FRII sources at z>0.5: X-ray properties of the core and extended emission

Peer reviewe

The tilt of the Fundamental Plane of Early-type galaxies: wavelength dependence

The photometric parameters R_e and mu_e of 74 early-type (E+S0+S0a) galaxies in the Coma cluster are derived for the first time in the near IR H band. These are used, coupled with measurements of the central velocity dispersion found in the literature, to determine the H band Fundamental Plane (FP) relation of this cluster. The same procedure is applied to previously available photometric data in the B, V, r, I, and K bands, to perform a multi-wavelength study of the FP. Because systematic uncertainties in the value of the FP parameters are introduced both by the choice of the fitting algorithm, and by the presence of statistical biases connected with the sample selection procedure, we emphasize the importance of deriving the FP parameters in the six photometric bands using an identical fitting algorithm, and appropriate corrections to eliminate the effects of sample incompleteness. We find that the FP mu_e coefficient is stable with wavelength, while the sigma coefficient increases significantly with increasing wavelength, in agreement with an earlier result presented by Pahre & Djorgovski. The slope of the FP relation, although changing with wavelength, never approaches the virial theorem expectation. We also find that the magnitude of the slope change can be entirely explained by the presence of the well known relation between color and magnitude among early-type galaxies. We conclude that the tilt of the Fundamental Plane is significant, and must be due to some form of broken homology among early-type galaxies, while its wavelength dependence derives from whatever mechanism (currently the preferred one is the existence of a mass-metal content sequence) produces the color-magnitude relation in those galaxies.Comment: 8 pages, 7 figures, 6 tables; table 3 should be printed in landscape mode, and inserted into the text. Accepted for publication in MNRA

Merging clusters of galaxies observed with XMM-Newton

We present results from the XMM-Newton observations of our ongoing program on merging clusters. To date three clusters have been observed, covering the temporal sequence from early to late stage mergers: A1750, A2065 and A3921. Using spatially-resolved spectroscopy of discrete regions, hardness ratio and temperature maps, we show that all three clusters display a complex temperature structure. In the case of A1750, a double cluster, we argue that the observed temperature structure is not only related to the ongoing merger but also to previous merger events. A2065 seems an excellent example of a `compact merger', i.e. when the centres of the two clusters have just started to interact, producing a shock in the ICM. Using comparisons with numerical simulations and complementary optical data, the highly complex temperature structure evident in A3921 is interpreted as an off-axis merger between two unequal mass components. These results illustrate the complex physics of merger events. The relaxation time can be larger than the typical time between merger events, so that the present day morphology of clusters depends not only on on-going interaction but also on the more ancient formation history.Comment: 10 pages, 3 figures. Use elsart.cls. Accepted for publication in Advances in Space Research. A version with full resolution figures can be found at http://www.star.bris.ac.uk/elena/cospar_3clusters.pd

XMM -Newton observations of merging clusters of galaxies: A3921 and A1750

We show the XMM-Newton guaranted time observations of 2 clusters of galaxies in a different stage of merger.Comment: 4 pages, LaTex, 9 figures. To appear in the Proceedings of the Conference "New Visions of the X-ray Universe in the XMM-Newton and Chandra era" -ESTEC - Noordwijk, The Netherlands, Nov 200

An X-ray study of magnetic field strengths and particle content in FRII radio sources

We present a Chandra and XMM-Newton study of X-ray emission from the lobes of 33 classical double radio galaxies and quasars. We report new detections of lobe-related X-ray emission in 11 sources. Together with previous detections we find that X-ray emission is detected from at least one radio lobe in ~75 percent of the sample. For all of the lobe detections, we find that the measured X-ray flux can be attributed to inverse-Compton scattering of the cosmic microwave background radiation, with magnetic field strengths in the lobes between (0.3 - 1.3) B_eq, where the value B_eq corresponds to equipartition between the electrons and magnetic field assuming a filling factor of unity. There is a strong peak in the magnetic field strength distribution at B ~ 0.7 B_eq. We find that > 70 percent of the radio lobes are either at equipartition or electron dominated by a small factor. The distribution of measured magnetic field strengths differs for narrow-line and broad-line objects, in the sense that broad-line radio galaxies and quasars appear to be further from equipartition; however, this is likely to be due to a combination of projection effects and worse systematic uncertainty in the X-ray analysis for those objects. Our results suggest that the lobes of classical double radio sources do not contain an energetically dominant proton population, because this would require the magnetic field energy density to be similar to the electron energy density rather than the overall energy density in relativistic particles.Comment: 44 pages, 4 figures. Accepted for publication in Ap

X-ray Properties of the GigaHertz-Peaked and Compact Steep Spectrum Sources

We present {\it Chandra} X-ray Observatory observations of Giga-Hertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. The {\it Chandra} sample contains 13 quasars and 3 galaxies with measured 2-10 keV X-ray luminosity within $10^{42} - 10^{46}$ erg s$^{-1}$. We detect all of the sources, five of which are observed in X-ray for the first time. We study the X-ray spectral properties of the sample. The measured absorption columns in the quasars are different than those in the galaxies in the sense that the quasars show no absorption (with limits $\sim 10^{21} \rm cm^{-2}$) while the galaxies have large absorption columns ($> 10^{22} \rm cm^{-2}$) consistent with previous findings. The median photon index of the sources with high S/N is $\Gamma=1.84 \pm0.24$ and it is larger than the typical index of radio loud quasars. The arcsec resolution of {\it Chandra} telescope allows us to investigate X-ray extended emission, and look for diffuse components and X-ray jets. We found X-ray jets in two quasars (PKS 1127-145, B2 0738+32), an X-ray cluster surrounding a CSS quasar (z=1.1, 3C 186), detected a possible binary structure in 0941-080 galaxy and an extended diffuse emission in galaxy PKS B2 1345+12. We discuss our results in the context of X-ray emission processes and radio source evolution. We conclude that the X-ray emission in these sources is most likely unrelated to a relativistic jet, while the sources' radio-loudness may suggest a high radiative efficiency of the jet power in these sources.Comment: 15 pages, to be published in Ap

The X-ray luminous cluster underlying the z = 1.04 quasar PKS1229-021

We present a 100 ks Chandra observation studying the extended X-ray emission around the powerful z=1.04 quasar PKS1229-021. The diffuse cluster X-ray emission can be traced out to ~15 arcsec (~120 kpc) radius and there is a drop in the calculated hardness ratio inside the central 5 arcsec consistent with the presence of a cool core. Radio observations of the quasar show a strong core and a bright, one-sided jet leading to the SW hot spot and a second hot spot visible on the counter-jet side. Although the wings of the quasar PSF provided a significant contribution to the total X-ray flux at all radii where the extended cluster emission was detected, we were able to accurately subtract off the PSF emission using ChaRT and marx simulations. The resulting steep cluster surface brightness profile for PKS1229-021 appears similar to the profile for the FRII radio galaxy 3C444, which has a similarly rapid surface brightness drop caused by a powerful shock surrounding the radio lobes (Croston et al.). Using a model surface brightness profile based on 3C444, we estimated the total cluster luminosity for PKS1229-021 to be L_X ~ 2 x 10^{44} erg/s. We discuss the difficulty of detecting cool core clusters, which host bright X-ray sources, in high redshift surveys.Comment: 10 pages, 9 figures, accepted by MNRA

Structure and scaling of the entropy in nearby galaxy clusters

Using XMM-Newton observations, we investigate the scaling and structural properties of the ICM entropy in a sample of 10 nearby (z < 0.2) relaxed galaxy clusters in the temperature range 2-9 keV. We derive the local entropy-temperature (S-T) relation at R = 0.1, 0.2, 0.3 and 0.5 R_200. The logarithmic slope of the relation is the same within the 1\sigma error at all scaled radii. However, the intrinsic dispersion about the best fitting relation is significantly higher at 0.1 R_200. The slope is 0.64\pm0.11 at 0.3 R_200, in excellent agreement with previous work. We also investigate the entropy-mass relation at density contrasts \delta=5000, 2500 and 1000. We find a shallower slope than that expected in simple self-similar models, which is in agreement with the observed empirically-determined entropy-temperature and mass-temperature scaling. The dispersion is smaller than for the S-T relation. Once scaled appropriately, the entropy profiles appear similar beyond ~0.1 R_200, with an intrinsic dispersion of ~15 per cent and a shape consistent with gravitational heating (S(r) \propsim r^{1.1}). However, the scatter in scaled entropy profiles increases with smaller scaled radius, to more than 60 per cent at R \lesssim 0.05 R_200. Our results are in qualitative agreement with models which boost entropy production at the accretion shock. However, localised entropy modification may be needed to explain the dispersion in the inner regions.Comment: 9 pages, 8 colour figures, to appear in A&A. Title changed, minor text clarification