Speaker
Description
Due to its high sensitivity in the soft X-ray band, eROSITA provides the perfect opportunity to study the diffuse X-ray emission of nearby galaxies. A Catalog of Neighboring Galaxies, presented by Karachentsev et al. (2013), was used to establish a sample of 72 nearby galaxies with distances $d \lesssim 17\,\mathrm{Mpc}$. For the 10 most luminous galaxies, the distribution and spectra were analyzed to constrain the physical properties of the hot phase of the interstellar medium (ISM). Furthermore, stacked spectra have been analyzed for sub-samples of high, medium and low star formation rate (SFR) galaxies.
The results indicate, that the gas is in collisional ionization equilibrium. Most galaxies exhibit a thermal plasma component at temperatures of $\sim 0.2 − 0.3\,\mathrm{keV}$. Flux calculations indicate, that $\sim 53 − 68\%$ of the diffuse X-ray flux in $0.25 − 2\, \mathrm{keV}$ is produced by thermal plasma, whereas unresolved X-ray binaries contribute $\sim 32 − 47\%$. A comparison with SFRs from previous studies (e.g. Leroy et al. 2021) yields a $L/\mathrm{SFR}$ scaling factor of $(7.0 \pm 0.9) \cdot 10^{38}\,\mathrm{(erg\,s^{−1})/(M_⊙\,yr^{−1})}$ and indicates that contributions from unresolved stellar sources become non-negligible for $\mathrm{SFRs} < 0.1\,\mathrm{M_⊙\,yr^{−1}}$.
