Mark Strovink

We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy clusters at 0.9 < z < 1.46 from the Hubble Space Telescope Cluster Supernova Survey. This is the first cluster SN Ia rate measurement with detected z > 0.9 SNe. Finding 8 ± 1 cluster SNe Ia, we determine an SN Ia rate of 0.50^+0.23 _–0.19 (stat) ^+0.10 _–0.09 (sys) h ² ₇₀ SNuB (SNuB ≡ 10^–12 SNe L ^–1 _{☉, B} yr^–1). In units of stellar mass, this translates to 0.36^+0.16 _–0.13 (stat) ^+0.07 _–0.06 (sys) h ² ₇₀ SNuM (SNuM ≡ 10^–12 SNe M ^–1 _☉ yr^–1). This represents a factor of ≈5 ± 2 increase over measurements of the cluster rate at z < 0.2. We parameterize the late-time SN Ia delay time distribution (DTD) with a power law: Ψ(t)∝t^s . Under the approximation of a single-burst cluster formation redshift of z_f = 3, our rate measurement in combination with lower-redshift cluster SN Ia rates constrains s = –1.41^+0.47 _–0.40, consistent with measurements of the DTD in the field. This measurement is generally consistent with expectations for the "double degenerate" scenario and inconsistent with some models for the "single degenerate" scenario predicting a steeper DTD at large delay times. We check for environmental dependence and the influence of younger stellar populations by calculating the rate specifically in cluster red-sequence galaxies and in morphologically early-type galaxies, finding results similar to the full cluster rate. Finally, the upper limit of one hostless cluster SN Ia detected in the survey implies that the fraction of stars in the intra-cluster medium is less than 0.47 (95% confidence), consistent with measurements at lower redshifts.

We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out to z 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In observations spanning 189 orbits with the Advanced Camera for Surveys we discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia are located in the foregrounds and backgrounds of the clusters targeted in the survey. Using these new data, we derive the volumetric SN Ia rate in four broad redshift bins, finding results consistent with previous measurements at z 1 and strengthening the case for an SN Ia rate that is 0.6 × 10^–4 h ³ ₇₀ yr^–1 Mpc^–3 at z ~ 1 and flattening out at higher redshift. We provide SN candidates and efficiency calculations in a form that makes it easy to rebin and combine these results with other measurements for increased statistics. Finally, we compare the assumptions about host-galaxy dust extinction used in different high-redshift rate measurements, finding that different assumptions may induce significant systematic differences between measurements.

DOI: https://doi.org/10.1103/PhysRevLett.100.139901

We present a new measurement of the volumetric rate of SNe Ia up to a redshift of 1.7, using the HST GOODS data combined with an additional HST data set covering the GOODS-North field collected in 2004. We employ a novel technique that does not require spectroscopic data for identifying SNe Ia (although spectroscopic measurements of redshifts are used for over half the sample); instead, we employ a Bayesian approach using only photometric data to calculate the probability that an object is an SN Ia. This Bayesian technique can easily be modified to incorporate improved priors on SN properties, and it is well-suited for future high-statistics SN searches in which spectroscopic follow-up of all candidates will be impractical. Here the method is validated on both ground- and space-based SN data having some spectroscopic follow-up. We combine our volumetric rate measurements with low-redshift SN data and fit to a number of possible models for the evolution of the SN Ia rate as a function of redshift. The data do not distinguish between a flat rate at redshift >0.5 and a previously proposed model, in which the Type Ia rate peaks at redshift ~1 due to a significant delay from star formation to the SN explosion. Except for the highest redshifts, where the signal-to-noise ratio is generally too low to apply this technique, this approach yields uncertainties that are smaller than or comparable to previous work. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555, under programs GO-9583, GO-9425, GO-9727, and GO-9728