For refcode 2006ApJ...642....1C: Retrieve 16 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by American Astronomical Society.
Reproduced by permission
2006ApJ...642....1C
Hubble Space Telescope and Groundbased 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, Jose Luis Prieto, David Reiss, Adam G. Riess, Robert
Schommer, R. Chris Smith, Alicia Soderberg, Jason Spyromilio,
Christopher Stubbs, Nicholas B. Suntzeff, John L. Tonry, and Patrick
Woudt
Abstract. 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 InterAmerican
Observatory by the Highz Supernova Search Team (HZT) and subsequently
followed with many groundbased 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 highz 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 {LAMBDA}CDM cosmology, we estimate the cosmological parameters
that best fit our measurements. For a sample of 75 lowredshift and 47
highredshift SNe Ia with MLCS2k2 (Jha and coworkers) luminosity
calibration we obtain {OMEGA}_M_=0.79^+0.15^_0.18_ and
{OMEGA}_{LAMBDA}_=1.57^+0.24^_0.32_ (1 {sigma} uncertainties) if no
constraints are imposed, or {OMEGA}_M_=0.29^+0.06^_0.05_ if
{OMEGA}_M_+{OMEGA}_{LAMBDA}_=1 is assumed. For a different sample of 58
lowredshift and 48 highredshift SNe Ia with luminosity calibrations done
using the PRES method (a generalization of the {DELTA}m_15_ method), the
results are {OMEGA}_M_=0.43^+0.17^_0.19_ and
{OMEGA}_{LAMBDA}_=1.18^+0.27^_0.28_ (1 {sigma} uncertainties) if no
constraints are imposed, or {OMEGA}_M_=0.18^+0.05^_0.04_ if
{OMEGA}_M_+{OMEGA}_{LAMBDA}_=1 is assumed.
Key words: Cosmology: Observations, Cosmology: Distance Scale, Galaxies:
Distances and Redshifts, Stars: Supernovae: General
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