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Explaining excess dipole in NVSS data using superhorizon perturbation

Das, Kaustav K. and Sankharva, Kishan and Jain, Pankaj (2021) Explaining excess dipole in NVSS data using superhorizon perturbation. Journal of Cosmology and Astroparticle Physics, 2021 (7). Art. No. 035. ISSN 1475-7516. doi:10.1088/1475-7516/2021/07/035.

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Many observations in recent times have shown evidence against the standard assumption of isotropy in the Big Bang model. Introducing a superhorizon scalar metric perturbation has been able to explain some of these anomalies. In this work, we probe the net velocity arising due to the perturbation. We find that this extra component does not contribute to the CMB dipole amplitude while it does contribute to the dipole in large scale structures. Thus, within this model's framework, our velocity with respect to the large scale structure is not the same as that extracted from the CMB dipole, assuming it to be of purely kinematic origin. Taking this extra velocity component into account, we study the superhorizon mode's implications for the excess dipole observed in the NRAO VLA Sky Survey (NVSS). We find that the mode can consistently explain both the CMB and NVSS observations. We also find that the model leads to small contributions to the local bulk flow and the dipole in Hubble parameter, which are consistent with observations. The model leads to several predictions which can be tested in future surveys. In particular, it implies that the observed dipole in large scale structure should be redshift dependent and should show an increase in amplitude with redshift. We also find that the Hubble parameter should show a dipole anisotropy whose amplitude must increase with redshift in the CMB frame. Similar anisotropic behaviour is expected for the observed redshift as a function of the luminosity distance.

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Additional Information:© 2021 IOP Publishing Ltd and Sissa Medialab. Received 9 February 2021; Accepted 4 July 2021; Published 19 July 2021. We thank Shamik Ghosh for useful comments. We also thank Prabhakar Tiwari for a very useful input. We would like to thank the anonymous referee for useful comments. We acknowledge funding from the Science and Engineering Research Board (SERB), Government of India, grant number EMR/2016/004070.
Funding AgencyGrant Number
Science and Engineering Research Board (SERB)EMR/2016/004070
Issue or Number:7
Record Number:CaltechAUTHORS:20210723-172412152
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Official Citation:Kaustav K. Das et al JCAP07(2021)035
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109998
Deposited By: Tony Diaz
Deposited On:26 Jul 2021 19:01
Last Modified:12 Jul 2022 17:28

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