The XMM-Newton bright serendipitous survey - Identification and optical spectral properties

Aims. We present the optical classification and redshift of 348 X-ray selected sources from the XMM-Newton Bright Serendipitous Survey (XBS), which contains a total of 400 objects (identification level = 87%). About 240 are new identifications. In particular, we discuss in detail the classification criteria adopted for the active galactic nuclei (AGNs) population.Methods. By means of systematic spectroscopic campaigns using various telescopes and through the literature search, we have collected an optical spectrum for the large majority of the sources in the XBS survey and applied a well-defined classification "flow chart".Results. We find that the AGNs represent the most numerous population at the flux limit of the XBS survey (similar to 10(-13) erg cm(-2) s(-1)) constituting 80% of the XBS sources selected in the 0.5-4.5 keV energy band and 95% of the "hard" (4.5-7.5 keV) selected objects. Galactic sources populate the 0.5-4.5 keV sample significantly (17%) and only marginally (3%) the 4.5-7.5 keV sample. The remaining sources in both samples are clusters/groups of galaxies and normal galaxies (i.e. probably not powered by an AGN). Furthermore, the percentage of type 2 AGNs (i.e. optically absorbed AGNs with A(V) > 2 mag) dramatically increases going from the 0.5-4.5 keV sample (f = N-AGN2/N-AGN = 7%) to the 4.5-7.5 keV sample (f = 32%). We finally propose two simple diagnostic plots that can be easily used to obtain the spectral classification for relatively low-redshift AGNs even if the quality of the spectrum is not good.

[1]  Yoshiaki Taniguchi,et al.  The Narrow-Line Region of Seyfert Galaxies: Narrow-Line Seyfert 1 Galaxies versus Broad-Line Seyfert 1 Galaxies , 2001 .

[2]  Dawei Xu,et al.  An AGN sample with high X-ray-to-optical flux ratio from RASS. I. The optical identification , 1999 .

[3]  M. M. De Robertis,et al.  The Central Engines in Narrow-Line Seyfert 1 Galaxies , 2004 .

[4]  James Liebert,et al.  The Einstein Observatory Medium Sensitivity Survey - Optical identifications for a complete sample of X-ray sources , 1983 .

[5]  Richard G. McMahon,et al.  QSOs with narrow emission lines , 1988 .

[6]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[7]  Warrick J. Couch,et al.  Quasars from a complete spectroscopic survey , 2001 .

[8]  Geoffrey Burbidge,et al.  QSOs in the Field of the Seyfert 1 Galaxy NGC 5548 , 2002 .

[9]  P. Ciliegi,et al.  The HELLAS2XMM survey IV. Optical identifications and the evolution of the accretion luminosity in the Universe , 2003, astro-ph/0306556.

[10]  A. Fontana,et al.  The K20 survey. VII. The spectroscopic catalogue: spectral properties and evolution of the galaxy population ⋆, ⋆⋆ , 2005, astro-ph/0504248.

[11]  Thomas L. Aldcroft,et al.  A Uniform Analysis of the Lyα Forest at z = 0-5. III. Hubble Space Telescope Faint Object Spectrograph Spectral Atlas , 2002 .

[12]  V. Zitelli,et al.  A spectroscopically complete sample of quasars with $B_J\le22.0$⋆ , 1992 .

[13]  Isabella M. Gioia,et al.  The Einstein Observatory Extended Medium-Sensitivity Survey. II - The optical identifications , 1991 .

[14]  E. Joseph Wampler,et al.  Emission-line properties of optically and radio-selected complete quasar samples , 1989 .

[15]  Daniela Calzetti,et al.  The Nature of the Ultraviolet Continuum in Type 2 Seyfert Galaxies , 1995 .

[16]  Keith A. Arnaud,et al.  EXOSAT observations of a strong soft X-ray excess in MKN 841. , 1985 .

[17]  A. Caccianiga,et al.  The CLASS blazar survey — I. Selection criteria and radio properties , 2001 .

[18]  Xavier Barcons,et al.  The ROSAT International X-ray/Optical Survey (RIXOS): source catalogue , 2000 .

[19]  R. Nichol,et al.  The Sloan Digital Sky Survey Quasar Catalog. II. First Data Release , 2003, astro-ph/0308443.

[20]  S. Dye,et al.  The evolution of faint AGN between z ' 1 and z ' 5 from the COMBO-17 survey , 2003 .

[21]  W. N. Brandt,et al.  DEEP EXTRAGALACTIC X-RAY SURVEYS , 2005 .

[22]  Frederic H. Chaffee,et al.  The Large Bright Quasar Survey.VI.Quasar Catalog and Survey Parameters , 1995 .

[23]  Silvia Mateos,et al.  The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM-Newton deep fields , 2005 .

[24]  E. Perlman,et al.  Discovery of a Very X-Ray Luminous Galaxy Cluster at z = 0.89 in the Wide Angle ROSAT Pointed Survey , 2000 .

[25]  G. C. Perola,et al.  Spectroscopic identification of ten faint hard X-ray sources discovered by Chandra , 2000 .

[26]  Germany,et al.  The classification of BL Lacertae objects: the Ca H&K break , 2002, astro-ph/0207075.

[27]  Donald E. Osterbrock,et al.  Spectral Classification of Emission-Line Galaxies , 1987 .

[28]  Stuart Lumsden,et al.  Optical Classification of Southern Warm Infrared Galaxies , 2001 .

[29]  Alexei V. Filippenko,et al.  A Search for “Dwarf'' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies , 1997, astro-ph/9704107.

[30]  R. J. Smith,et al.  The 2dF QSO Redshift Survey — V. The 10k catalogue , 2001, astro-ph/0104095.

[31]  M. Page,et al.  XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs , 2004, astro-ph/0410432.

[32]  M. J. Page,et al.  Elusive AGN in the XMM-Newton bright serendipitous survey , 2007, 0705.2985.

[33]  Frederic H. Chaffee,et al.  The large, bright QSO survey. V - QSOs in three southern fields , 1991 .

[34]  P. Veron,et al.  A spectrophotometric atlas of narrow-line seyfert 1 galaxies , 2001 .

[35]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[36]  R. Della Ceca,et al.  The luminosity function and cosmological evolution of X-ray-selected BL lacertae objects , 1991 .

[37]  M. S. Oey,et al.  Atlas of quasar energy distributions , 1994 .

[38]  Arjun Dey,et al.  Chandra Detection of a Type II Quasar at z = 3.288 , 2001, astro-ph/0111513.

[39]  M. J. Page,et al.  Optical and X-ray properties of the RIXOS AGN — II. Emission lines , 1997, astro-ph/9708199.

[40]  Paolo Giommi,et al.  The Deep X-Ray Radio Blazar Survey. I. Methods and First Results , 1998, astro-ph/9801024.

[41]  Chris Impey,et al.  Quasars as Absorption Probes of the Hubble Deep Field , 1999 .

[42]  Belinda J. Wilkes,et al.  The Cambridge-Cambridge ROSAT Serendipity Survey — V. Catalogue and optical identifications , 1997 .

[43]  R. Della Ceca,et al.  The stellar content of the XMM-Newton bright serendipitous survey , 2006, astro-ph/0610354.

[44]  Frederic H. Chaffee,et al.  The large, bright QSO survey. III, QSOs in six equatorial fields , 1991 .

[45]  Cambridge,et al.  1WGAJ1226.9+3332: a high redshift cluster discovered by Chandra , 2001 .

[46]  Stefano Cristiani,et al.  Observations of variable quasar candidates , 1990 .

[47]  O. Le Fevre,et al.  The Canada–France Redshift Survey – VII. Optical counterparts of microjansky radio sources , 1995 .

[48]  M. J. Page,et al.  Exploring the X-ray sky with the XMM-Newton bright serendipitous survey , 2004, astro-ph/0407481.

[49]  M. Véron-Cetty,et al.  A catalogue of quasars and active nuclei: 11th edition , 1998 .

[50]  R. Giacconi,et al.  A Classic Type 2 QSO , 2001, astro-ph/0103198.

[51]  Silvano Molendi,et al.  The HELLAS2XMM 1dF Survey: On the Nature of High X-Ray/Optical Flux Sources , 2004 .

[52]  X. Barcons,et al.  XMM-Newton observations reveal AGN in apparently normal galaxies , 2003 .

[53]  P. Hewett,et al.  A High Signal-to-Noise Ratio Composite Quasar Spectrum , 1991 .

[54]  F. J. Carrera,et al.  An X-ray bright ERO hosting a type 2 QSO , 2006 .

[55]  H. Arp,et al.  A Possible X-ray Jet from the Starburst Galaxy NGC 6217 , 2001, astro-ph/0107161.

[56]  E. Greisen,et al.  The NRAO VLA Sky Survey , 1996 .

[57]  Luis C. Ho,et al.  A Search for ``Dwarf'' Seyfert Nuclei. II. an Optical Spectral Atlas of the Nuclei of Nearby Galaxies , 1995 .

[58]  Cesare Barbieri,et al.  The SA 94 QSO surveys. V - an UVx sample of 97 QSOs with B not greater than 19.9 , 1992 .

[59]  Australian National University,et al.  Optical Polarization of 52 Radio-loud QSOs and BL Lacertae Objects , 1998, astro-ph/9808060.

[60]  E. M. Burbidge,et al.  A Group of Quasi-stellar Objects Closely Associated with NGC 1068 , 1999 .

[61]  UC San Diego,et al.  QSOs and Absorption-Line Systems surrounding the Hubble Deep Field , 2000, astro-ph/0003203.

[62]  M. J. Page,et al.  The XMM-Newton HBS28 sample: Studying the obscuration in hard X-ray selected AGNs , , 2004 .

[63]  P. J. Wheatley,et al.  The XMM-Newton serendipitous survey - IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS) , 2007, 0710.0402.

[64]  Hawaii,et al.  The Bright SHARC Survey: The Cluster Catalog , 1999, astro-ph/9907401.