The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies
Context. Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Aims. Our main goal is to determine whether the revised IRAC criteria of D...
| Authors: | ; ; ; ; ; ; ; ; ; |
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| Format: | Article |
| Publication date: | 2013 |
| Country: | España |
| Institution: | Universidad Complutense de Madrid (UCM) |
| Repository: | Docta Complutense |
| Language: | English |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/35208 |
| Online Access: | https://hdl.handle.net/20.500.14352/35208 |
| Access Level: | Open access |
| Keyword: | 52 Active galactic nuclei Spitzer-space-telescope Spectral energy-distribution Quasi-stellar objects Star-forming galaxies Field-south survey X-ray sources Midinfrared selection Synthesis models Source catalogs Astrofísica Astronomía (Física) |
| _version_ | 1878739967618842624 |
|---|---|
| author | Castelló Mor, N. |
| author2 | Carrera, F. J. Alonso Herrero, A. Mateos, S. Barcons, X. Ranalli, P. Pérez González, Pablo Guillermo Comastri, A. Vignali, C. Georgantopoulos, I. |
| author2_role | author author author author author author author author author |
| author_browse | Alonso Herrero, A. Barcons, X. Carrera, F. J. Castelló Mor, N. Comastri, A. Georgantopoulos, I. Mateos, S. Pérez González, Pablo Guillermo Ranalli, P. Vignali, C. |
| author_facet | Castelló Mor, N. Carrera, F. J. Alonso Herrero, A. Mateos, S. Barcons, X. Ranalli, P. Pérez González, Pablo Guillermo Comastri, A. Vignali, C. Georgantopoulos, I. |
| author_role | author |
| collection | Docta Complutense |
| description | Context. Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Aims. Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012, ApJ, 748, 142; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N_H > 10^22 cm^-2). Methods. We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component. Results. We find 21/147 sources to be heavily absorbed but the uncertainties in their obscuring column densities do not allow us to confirm their Compton-Thick nature without resorting to additional criteria. Although IR power-law galaxies are less numerous in our sample than IR non-power-law galaxies (60 versus 87 respectively), we find that the fraction of absorbed (N_H^intr > 10^22 cm^-2) AGN is significantly higher (at about 3 sigma level) for IR-power-law sources (similar to 2/3) than for those sources that do not meet this IR selection criteria (~1/2). This behaviour is particularly notable at low luminosities, but it appears to be present, although with a marginal significance, at all luminosities. Conclusions. We therefore conclude that the IR power-law method is efficient in finding X-ray-absorbed sources. We would then expect that the long-sought dominant population of absorbed AGN is abundant among IR power-law spectral shape sources not detected in X-rays. |
| eu_rights_str_mv | openAccess |
| format | article |
| id | ES_cb4e5f6a3ec3b81c8a6b6c4e6aa89588 |
| institution | Universidad Complutense de Madrid (UCM) |
| instname_str | Universidad Complutense de Madrid (UCM) |
| language | eng |
| network_acronym_str | ES |
| network_name_str | España |
| oai_identifier_str | oai:docta.ucm.es:20.500.14352/35208 |
| publishDate | 2013 |
| publishDateSort | 2013 |
| publisher | EDP Sciencies |
| publisherStr | EDP Sciencies |
| reponame_str | Docta Complutense |
| spelling | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies Castelló Mor, N. Carrera, F. J. Alonso Herrero, A. Mateos, S. Barcons, X. Ranalli, P. Pérez González, Pablo Guillermo Comastri, A. Vignali, C. Georgantopoulos, I. 52 Active galactic nuclei Spitzer-space-telescope Spectral energy-distribution Quasi-stellar objects Star-forming galaxies Field-south survey X-ray sources Midinfrared selection Synthesis models Source catalogs Astrofísica Astronomía (Física) Context. Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Aims. Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012, ApJ, 748, 142; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N_H > 10^22 cm^-2). Methods. We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component. Results. We find 21/147 sources to be heavily absorbed but the uncertainties in their obscuring column densities do not allow us to confirm their Compton-Thick nature without resorting to additional criteria. Although IR power-law galaxies are less numerous in our sample than IR non-power-law galaxies (60 versus 87 respectively), we find that the fraction of absorbed (N_H^intr > 10^22 cm^-2) AGN is significantly higher (at about 3 sigma level) for IR-power-law sources (similar to 2/3) than for those sources that do not meet this IR selection criteria (~1/2). This behaviour is particularly notable at low luminosities, but it appears to be present, although with a marginal significance, at all luminosities. Conclusions. We therefore conclude that the IR power-law method is efficient in finding X-ray-absorbed sources. We would then expect that the long-sought dominant population of absorbed AGN is abundant among IR power-law spectral shape sources not detected in X-rays. EDP Sciencies https://hdl.handle.net/20.500.14352/35208 |
| spellingShingle | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies Castelló Mor, N. 52 Active galactic nuclei Spitzer-space-telescope Spectral energy-distribution Quasi-stellar objects Star-forming galaxies Field-south survey X-ray sources Midinfrared selection Synthesis models Source catalogs Astrofísica Astronomía (Física) |
| title | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| title_full | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| title_fullStr | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| title_full_unstemmed | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| title_short | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| title_sort | The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies |
| topic | 52 Active galactic nuclei Spitzer-space-telescope Spectral energy-distribution Quasi-stellar objects Star-forming galaxies Field-south survey X-ray sources Midinfrared selection Synthesis models Source catalogs Astrofísica Astronomía (Física) |
| topic_facet | 52 Active galactic nuclei Spitzer-space-telescope Spectral energy-distribution Quasi-stellar objects Star-forming galaxies Field-south survey X-ray sources Midinfrared selection Synthesis models Source catalogs Astrofísica Astronomía (Física) |
| url | https://hdl.handle.net/20.500.14352/35208 |