The delay-time distribution of Type Ia supernovae from Sloan II

Abstract

We derive the delay-time distribution (DTD) of type-Ia supernovae (SNe Ia)\nusing a sample of 132 SNe Ia, discovered by the Sloan Digital Sky Survey II\n(SDSS2) among 66,000 galaxies with spectral-based star-formation histories\n(SFHs). To recover the best-fit DTD, the SFH of every individual galaxy is\ncompared, using Poisson statistics, to the number of SNe that it hosted (zero\nor one), based on the method introduced in Maoz et al. (2011). This SN sample\ndiffers from the SDSS2 SN Ia sample analyzed by Brandt et al. (2010), using a\nrelated, but different, DTD recovery method. Furthermore, we use a\nsimulation-based SN detection-efficiency function, and we apply a number of\nimportant corrections to the galaxy SFHs and SN Ia visibility times. The DTD\nthat we find has 4-sigma detections in all three of its time bins: prompt (t <\n420 Myr), intermediate (0.4 < t < 2.4 Gyr), and delayed (t > 2.4 Gyr),\nindicating a continuous DTD, and it is among the most accurate and precise\namong recent DTD reconstructions. The best-fit power-law form to the recovered\nDTD is t^(-1.12+/-0.08), consistent with generic ~t^-1 predictions of SN Ia\nprogenitor models based on the gravitational-wave induced mergers of binary\nwhite dwarfs. The time integrated number of SNe Ia per formed stellar mass is\nN_SN/M = 0.00130 +/- 0.00015 Msun^-1, or about 4% of the stars formed with\ninitial masses in the 3-8 Msun range. This is lower than, but largely\nconsistent with, several recent DTD estimates based on SN rates in galaxy\nclusters and in local-volume galaxies, and is higher than, but consistent with\nN_SN/M estimated by comparing volumetric SN Ia rates to cosmic SFH.\n