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

By A. Clocchiatti, B. Schmidt, A. Filippenko, P. Challis, A. Coil, R. Covarrubias, A. Diercks, P. Garnavich, L. Germany, R. Gilliland and 19 more. 2005

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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 ΩM = 0.79 and ΩΛ = 1.57 (1 σ uncertainties) if no constraints are imposed, or ΩM = 0.29 if ΩM + ΩΛ = 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 and ΩΛ = 1.18 (1 σ uncertainties) if no constraints are imposed, or ΩM = 0.18 if ΩM + ΩΛ = 1 is assumed.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/93527daed33ec497d8697f753ec63532a4ce9ad5

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Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey (2007, result): “…as was done for the results of the HZT and its successors Riess et al. (1998); Tonry et al. (2003); Barris et al. (2004); Krisciunas et al. (2005); Clocchiatti et al. (2006), by Knop et al. (2003), by Riess et al. (2004) for the very high redshift HST supernova program, and for the low-z data of…”
Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology (2006, unknown): “…Montroy et al. 2006; O'Dwyer et al. 2005); much larger samples of highredshift supernova (Riess et al. 2004; Astier et al. 2005; Nobili et al. 2005; Clocchiatti et al. 2006; Krisciunas et al. 2005); and significant improvements in the lensing data (Refregier 2003; Heymans et al. 2005;…”
The haloes of bright satellite galaxies in a warm dark matter universe (2011, background): “…Komatsu et al. 2011), of galaxy clustering on large scales (e.g. Cole et al. 2005), and of the currently accelerated expansion of the Universe (e.g Clocchiatti et al. 2006; Guy et al. 2010) have confirmed the “Lambda cold dark matter” (ΛCDM) model, first explored theoretically 25 years ago (Davis…”