Harnessing the XMM-Newton data: X-ray spectral modelling of 4XMM-DR11 detections and 4XMM-DR11s sources

TL;DR

This work leverages 4XMM-DR11/DR11s data to construct four public catalogues of X-ray spectral measurements, applying automated, Bayesian spectral fitting within the XMM2ATHENA framework. It employs a consistent background model and simple to physically motivated spectral models, including absorbed power-law and class-specific fits (AGN, stars, XRBs, CVs), with photometric redshifts for AGN and multi-wavelength counterpart associations. The catalogues enable population-level studies of $N_{ m H}$, $ Gamma$, and $f_X$ distributions, validate count-rate based low-resolution spectra for broad population analyses, and demonstrate that common optical/MIR colour criteria are insufficient to uniquely select absorbed AGN. The results provide a robust foundation for future large-scale X-ray surveys and preparation for Athena-era data analysis, while offering practical tools for cross-wavelength studies and AGN obscuration investigations.

Abstract

The XMM-Newton X-ray observatory has played a prominent role in astrophysics, conducting precise and thorough observations of the X-ray sky for the past two decades. The most recent iteration of the 4XMM catalogue and one of its latest data releases DR11 mark significant improvements over previous XMM-Newton catalogues, serving as a cornerstone for comprehending the diverse inhabitants of the X-ray sky. We employ detections and spectra extracted from the 4XMM-DR11 catalogue, subjecting them to fitting procedures using simple models. Our study operates within the framework of the XMM2ATHENA project, which focuses on developing state-of-the-art methods that exploit existing XMM-Newton data. We introduce and publicly release four catalogues containing measurements derived from X-ray spectral modelling of sources. The first catalogue encompasses outcomes obtained by fitting an absorbed power law model to all the extracted spectra for individual detections within the 4XMM-DR11 dataset. The second catalogue presents results obtained by fitting both an absorbed power law and an absorbed blackbody model to all unique physical sources listed in the 4XMM-DR11s catalogue, which documents source detection results from overlapping XMM-Newton observations. For the third catalogue we use the five band count rates derived from the pipe line detection of X-ray sources to mimic low resolution spectra to get a rough estimate of the spectral shape (absorbed power-law) of all 4XMM-DR11 detections. In the fourth catalogue, we conduct spectral analyses for the subset of identified sources with extracted spectra, employing various models based on their classification into categories such as AGN, stars, X-ray binaries, and cataclysmic variables. The scientific potential of these catalogues is highlighted by discussing the capabilities of optical and mid-infrared colours for selecting absorbed AGN. (abridged)

Figures (14)

• Figure 1: Distributions of the $p$-values (top-left panel), flux (top-right panel), $N_{\rm H}$ (middle-left panel), photon index (middle-right panel), IIN (bottom-left panel) and blackbody temperature (bottom-right panel) of the sources included in the Good fit samples of C1, C2 and C3, as indicated in the legends.
• Figure 2: Distributions of the $p$-values (top-left panel), flux (top-right panel), $N_{\rm H}$ (middle-left panel), IIN (middle-right panel), blackbody temperature (bottom-left panel) and photon index (bottom-right panel) of the sources included in the Good fit sample of C4. Blue lines present the results for AGN ( zpltb model), green lines display the measurements for stars ( APEC model), orange lines show the calculations for XRB ( bbpl model) and red lines illustrate the results for CV ( bremss model).
• Figure 3: Top panel: decimal logarithm of the $2-10\,{\rm keV}$ rest-frame intrinsic luminosity versus the redshift of the reliable AGN sample. Grey dots corresponds to the unabsAGN and red dots correspond to the absAGN. Note that due to the discreteness of the zmode0 from tpz (see the text for the details), the redshift value plotted here is offset by a random number between $-0.05$ and $0.05$. Bottom panel: histogram of the redshift (left) and luminosity (right) of the Good fit and reliable absAGN and unabsAGN samples.
• Figure 4: Fraction of absorbed AGN as a function of redshift (top) and luminosity (bottom) both for the Good fitAGN sample (grey dots) and for the reliable AGN sample (red triangles).
• Figure 5: Distribution of $g-i$ (top), $r-W2$ (middle) and $W1-W2$ (bottom) colours of our reliable AGN samples, with absAGN in red and unabsAGN in grey. In the bottom plot we also show the simple $W1-W2$ colour criterion to select AGN from Stern2005.