Deep XMM-Newton observations of the northern disk of M31 II: Tracing the
  hot interstellar medium
  Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to
trace the hot interstellar medium (ISM) in unprecedented detail and to
characterise the physical properties of the X-ray emitting plasmas. Methods: We
used all XMM-Newton data up to and including our new observations to produce
the most detailed image yet of the hot ISM plasma in a grand design spiral
galaxy such as our own. We compared the X-ray morphology to multi-wavelength
studies in the literature to set it in the context of the multi-phase ISM. We
performed spectral analyses on the extended emission using our new observations
as they offer sufficient depth and count statistics to constrain the plasma
properties. Data from the Panchromatic Hubble Andromeda Treasury were used to
estimate the energy injected by massive stars and their supernovae. We compared
these results to the hot gas properties. Results: The brightest emission
regions were found to be correlated with populations of massive stars, notably
in the 10 kpc star-forming ring. The plasma temperatures in the ring regions
are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in
massive stellar clusters and superbubbles. We derived X-ray luminosities,
densities, and pressures for the gas in each region. We also found large
extended emission filling low density gaps in the dust morphology of the
northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We
propose that the hot gas was heated and expelled into the gaps by the
populations of massive stars in the rings. Conclusions. It is clear that the
massive stellar populations are responsible for heating the ISM to X-ray
emitting temperatures, filling their surroundings, and possibly driving the hot
gas into the low density regions. Overall, the morphology and spectra of the
hot gas in the northern disk of M 31 is similar to other galaxy disks.
