The Hubble Space Telescope Cluster Supernova Survey. V. Improving the Dark-energy Constraints above z > 1 and Building an Early-type-hosted Supernova Sample

Creators: Suzuki, N.; Melbourne, J.; Rhodes, J.; Supernova Cosmology Project

Abstract

We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 < z < 1.415. Of these SNe Ia, 14 pass our strict selection cuts and are used in combination with the world's sample of SNe Ia to derive the best current constraints on dark energy. Of our new SNe Ia, 10 are beyond redshift z = 1, thereby nearly doubling the statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed analysis corrects for the recently identified correlation between SN Ia luminosity and host galaxy mass and corrects the NICMOS zero point at the count rates appropriate for very distant SNe Ia. Adding these SNe improves the best combined constraint on dark-energy density, ρ_(DE)(z), at redshifts 1.0 < z < 1.6 by 18% (including systematic errors). For a flat ΛCDM universe, we find ΩΛ = 0.729 ± 0.014 (68% confidence level (CL) including systematic errors). For a flat wCDM model, we measure a constant dark-energy equation-of-state parameter w = –1.013^(+0.068)_( –0.073) (68% CL). Curvature is constrained to ~0.7% in the owCDM model and to ~2% in a model in which dark energy is allowed to vary with parameters w_0 and w_a . Further tightening the constraints on the time evolution of dark energy will require several improvements, including high-quality multi-passband photometry of a sample of several dozen z > 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on board HST. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union.

Additional Information

© 2012 The American Astronomical Society. Received 2011 February 15; accepted 2011 July 6; published 2012 January 27. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555. The observations are associated with program GO-10496. Financial support for this work was provided by NASA through program GO-10496 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. This work was also supported in part by the Director, Office of Science, Office of High Energy and Nuclear Physics, of the U.S. Department of Energy under contract No. AC02-05CH11231, as well as a JSPS core-to-core program "International Research Network for Dark Energy" and by JSPS research grant 20040003. Support for M.B. was provided by the W. M. Keck Foundation. The work of S.A.S. was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under contract DE-AC52-07NA27344. The work of P.E., J.R., and D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. T.M. and Y.I. have been financially supported by the Japan Society for the Promotion of Science through its Research Fellowship. H.H. acknowledges support from a VIDI grant from the Netherlands Organization for Scientific Research (NWO) and a Marie Curie International Reintegration Grant. N.S., C.L., and S.P. wish to thank the support and hospitality of the Aspen Center for Physics, where much of this paper was written. We thank Jay Anderson, L. E. Bergeron, Ralph Bohlin, Roelof de Jong, Anton Koekemoer, Jennifer Mack, Bahram Mobasher, Adam Riess, Kenneth Sembach, and ACS and NICMOS teams at the Space Telescope Science Institute for their advice on the HST data calibration. We also thank Alex Conley for calibration discussions. Finally, we thank our referee, who carefully read our paper and gave valuable feedback.

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