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Unbiased Estimate of Dark Energy Density from Type Ia Supernova Data | | Yun Wang
; & Geoffrey Lovelace
; | | Date: |
17 Sep 2001 | | Journal: | Astrophys.J. 562 (2001) L115-L120 | | Subject: | astro-ph hep-ph | | Abstract: | Type Ia supernovae (SNe Ia) are currently the best probes of the dark energy in the universe. To constrain the nature of dark energy in a model-independent manner, we allow the density of dark energy, $
ho_X(z)$, to be an arbitrary function of redshift. Using simulated data from a space-based supernova pencil beam survey, we find that by optimizing the number of parameters used to parametrize the dimensionless dark energy density, $f(z)=
ho_X(z)/
ho_X(z=0)$, we can obtain an unbiased estimate of both f(z) and $Omega_m$ (assuming a flat universe and that the weak energy condition is satisfied). A plausible supernova pencil beam survey (with a square degree field of view and for an observational duration of one year) can yield about 2000 SNe Ia with $0le z le 2$. Such a survey in space would yield SN peak luminosities with a combined intrinsic and observational dispersion of $sigma (m_{int})=0.16$ mag. We find that for such an idealized survey, $Omega_m$ can be measured to 10% accuracy, and f(z) can be estimated to $sim$ 20% to $z sim 1.5$, and $sim$ 20-40% to $z sim 2$, depending on the time dependence of the true dark energy density. Dark energy densities which vary more slowly can be more accurately measured. For the anticipated SNAP mission, $Omega_m$ can be measured to 14% accuracy, and f(z) can be estimated to $sim$ 20% to $z sim 1.2$. Our results suggest that SNAP may gain much sensitivity to the time-dependence of f(z) and $Omega_m$ by devoting more observational time to the central pencil beam fields to obtain more SNe Ia at z>1.2. We also find that Monte Carlo analysis gives a more accurate estimate of the dark energy density than the maximum likelihood analysis. (abridged) | | Source: | arXiv, astro-ph/0109233 | | Services: | Forum | Review | PDF | Favorites | |
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