SPECTROSCOPIC IDENTIFICATIONS OF SPITZER SOURCES IN THE SWIRE/XMM-NEWTON/ELAIS-S1 FIELD: A LARGE FRACTION OF ACTIVE GALACTIC NUCLEI WITH HIGH F(24 {mu}m)/F(R) RATIO

Journal Article · Thu Oct 01 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/703/2/1778· OSTI ID:21371856

Sacchi, N; La Franca, F; Matute, I ^[1]; Feruglio, C; Fiore, F; Cocchia, F; Maiolino, R ^[2]; Puccetti, S ^[3]; Berta, S; Brusa, M ^[4]; Cimatti, A; Pozzi, F; Vignali, C ^[5]; Comastri, A; Gruppioni, C; Pozzetti, L; Zamorani, G ^[6]; Franceschini, A ^[7]; Polletta, M ^[8]; Oliver, S ^[9]

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1. Dipartimento di Fisica, Universita Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy)
2. INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040, Monteporzio Catone (Italy)
3. ASI Science Data Center, via G. Galilei, I-00044 Frascati (Italy)
4. Max Planck Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany)
5. Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
6. INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
7. Dipartimento di Astronomia, Universita di Padova, vicolo dell'Osservatorio 2, I-35122 Padova (Italy)
8. INAF-IASF Milano, via E. Bassini 15, I-20133 Milano (Italy)
9. Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QJ (United Kingdom)

We present a catalog of optical spectroscopic identifications of sources detected by Spitzer at 3.6 or 24 {mu}m down to {approx}10 and {approx}280 {mu}Jy, respectively, in the SWIRE/XMM-Newton/ELAIS-S1 field and classified via line width analysis and diagnostic diagrams. A total of 1376 sources down to R {approx} 24.2 mag have been identified (1362 detected at 3.6 {mu}m, 419 at 24 {mu}m, and 405 at both) by low-resolution optical spectroscopy carried out with FORS2, VIMOS, and EFOSC2 at the Very Large Telescope and 3.6 m ESO telescope. The spectroscopic campaigns have been carried out over the central 0.6 deg{sup 2} area of ELAIS-S1 which, in particular, has also been observed by XMM-Newton and Chandra. We find the first direct optical spectroscopic evidence that the fraction of active galactic nuclei (AGNs; mostly AGN2) increases with increasing F(24 {mu}m)/F(R) ratio, reaching values of 70(+-20)% in the range 316 < F(24 {mu}m)/F(R) < 1000. We present an Infrared Array Camera-Multiband Imaging Photometer color-color diagram able to separate AGN1 from obscured AGN2 candidates. After having corrected for the spectroscopic incompleteness of our sample, the result is that the AGN fraction at F(24 {mu}m) {approx}0.8 mJy is {approx}22(+-7)% and decreases slowly to {approx}19(+-5)% down to F(24 {mu}m) {approx} 0.3 mJy.

• OSTI ID: 21371856
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 703; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
COLOR
DOCUMENT TYPES
GALAXIES
GALAXY NUCLEI
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHOTOMETERS
PHYSICAL PROPERTIES
SPECTROSCOPY
TELESCOPES