XMM-Newton spectral-fit database

XMMFITCAT-Z


Introduction

The 3XMM catalogue of sources detected with XMM-Newton is the largest X-ray source catalogue ever produced. This catalogue currently contains about 400,000 unique sources covering a total area of 877 sq. degrees of the sky with about two thirds of these located at high Galactic latitude, |b|>20°, the vast majority of them being extragalactic sources. The XMM-Newton Survey Science Center (SSC), responsible for the catalogue production, plans to increase its size by ~ 10% every year via incremental versions of 3XMM.

The 3XMM catalogue has been enriched with added-value products thanks to the XMMFITCAT and ARCHES projects. XMMFITCAT provides the spectral-fitting results for more than 99,000 sources with the highest photon statistics within the Data Release 6 of 3XMM (3XMM-DR6). The ARCHES project (funded by the EU FP7 program) enhanced the 3XMM catalogue by providing cross-matches with several multi-wavelength catalogues, and by constructing Spectral Energy Distributions (SEDs) based on reliable photometry. However, the huge potential of these catalogues for extragalactic astronomy remains practically untapped because most of these sources lack a redshift. There are many source properties that cannot be derived or properly constrained without a distance/redshift estimate, such as: luminosities, plasma temperatures, rest-frame obscuring column densities, and rest-frame energies of emission and absorption features.

XMMFITCAT-Z will combine the output of the XMMFITCAT and ARCHES projects to derive photometric redshifts for the sources in the 3XMM catalogue, and will use this information to construct a new database of redshift-dependent spectral-fitting results, providing a new set of high-level products and thus, upgrading their scientific applications.


Methods

The multi-wavelength data necessary to derive photometric redshifts will be obtained from the SDSS, VST-ATLAS, DES, and Pan-STARRS surveys. The source matching will be achieved using the ARCHES group cross-correlation tool, which matches symmetrically an arbitrary number of catalogues providing a Bayesian probability of association or non-association (Pineau et al., 2017). XMMFITCAT-Z will also include cross-matches (and photometric data) from the WISE all-sky catalogue (3.6 and 4.5μm), and NIR data from UKIDSS, 2MASS, and VISTA-VHS, to increase the photo-z accuracy. Besides deriving photometric redshifts, the optical/near-IR data can be used to obtain source classifications. For example, they can be used to separate galaxies from stars, and to indentify AGN. Finally, we will use machine learning techniques to derive the photometric redshifts from the multi-wavelength data; and the XMMFITCAT fitting pipeline, modified by redshift as for the XMM-SDSS sample, to obtain redshift-dependent spectral-fitting results.


Project output

A multi-wavelength catalogue containing all available photometric data for each X-ray source, and the derived photmetric redhsifts will be released. Besides, once the redshifts are available, we will construct XMMFITCAT-Z, which will include, according to our estimations, redshift-dependent spectral-fitting results for at least ~ 40,000 X-ray sources.