EDP Sciences
Free access
Volume 445, Number 2, January II 2006
Page(s) 387 - 402
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20053552

A&A 445, 387-402 (2006)
DOI: 10.1051/0004-6361:20053552

Spectroscopy of twelve type Ia supernovae at intermediate redshift

C. Balland1, 2, 3, M. Mouchet2, 4, R. Pain1, N. A. Walton5, R. Amanullah6, P. Astier1, R. S. Ellis5, 7, S. Fabbro8, A. Goobar6, D. Hardin1, I. M. Hook9, M. J. Irwin5, R. G. McMahon5, J. M. Mendez10, 11, P. Ruiz-Lapuente10, G. Sainton1, K. Schahmaneche1 and V. Stanishev6

1  LPNHE, CNRS-IN2P3 and Universities of Paris 6 & 7, 75252 Paris Cedex 05, France
    e-mail: christophe.balland@ias.u-psud.fr
2  APC, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France
3  IAS, UMR 8617 CNRS and Université Paris-Sud 11, 91405 Orsay, France
4  LUTH, UMR 8102 CNRS, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France
5  Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
6  Department of Physics, Stockholm University, 10691 Stockholm, Sweden
7  California Institute of Technology, Pasadena, CA 91125, USA
8  CENTRA-Centro M. de Astrofisica and Department of Physics, IST, Lisbon, Portugal
9  Astrophysics, Denys Wilkinson Building, Keble Road, OX1 3RH, Oxford, UK
10  Department of Astronomy, University of Barcelona, 08028, Barcelona, Spain
11  Isaac Newton Group of Telescopes, Apartado 321, 38700 Santa Cruz de La Palma, Spain

(Received 2 June 2005 / Accepted 28 July 2005)

We present spectra of twelve type Ia supernovae obtained in 1999 at the William Herschel Telescope and the Nordic Optical Telescope during a search for type Ia supernovae (SN Ia) at intermediate redshift. The spectra range from z=0.178 to z=0.493, including five high signal-to-noise ratio SN Ia spectra in the still largely unexplored range $0.15\leq z \leq 0.3$. Most of the spectra were obtained before or around restframe B-band maximum light. None of them shows the peculiar spectral features found in low-redshift over- or under-luminous SN Ia. Expansion velocities of characteristic spectral absorption features such as Si II at 6355 Å, S II at 5640 Å and Ca II at 3945 Å are found to be consistent with those of their low-z SN Ia  counterparts.

Key words: cosmology: observations -- supernovae: general

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