Improved Cosmological Constraints from New, Old, and Combined Supernova Data Sets

Creators: Kowalski, M.; Rubin, D.; Aldering, G.; Agostinho, R. J.; Amadon, A.; Amanullah, R.; Balland, C.; Barbary, K.; Blanc, G.; Challis, P. J.; Conley, A.; Connolly, N. V.; Covarrubias, R.; Dawson, K. S.; Deustua, S. E.; Ellis, R.; Fabbro, S.; Fadeyev, V.; Fan, X.; Farris, B.; Folatelli, G.; Frye, B. L.; Garavini, G.; Gates, E. L.; Germany, L.; Goldhaber, G.; Goldman, B.; Goobar, A.; Groom, D. E.; Haissinski, J.; Hardin, D.; Hook, I.; Kent, S.; Kim, A. G.; Knop, R. A.; Lidman, C.; Linder, E. V.; Mendez, J.; Meyers, J.; Miller, G. J.; Moniez, M.; Mourão, A. M.; Newberg, H.; Nobili, S.; Nugent, P. E.; Pain, R.; Perdereau, O.; Perlmutter, S.; Phillips, M. M.; Prasad, V.; Quimby, R.; Regnault, N.; Rich, J.; Rubenstein, E. P.; Ruiz-Lapuente, P.; Santos, F. D.; Schaefer, B. E.; Schommer, R. A.; Smith, R. C.; Soderberg, A. M.; Spadafora, A. L.; Strolger, L. G.; Strovink, M.; Suntzeff, N. B.; Suzuki, N.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yun, J. L.

Abstract

We present a new compilation of Type Ia supernovae (SNe Ia), a new data set of low-redshift nearby-Hubble-flow SNe, and new analysis procedures to work with these heterogeneous compilations. This "Union" compilation of 414 SNe Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older data sets, as well as the recently extended data set of distant supernovae observed with the Hubble Space Telescope (HST). A single, consistent, and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density is Ω_Λ = 0.713^(+0.027)_(−0.029)(stat)^(+ 0.036)_(−0.039)(sys), for a flat, ΛCDM universe. Assuming a constant equation of state parameter, w, the combined constraints from SNe, BAO, and CMB give w = − 0.969^(+ 0.059)_(−0.063)(stat)^(+ 0.063)_(−0.066)(sys) . While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a w that varies with redshift. In particular, the current SN data do not yet significantly constrain w at z > 1. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available.

Additional Information

© 2008 American Astronomical Society. Received 2007 October 25, accepted for publication 2008 April 2. This work is based on observations made with: the Lick and Keck Observatories; the Cerro Tololo Inter-American Observatory 4m Blanco Telescope; the Yale/AURA/Lisbon/OSU(YALO) 1 m Telescope at Cerro Tololo Inter-American Observatory; the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium; the WIYN Observatory, owned and operated by the WIYN Consortium, which consists of the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatory (NOAO); the Isaac Newton Telescope, which is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofısica Canarias; the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias; and the MDM Observatory 2.4m Hiltner Telescope. The authors wish to thank the telescope allocation committees and the observatory staffs for their support for the extensive supernova search campaign and follow-up observations that contributed to the results reported here. In particular, we wish to thank C. Bailyn and S. Tourtellotte for assistance with YALO observations, D. Harner for obtaining WIYN data, and D. Folha and S. Smartt for the INT 2.5 m service observing. For their efforts in the coordinated supernova search, we wish to acknowledge the NEAT search team (E.Helin, S. Pravdo, D. Rabinowitz, and K. Lawrence) at JPL and the Spacewatch program at the University of Arizona (which includes R. S. McMillan, T. Gehrels, J.A. Larsen, J. L. Montani, J. V. Scotti, N. Danzl, and A. Gleason). We also wish to thank B. Schmidt, A. Filippenko, M. Schwartz, A. Gal-Yam, and D. Maoz for providing us with early announcements of supernova candidates. This work was supported in part by the Director, Office of Science, Office of High Energy and Nuclear Physics, US Department of Energy, through contract DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under contract DEAC02- 05CH11231. The use of Portuguese time for the YALO telescope was supported by Fundacao para a Ciencia e Tecnologia, Portugal, and by Project PESO/ESO/P/PRO/1257/98. M. K. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG). P. E. N. acknowledges support from the US Department of Energy Scientific Discovery through Advanced Computing program under contract DE-FG02-06ER06-04. A. M. M. acknowledges financial support from Fundacao para a Ciencia e Tecnologia (FCT), Portugal, through project PESO/P/PRO/ 15139/99.

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