From: Tony Spadafora (ALSpadafora@lbl.gov)
Date: Mon Aug 11 2003 - 18:48:05 PDT
of interest to SCP group:
http://www.arxiv.org/abs/astro-ph/0308185
Identification of Type Ia Supernovae at Redshift 1.3 and Beyond with the Advanced
Camera for Surveys on HST
Authors: Adam G. Riess, Louis-Gregory Strolger, John Tonry, Zlatan
Tsvetanov, Stefano Casertano, Henry C. Ferguson, Bahram Mobasher, Peter
Challis, Nino Panagia, Alexei V. Filippenko, Weidong Li, Ryan Chornock,
Robert P. Kirshner, Bruno Leibundgut, Mark Dickinson, Anton Koekemoer,
Norman A. Grogin, Mauro Giavalisco
Comments: accepted for publication, ApJ Letters
We present discoveries of SNe Ia at z > 1 and the photometric diagnostic
used to discriminate them from other types of SNe detected during the
GOODS Hubble Space Telescope Treasury program with the Advanced Camera
for Surveys (ACS). Photometric redshift measurements of the hosts
combined with deep f606w, f775w, and f850lp imaging discriminates
hydrogen-rich SNe II from SNe I at z > 1 by exploiting the ultraviolet
(UV) deficit in the energy distributions of SNe Ia. This sorting allows
rapid follow-up of space-based discoveries. Subsequent spectroscopy of
11 GOODS SNe Ia obtained from the ground and with the grism on ACS
confirmed the reliability of our photometric screening. We present the
highest-redshift spectrum of any supernova published to date, SN Ia
2002fw at z = 1.3 observed near maximum brightness with the ACS grism.
The lack of UV flux for true SNe Ia provides an effective tool for our
ongoing efforts to build a sample of SNe Ia at 1.2 < z < 1.8 which will
extend the useful range of the magnitude-redshift relation of SNe Ia.
-- Tony Spadafora ALSpadafora@lbl.gov Physics Division Tel: (510) 495-2316 Lawrence Berkeley National Lab FAX: (510) 486-6738 1 Cyclotron Road BLDG 50R5032 Berkeley, CA 94720-8160
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