AAS 201st Meeting, January, 2003
Session 123. Supernovae and Other Distance Indicators
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[123.04] Photometry of six Type Ia supernovae with redshifts between 0.47 and 0.89 observed in 1998

K. Krisciunas (CTIO/OCIW), N. B. Suntzeff, R. A. Schommer, R. C. Smith, P. Candia (CTIO), M. M. Phillips (OCIW), B. Barris, J. L. Tonry (UH), P. Challis, R. P. Kirshner, T. Matheson (CfA), A. Clocchiatti (PUC), A. L. Coil, A. V. Filippenko, S. Jha, D. C. Leonard (UCB), R. Covarrubias, A. Diercks, C. Hogan, C. Stubbs (UW), P. Garnavich, S. T. Holland (NDU), B. Leibundgut, J. Spyromilio (ESO), A. G. Riess (STScI), B. P. Schmidt (MSSSO)

We present photometry for six high redshift supernovae with redshifts in the range 0.47 to 0.89 observed by the High-Z Supernova Search Team in 1998. These supernovae appear fainter than expected for a matter dominated universe and support the conclusions of Riess et al. (1998) and Perlmutter et al. (1999) for a universe with a positive cosmological constant. One of the specific goals of the project was to tie together the ground-based and HST photometry of the field stars used to calibrate the SNe. We find that the ground-based RI photometry and the HST photometry done with the F675W and F814W filters converted to RI photometry, using the prescriptions of Holtzman et al. (1995) and Dolphin (2000), agree at the 0.02 mag level. This means that the faintness of the observed supernovae with respect to a matter dominated universe is not due to zeropoint differences between the ground-based and HST data. We present our photometry as natural system magnitudes based on a Vega magnitude scale. Our light curve fits were obtained by matching transformed light curves of nearby SNe to the natural-system magnitudes of the high-z objects, using the sensitivity functions defined by the various telescope-filter-CCD combinations.

Colleague R. A. Schommer passed away 12 December 2001.

We thank STScI for the following support: HST GO-07505.02-A, HST-GO-08641.07-A, HST-GO-8177.06 (the High-Z Supernova Team survey) and HST-GO-08648.10-A (the SInS collaboration).

The author(s) of this abstract have provided an email address for comments about the abstract: kevin@ctiosz.ctio.noao.edu

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.