24-28 october 2005 elena belsole university of bristol distant clusters of galaxies ringberg...
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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?