  The interstellar medium (ISM) in starburst galaxies contains plenty of
chemical elements synthesised by core-collapse supernova explosions. By
measuring the abundances of these metals, we can study the chemical enrichment
within galaxies and the transportation of metals into circumgalactic
environments through powerful outflows. We perform the spectral analysis of the
X-ray emissions from the M82 core using the Reflection Grating Spectrometer
(RGS) onboard XMM-Newton to accurately estimate the metal abundances in the
ISM. We analyse over 300 ks of RGS data observed with fourteen position angles,
covering an 80 arcsec cross-dispersion width. We employ multi-temperature
thermal plasma components in collisional ionisation equilibrium (CIE) to
reproduce the observed spectra, each exhibiting different spatial broadenings.
The O vii band CCD image shows a broader distribution compared to those for O
viii and Fe-L bands. The O viii line profiles have a prominent double-peaked
structure, corresponding to the northward and southward outflows. The O vii
triplet feature exhibits marginal peaks, and a single CIE component, convolved
with the O vii band image, approximately reproduces the spectral shape.
Combining a CIE model with a charge-exchange emission model also successfully
reproduces the O vii line profiles. However, the ratio of these two components
varies significantly with the observed position angles, which is physically
implausible. Spectral fitting of the broadband spectra suggests a
multi-temperature phase in the ISM, approximated by three components at 0.1,
0.4, and 0.7 keV. Notably, the 0.1 keV component exhibits a broader
distribution than the 0.4 and 0.7 keV plasmas. The derived abundance pattern
shows super-solar N/O, solar Ne/O and Mg/O, and half-solar Fe/O ratios. These
results indicate the chemical enrichments by core-collapse supernovae in
starburst galaxies.
