The Multi-Epoch Nearby Cluster Survey: type Ia supernova rate
  measurement in z~0.1 clusters and the late-time delay time distribution
  We describe the Multi-Epoch Nearby Cluster Survey (MENeaCS), designed to
measure the cluster Type Ia supernova (SN Ia) rate in a sample of 57 X-ray
selected galaxy clusters, with redshifts of 0.05 < z < 0.15. Utilizing our real
time analysis pipeline, we spectroscopically confirmed twenty-three cluster SN
Ia, four of which were intracluster events. Using our deep CFHT/Megacam
imaging, we measured total stellar luminosities in each of our galaxy clusters,
and we performed detailed supernova detection efficiency simulations. Bringing
these ingredients together, we measure an overall cluster SN Ia rate within
R_{200} (1 Mpc) of 0.042^{+0.012}_{-0.010}^{+0.010}_{-0.008} SNuM
(0.049^{+0.016}_{-0.014}^{+0.005}_{-0.004} SNuM) and a SN Ia rate within red
sequence galaxies of 0.041^{+0.015}_{-0.015}^{+0.005}_{-0.010} SNuM
(0.041^{+0.019}_{-0.015}^{+0.005}_{-0.004} SNuM). The red sequence SN Ia rate
is consistent with published rates in early type/elliptical galaxies in the
`field'. Using our red sequence SN Ia rate, and other cluster SNe measurements
in early type galaxies up to $z\sim1$, we derive the late time (>2 Gyr) delay
time distribution (DTD) of SN Ia assuming a cluster early type galaxy star
formation epoch of z_f=3. Assuming a power law form for the DTD, \Psi(t)\propto
t^s, we find s=-1.62\pm0.54. This result is consistent with predictions for the
double degenerate SN Ia progenitor scenario (s\sim-1), and is also in line with
recent calculations for the double detonation explosion mechanism (s\sim-2).
The most recent calculations of the single degenerate scenario delay time
distribution predicts an order of magnitude drop off in SN Ia rate \sim 6-7 Gyr
after stellar formation, and the observed cluster rates cannot rule this out.
