Probing Cosmological Principle using the spectral index of quasar flux distribution

2023/12/11 by Mohit Panwar, Pankaj Jain, Panwar, Mohit +1
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena

paper · pdf · doi:10.48550/arxiv.2312.07596

openalex publication_date 2023/12/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We study the dipole signal in the spectral index (x) of the differential number counts using quasars in the CatWISE2020 catalog of infrared sources. The index is extracted by using the log-likelihood method. We obtain the value x=1.579 ± 0.001 for a quasar sample of 1355352 sources. We extract the dipole signal in this parameter by employing χ² minimization, assuming a sky model of x up to the quadrupole term. We find that the dipole amplitude |D| is 0.005 ± 0.002 and dipole direction (l, b) in Galactic coordinate system equal to (201.50^∘ ± 27.87^∘, -29.37^∘ ± 19.86^∘). The direction of dipole anisotropy is found to be very close to the hemispherical power asymmetry (l,b)=(221^∘,-27^∘) in the Cosmic Microwave Background (CMB). We also obtain a signal of quadrupole anisotropy which is correlated with the ecliptic poles and can be attributed to ecliptic bias.

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