Lawrence Berkeley National Laboratory Recent Work Title Spectra of high-redshift type Ia supernovae and a comparison with their low-redshift counterparts Permalink

We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted Ca H&K are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these lowand high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift. Subject headings: supernovae:general Department of Physics, University of Oxford, Nuclear & Astrophysics Laboratory, Keble Road, Oxford, OX1 3RH, UK Department of Astronomy and Astrophysics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 3H8, Canada E. O. Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, USA Department of Physics, Stockholm University, Albanova University Center, S-106 91 Stockholm, Sweden Colorado College, 14 East Cache La Poudre St., Colorado Springs, CO 80903 Department of Physics, University of California Berkeley, Berkeley, 94720-7300 CA, USA American Astronomical Society, 2000 Florida Ave, NW, Suite 400, Washington, DC, 20009 USA. California Institute of Technology, E. California Blvd, Pasadena, CA 91125, USA CENTRA-Centro M. de Astrof́ısica and Department of Physics, IST, Lisbon, Portugal LPNHE, CNRS-IN2P3, University of Paris VI & VII, Paris, France Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37240, USA European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile Department of Astronomy, University of Barcelona, Barcelona, Spain Louisiana State University, Department of Physics and Astronomy, Baton Rouge, LA, 70803, USA Institute of Astronomy, Madingley Road, Cambridge