Do sub-galactic regions follow the galaxy-wide X-ray scaling relations?
  The example of NGC 3310 and NGC 2276
  We present results from Chandra observations of the X-ray starburst galaxies
NGC 3310 and NGC 2276. We detect 27 discrete sources in NGC 3310, and 19
discrete sources in NGC 2276 with luminosities above $\mathrm{1.0\times
10^{38}\ erg\ s^{-1}}$. The majority of the sources have photon indices of
1.7-2.0, typical for X-ray binaries. Both galaxies have large numbers of
ultra-luminous X-ray sources (ULXs; sources with $\mathrm{L(0.3-10.0\
keV)>10^{39}\ erg\ s^{-1}}$), 14 for NGC 3310 concentrated on the circumnuclear
star-forming ring and north spiral arm and 11 for NGC 2276 with the brighter
ones on the west side of the galaxy which is compressed due to harassment by
the intra-group medium it is moving into. We find for both galaxies that the
ULX-hosting areas are located above the general Lx-SFR scaling relations while
other areas either follow or fall below the scaling relations. This indicates
that sub-galactic regions follow the galaxy-wide scaling relations but with
much larger scatter resulting from the age (and possibly metallicity) of their
local stellar populations in agreement with recent theoretical and
observational results. Such differences in age could be the origin of the
scatter we observe in the low SFR regime in the Lx-SFR scaling relations.
