The Type Ia Supernova Rate at z ≈ 0.5 from the Supernova Legacy Survey

Creators: Neill, J. D.; Ellis, R. S.

Abstract

We present a measurement of the distant Type Ia supernova (SN Ia) rate derived from the first 2 yr of the Canada-France-Hawaii Telescope Supernova Legacy Survey. We observed four 1° × 1° fields with a typical temporal frequency of (Δt) ~ 4 observer-frame days over time spans of 158-211 days per season for each field, with breaks during the full Moon. We used 8-10 m class telescopes for spectroscopic follow-up to confirm our candidates and determine their redshifts. Our starting sample consists of 73 spectroscopically verified SNe Ia in the redshift range 0.2 < z < 0.6. We derive a volumetric SN Ia rate of r_V((z) = 0:47) [0:42^(+0:13)-(-0:09)(syst:) ± 0:06(stat:)]x 10^-4 yr^-1 Mpc^3, assuming h = 0:7, Ω_m = 0:3, and a flat cosmology. Using recently published galaxy luminosity functions derived in our redshift range, we derive a SN Ia rate per unit luminosity of r_L((z) = 0:47) = 0:154^(+0:048)_(-0:033)(syst:)^(+0:039)_(-0:031)(stat:) SN units. Using our rate alone, we place an upper limit on the component of SN Ia production that tracks the cosmic star formation history of 1 SN Ia per 10^3 M_☉ of stars formed. Our rate and other rates from surveys using spectroscopic sample confirmation display only a modest evolution out to z = 0:55.

Additional Information

© 2006 The American Astronomical Society. Received 2006 January 23; accepted 2006 May 1. Based on observations obtained with MegaPrime/MegaCam, a joint project of the Canada-France-Hawaii Telescope (CFHT) and CEA/DAPNIA, at CFHT, which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. This work is also based on observations obtained at the European Southern Observatory using the Very Large Telescope on the Cerro Paranal (ESO Large Program 171.A-0486), and on observations (programs GN-2004A-Q-19, GS-2004A-Q-11, GN-2003B-Q-9, and GS-2003B-Q-8) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation (NSF) on behalf of the Gemini partnership: the NSF (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina). This work is also based on observations 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are grateful for our opportunity to conduct observations on this mountain. We acknowledge invaluable assistance from the CFHT Queued Service Observations team, led by P. Martin (CFHT). Our research would not be possible without the assistance of the support staff at CFHT, especially J.-C. Cuillandre. The real-time pipelines for supernova detection run on computers integrated in the CFHT computing system and are very efficiently installed, maintained, and monitored by K. Withington (CFHT). We also heavily rely on the real-time Elixir pipeline, which is operated and monitored by J.-C. Cuillandre, E.Magnier, and K. Withington. We are grateful to L. Simard (CADC) for setting up the image delivery system and his kind and efficient responses to our suggestions for improvements. The Canadian collaboration members acknowledge support from NSERC and CIAR and the French collaboration members from CNRS/ IN2P3, CNRS/INSU, PNC, and CEA. This work was supported in part by the Director, Office of Science, Office of High Energy and Nuclear Physics, of the US Department of Energy. The France-Berkeley Fund provided additional collaboration support. S. Fabbro and A. C. Gonçalves acknowledge support from FCT, Portugal, under grants SFRH/BPD/14682/2003 and SFRH/BPD/11641/2002, respectively. We are indebted to A. Hopkins and J. Beacom for providing us with a draft of their work on SFH prior to its publication. The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, the Department of Defense, or the US Government.

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