• S. Bharadwaj

      Articles written in Journal of Astrophysics and Astronomy

    • Fisher Matrix Predictions for Detecting the Cosmological 21-cm Signal with the Ooty Wide Field Array (OWFA)

      S. Bharadwaj A. K. Sarkar Sk. Saiyad Ali

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      We have used the Fisher matrix formalism to quantify the prospects of detecting the 𝑧 = 3.35 redshifted 21-cm HI power spectrum with the upcoming radio-imterferometric array OWFA. OWFA’s frequency and baseline coverage spans comoving Fourier modes in the range 1.8 × 10−2 ≤ k ≤ 2.7 Mpc−1. The OWFA HI signal, however, is predominantly from the range 𝑘 ≤ 0.2 Mpc−1. The larger modes, though abundant, do not contribute much to the HI signal. In this work, we have focused on combining the entire signal to achieve a detection. We find that a 5 - 𝜎 detection of 𝐴HI is possible with ∼ 150 h of observations, here $A^{2}_{\text{HI}}$ is the amplitude of the HI power spectrum. We have also carried out a joint analysis for 𝐴HI and 𝛽 the redshift space distortion parameter. Our study shows that OWFA is very sensitive to the amplitude of the HI power spectrum. However, the anisotropic distribution of the k modes does not make it very suitable for measuring 𝛽.

    • Redshifted HI 21-cm Signal from the Post-Reionization Epoch: Cross-Correlations with Other Cosmological Probes

      T. Guha Sarkar K. K. Datta A. K. Pal T. Roy Choudhury S. Bharadwaj

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      Tomographic intensity mapping of the HI using the redshifted 21-cm observations opens up a new window towards our understanding of cosmological background evolution and structure formation. This is a key science goal of several upcoming radio telescopes including the Square Kilometer Array (SKA). In this article, we focus on the post-reionization signal and investigate the cross correlating of the 21-cm signal with other tracers of the large scale structure. We consider the cross-correlation of the post-reionization 21-cm signal with the Lyman- α forest, Lyman-break galaxies and late time anisotropies in the CMBR maps like weak lensing and the integrated Sachs Wolfe effect. We study the feasibility of detecting the signal and explore the possibility of obtaining constraints on cosmological models using it.

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      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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      Posted on July 25, 2019

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