According to the cosmological principle, the universe should appear isotropic, without any preferred directions, to a comoving observer. However a peculiar motion of the observer, or equivalently of the solar system, might introduce a dipole anisotropy in the observed properties of a class of objects. The peculiar motion of the solar system, determined from the Cosmic Microwave Background Radiation (CMBR), gave a velocity 370 km /s along l=264, b=48 deg. Dipoles subsequently observed in the number counts, sky brightness or redshift distributions in large samples of distant radio galaxies and quasars have yielded peculiar velocities many times larger than that from the CMBR, though in all cases the directions matched with the CMBR dipole. We have now determined our peculiar motion from the MIRAGN (Mid Infra Red Active Galactic Nuclei) sample of more than a million quasars, originally drawn from the CATAWISE survey of more than a billion objects. We find a peculiar velocity more than an order of magnitude higher than the CMBR value, although the direction seems within 1.2 sigma of the CMBR dipole. Since a genuine solar peculiar velocity cannot vary from one dataset to the other, an order of magnitude, statistically significant, discordant dipoles, could imply that we may instead have to look for some other cause for the genesis of these dipole, including that of the CMBR. A common direction for all these dipoles, determined from completely independent surveys by different groups, does indicate that these dipoles are not merely due to some systematics in the observations or in the data analysis, and it might suggest a preferred direction in the universe implying an inherent anisotropy, which, in turn, would violate the cosmological principle, a cornerstone of the modern cosmology.
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Solar System Peculiar Motion from Mid Infra Red Quasars and Implications for the Cosmological Principle
Published: 22 February 2021 by MDPI in 1st Electronic Conference on Universe session The Universe of Andrei Sakharov
Keywords: Quasars surveys; cosmic background radiation; large-scale structure of universe