Elena Belsole

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X-ray constraints on cluster-scale emission
around high-redshift radio galaxies Elena
Belsole in collaboration with D. Worrall M.
Hardcastle
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• 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

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• Introduction
• Powerful (P178 Mhz gt 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

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• Introduction
• Advantages
• 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, ? ? (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?

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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 zgt0.5
Worrall et al. 94, Crawford Fabian 96,
Hardcastle Worrall 99, Crawford et al.
99 Question is still open
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Observational status the new generation X-ray
satellites
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3C292 z0.71 XMM exposure time 20 ks
Belsole et al. 2004
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3C292
Lobes Unabsorbed power law ?1.90.3 Flux (1
keV) 4 nJy Total IC flux 2.4 nJy
Environment ß0.8 , rc 19.7 arcsec kT 2.2
3.12 -0.85 keV LX (bol) 6.5 1043 erg/s
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3C184 z0.994
XMM/EPIC image 54 ks (MOS) 16 ks (pn)
Belsole et al. 2004
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3C184
Point source ? model ? 0.66, rc 200
kpc evidence of extended emission LX 5.9 x 1043
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3C184
HST (Deltorn et al. 97) Excess of galaxies 11
galaxies at z1 Arc detection and mass within
arc 2 x 1013 Msun
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 gt the galaxy is expanding
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Observational status summary of current
results FRII in the 3CRR and with 0.5ltzlt1.0
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 T3.5 keV (Belsole et al.
2004) 3C292 T2.2 keV (Belsole et al.
2004) Luminosities are easier to estimate
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(No Transcript)
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Observational status summary of current
results FRII in the 3CRR and with zgt0.5 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 T3.5 keV
(Belsole et al. 2004) 3C292 T2.2 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)
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• Conclusions
• Detection of diffuse emission from most of the
  radio sources at zgt0.5
• 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!

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• 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?