Peculiar motion of the solar system derived from a dipole anisotropy in the redshift distribution of distant quasars

Abstract

An observer stationary with respect to comoving coordinates of the expanding universe should find the redshift distribution to be isotropic. However, a peculiar motion of the observer would introduce a dipole anisotropy in the observed redshift distribution. Conversely, a dipole anisotropy in observed redshift distribution could be exploited to infer our peculiar motion, or rather of our solar system. We determine here our peculiar velocity by studying the dipole anisotropy in the redshift distribution of a large sample of quasars. The magnitude of the peculiar velocity thus determined turns out to be $2350\pm 280$ km s${}^{-1}$, not only much larger than 370 km s${}^{-1}$ determined from the dipole anisotropy in the Cosmic Microwave Background Radiation (CMBR), but also nearly in an opposite direction. Such large values for peculiar velocity have been found in a couple of radio surveys too, but with a direction along the CMBR dipole. Large genuine differences in the inferred motion, whether in magnitude or direction, are rather disconcerting since a solar peculiar velocity should not depend upon the method of its determination. Such discordant dipoles imply perhaps an anisotropic universe, violating the cosmological principle, a cornerstone of the modern cosmology.

5 pages, 3 figures, 2 tables, accepted in MNRAS

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