Speaker
Description
The eROSITA all-sky X-ray (0.2-8.0 keV) survey, provides the first unbiased census of the X-ray emission of galaxies, allowing us to study the emission from X-ray binaries (XRBs) and the hot interstellar medium in the full range of stellar population parameters present in the local Universe. By combining the updated version of the HECATE v2.0 value-added catalogue of nearby galaxies (z$<$0.048) with the X-ray data obtained from the eRASS1, we study the integrated X-ray emission from normal galaxies as a function of their stellar population parameters (i.e. star formation rate-SFR-; stellar mass-M$_{\star}$-; Metallicity, and stellar population age). This allows us to investigate the L$_{X}$-SFR-M$_{\star}$-Metallicity relation with a larger and less biased sample than any other previous study. Our analysis reveals a sub-population of very X-ray luminous starburst galaxies (up to ~2 dex excess with respect to that expected from the current scaling relations) with higher specific SFRs, lower metallicities, and younger stellar populations. We discuss the role of several different contributors to this excess (e.g. hot-gas, LMXBs, or stochastic sampling of the X-ray binary X-ray luminosity function) as well as the contamination from background AGN, and low-luminosity AGN (including tidal disruption events). These results demonstrate the power of large blind surveys such as eRASS which can provide a more complete picture of the X-ray emitting galaxy population and their diversity. In addition, the more sensitive observations of the eRASS:4, and the inclusion of galaxies beyond the volume covered by the HECATE, allow us to set better constraints on the L$_{X}$-SFR-M$_{*}$-Metallicity relation, and has the prospect of revealing rare populations of objects and recovering unbiased underlying correlations between X-ray emission and host galaxy properties.
