DISSECTING PHOTOMETRIC REDSHIFT FOR ACTIVE GALACTIC NUCLEUS USING XMM- AND CHANDRA-COSMOS SAMPLES

By Mara Salvato, O. Ilbert, G. Hasinger, A. Rau, F. Civano, G. Zamorani, M. Brusa, M. Elvis, C. Vignali, H. Aussel and 56 more. 2011

191 citations recorded by the source corpus.

In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg2 of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by Δz > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (HAB = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0a9097913b886746daa48ba69127f479a66e82f1

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

The incidence of obscuration in active galactic nuclei (2013, background): “…568 sources, for which only photometric redshifts are available, the source classification in type-1 and type-2 was performed on the basis of the template that best describes their SED as derived from Salvato et al. (2011); we have 130 ‘photometric’ type-1 and 438 ‘photometric’ type-2 AGN.”
The Herschel census of infrared SEDs through cosmic time (2013, methodology): “For the sources which host X-ray detected AGN, we substitute the Ilbert et al. redshift with a photometric redshift from Salvato et al. (2009, 2011).”
X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue (2014, methodology): “…approach is often not applicable, (ii) a large fraction of the deep field X-ray sources have redshifts measured via photometric methods (e.g. Salvato et al. 2009, 2011) and therefore suffer uncertainties that affect the inferred X-ray spectral parameters, (iii) it is often difficult for…”
X-shooter reveals powerful outflows in z ∼ 1.5 X-ray selected obscured quasi-stellar objects (2014, methodology): “This is true in particular for AGN where the relative galaxy/AGN contribution is unknown and the libraries of templates change, depending on the type of sources we want to fit (Salvato et al. 2011).”
A HUBBLE DIAGRAM FOR QUASARS (2015, methodology): “…Sample We considered an updated version of the catalog already published by Brusa et al. (2010), which includes the photometric redshift catalog by Salvato et al. (2011) and new spectroscopic redshift measurements.5 We have selected 1375 X-ray sources detected in the 0.5–2 keV band at a flux…”
Bolometric luminosities and Eddington ratios of X-ray selected active galactic nuclei in the XMM-COSMOS survey (2012, methodology): “The spectroscopic coverage with VIMOS/VLT and IMACS/Magellan, coupled with the reliable photometric redshifts derived from multiband fitting (Salvato et al. 2011, herefter S11), allows us to build a large and homogeneous sample of AGN with a well sampled spectral coverage and to keep selection…”
THE COSMOS2015 CATALOG: EXPLORING THE 1 < z < 6 UNIVERSE WITH HALF A MILLION GALAXIES (2016, methodology): “For those sources, the photometric redshift are computed with a specific tuning and are presented in Salvato et al. (2011).”
EVIDENCE FOR WIDE-SPREAD ACTIVE GALACTIC NUCLEUS-DRIVEN OUTFLOWS IN THE MOST MASSIVE z ∼ 1–2 STAR-FORMING GALAXIES (2014, background): “High-z AGNs of luminosity as detected in X-ray deep fields vary by few tenths of a magnitude over a few year timescale (Salvato et al. 2011; Wold et al. 2007).”
OBSCURATION-DEPENDENT EVOLUTION OF ACTIVE GALACTIC NUCLEI (2015, methodology): “This is essential for reliable photometric redshifts, especially in the case of bright X-ray samples like the XMM-XXL (e.g. Salvato et al. 2011).”
Euclid preparation (2021, background): “Salvato et al. (2011) find, however, that standard galaxy SED libraries are sufficient to obtain accurate photo-z for such sources.”
Accreting supermassive black holes in the COSMOS field and the connection to their host galaxies (2012, methodology): “In practice, the source classification for photo-z AGNs was performed following Salvato et al. (2011) on the basis of the template2 that best describes their SED, and applying the same threshold in X-ray luminosity (L[2−10] keV > 2 × 1042 erg s−1).”
The Atacama Cosmology Telescope: A Catalog of >4000 Sunyaev–Zel’dovich Galaxy Clusters (2020, methodology): “We used a subset of the spectral templates used in the COSMOS survey (Ilbert et al. 2009; Salvato et al. 2011), representing a range of normal galaxies and active galactic nuclei (AGNs), removing all elliptical templates based on Bruzual & Charlot (2003) stellar population synthesis models (as…”
The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day (2014, background): “The more common moderate luminosity AGNs can still be fit properly with galaxy templates (Salvato et al. 2011).”
THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS (2015, methodology): “Photometric redshifts have been produced following the same procedure described in detail in Salvato et al. (2011), without any further training sample.”
IDENTIFYING LUMINOUS ACTIVE GALACTIC NUCLEI IN DEEP SURVEYS: REVISED IRAC SELECTION CRITERIA (2012, methodology): “For the remaining Chandra sources, we adopt the AGN-specific photometric redshifts of Salvato et al. (2011).”
What drives the growth of black holes (2011, background): “…(with spectroscopic or photometric data; e.g., Barger et al. 2003b; Szokoly et al. 2004; Zheng et al. 2004; Cardamone et al. 2010; Luo et al. 2010; Salvato et al. 2011), since the optical/near-IR counterparts for many of the AGNs are very faint (e.g., Alexander et al., 2001; Mainieri et al.,…”
The DEIMOS 10K Spectroscopic Survey Catalog of the COSMOS Field (2018, methodology): “The Cosmic Evolution Survey (COSMOS; Scoville et al. 2007b) is a galaxy survey designed to probe the formation and evolution of galaxies, star formation, and active galactic nuclei (AGNs), both over cosmic time (redshift z=0.5–6) and as a function of the local galaxy environment defined by the dark ”
THE CHANDRA COSMOS SURVEY. III. OPTICAL AND INFRARED IDENTIFICATION OF X-RAY POINT SOURCES (2012, methodology): “The same catalog is used in Ilbertet al. (2009, 2010) and Salvato et al. (2009, 2011).”