THE CHANDRA COSMOS-LEGACY SURVEY : THE z > 3 SAMPLE

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Marchesi , S , Civano , F , Salvato , M , Shankar , F , Comastri , A , Elvis , M , Lanzuisi , G , Trakhtenbrot , B , Vignali , C , Zamorani , G , Allevato , V , Brusa , M , Fiore , F , Gilli , R , Griffiths , R , Hasinger , G , Miyaji , T , Schawinski , K , Treister , E & Urry , C M 2016 , ' THE CHANDRA COSMOS-LEGACY SURVEY : THE z > 3 SAMPLE ' , Astrophysical Journal , vol. 827 , no. 2 , 150 . https://doi.org/10.3847/0004-637X/827/2/150

Title: THE CHANDRA COSMOS-LEGACY SURVEY : THE z > 3 SAMPLE
Author: Marchesi, S.; Civano, F.; Salvato, M.; Shankar, F.; Comastri, A.; Elvis, M.; Lanzuisi, G.; Trakhtenbrot, B.; Vignali, C.; Zamorani, G.; Allevato, V.; Brusa, M.; Fiore, F.; Gilli, R.; Griffiths, R.; Hasinger, G.; Miyaji, T.; Schawinski, K.; Treister, E.; Urry, C. M.
Contributor: University of Helsinki, Department of Physics
Date: 2016-08-20
Language: eng
Number of pages: 16
Belongs to series: Astrophysical Journal
ISSN: 0004-637X
URI: http://hdl.handle.net/10138/183623
Abstract: We present the largest high-redshift (3 <z <6.85) sample of X-ray-selected active galactic nuclei (AGNs) on a contiguous field, using sources detected in the Chandra COSMOS-Legacy survey. The sample contains 174 sources, 87 with spectroscopic redshift and the other 87 with photometric redshift (z(phot)). In this work, we treat z(phot) as a probability-weighted sum of contributions, adding to our sample the contribution of sources with zphot. <3 but zphot probability distribution > 0 at z > 3. We compute the number counts in the observed 0.5-2 keV band, finding a decline in the number of sources at z > 3 and constraining phenomenological models of the X-ray background. We compute the AGN space density at z. > 3 in two different luminosity bins. At higher luminosities (logL(2-10 keV) > 44.1 erg s(-1)), the space density declines exponentially, dropping by a factor of similar to 20 from z similar to 3 to z similar to 6. The observed decline is similar to 80% steeper at lower luminosities (43.55 erg s(-1) <logL(2-10 keV) <44.1 erg s(-1)) from z similar to 3 to z similar to 4.5. We study the space density evolution dividing our sample into optically classified Type 1 and Type 2 AGNs. At logL (2-10 keV) > 44.1 erg s(-1), unobscured and obscured objects may have different evolution with redshift, with the obscured component being three times higher at z similar to 5. Finally, we compare our space density with predictions of quasar activation merger models, whose calibration is based on optically luminous AGNs. These models significantly overpredict the number of expected AGNs at logL (2-10 keV) > 44.1 erg s(-1) with respect to our data.
Subject: galaxies: active
galaxies: evolution
X-rays: galaxies
ACTIVE GALACTIC NUCLEI
X-RAY LUMINOSITY
SUPERMASSIVE BLACK-HOLES
DEEP-FIELD-SOUTH
SPECTRAL ENERGY-DISTRIBUTIONS
HIGH-REDSHIFT QUASARS
POINT-SOURCE CATALOG
STAR-FORMING GALAXY
SIMILAR-TO 4
MULTIWAVELENGTH PROJECT
115 Astronomy, Space science
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