Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/56648

Title

Hubble Space Telescope and ground-based observations of type Ia supernovae at redshift 0.5: cosmological implications

Author(s)

Clocchiatti, Alejandro;  Schmidt, Brian P.;  Filippenko, Alexei V.;  Challis, Peter;  Coil, Alison L.;  Covarrubias, R.;  Diercks, Alan;  Garnavich, Peter;  Germany, Lisa;  Gilliland, Ron;  Hogan, Craig;  Jha, Saurabh;  Kirshner, Robert P.;  Leibundgut, Bruno;  Leonard, Doug;  Li, Weidong;  Matheson, Thomas;  Phillips, Mark M.;  Prieto, Jose L.;  Reiss, David J.;  Riess, Adam G.;  Schommer, R.obert;  Smith, R. Chris;  Soderberg, Alicia;  Spyromilio, Jason;  Stubbs, Christopher;  Suntzeff, Nicholas B.;  Tonry, John L.;  Woudt, Patrick

Abstract

We present observations of the Type I Supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshiftz 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. Atz ≈ 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 la 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 la with MLCS2k2 (Jha and coworkers) luminosity calibration we obtain ΩM = 0.79 +0.15/-0.18 and Ω∧ = 1.57 +0.24/-0.32 (1 σ uncertainties) if no constraints are imposed, or ΩM = 0.29 +0.06/-0.05 if ΩM + Ω∧ = 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 Δm15 method), the results are ΩM = 0.43 +0.17/-0.19 and Ω∧ = 1-18 +0.27/-0.28 (1 σ uncertainties) if no constraints are imposed, or ΩM = 0.18 -0.04+0.05 if ΩM + Ω∧ = 1 is assumed.

Publication type

Journal article

Source

Astrophysical Journal, Vol. 642, no. 1 I (2006), pp. 1-21

Publication year

2006

FOR Code(s)

0201 Astronomical and Space Sciences;  020110 Stellar Astronomy and Planetary Systems

Keyword(s)

Cosmology;  Distance scale;  HST;  Hubble Space Telescope;  Luminosity distance;  Redshift;  Stars;  Supernovae

Publisher

University of Chicago Press

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1086/498491

Copyright

Copyright © 2006 The American Astronomical Society. All rights reserved. Publisher does not officially support author/institution self-archiving of either the postprint (final, revised accepted draft) or published version of full text.

Peer reviewed