https://doi.org/10.1140/epjc/s10052-024-12417-1
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A study of dipolar signal in distant Quasars with various observables
1
Department of Physics and Astronomy, University of the Western Cape, 7535, Cape Town, South Africa
2
School of Physical Sciences, Indian Institute of Technology Mandi, 175005, Mandi, Himachal Pradesh, India
3
Department of Physics, Indian Institute of Technology, 208016, Kanpur, India
4
National Astronomical Observatories, Chinese Academy of Science, 100101, Beijing, People’s Republic of China
5
Department of Physics, Guangdong Technion–Israel Institute of Technology, 515063, Shantou, Guangdong, People’s Republic of China
6
Department of Space, Science and Astronomy, Indian Institute of Technology, 208016, Kanpur, India
a
quantummechanicskothari@gmail.com
Received:
15
August
2023
Accepted:
8
January
2024
Published online:
24
January
2024
We study the signal of anisotropy in AGNs/quasars of CatWISE2020 catalogue using different observables. It has been reported earlier that this data shows a strong signal of dipole anisotropy in the source number counts. We test this claim using two independent data analysis procedures and find our number count dipole consistent with the earlier results. In addition to number counts, we test for the anisotropy signal in two other observables – mean spectral index 
and mean flux density 
. We find a strong dipole signal both in the mean spectral index and the mean flux density. The dipole in mean flux density points towards the galactic center and becomes very weak after imposing a flux cut to remove sources with flux greater than 1 mJy. This can be attributed to the presence of some (
26,600) bright sources. The signal in the mean spectral index, however, is relatively stable as a function of both flux and galactic cuts. The dipole in this observable points roughly opposite to the galactic center and hence most likely arises due to galactic bias. We consider a simple model of galactic extinction which nicely explains the dipole both in mean spectral index and mean flux density for a wide range of flux and galactic cuts. Hence, the signal in both these parameters does not appear to be of cosmological origin.
© The Author(s) 2024
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