Fe K lines in the nuclear region of M82
  We study the spatial distribution of the Fe 6.4 and 6.7 keV lines in the
nuclear region of M82 using the Chandra archival data with a total exposure
time of 500 ks. The deep exposure provides a significant detection of the Fe
6.4 keV line. Both the Fe 6.4 and 6.7 keV lines are diffuse emissions with
similar spatial extent, but their morphology do not exactly follow each other.
Assuming a thermal collisional-ionization-equilibrium model, the fitted
temperatures are around 5-6 keV and the Fe abundances are about 0.4-0.6 solar
value. We also report the spectrum of a point source, which shows a strong Fe
6.7 keV line and is likely a supernova remnant or a superbubble. The fitted Fe
abundance of the point source is 1.7 solar value. It implies that part of the
iron may be depleted from the X-ray emitting gases as the predicted abundance
is about 5 solar value assuming complete mixing. If this is a representative
case of the Fe enrichment, a mild mass-loading of a factor of 3 will make the
Fe abundance of the point source in agreement with that of the hot gas, which
then implies that most of the hard X-ray continuum (2-8 keV) of M82 has a
thermal origin. In addition, the Fe 6.4 keV line is consistent with the
fluorescence emission irradiated by the hard photons from nuclear point
sources.
