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

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

Research output: Contribution to journalArticlepeer-review

171 Scopus citations


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 Ω M = 0.79-0.18+0.15 and Ω Λ = 1.57-0.32+0.24 (1 σ uncertainties) if no constraints are imposed, or ΩM = 0.29 -0.05+0.06 if ΩM + 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 Δm15 method), the results are ΩM = 0.43-0.19+0.17 and Ω Λ = 1-18-0.28+0.27 (1 σ uncertainties) if no constraints are imposed, or ΩM= 0.18 -0.04+0.05 if ΩM + Ω Λ = 1 is assumed.

Original languageEnglish (US)
Pages (from-to)1-21
Number of pages21
JournalAstrophysical Journal
Issue number1 I
StatePublished - May 1 2006

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Hubble Space Telescope and ground-based observations of type Ia supernovae at redshift 0.5: Cosmological implications'. Together they form a unique fingerprint.

Cite this