Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...209.9819d&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #98.19; Bulletin of the American Astronomical Society, V
Mathematics
Logic
Scientific paper
SNAP's primary science goal is investigating dark energy properties, and thereby distinguishing amongst the families of theoretical models. This places requirements on the precision of the determination of dark energy equation of state parameters (w(z) =w0 + wa(1+ z), where w = -ρ/p (density/pressure) ), corresponding to uncertainties on w0 to 0.05 and wa to 0.3 or better. In this paper we concentrate on the calibration constraints set by the need to obtain multicolor light curves and peak magnitudes of SNe Ia at redshifts between z=0.3 and z=1.7. The key factor in using the SNe Ia magnitude-redshift relation for determining cosmological parameters is the B-band peak magnitude. Thus, to standardize SNe Ia brightnesses, we take the ratios of the observed rest frame B-band magnitudes m(z) to that of a SNe Ia at z=0, e.g. B-J = -2.5 log fB/fJ. Therefore the calibration requirement is on the need for accurate and precise colors and hence on accurate knowledge of the slope of spectral energy distribution of calibrating sources -corresponding to an uncertainty of 1% per filter, and 2% in color.
The problem we must solve is how to precisely and accurately measure colors of faint objects in the visible and in the near-infrared, and maintain the reliability or scale of the calibration during the lifetime of the mission. Some of the challenges we need to overcome are the large (ten or more) magnitude difference between current, faint spectrophotometric standards (V 13 mag) and the science targets with magnitudes as faint as 27 mag, the difference is SEDs between stars and supernovae, and the calibration of a half-billion silicon and MgCdTe pixels.
This paper briefy describes the calibration methodology needed to ensure that the desired calibration requirements can be met and the calibration scale maintained throughout the SNAP mission.
Allam Sahar S.
Bohlin Ralph
Deustua Susana E.
Kent Stephen
Lampton Michael L.
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