VLT Optical BVR observations of two bright Supernova Ia hosts in the
  Virgo cluster
  We study the two galaxies NGC4621 and NGC4374 in the Virgo cluster to derive
their distances and stellar population properties. The targets have hosted
three type Ia Supernova events allowing to investigate the correlations between
the SNeIa and their host stellar systems. Using deep BVR data, obtained with
FORS2 at the VLT, we analyse the Surface Brightness Fluctuations (SBF)
properties of the targets. We adopt our measurements and existing calibrations
to estimate the distance of NGC4621 and NGC4374. For stellar population
analysis, we measured SBF amplitudes in different galaxy regions. We present a
detailed comparison between data and models to constrain the characteristics of
the dominant stellar components at i) various galactic radii, and ii) in the
regions where SNeIa were recorded. Our V and R SBF measures provide distances
in agreement with literature estimates. The median of our and literature
SBF-based distances agrees with the one from non-SBF methods. Comparing data
with models we find that stellar populations properties do not change
significantly along galactic radius, with a dominant population having old age
and solar chemical composition. The galaxies appear similar in all properties
analysed, except for B-band SBF. Since the SBF magnitudes in this band are
sensitive to the properties of a hot stellar component, we speculate that such
behaviour is a consequence of different diffuse hot components in the galaxies.
We find that the presence of a percentage of hot-HB stars in old and metal rich
stellar populations could be at the origin of the observed differences. We find
a good uniformity in the V and R SBF and integrated colours in the regions
where the three SNeIa exploded. On the other hand, the B-band SBF signal shows
intriguing differences.
