The Type Ia Supernova Rate in Redshift 0.5-0.9 Galaxy Clusters

Creators: Sharon, Keren; Gal-Yam, Avishay; Maoz, Dan; Filippenko, Alexei V.; Foley, Ryan J.; Silverman, Jeffrey M.; Ebeling, Harald; Ma, Cheng-Jiun; Ofek, Eran O.; Kneib, Jean-Paul; Donahue, Megan; Ellis, Richard S.; Freedman, Wendy L.; Kirshner, Robert P.; Mulchaey, John S.; Sarajedini, Vicki L.; Voit, G. Mark

Abstract

Supernova (SN) rates are potentially powerful diagnostics of metal enrichment and SN physics, particularly in galaxy clusters with their deep, metal-retaining potentials and relatively simple star formation histories. We have carried out a survey for SNe in galaxy clusters, at a redshift range of 0.5 < z < 0.9, using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. We reimaged a sample of 15 clusters that were previously imaged by ACS, thus obtaining two to three epochs per cluster in which we discovered five likely cluster SNe, six possible cluster Type Ia supernovae, two hostless SN candidates, and several background and foreground events. Keck spectra of the host galaxies were obtained to establish cluster membership. We conducted detailed efficiency simulations, and measured the stellar luminosities of the clusters using Subaru images. We derive a cluster SN rate of 0.35SNu_B ^(+0.17)_(–0.12)(statistical) ±0.13(classification) ±0.01(systematic) (where SNu_B = SNe (100 yr 10^(10) L_(B,⊙))^(–1)) and 0.112SNu_M ^(+0.055)_(–0.039)(statistical) ±0.042(classification) ±0.005(systematic) (where SNu_M = SNe (100 yr 10^(10) M_⊙)^(–1)). As in previous measurements of cluster SN rates, the uncertainties are dominated by small-number statistics. The SN rate in this redshift bin is consistent with the SN rate in clusters at lower redshifts (to within the uncertainties), and shows that there is, at most, only a slight increase of cluster SN rate with increasing redshift. The low and fairly constant SN Ia rate out to z ≈ 1 implies that the bulk of the iron mass in clusters was already in place by z ≈ 1. The recently observed doubling of iron abundances in the intracluster medium between z = 1 and 0, if real, is likely to be the result of redistribution of existing iron, rather than new production of iron.

Additional Information

© 2010 The American Astronomical Society. Received 2009 October 26; accepted 2010 June 3; published 2010 July 7. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-10493 and GO-10793, and with archival programs GO-9033, GO-9090, GO-9290, GO-9292, GO-9722, GO-9744, GO-9836, and GO-10509. Based in part on data collected at the Subaru telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; it was made possible by the generous financial support of the W. M. Keck Foundation. We thank the anonymous referee for very useful comments that greatly improved the paper. We thank D. Poznanski and M. Sullivan for useful discussions and help with the Keck observations. K.S. acknowledges support from the Kersten Visiting Fellowship Fund, and thanks the Department of Astronomy and Astrophysics at the University of Chicago for their hospitality during the time some of this research was conducted. A.G. and J.P.K. acknowledge support by the grant 07AST-F9 from the Ministry of Science, Culture & Sport, Israel, & the Ministry of Research, France. A.G. is also supported by the Israeli Science Foundation, an EU Seventh Framework Programme Marie Curie IRG fellowship, and the Benoziyo Center for Astrophysics, a research grant from the Peter and Patricia Gruber Awards, and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute. D.M. acknowledges support by the Israel Science Foundation. This research was supported by National Science Foundation grants AST–0607485 and AST–0908886 to A.V.F., as well as by NASA/HST grant GO-10793 from the Space Telescope Science Institute (STScI), which is operated by AURA, Inc., under NASA contract NAS 5-26555. A.V.F. is also grateful for the Department of Energy grant DE-FG02-08ER41563. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea (where the Subaru and Keck data were obtained) has always had within the indigenous Hawaiian community; we are most fortunate to have the opportunity to conduct observations from this mountain.

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