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تسجيل مستخدم جديدA Measurement of the Rate of type-Ia Supernovae at Redshift $zapprox$ 0.1 from the First Season of the SDSS-II Supernova Survey
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We present a measurement of the rate of type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift $zle0.12$. Assuming a flat cosmology with $Omega_m = 0.3=1-Omega_Lambda$, we find a volumetric SN Ia rate of $[2.93^{+0.17}_{-0.04}({rm systematic})^{+0.90}_{-0.71}({rm statistical})] times 10^{-5} {rm SNe} {rm Mpc}^{-3} h_{70}^3 {rm year}^{-1}$, at a volume-weighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift-evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rate, $r_V propto (1+z)^{beta}$, we obtain a value of $beta = 1.5 pm 0.6$, i.e. the SN Ia rate is determined to be an increasing function of redshift at the $sim 2.5 sigma$ level. Fitting the results to a model in which the volumetric SN rate, $r_V=Arho(t)+Bdot rho(t)$, where $rho(t)$ is the stellar mass density and $dot rho(t)$ is the star formation rate, we find $A = (2.8 pm 1.2) times 10^{-14} mathrm{SNe} mathrm{M}_{sun}^{-1} mathrm{year}^{-1}$, $B = (9.3^{+3.4}_{-3.1})times 10^{-4} mathrm{SNe} mathrm{M}_{sun}^{-1}$.
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