ИСТИНА

Type Ia supernovae are used as a distance indicators since they have lessluminosity dispersion at maximum light. Cosmological parameters are estimated from the “luminosity distance-redshift” relation of SNe using the Hubble diagrams. Currently a lot of attention is paid to increase of the accuracy of luminosity distance determination of SNe. The uncertainty on the redshift is quite often considered negligible. The redshift used in “luminosity distance-redshift” relation is a cosmological redshift, i.e. the redshift due to the expansion of the Universe. In fact the redshift observed on the Earth also includesthe contribution from the unknown peculiar velocities. To minimize the influence of poorly constrained peculiar velocities, in cosmological analyses a standard value of 300-400 km/s peculiar velocity dispersion is added in quadratureto the redshift uncertainty. It has nonetheless been observed that velocity dispersion can exceed 1000 km/s in galaxy clusters and therefore, the dispersion insidethe cluster can be greater than the one usually assumed in cosmological analyses and can affect the distance measurements. To take this effect into accountwe study SNe Ia that are exploded in the galaxy clusters. As a supernova samplewe use “Pantheon” the largest combined sample of SN Ia consisting of a total of 1048 objects. For those SNe Ia that belong to the galaxy clusters we are going to use the galaxy cluster redshift instead of the host galaxy redshift and examine theeffect of this correction on the Hubble diagram.