•  4
    The Hubble diagram of type Ia supernovae as a function of host galaxy morphology
    with R. S. Ellis, G. Aldering, R. Amanullah, P. Astier, G. Blanc, M. S. Burns, A. Conley, S. E. Deustua, M. Doi, S. Fabbro, G. Folatelli, A. S. Fruchter, G. Garavini, R. Gibbons, G. Goldhaber, A. Goobar, D. de GroomHardin, I. Hook, M. da HowellIrwin, A. G. Kim, R. A. Knop, C. Lidman, R. McMahon, J. Mendez, S. Nobili, P. E. Nugent, R. Pain, N. Panagia, C. R. Pennypacker, S. Perlmutter, R. Quimby, J. Raux, N. Regnault, P. Ruiz-Lapuente, B. Schaefer, K. Schahmaneche, A. L. Spadafora, N. A. Walton, L. Wang, W. M. Wood-Vasey, and N. Yasuda
    We present new results on the Hubble diagram of distant type Ia supernovae segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies support earlier claims for a cosmological constant, which we demonstrate at ≃5σ significa…Read more
  •  1
    The distant type Ia supernova rate
    with R. Pain, S. Fabbro, R. S. Ellis, G. Aldering, P. Astier, S. E. Deustua, A. S. Fruchter, G. Goldhaber, A. Goobar, D. de GroomHardin, I. M. Hook, M. J. da HowellIrwin, A. G. Kim, M. Y. Kim, R. A. Knop, J. C. Lee, C. Lidman, R. G. McMahon, P. E. Nugent, N. Panagia, C. R. Pennypacker, S. Perlmutter, P. Ruiz-Lapuente, K. Schahmaneche, B. Schaefer, and N. A. Walton
    We present a measurement of the rate of distant Type la supernovae derived using four large subsets of data from the Supernova Cosmology Project. Within this fiducial sample, which surveyed about 12 deg2, 38 supernovae were detected at redshifts 0.25-0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type la supernova rate at a mean redshift z ≃ 0.55 of 1.53-0.25-0.31-0.28-0.32 × 10-4 h 3 Mpc-3 yr-1 or 0.58…Read more