PHOTOMETRIC REDSHIFT AND CLASSIFICATION FOR THEXMM-COSMOS SOURCES

Abstract

We present photometric redshifts and spectral energy distribution (SED) classifications for a sample of 1542 optically identified sources detected with XMM in the COSMOS field. Our template fitting classifies 46 sources as stars and 464 as non-active galaxies, while the remaining 1032 require templates with an AGN contribution. High accuracy in the derived photometric redshifts was accomplished as the result of 1) photometry in up to 30 bands with high significance detections, 2) a new set of SED templates including 18 hybrids covering the far-UV to mid-infrared, which have been constructed by the combination of AGN and non-active galaxies templates, and 3) multi-epoch observations that have been used to correct for variability (most important for type 1 AGN). The reliability of the photometric redshifts is evaluated using the sub-sample of 442 sources with measured spectroscopic redshifts. We achieved an accuracy of σ ∆z/(1+zspec) = 0.014 for i * AB <22.5 (σ ∆z/(1+zspec) ∼ 0.015 for i * AB <24.5). The high accuracies were accomplished for both type 2 (where the SED is often dominated by the host galaxy) and type 1 AGN and QSOs out to z = 4.5. The number of outliers is a large improvement over previous photometric redshift estimates for X-ray selected sources (4.0% and 4.8% outliers for i * AB <22.5 and i * AB <24.5, respectively). We show that the intermediate band photometry is vital to achieving accurate photometric redshifts for AGN, whereas the broad SED coverage provided by mid infrared (Spitzer/IRAC) bands is important to reduce the number of outliers for normal galaxies.

Cold dust emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: dependence on luminosity, obscuration and AGN activity

“…For the AGN with photometric redshifts, type 1 AGN are considered to be those fit by templates 19-30 in Salvato et al (2011) whereas type 2 AGN are those fit by templates 1-18 or >100 (which correspond to galaxy templates). The photometric redshift accuracy is in general very good σ z /(1 + z) = 0.014 for i AB < 22.5 and 0.015 for i AB < 24.5 (Salvato et al 2009). Photometry at mid-infrared wavelengths is from the Spitzer S-COSMOS Survey (Sanders et al 2007).…”

NEW HIGH-z FERMI BL LACS WITH THE PHOTOMETRIC DROPOUT TECHNIQUE

“…Our first library is comprised of 60 power-law SED templates of the form l µ l b -F , such that β ranged from 0 to 3 in steps of 0.05, under the assumption that the UV-Optical-Near-Infrared regime for BL Lacs can be fit with a single power-law template. In addition, a library of galaxies and galaxy/AGN hybrids (Salvato et al 2009(Salvato et al , 2011 as well as a stellar library using templates from Pickles (1998), Bohlin et al (1995), and Chabrier et al (2000) were used. The results from the first two libraries are presented in Table 4.…”

The dark matter haloes of moderate luminosity X-ray AGN as determined from weak gravitational lensing and host stellar masses

“…The combined catalogue of X-ray sources contains ∼1800 objects from XMM-COSMOS and ∼950 objects from C-COSMOS. Details concerning the X-ray catalogues, the spectroscopic observing programme, and the spectroscopic/photometric classifications can be found in Brusa et al (2010), Civano et al (2012), and Salvato et al (2009Salvato et al ( , 2011.…”

“…All spectroscopically identified broad line AGN are removed from the sample. A photometric classification (Salvato et al 2009(Salvato et al , 2011) is used to identify obscured AGN when a spectroscopic classification is not available. Spectroscopic redshifts are available for 71 per cent of our sample (272/382).…”