Constructing X-Ray Spectral Models of Galaxies: Varying Contributions from X-Ray Binary Populations with Host Galaxy Properties
Abstract
Recent work has shown that the emission from X-ray binary (XRB) populations in galaxies varies with stellar mass ( M ⋆ ), star formation rate (SFR), and metallicity ( Z ). Such scaling relations are widely used to predict the XRB contributions to galaxy-integrated X-ray luminosities including studies focused on dwarf active galactic nuclei (AGN) and the X-ray radiation field during the epoch of heating in the early ( z ≥ 8) Universe. However, as galaxies approach low SFR and low Z , the relatively shallow slope of the XRB luminosity function (XLF) can yield very large stochastic variations in the total X-ray luminosity expected from the XRB population for fixed values of M ⋆ , SFR, and Z . We have created a procedure to statistically sample any XLF and model total X-ray spectra for XRB populations and their stochastic uncertainties. We demonstrate the accuracy of this procedure using data for galaxies ranging from high to low M ⋆ , SFR, and Z and generating X-ray spectral models consistent with Chandra observations. For galaxies that lie on the galactic main sequence, we can relate SFR and Z to M ⋆ using established M ⋆ –SFR and M ⋆ – Z relations. Applying these relations, we construct main-sequence XRB spectral models, which provide typical XRB spectral shapes, normalizations, and uncertainties as a function of M ⋆ . The spectral model library associated with this work is available at doi: 10.5281/zenodo.20126734 .
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BibTeX
@article{gehr2026constructing,
title = {{Constructing X-Ray Spectral Models of Galaxies: Varying Contributions from X-Ray Binary Populations with Host Galaxy Properties}},
author = {Emerson Gehr and Bret Lehmer and Antara Basu-Zych and Konstantinos Kovlakas and Vianney Lebouteiller and Erik Monson and Izabela Pavel and Chris Richardson and Maxime Varese and Zachary Wilson},
journal = {The Astrophysical Journal},
year = {2026},
month = sep,
doi = {10.3847/1538-4357/ae9543},
eprint = {2608.10180},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05828849v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Constructing X-Ray Spectral Models of Galaxies: Varying Contributions from X-Ray Binary Populations with Host Galaxy Properties
AU - Emerson Gehr
AU - Bret Lehmer
AU - Antara Basu-Zych
AU - Konstantinos Kovlakas
AU - Vianney Lebouteiller
AU - Erik Monson
AU - Izabela Pavel
AU - Chris Richardson
AU - Maxime Varese
AU - Zachary Wilson
PY - 2026
DA - 2026/09/16
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae9543
UR - https://hal.science/hal-05828849v1
AB - Recent work has shown that the emission from X-ray binary (XRB) populations in galaxies varies with stellar mass ( M ⋆ ), star formation rate (SFR), and metallicity ( Z ). Such scaling relations are widely used to predict the XRB contributions to galaxy-integrated X-ray luminosities including studies focused on dwarf active galactic nuclei (AGN) and the X-ray radiation field during the epoch of heating in the early ( z ≥ 8) Universe. However, as galaxies approach low SFR and low Z , the relatively shallow slope of the XRB luminosity function (XLF) can yield very large stochastic variations in the total X-ray luminosity expected from the XRB population for fixed values of M ⋆ , SFR, and Z . We have created a procedure to statistically sample any XLF and model total X-ray spectra for XRB populations and their stochastic uncertainties. We demonstrate the accuracy of this procedure using data for galaxies ranging from high to low M ⋆ , SFR, and Z and generating X-ray spectral models consistent with Chandra observations. For galaxies that lie on the galactic main sequence, we can relate SFR and Z to M ⋆ using established M ⋆ –SFR and M ⋆ – Z relations. Applying these relations, we construct main-sequence XRB spectral models, which provide typical XRB spectral shapes, normalizations, and uncertainties as a function of M ⋆ . The spectral model library associated with this work is available at doi: 10.5281/zenodo.20126734 .
SN - 0004-637X
SN - 1538-4357
ER -