57
The older regions in the galaxy are mostly the larger, di use regions in areas
of less concentrated star formation regions 30, 35
,
37. The oldest region,
region 37, has a derived age of
10 Myr. It is most likely much older than this,
but di culties in measuring the H ux at this level do not allow the limit to
be constrained further. The origin of di use FUV emission found in a galaxy is
sometimes hard to determine. Possible sources include scattering from dust grains
and light from a spatially unresolved population of hot stars. In a low metallicity
galaxy with low global extinction, scattering of UV light is not problematic and
allows direct imaging of high-mass star formation. Therefore, the di use light
in the larger apertures is most likely a spatially dispersed population of B stars
formed over the past few 100 Myr.
5.2.2 IC2574
In contrast to the mix of ages found in HoII, the majority of the ages found
in IC2574, shown in Fig. 5.10 are young. This follows the SFR analysis, which
suggested that of the three galaxies, IC2574 traced a larger fraction of massive
stars with H observations than with FUV. The galaxy does not contain any
regions in group 4 and only has 5 regions belonging to group 3. These older
regions are concentrated in the center of the galaxy while the outer portions of
the spiral pattern only contains younger regions. For example, the group in the
northern arm surrounding region 9 only contains regions of group 1 and 2. The
galaxy lacks the large, di use FUV regions seen in HoII and is dominated by
young regions bright in the H .
5.2.3 Sextans A
Sextans A shows a complete mix of ages in Fig. 5.11. Roughly half the ages
are in groups 1 and 2 and half are in groups 3 and 4. The galaxy shows the
largest percentage of regions in group 4 and the least in group 1 than the other
