X-ray measurements of the elemental abundances for the diffuse emission in the nuclear starburst galaxy NGC 3079

Outflows driven by feedback leave imprints on a galaxy’s diffuse X-ray emission. Elemental abundances provide key diagnostics of feedback-driven chemical enrichment. We present a spectroscopic study of the diffuse X-ray emission in NGC 3079 using XMM-Newton RGS and EPIC, focusing on the nuclear region and the extended galactic-scale superbubble (GSB). We analyzed the high-resolution RGS spectrum of the central $\sim 4\mathrm{k}\mathrm{p}\mathrm{c}$ region, encompassing the $\sim 1\mathrm{k}\mathrm{p}\mathrm{c}$ nuclear superbubble (NSB), and the EPIC spectrum of the GSB out to $5^{\mathrm{\prime }}(\sim 25\mathrm{k}\mathrm{p}\mathrm{c})$. The nuclear spectrum is best described by a multi-temperature thermal-plasma model plus a charge-exchange (CX) component, which contributes approximately $13\mathrm{\%}$ of the total observed energy flux in the $0.2-2\mathrm{k}\mathrm{e}\mathrm{V}$ band. The best-fit O/Fe and Ne/Fe ratios are $0.47$ and $0.77$ in solar units. Comparing these ratios with IMF-weighted core-collapse supernova (SNcc) yields gives an upper progenitor-mass cutoff of $M_{\mathrm{u}}\simeq 13-15M_{\odot }$ for pure SNcc enrichment. For the best-fit spectral model, including an SNIa contribution increases the inferred cutoff, but its $1\sigma$ upper limit remains below $25M_{\odot }$ for SNIa fractions up to $10\mathrm{\%}$ within the adopted yield models. The characteristic ages of the NSB and GSB are $0.92_{-0.46}^{+0.39}\mathrm{M}\mathrm{y}\mathrm{r}$ and $29.6_{-2.9}^{+1.6}\mathrm{M}\mathrm{y}\mathrm{r}$, respectively, suggesting episodic feedback in NGC 3079.