The ISO-2MASS AGN survey: On the type-1 sources

Abstract

We combined the ISOCAM Parallel Mode Survey at 6.7 micron (LW2 filter) with the Two Micron All Sky Survey in order to obtain a powerful tool to search for AGN independent of dust extinction. Using moderate colour criteria H-K>0.5 and K-LW2>2.7 we have selected a sample of 77 AGN candidates in an effective area of about 10 square degrees. By means of optical spectroscopy we find 24 (30%) type-1 QSOs at redshifts 0.1<z<2.3; nine of them have z>0.8. About one third of the ISO-2MASS QSOs show so red optical colours, that they are missed in optical and UV AGN surveys like SDSS, 2DF, or HES. With a surface density of about 2 deg^(-2) down to R<18 mag the ISO-2MASS QSOs outnumber the 1.35 deg^(-2) of the SDSS quasar survey by 50%; we find a combined optical-IR QSO surface density of 2.7 deg^(-2). Since only two of the ISO-2MASS QSOs have also J-K>2, the inclusion of the ISO mid-infrared photometry significantly extends the capabilities of the pure 2MASS red AGN survey. We suggest that the newly found red AGN resemble young members of the quasar population, and that quasars spend much of their lifetime in a dust enshrouded phase.

5 pages, 5 figures, accepted for publication as A&A Letter

References in corpus (14)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The USNO-B Catalog
• The u'g'r'i'z' Standard Star Network
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• Obscured and unobscured active galactic nuclei in the Spitzer Space Telescope First Look Survey
• The 2dF QSO Redshift Survey - XII. The spectroscopic catalogue and luminosity function
• Elusive Active Galactic Nuclei
• Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope: Early Results on Mrk 1014, Mrk 463, and UGC 5101
• A Chandra Survey of the Nearest ULIRGs: Obscured AGN or Super-Starbursts?
• FIRST-2MASS Sources Below the APM Detection Threshold: A Population of Highly Reddened Quasars
• X-ray properties of Red Active Galactic Nuclei
• An Empirical Calibration of the Completeness of the SDSS Quasar Survey
• An Unbiassed Census of Active Galactic Nuclei in the Two Micron All Sky Survey
• Mid-infrared selection of AGN

Cited by in corpus (14)

• Optical spectroscopy and X-ray detections of a sample of quasars and AGN selected in the mid-infrared from two Spitzer wide-area surveys
• Spitzer Power-law AGN Candidates in the Chandra Deep Field-North
• Ultraluminous Infrared Galaxies
• A population of high-redshift type-2 quasars-I. Selection Criteria and Optical Spectra
• Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material
• Quantifying the anisotropy in the infrared emission of powerful AGN
• The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources
• A population of high-redshift type-2 quasars-II. Radio Properties
• Early Science Result from the Japanese Virtual Observatory: AGN and Galaxy Clustering at z = 0.3 to 3.0
• Narrow-line AGN in the ISO-2MASS Survey
• Investigating the complex X-ray spectrum of a broad-line 2MASS red quasar: XMM-Newton observation of FTM 0830+3759
• Quasars and their host galaxies
• The reddest ISO-2MASS quasar
• Polycyclic aromatic hydrocarbon selected galaxies