TYPED SUPERNOVAE ARE PREFERENTIALLY FOUND IN
HUCHRA AND GELLER GALAXY GROUPS
Our preliminary investigations indicate that the likelihood of finding a
supernova in nearby (Vo(3K) <
3,000 km/sec) Sbc-Sdm spiral galaxies is dependent on the parent galaxy’s
intergalactic environment.
Our study shows that that there are 567 Sbc-Sdm galaxies in the NGC catalogue
with recession velocities Vo(3K) <
3,000 km/sec. 491 of these galaxies are within the survey limits of the
Huchra and Geller (HG/Cfa) galaxy group survey. Out of these 491 galaxies,
96 (19.6 %) have had historical SN (1885A to 1998BP) with designated
types - SN II/(II), SNIb/Ic and SNIa/I*/(I).
Using this sample, we find that 78/271 (28.8 % ) of all Sbc-Sdm galaxies
in (HG/Cfa) galaxy groups have had typed SN, while only 25/224 (11.2%
) of these type of spirals that are NOT in HG/Cfa galaxy groups have had
typed SN. At face value, this means that SN are 2.6 times more likely
to occur in Sbc-Sdm galaxies that are in HG/Cfa groups than Sbc-Sdm galaxies
that lie outside these groups.
We also find that the likelihood of seeing SNIa/I* in Sbc-Sdm galaxies in
HG/Cfa groups is 4.3 times higher than the likelihood of seeing them
in galaxies outside HG/Cfa groups, while the corresponding enhancement for
SN II is only 2.1. However, this result must treated with caution
because of the small number statistics for the SNIa/I*/(I) type.
We have investigated a number of observational biases which might affect
our result e.g. the propensity for SN to target nearby face-on spirals that
have bright blue magnitudes, however, we find that these biases do not affect
our result.
We speculate that the increased likelihood of tidal interactions between
galaxies caused by the higher galaxian density within HG/Cfa groups, is
the most likely explanation for the preference for SN to occur in these
galaxy groups.