We present a measurement of the rate of type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift z ≤ 0.12. Assuming a flat cosmology with m = 0.3 = 1 − , we find a volumetric SN Ia rate of [2.93+0.17 −0.04(systematic)+0.90 −0.71(statistical)]×10−5 SNe Mpc−3 h3 70 year−1, at a volumeweighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift-evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rate, rV ∝ (1 + z) , we obtain a value of β = 1.5 ± 0.6, i.e. the SN Ia rate is determined to be an increasing function of redshift at the ∼ 2.5σ level. Fitting the results to a model in which the volumetric SN rate, rV = Aρ(t) + Bρ˙(t), where ρ(t) is the stellar mass density and ρ˙(t) is the star formation rate, we find A = (2.8 ± 1.2) × 10−14 SNe M−1 ⊙ year−1, B = (9.3+3.4 −3.1) × 10−4 SNe M−1 ⊙ .
Department, Program, or Center
School of Physics and Astronomy (COS)
Astrophysical Journal 682 (2008) 262-282
RIT – Main Campus