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Hubble Space Telescope and Ground-based Observations of Type Ia Supernovae at Redshift 0.5: Cosmological Implications

Clocchiatti, Alejandro and Leonard, Doug and Soderberg, Alicia (2006) Hubble Space Telescope and Ground-based Observations of Type Ia Supernovae at Redshift 0.5: Cosmological Implications. Astrophysical Journal, 642 (1). pp. 1-21. ISSN 0004-637X.

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We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z ≈ 0.5. They were discovered in early 1999 with the 4.0 m Blanco telescope at Cerro Tololo Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble Space Telescope. We computed luminosity distances to the new SNe using two methods and added them to the high-z Hubble diagram that the HZT has been constructing since 1995. The new distance moduli confirm the results of previous work. At z ≈ 0.5, luminosity distances are larger than those expected for an empty universe, implying that a "cosmological constant," or another form of "dark energy," has been increasing the expansion rate of the universe during the last few billion years. Combining these new HZT SNe Ia with our previous results and assuming a ΛCDM cosmology, we estimate the cosmological parameters that best fit our measurements. For a sample of 75 low-redshift and 47 high-redshift SNe Ia with MLCS2k2 (Jha and coworkers) luminosity calibration we obtain Ω_M = 0.79^(+0.15)_(-0.18) and Ω_Λ = 1.57^(+0.24)_(-0.32) (1 σ uncertainties) if no constraints are imposed, or Ω_M = 0.29^(+0.06)_(-0.05) if Ω_M + Ω_Λ = 1 is assumed. For a different sample of 58 low-redshift and 48 high-redshift SNe Ia with luminosity calibrations done using the PRES method (a generalization of the Δ_m_15 method), the results are Ω_M = 0.43^(+0.17)_(-0.19) and Ω_Λ = 1.18^(+0.27)_(-0.28) (1 σ uncertainties) if no constraints are imposed, or Ω_M = 0.18^(+0.05)_(-0.04) if Ω_M + Ω_Λ = 1 is assumed.

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Additional Information:© 2006 American Astronomical Society. Received 2004 June 18; accepted 2005 October 3. We thank the staffs of the many facilities we used for their assistance with the observations. Financial support for this work was provided by NASA through grants GO-08177, GO-08641, and GO-09118 fromthe Space Telescope Science Institute,which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Funding was also provided byNational Science Foundation grants AST 00-98557 at the University of Washington, AST 02-06329, AST 03-07894, and AST 04-43378. A. C. acknowledges the support of CONICYT (Chile) through FONDECYT grants 1980803, 1000524, 7000524, and 1051061, as well as the Directors of CTIO and MSSSO for support during periods of work in La Serena and Canberra, respectively. A. V. F. is grateful for a Miller Research Professorship at UC Berkeley during which part of this work was completed.C. S. acknowledges the support of Harvard University. B. P. S. is supported by ARC grants DP0209028, LX0454445, and DP0559024.
Funding AgencyGrant Number
NSFAST 00-98557
NSFAST 02-06329
NSFAST 03-07894
NSFAST 04-43378
CONICYT (Chile)FONDECYT grant 1980803
CONICYT (Chile)FONDECYT grant 1000524
CONICYT (Chile)FONDECYT grant 7000524
CONICYT (Chile)FONDECYT grant 1051061
Miller Research Professorship at UC BerkeleyUNSPECIFIED
Harvard UniversityUNSPECIFIED
ARC (Australian Research Council)DP0209028
ARC (Australian Research Council)LX0454445
ARC (Australian Research Council)DP0559024
Subject Keywords:cosmology: observations; distance scale — galaxies: distances and redshifts; supernovae: general
Issue or Number:1
Record Number:CaltechAUTHORS:20110218-095711693
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Official Citation:Alejandro Clocchiatti et al. 2006 ApJ 642 1 doi: 10.1086/498491
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22377
Deposited By: Jason Perez
Deposited On:20 Feb 2011 02:53
Last Modified:03 Oct 2019 02:37

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