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Titolo:
The ROSAT Deep Survey - VI. X-ray sources and optical identifications of the ultra deep survey
Autore:
Lehmann, I; Hasinger, G; Schmidt, M; Giacconi, R; Trumper, J; Zamorani, G; Gunn, JE; Pozzetti, L; Schneider, DP; Stanke, T; Szokoly, G; Thompson, D; Wilson, G;
Indirizzi:
Astrophys Inst Potsdam, D-14482 Potsdam, Germany Astrophys Inst Potsdam Potsdam Germany D-14482 D-14482 Potsdam, Germany Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA PennState Univ University Pk PA USA 16802 s, University Pk, PA 16802 USA CALTECH, Pasadena, CA 91125 USA CALTECH Pasadena CA USA 91125CALTECH, Pasadena, CA 91125 USA Assoc Univ Inc, Washington, DC 20036 USA Assoc Univ Inc Washington DC USA20036 Univ Inc, Washington, DC 20036 USA Max Planck Inst Extraterr Phys, D-85748 Garching, Germany Max Planck Inst Extraterr Phys Garching Germany D-85748 arching, Germany CNR, Ist Radioastron, I-40129 Bologna, Italy CNR Bologna Italy I-40129CNR, Ist Radioastron, I-40129 Bologna, Italy Osservatorio Astron Bologna, I-40127 Bologna, Italy Osservatorio Astron Bologna Bologna Italy I-40127 I-40127 Bologna, Italy Princeton Univ Observ, Princeton, NJ 08540 USA Princeton Univ Observ Princeton NJ USA 08540 erv, Princeton, NJ 08540 USA Max Planck Inst Radioastron, D-53010 Bonn, Germany Max Planck Inst Radioastron Bonn Germany D-53010 , D-53010 Bonn, Germany Brown Univ, Dept Phys, Providence, RI 02912 USA Brown Univ Providence RI USA 02912 v, Dept Phys, Providence, RI 02912 USA
Titolo Testata:
ASTRONOMY & ASTROPHYSICS
fascicolo: 3, volume: 371, anno: 2001,
pagine: 833 - 857
SICI:
1432-0746(200106)371:3<833:TRDS-V>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
SERENDIPITY SURVEY; EMISSION-LINES; LOCKMAN FIELD; GALAXIES; REDSHIFT; TELESCOPE; EXTRACTION; CONTINUUM; CLUSTERS; SPECTRA;
Keywords:
surveys; galaxies : active; galaxies : clusters : general; quasars : emission lines; galaxies : Seyferts; X-rays : galaxies;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
57
Recensione:
Indirizzi per estratti:
Indirizzo: Lehmann, I Astrophys Inst Potsdam, Sternwarte 16, D-14482 Potsdam, GermanyAstrophys Inst Potsdam Sternwarte 16 Potsdam Germany D-14482 y
Citazione:
I. Lehmann et al., "The ROSAT Deep Survey - VI. X-ray sources and optical identifications of the ultra deep survey", ASTRON ASTR, 371(3), 2001, pp. 833-857

Abstract

The ROSAT Deep Surveys in the direction of the Lockman Hole are the most sensitive X-ray surveys performed with the ROSAT satellite. About 70-80% of the X-ray background has been resolved into discrete sources at a flux limit of similar to 10(-15) erg cm(-2) s(-1) in the 0.5-2.0 keV energy band. A nearly complete optical identification of the ROSAT Deep Survey (RDS) has shown that the great majority of sources are AGNs. We describe in this paperthe ROSAT Ultra Deep Survey (UDS), an extension of the RDS in the Lockman Hole. The Ultra Deep Survey reaches a flux level of 1.2 10(-15) erg cm(-2) s(-1) in 0.5-2.0 keV energy band, a level similar to4.6 times fainter than the RDS. We present nearly complete spectroscopic identifications (90%) of the sample of 94 X-ray sources based on low-resolution Keck spectra. The majority of the sources (57) are broad emission line AGNs (type I), whereas afurther 13 AGNs show only narrow emission lines or broad Balmer emission lines with a large Balmer decrement (type II AGNs) indicating significant optical absorption. The second most abundant class of objects (10) are groupsand clusters of galaxies (similar to 11%). Further we found five galactic stars and one "normal" emission line galaxy. Eight X-ray sources remain spectroscopically unidentified. We see no evidence for any change in population from the RDS survey to the UDS survey. The photometric redshift determination indicates in three out of the eight sources the presence of an obscured AGN. Their photometric redshifts, assuming that the spectral energy distribution (SED) in the optical/near-infrared is due to stellar processes, arein the range of 1.2 less than or equal to z less than or equal to 2.7. These objects could belong to the long-sought population of type 2 QSOs, whichare predicted by the AGN synthesis models of the X-ray background. Finally, we discuss the optical and soft X-ray properties of the type I AGN, type II AGN, and groups and clusters of galaxies, and the implication to the X-ray background.

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Documento generato il 05/12/20 alle ore 19:30:16