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Volume 306 - XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop (MULTIF2017) - Cosmology
Supernovae - a tool for observational cosmology
M. Pruzhinskaya,* P.F. Leget
*corresponding author
Full text: pdf
Pre-published on: 2018 March 28
Published on: 2018 May 30
Type Ia Supernovae (SNe) are excellent distance indicators in the Universe. Observations of distant SNe~Ia led to the discovery of the accelerating expansion of the Universe. The most recent analysis of SNe Ia indicates that considering a flat $\Lambda$CDM cosmology, the contribution of dark energy in the total density of the Universe is $\sim$70%. Cosmological parameters are estimated from the ``luminosity distance-redshift'' relation of SNe. Currently a lot of attention is paid to standardization of SNe, i.e. to increase of the accuracy of luminosity distance determination. The uncertainty on the redshift is quite often considered negligible. The redshift most often used corresponds to the one of SN host galaxy relative to CMB frame. In fact the redshift observed on the Earth also includes the contribution from the Doppler effect induced by peculiar velocities related to the Hubble flow. The existing methods to correct redshift for peculiar velocity contribution do not work in clusters of galaxies, the biggest virialized systems in the Universe where peculiar velocities can reach 1000 km~s$^{-1}$. To count for the effect of peculiar velocities in galaxy clusters we studied 145 SNe from the Nearby Supernova Factory and found 11 objects that belong to the clusters. We used the galaxy cluster redshift instead the host galaxy redshift to construct the Hubble diagram. The applied technique allowed to improve the redshift measurements and to decrease the spread on the Hubble diagram. The peculiar velocity correction of galaxies inside galaxy clusters has to be taken into account in future cosmological surveys such as LSST.
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