Volume 618, October 2018
|Number of page(s)||16|
|Section||Catalogs and data|
|Published online||15 October 2018|
XMMPZCAT: A catalogue of photometric redshifts for X-ray sources
Institute for Astronomy, Astrophysics, Space Applications, and Remote Sensing (IAASARS), National Observatory of Athens, 15236 Penteli, Greece
2 Instituto de Física de Cantabria (UC-CSIC), Av. de los Castros s/n, 39005 Santander, Spain
Accepted: 10 July 2018
Aims. The third version of the XMM-Newton serendipitous catalogue (3XMM), containing almost half million sources, is now the largest X-ray catalogue. However, its full scientific potential remains untapped due to the lack of distance information (i.e. redshifts) for the majority of its sources. Here we present XMMPZCAT, a catalogue of photometric redshifts (photo-z) for 3XMM sources.
Methods. We searched for optical counterparts of 3XMM-DR6 sources outside the Galactic plane in the SDSS and Pan-STARRS surveys, with the addition of near-(NIR) and mid-infrared (MIR) data whenever possible (2MASS, UKIDSS, VISTA-VHS, and AllWISE). We used this photometry data set in combination with a training sample of 5157 X-ray selected sources and the MLZ-TPZ package, a supervised machine learning algorithm based on decision trees and random forests for the calculation of photo-z.
Results. We have estimated photo-z for 100 178 X-ray sources, about 50% of the total number of 3XMM sources (205 380) in the XMM-Newton fields selected to build this catalogue (4208 out of 9159). The accuracy of our results highly depends on the available photometric data, with a rate of outliers ranging from 4% for sources with data in the optical + NIR + MIR, up to ~40% for sources with only optical data. We also addressed the reliability level of our results by studying the shape of the photo-z probability density distributions.
Key words: catalogs / galaxies: active / X-rays: general / X-rays: galaxies
© ESO 2018
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