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19 results on '"Ponman, T."'

3. GALAXY AND MASS ASSEMBLY (GAMA): WITNESSING THE ASSEMBLY OF THE CLUSTER ABELL 1882

Author

Owers, M. S., primary, Baldry, I. K., additional, Bauer, A. E., additional, Bland-Hawthorn, J., additional, Brown, M. J. I., additional, Cluver, M. E., additional, Colless, M., additional, Driver, S. P., additional, Edge, A. C., additional, Hopkins, A. M., additional, van Kampen, E., additional, Lara-Lopez, M. A., additional, Liske, J., additional, Loveday, J., additional, Pimbblet, K. A., additional, Ponman, T., additional, and Robotham, A. S. G., additional

Published
2013
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14. ChandraStudy of an Overdensity of X‐Ray Sources around Two Distant (z ∼ 0.5) Clusters

Author

Cappi, M., primary, Mazzotta, P., additional, Elvis, M., additional, Burke, D. J., additional, Comastri, A., additional, Fiore, F., additional, Forman, W., additional, Fruscione, A., additional, Green, P., additional, Harris, D., additional, Hooper, E. J., additional, Jones, C., additional, Kaastra, J. S., additional, Kellogg, E., additional, Murray, S., additional, McNamara, B., additional, Nicastro, F., additional, Ponman, T. J., additional, Schlegel, E. M., additional, Siemiginowska, A., additional, Tananbaum, H., additional, Vikhlinin, A., additional, Virani, S., additional, and Wilkes, B., additional

Published
2001
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16. ChandraObservation of Abell 2142: Survival of Dense Subcluster Cores in a Merger

Author

Markevitch, M., primary, Ponman, T. J., additional, Nulsen, P. E. J., additional, Bautz, M. W., additional, Burke, D. J., additional, David, L. P., additional, Davis, D., additional, Donnelly, R. H., additional, Forman, W. R., additional, Jones, C., additional, Kaastra, J., additional, Kellogg, E., additional, Kim, D.‐W., additional, Kolodziejczak, J., additional, Mazzotta, P., additional, Pagliaro, A., additional, Patel, S., additional, Van Speybroeck, L., additional, Vikhlinin, A., additional, Vrtilek, J., additional, Wise, M., additional, and Zhao, P., additional

Published
2000
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17. [ITAL]Chandra[/ITAL] X-Ray Detection of the Radio Hot Spots of 3C 295

Author

Harris, D. E., primary, Nulsen, P. E. J., additional, Ponman, T. J., additional, Bautz, M., additional, Cameron, R. A., additional, David, L. P., additional, Donnelly, R. H., additional, Forman, W. R., additional, Grego, L., additional, Hardcastle, M. J., additional, Henry, J. P., additional, Jones, C., additional, Leahy, J. P., additional, Markevitch, M., additional, Martel, A. R., additional, McNamara, B. R., additional, Mazzotta, P., additional, Tucker, W., additional, Virani, S. N., additional, and Vrtilek, J., additional

Published
2000
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19. ChandraStudy of an Overdensity of X-Ray Sources around Two Distant (z~ 0.5) Clusters

Author

Cappi, M., Mazzotta, P., Elvis, M., Burke, D. J., Comastri, A., Fiore, F., Forman, W., Fruscione, A., Green, P., Harris, D., Hooper, E. J., Jones, C., Kaastra, J. S., Kellogg, E., Murray, S., McNamara, B., Nicastro, F., Ponman, T. J., Schlegel, E. M., Siemiginowska, A., Tananbaum, H., Vikhlinin, A., Virani, S., and Wilkes, B.

Abstract

We present results from a ChandraX-Ray Observatorystudy of the field X-ray source populations in four different observations: two high-redshift (z~ 0.5) clusters of galaxies 3C 295 and RX J003033.2+261819; and two noncluster fields with similar exposure time. Surprisingly, the 0.5-2 keV source surface densities (~900-1200 sources deg-2at a flux limit of 1.5 × 10-15ergs cm-2s-1) measured in an ~8' × 8' area surrounding each cluster exceed by a factor of ~2 the value expected on the basis of the ROSATand Chandralog N- log S, with a significance of ~2 ? each, or ~3.5 ? when the two fields are combined (i.e., a probability to be a statistical fluctuation of <1% and <0.04%, respectively). The same analysis performed on the noncluster fields and on the outer chips of the cluster fields does notshow evidence of such an excess. In both cluster fields, the summed 0.5-10 keV spectrum of the detected objects is well fitted by a power law with ? ~ 1.7 similar to active galactic nuclei (AGNs) and shows no sign of intrinsic absorption. The few (~10 of 35) optical identifications available to date confirm that most of them are, as expected, AGNs, but the number of redshifts available is too small to allow conclusions on their nature. We discuss possible interpretations of the overdensity in terms of a statistical variation of cosmic background sources; a concentration of AGNs and/or powerful starburst galaxies associated with the clusters; and gravitational lensing of background QSOs by the galaxy clusters. All explanations, however, are difficult to reconcile with the large number of excess sources detected. Deeper X-ray observations and more redshifts measurements are clearly required to settle the issue.

Published
2001
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