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

This workshop explores the observational status and future prospects of using X-ray emissions to study the environments and confinement of high-redshift radio galaxies. It discusses the advantages and disadvantages of using radio observations and presents recent findings on the detection of diffuse emission in these sources. The workshop concludes with future prospects and the potential for using FRII radio galaxies as unbiased tracers of the structures in the Universe.

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

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  1. X-ray constraints on cluster-scale emission around high-redshift radio galaxies Elena Belsole in collaboration with D. Worrall & M. Hardcastle Distant clusters of Galaxies Ringberg Workshop

  2. 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 Distant clusters of Galaxies Ringberg Workshop

  3. 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 Distant clusters of Galaxies Ringberg Workshop

  4. 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, : 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? Distant clusters of Galaxies Ringberg Workshop

  5. 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 Distant clusters of Galaxies Ringberg Workshop

  6. Observational status: the new generation X-ray satellites Distant clusters of Galaxies Ringberg Workshop

  7. 3C292 z=0.71 XMM exposure time: 20 ks Belsole et al. 2004 Distant clusters of Galaxies Ringberg Workshop

  8. 3C292 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 Distant clusters of Galaxies Ringberg Workshop

  9. 3C184 z:0.994 XMM/EPIC image 54 ks (MOS) 16 ks (pn) Belsole et al. 2004 Distant clusters of Galaxies Ringberg Workshop

  10. 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 Point source +  model  = 0.66, rc = 200 kpc evidence of extended emission LX ~ 5.9 x 1043 Distant clusters of Galaxies Ringberg Workshop

  11. 3C184 HST (Deltorn et al. 97) Excess of galaxies + 11 galaxies at z~1 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 ==> the galaxy is expanding Distant clusters of Galaxies Ringberg Workshop

  12. 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 Distant clusters of Galaxies Ringberg Workshop

  13. N Bolometric LX (1043 erg/s) Distant clusters of Galaxies Ringberg Workshop

  14. 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) Distant clusters of Galaxies Ringberg Workshop

  15. 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! Distant clusters of Galaxies Ringberg Workshop

  16. 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? Distant clusters of Galaxies Ringberg Workshop

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