Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array

Ghosh, Shamik; Jain, Pankaj; Kashyap, Gopal; Kothari, Rahul; Nadkarni-Ghosh, Sharvari; Tiwari, Prabhakar

doi:10.1007/s12036-016-9395-8

Cited by 28 publications

(19 citation statements)

References 62 publications

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“…Hence, the retrieved signal profile obtained in this paper satisfies the observational requirement at both small and large angular scales. The profile of the power-law signal obtained in this analysis will be useful guide in any pursuit of a theoretical understanding of CHA signal and also to make predictions for other cosmological probes including CMB polarization [66][67][68][69][70][71]. Bayesian inference of the BipoSH coefficients using HMC discussed in this work can be generalized to CMB polarization.…”

Section: Discussionmentioning

confidence: 99%

Joint Bayesian analysis of large angular scale CMB temperature anomalies

Shaikh

Mukherjee

Das

et al. 2019

J. Cosmol. Astropart. Phys.

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Cosmic microwave background measurements show an agreement with the concordance cosmology model except for a few notable anomalies: Power Suppression, the lack of large scale power in the temperature data compared to what is expected in the concordance model, and Cosmic Hemispherical Asymmetry, a dipolar breakdown of statistical isotropy. An expansion of the CMB covariance in Bipolar Spherical Harmonics naturally parametrizes both these large-scale anomalies, allowing us to perform an exhaustive, fully Bayesian joint analysis of the power spectrum and violations of statistical isotropy up to the dipole level. Our analysis sheds light on the scale dependence of the Cosmic Hemispherical Asymmetry. Assuming a scale-dependent dipole modulation model with a two-parameter power law form, we explore the posterior pdf of amplitude A(l = 16) and the power law index α and find the maximum a posteriori values A * (l = 16) = 0.064 ± 0.022 and α * = −0.92 ± 0.22. The maximum a posteriori direction associated with the Cosmic Hemispherical Asymmetry is (l, b) = (247.8 o , −19.6 o ) in Galactic coordinates, consistent with previous analyses. We evaluate the Bayes factor B SI−DM to compare the Cosmic Hemispherical Asymmetry model with the isotropic model. The data prefer but do not substantially favor the anisotropic model (B SI−DM = 0.4). We consider several priors and find that this evidence ratio is robust to prior choice. The large-scale power suppression does not soften when jointly inferring both the isotropic power spectrum and the parameters of the asymmetric model, indicating no evidence that these anomalies are coupled.

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Section: Discussionmentioning

confidence: 99%

Joint Bayesian analysis of large angular scale CMB temperature anomalies

Shaikh

Mukherjee

Das

et al. 2019

J. Cosmol. Astropart. Phys.

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“…The statistical isotropy of the universe is being tested for many extragalactic objects like Radio sources (Blake & Wall 2002;Ghosh et al 2016), Gamma-ray bursts (Bernui et al 2008a;Tarnopolski 2017;Řípa & Shafiello 2018), galaxy clusters (Bengaly et al 2017a), and galaxy datasets like the WISE (Yoon et al 2014;Bengaly et al 2017b;Novaes et al 2018) and the SDSS catalogues (Sarkar et al 2019), where all these analyses show a good concordance with the isotropy of the universe. The Planck Convergence and Cosmic Microwave Background temperature fluctuations maps have been examined and are also consistent with statistical isotropy at small angular scales (Ade et al 2016;Novaes et al 2016;Marques et al 2018), although some controversy remains at large angles (Bernui 2008b;Gruppuso et al 2013; Polase-mail: felipeavila@on.br tri, Gruppuso & Natoli 2015;Schwarz et al 2016;Aluri, Ralston & Weltman 2017;Rath et al 2017;Bernui et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The angular scale of homogeneity in the local Universe with the SDSS blue galaxies

Avila

Novaes

Bernui

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We probe the angular scale of homogeneity in the local Universe using blue galaxies from the SDSS survey as a cosmological tracer. Through the scaled counts in spherical caps, N (< θ), and the fractal correlation dimension, D 2 (θ), we find an angular scale of transition to homogeneity for this sample of θ H = 22.19 • ±1.02 • . A comparison of this measurement with another obtained using a different cosmic tracer at a similar redshift range (z < 0.06), namely, the HI extragalactic sources from the ALFALFA catalogue, confirms that both results are in excellent agreement (taking into account the corresponding bias correction). We also perform tests to asses the robustness of our results. For instance, we test if the size of the surveyed area is large enough to identify the transition scale we search for, and also we investigate a reduced sample of blue galaxies, obtaining in both cases a similar angular scale for the transition to homogeneity. Our results, besides confirming the existence of an angular scale of transition to homogeneity in different cosmic tracers present in the local Universe, show that the observed angular scale θ H agrees well with what is expected in the ΛCDM scenario. Although we can not prove spatial homogeneity within the approach followed, our results provide one more evidence of it, strengthening the validity of the Cosmological Principle.

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“…According to Ghosh et al (2016) -The tantalizing possibility that the cosmological principle may be violated is indicated by many observations. The most prominent of these effects is the so-called Virgo alignment, which refers to a wide range of phenomena indicating a preferred direction pointing towards Virgo.…”

Section: Discussionmentioning

confidence: 99%

A Practical Model of Godel–Planck–Hubble–Birch Universe

U.V¹,

Lakshminarayana²

2019

AJS

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By considering 'Planck mass' as a characteristic massive seed and by replacing big bang with a growing Planck ball, an evolving model of quantum cosmology can be developed. With reference to increasing support for large scale cosmic anisotropy, preferred directions, quantum mechanical demand of cosmic spin and by considering a decreasing trend of angular velocity, from the beginning of Planck scale, we have developed a procedure for estimating the trend of all cosmic physical parameters. From and about the baby universe, in all directions, cosmic acceleration can be understood with increasing expansion velocity and decreasing total matter density ratio. We would like suggest that, from the beginning of Planck scale, 1) Dark matter can be considered as a kind of cosmic foam responsible for formation of galaxies. 2) Cosmic angular velocity decreases with square of the decreasing cosmic temperature. 3) Increasing ratio of Hubble parameter to angular velocity plays a crucial role in estimating increasing cosmic expansion velocity and decreasing total matter density ratio. 4) There is no need to consider dark energy for understanding cosmic acceleration. With further study, cosmological nucleosynthesis and dark matter synthesis along with mass generation mechanism can be reviewed in a quantum cosmological approach.

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Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array

Cited by 28 publications

References 62 publications

Joint Bayesian analysis of large angular scale CMB temperature anomalies

Joint Bayesian analysis of large angular scale CMB temperature anomalies

The angular scale of homogeneity in the local Universe with the SDSS blue galaxies

A Practical Model of Godel–Planck–Hubble–Birch Universe

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