A fundamental plane in X-ray binary activity of external galaxies

We construct a new catalog of extragalactic X-ray binaries (XRBs) by matching the latest Chandra source catalog with local galaxy catalogs. Our XRB catalog contains 4430 XRBs hosted by 237 galaxies within ∼130 Mpc. As XRBs dominate the X-ray activity in galaxies, the catalog enables us to study the correlations between the total X-ray luminosity of a galaxy LX,tot, star formation rate $\dot{\rho }_\star$, and stellar mass M⋆. As previously reported, LX,tot is correlated with $\dot{\rho }_\star$ and M⋆. In particular, we find that there is a fundamental plane in those three parameters; $\log L_{\rm X,tot}={38.80^{+0.09}_{-0.12}}+\log (\dot{\rho }_\star + \alpha M_\star )$, where α = (3.36 ± 1.40) × 10⁻¹¹ yr⁻¹. In order to investigate this relation, we construct a phenomenological binary population synthesis model. We find that the high-mass XRB and low-mass XRB fraction in formed compact object binary systems is $\sim\! 9\%$ and ${0.04}\%$, respectively. Utilizing the latest XMM-Newton and Swift X-ray source catalog data sets, additional XRB candidates are also found, resulting in a total of 5757 XRBs hosted by 311 galaxies.