A Multiwavelength Analysis of the Strong Lensing Cluster RCS 022434-0002.5 at z=0.778

The Astrophysical Journal (Impact Factor: 6.28). 08/2007; DOI: 10.1086/522879
Source: arXiv

ABSTRACT We present the results of two (101 ks total) Chandra observations of the z=0.778 optically selected lensing cluster RCS022434-0002.5, along with weak lensing and dynamical analyses of this object. An X-ray spectrum extracted within R(2500) (362 h(70)^(-1) kpc) results in an integrated cluster temperature of 5.1 (+0.9,-0.5) keV. The surface brightness profile of RCS022434-0002.5 indicates the presence of a slight excess of emission in the core. A hardness ratio image of this object reveals that this central emission is primarily produced by soft X-rays. Further investigation yields a cluster cooling time of 3.3 times 10^9 years, which is less than half of the age of the universe at this redshift given the current LCDM cosmology. A weak lensing analysis is performed using HST images, and our weak lensing mass estimate is found to be in good agreement with the X-ray determined mass of the cluster. Spectroscopic analysis reveals that RCS022434-0002.5 has a velocity dispersion of 900 +/- 180 km/s, consistent with its X-ray temperature. The core gas mass fraction of RCS022434-0002.5 is, however, found to be three times lower than expected universal values. The radial distribution of X-ray point sources within R(200) of this cluster peaks at ~0.7 R(200), possibly indicating that the cluster potential is influencing AGN activity at that radius. Correlations between X-ray and radio (VLA) point source positions are also examined. Comment: 32 pages, 9 figures. Accepted for publication in The Astrophysical Journal

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    ABSTRACT: Context: The study of the thermodynamical and chemical properties of the intra cluster medium (ICM) in high redshift clusters of galaxies is a powerful tool for investigating the formation and evolution of large scale structures. Here we discuss the X-ray properties of clusters of galaxies optically selected in the red-sequence cluster survey (RCS) observed with the Chandra satellite, at redshifts 0.6 < z < 1.2. Aims: We intend to assess the evolutionary stage of optically selected high-z clusters of galaxies, performing a spectral analysis of the diffuse emission from their ICM. We also investigate the distribution of active galactic nuclei (AGN) in their surroundings. Methods: The background subtracted spectra were analyzed and fitted with a single temperature model to measure average ICM temperature, X-ray bolometric luminosity and Fe abundance within typical radii between 200 and 350 kpc. We also analyzed the point source number density and spatial distribution in the RCS clusters fields as a function of the X-ray flux. Results: We detected emission for the majority of the clusters, except for three, for which we have only marginal detection at ˜ 3sigma. We find that the normalization of the luminosity-temperature relation for RCS clusters is a factor of ~2 lower than the one for X-ray selected clusters. We confirm that the Fe abundance in the detected objects is consistent with that of X-ray selected clusters at the same redshift. We also find an excess of low-luminosity AGN towards the center of the clusters. Conclusions: At z ~ 1, optically selected clusters with a well-defined red-sequence show extended X-ray emission in about 70% (8/11) of the cases. Nevertheless, their L_X-TX relation is significantly lower with respect to X-ray selected clusters at the same redshift, possibly indicating an incomplete virialization. The Fe abundance measured in the ICM of RCS clusters is comparable to the values measured for X-ray selected clusters at the same redshift, implying a substantial enrichment by SNe products. These two evidences add to the previously known studies of high-z, X-ray selected clusters, to confirm that the thermodynamical and chemical properties of the ICM are substantially established already at z > 1. Finally, we find the significant excess of medium and low luminosity AGN close to the centroid of the X-ray emission. Their X-ray emission is not dominating the ICM, but their presence may be relevant for studying the interaction between AGN and ICM.
    Astronomy and Astrophysics 10/2008; 489(3):967-979. · 4.48 Impact Factor
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    ABSTRACT: We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352–5452) was discovered while examining i- and z-band images being acquired in 2006 October during a BCS observing run. Follow-up spectroscopic observations with the Gemini Multi-Object Spectrograph instrument on the Gemini-South 8 m telescope confirmed the lensing nature of this system. Using weak-plus-strong lensing, velocity dispersion, cluster richness N 200, and fitting to a Navarro-Frenk-White (NFW) cluster mass density profile, we have made three independent estimates of the mass M 200 which are all very consistent with each other. The combination of the results from the three methods gives M 200 = (5.1 ± 1.3) × 1014 M ☉, which is fully consistent with the individual measurements. The final NFW concentration c 200 from the combined fit is c 200 = 5.4+1.4 – 1.1. We have compared our measurements of M 200 and c 200 with predictions for (1) clusters from ΛCDM simulations, (2) lensing-selected clusters from simulations, and (3) a real sample of cluster lenses. We find that we are most compatible with the predictions for ΛCDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to ΛCDM. Finally, using the flux measured from the [O II]3727 line we have determined the star formation rate of the source galaxy and find it to be rather modest given the assumed lens magnification.
    The Astrophysical Journal 11/2011; 742(1):48. · 6.28 Impact Factor
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    ABSTRACT: My Ph.D. Thesis is devoted to the study of groups and clusters of galaxies in the X-ray band. This field has been very active in the last ten years, thanks to the data gathered from the Chandra and XMM satellites. Clusters of galaxies are prominent X-ray sources thanks to thermal bremsstrahlung emission from the diffuse ICM heated to 10^7-10^8 K, which provides about 15% of their total mass. The analysis of the X-ray emission from groups and clusters allows to study the large scale structure of the Universe, to constrain the cosmological parameters, and to investigate the interaction between the ICM and the cluster galaxies. My scientific work is mainly focused on the realization of a new X-ray survey of galaxy clusters, the SXCS, obtained from the previously unexplored archive of the X-Ray Telescope (XRT) on board of the Swift satellite. The goal is not only to build a new catalogue, but also to characterize the thermodynamical and chemical properties of the brightest groups and clusters in the survey catalogue. Moreover, given the overall characteristics of the survey, I also expect to detect some clusters at redshift z>1, which will have a strong impact in the study of the large scale structure of the Universe and the cosmological parameters. During my work I also contributed substantially to the image simulator code of a new proposed X-ray mission submitted to the NASA Astro 2010 Decadal Survey: the Wide Field X-ray Telescope (WFXT). This work represents an important part of the scientific case of WFXT, since, for first time in the simulations I included realistic populations of all the source types contributing to the extragalactic X-ray sky, namely groups and clusters of galaxies, active galactic nuclei, and star-forming galaxies. Thanks to this work, the scientific cases of WFXT can now be tested on solid ground. Comment: PhD thesis, 265 pages

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