Mpc

•Jet propagation and termination require a gaseous environment for confinement (standard beam-model, Begelman et al. 84)

•X-ray emission traces the hot gas component.

Powerful radio galaxies are possible tracers of galaxy

groups and clusters

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

IntroductionAdvantages:

• Radio selection: not biased towards luminous clusters (unlike X-ray flux limited samples)

• Radio observations can be used alone to estimate the external gas density, if minimum energy condition applies, : ρ ∝ (B/vL)2 – ram pressure confinement eq.

• Easier than SZ for these sources

Disadvantages

• In X-ray: component separation and sensitivity (low SB objects)

• Not many active radio sources; are we looking at a particular class of object?

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Observational framework

Most powerful radio sources are at high redshift

By analogy to low-z sources (Cygnus A) minimum energy condition is assumed (e.g. Wellman et al. 97)

These studies predict clusters with ICM densities comparable to low-z clusters and similar shape.

ROSAT observations:

Evidence difficult to obtain for external environment around RGs and QSO at z>0.5 [Worrall et al. 94, Crawford & Fabian 96, Hardcastle & Worrall 99, Crawford et al. 99]

Question is still open

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Observational status:

the new generation X-ray satellites

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

3C292 z=0.71 XMM exposure time: 20 ks

Belsole et al. 2004

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Lobes

Unabsorbed power law

=1.9±0.3

Flux (1 keV) = 4 nJy

Total IC flux 2.4 nJy

Environment

β=0.8 , rc – 19.7 arcsec

kT = 2.2 +3.12 -0.85 keV

LX (bol)= 6.5 1043 erg/s

3C292

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

3C184 z:0.994

XMM/EPIC image

54 ks (MOS)

16 ks (pn) Belsole et al. 2004

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Point source + model

= 0.66, rc = 200 kpc

evidence of extended emission

LX ~ 5.9 x 1043

X-ray spectrum: 3 components

S = 1.5±1.0 from Chandra

NH =4.9 1023 cm-2; H = 1.4±0.35

kT = 3.6+ 14.1 -1.8 keV;

LX = 8.3±1.8 x 1043 erg/s

3C184

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

HST (Deltorn et al. 97)Excess of galaxies + 11 galaxies at z~1Arc detection and mass within arc ~2 x 1013 Msun

3C184

Chandra images and 5 GHz radio contours

the pressure of the external medium is a factor of 20 lower than the minimum internal pressure of the galaxy ==> the galaxy is expanding

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Observational status:

summary of current results

FRII in the 3CRR and with 0.5<z<1.0 [Donahue et al. 03; Crawford & Fabian 03; Hardcastle et al 02; Brunetti et al. 02]

Only 3 objects have measured X-ray temperature:

3C220.1 T~ 5.6 keV (Worrall et al. 2003)

3C184 T~3.5 keV (Belsole et al. 2004)

3C292 T~2.2 keV (Belsole et al. 2004)

Luminosities are easier to estimate

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Bolometric LX (1043 erg/s)

N

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Observational status:

summary of current results

FRII in the 3CRR and with z>0.5 [Donahue et al. 03; Crawford & Fabian 03; Hardcastle et al 02; Brunetti et al. 02]

Only 3 objects have measured X-ray temperature:

3C220.1 T~ 5.6 keV (Worrall et al. 2003)

3C184 T~3.5 keV (Belsole et al. 2004)

3C292 T~2.2 keV (Belsole et al. 2004)

Luminosities are easier to estimate …

and largely found to be ~ 3-4 1043 erg/s kT ~ 1.5-3.5 keV

Extended emission associated with lobes (IC) and hotspots (IC - SSC - Syn)

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Conclusions

• Detection of diffuse emission from most of the radio sources at z>0.5

• Most of the extended emission is radio related

• X-ray environment mostly of poor clusters (with few exceptions) but sufficient to confine the lobes

FRII radio galaxies are tracers of a broad range of environments ?

IF yes they provide an unbiased sample of the structures in the Universe

caveat

It is difficult to separate components!

Elena BelsoleUniversity of Bristol

Distant clusters of GalaxiesRingberg Workshop

24-28 October 2005

Future prospects

• Quantitative investigation of the X-ray environment .... In progress (see Belsole et al. 2005, MNRAS, sub; Belsole et al. 2006, in prep.)

• Comparison with lobe internal pressure (see also Croston et al. 2005) ; is the minimum energy condition satisfied?

• Comparison with lower redshift sources: evolution?