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Comparison of the colors of the close and remote supernovæ

The measurement of the color of the supernovæ enabled us to determine in an empirical way the law of correction for extra-Galactic absorption (the parameter $ \beta$ ). A possible systematic effect is the existence of a differential extinction between the batches of close relations and remote who would introduce a bias into the measurement of cosmology.

Figures 10.25 show the comparison of the colors $ U-v$ for the close and remote supernovæ. We do not note a systematic difference between the two batches (except for 2001gn). This indicates that there is not a significant differential extinction and that the objects are similar to the maximum.

Figure 10.24: Comparison of the colors $ B-v$ of the supernovæ close and remote in the reference frame of the supernova
\begin{figure}\it\begin{center} \epsfig{file=Images/BVProche.eps, width=12cm}\end{center}\end{figure}
 
Figure 10.25: Comparison of the colors $ U-b$ of the supernovæ close and remote in the reference frame of the supernova
\begin{figure}\it\begin{center} \epsfig{file=Images/UBProche.eps, width=12cm}\end{center}\end{figure}

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Julien Raux 2004-05-04