Prior to the first use of spectroscopes with digital detectors in the late 1970’s, very few supernovae had follow up spectra taken unless their maximum apparent B magnitudes were brighter than ~16 (Barbon et. al. 1973, 1979). This fundamental constraint on spectrally classifying supernovae places a crude upper limit on the recession velocity for the spirals in our galaxy sample. Note: Since the average blue absolute magnitude for SN Ia at maximum light is about two magnitudes brighter than that for SN II, it is the absolute blue magnitude of the latter which sets this limit.

If we adopt a blue absolute magnitude for SN II at maximum light of –17.1 (H_O = 75 Mpc/km/sec; Barbon et. al. 1979), a magnitude limit of 16 corresponds to a recession velocity cut-off in the range 2500 - 3100 km/sec, assuming a blue magnitude extinction (A_B) in the range 0.5 - 0.0.

Of course, the blue absolute magnitude for SN II at maximum light of -17.1 is an average magnitude for this supernovae type. In reality, this magnitude can vary from ~ -13.5 to -19 (assuming H_O = 75 Mpc/km/sec) depending on the blue absolute magnitude of the underlying parent galaxy (van den Bergh 1988). This dependency is in the sense that the most luminous SN II are found in the galaxies with the brightest blue absolute magnitudes (van den Bergh 1988).

Hence, for the purposes of this study, we will limit galaxies in our supernovae sample to those:

a) that are Sbc-Sdm spirals in RC3 catalogue with Vo (3K) < 3000 km/sec that are members of the NGC
and Index Catalogue. Restricting the sample to spirals that are members of the NGC and Index Catalogue
ensures that most galaxies can have their SB_IR and L_IR/L_B values calculated from data published in the
RC3 catalogue. The choice of a recession velocity limit of 3,000 km/sec means that some intrinsically
faint SN II will be missed because of their faint blue magnitudes at maximum light. However, this should
not be a major problem in our study because we are looking for the presence of SN II (and the absence
of SN Ia) in spirals with high current to integrated star formation rates. These type of galaxies tend to have
high intrinsic luminosities and so they are more likely to produce relatively bright SN II.

b) that are not HI gas deficient i.e. those with an HI index < 2.9. The reasons for doing this have been
outlined in section II (ii).

c) that have had an historical supernova of type SN II, SN Ia/I*, or SNIb/Ic, which have been determined
from spectra rather than light curves. The first and foremost reason for doing this is that typing of SN is
based on spectroscopic criterion (Oke and Searle 1974). In addition, Doggett and Branch (1986) have
shown that the supernova light curves cannot be reliably used to distinguish between SN II with linear
light curves and SNIa.

d) that have had an historical supernova with designation between SN1885A and SN 2000DS.

The spectrally determined SN types are taken from two main sources. For supernovae between SN1885A and SN
1988M, we have used the SN types published by Branch (1986, 1989) and Kirshner (1989), while spectrally determinedSN types published in the I.A.U. circulars have been used for supernovae between SN1988N and 2000DS. (Note: We adopt Branch’s SN I* classification for all those SN that have insufficient spectral coverage to be able to differentiate SN Ia fromSN Ib/Ic. Most of these galaxies are probably SN Ia, however, we cannot rule out the possibility that some of the supernovae may be SN Ib/Ic.)

Galaxies in the SN sample are divided into two groups. Those that have had one or more SN II/Ib/Ic (hereafter referred to as SN II galaxies) and those that have not had SN II/Ib/Ic i.e. they have had SN Ia/I* only (hereafter referred to as SNI galaxies). A galaxy that has had both SN II/Ib/Ic and SN Ia/I* is classified as a SNII galaxy.

Table 2 shows that SN spectral types have been determined for supernovae in 103 sample galaxies. Of these, nine galaxies have HI indices > 2.9 and so are excluded from the sample because they are HI gas depleted. In addition, there are nine galaxies that have no HI index and so we cannot determine whether or not they are HI gas depleted. These galaxies are also excluded from the SN sample because of this uncertainty. This leaves 62 SN sample galaxies that have had either SNII or SN Ib/Ic and 23 SN sample galaxies that have had SN Ia.

TABLE 2

Galaxy Type	SNII	SNII Non-Gas Depleted Galaxies	SNIb/Ic	SNIb/Ic Non-Gas Depleted Galaxies	SNIa/I*	SNIa/I* Non-Gas Depleted Galaxies
Sbc	13	9	2	2	15	12
Sc	30	26	5	4	10	7
Scd-Sdm	21	20	1	1	6	4
All Types	64	55	8	7	31	23

Notes: 1. 13 galaxies: NGC 1058, NGC1084, NGC 2207, NGC 3198, NGC 3294, NGC 3913, NGC 3938, NGC 4254, N4303,
NGC 4321, NGC 5236, NGC 6946 and NGC 6951 have had two or more SN with known spectral types.

2. NGC 1058, NGC 1084, NGC 2207, NGC 3198, NGC 3938, NGC 4254, NGC 4303, NGC 5236, NGC 6946 and
NGC 6951 have each had at least one supernova that has been spectrally classified as SN II or SN Ib/Ic.
These galaxies are classified as SNII sample galaxies.

3. NGC 3294 and NGC 4321 are HI gas depleted and so they are not in the final SN sample.

4. NGC 3913 has had two SN Ia.

Table 3a includes all 55 SN II galaxies that are in the final SN galaxy sample. The five gas depleted SNII spirals and four SNII galaxies with no HI index (m ₂₁ – B_T ) have been included in this table for completeness.

Table 3a

SNII SN1885A – SN2000DS