Supernovae in Deep Hubble Space Telescope Galaxy Cluster Fields: Cluster Rates and Field Counts
Abstract
We have searched for high-redshift supernova (SN) candidates in multiple deep HST archival images of nine galaxy-cluster fields. We detect six apparent SNe, with I814 between 22.8 and 28.4 mag. There is roughly 1 SN per deep (flux limit I814 > 26 mag), doubly-imaged, WFPC2 cluster field. Two SNe are associated with cluster galaxies (at redshifts z=0.18 and z=0.83), two are probably in galaxies not in the clusters (at z=0.49 and z=0.98), and two are at unknown z. After accounting for observational efficiencies and uncertainties (statistical and systematic) we derive the rate of type-Ia SNe within the projected central 500 kpc of rich clusters: R=0.22(+0.94)(-0.21) SNu in clusters at z=0.18 to 0.37, and R=0.20(+0.59)(-0.19) SNu in clusters at z=0.83 to 1.27 (95% confidence interval; H_0=50; 1 SNu=1 SN per century per 10^10 L_B_sun). Combining the two redshift bins, the SN-Ia rate for a mean redshift of z=0.41, is R(z=0.41) = 0.20(+0.32)(-0.16) SNu. The upper bounds argue against SNe-Ia being the dominant source of the large iron mass observed in the intra-cluster medium. We also compare our observed counts of field SNe (i.e., non-cluster SNe of all types) to recent model predictions. The observed field count is one or zero SN with I814 < 26 mag, and 1 to 3 SNe with I814 < 27 mag. These counts are 2-5 times lower than some of the predictions. Since the counts at these magnitudes are likely dominated by type-II SNe, the discrepancy suggests obscuration of distant SNe-II, or a SN-II luminosity distribution devoid of a large high-luminosity tail.Keywords
All Related Versions
This publication has 0 references indexed in Scilit: