The Rate of Type Ia Supernovae at z~0.2 from SDSS-I Overlapping Fields

TL;DR

This study estimates the rate of Type Ia supernovae at redshift 0.2 using SDSS-I overlapping fields, finding results consistent with previous low-redshift measurements and suggesting larger datasets could improve accuracy.

Contribution

First measurement of Type Ia supernova rate at z~0.2 using SDSS-I archival data with Bayesian classification and bias correction.

Findings

SN rate at z~0.2: 14.0 (+2.5,1.4) -2.5 (-1.1) x 10^-14 h(70)^2 yr^-1 L_sun^-1

Volumetric SN rate: 1.89 (+0.42,0.18) -0.34 (-0.15) x 10^-5 yr^-1 h(70)^3 Mpc^-3

Results are consistent with other low-redshift SN rate measurements.

Abstract

In the course of the Sloan Digital Sky Survey (SDSS-I), a large fraction of the surveyed area was observed more than once due to field tiling overlap, usually at different epochs. We utilize some of these data to perform a supernova (SN) survey at a mean redshift of z=0.2. Our archival search, in ~ 5% of the SDSS-I overlap area, produces 29 SN candidates clearly associated with host galaxies. Using the Bayesian photometric classification algorithm of Poznanski et al., and correcting for classification bias, we find 17 of the 29 candidates are likely Type Ia SNe. Accounting for the detection efficiency of the survey and for host extinction, this implies a Type Ia SN rate of R=14.0+(2.5,1.4}-(2.5,1.1}+/-2.5 10^-14 h(70)^2 yr^-1 L_sun^-1, where the errors are Poisson error, systematic detection efficiency error, and systematic classification error, respectively. The volumetric rate is R=1.89+(0.42,0.18)-(0.34,0.15)+/-0.42 10^-5 yr^-1 h(70)^3 Mpc^-3. Our measurement is consistent with other rate measurements at low redshift. An order of magnitude increase in the number of SNe is possible by analyzing the full SDSS-I database.