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Probing Individual Sources during Reionization and Cosmic Dawn using Square Kilometre Array HI 21-cm Observations

  • Datta, Kanan K.1
  • Ghara, Raghunath2
  • Majumdar, Suman3
  • Choudhury, T. Roy2
  • Bharadwaj, Somnath4
  • Roy, Himadri1
  • Datta, Abhirup5
  • 1 Presidency University, Department of Physics, Kolkata, 700 073, India , Kolkata (India)
  • 2 National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune, 411 007, India , Pune (India)
  • 3 Imperial College, Department of Physics, Blackett Laboratory, London, SW7 2AZ, UK , London (United Kingdom)
  • 4 Indian Institute of Technology Kharagpur, Department of Physics & Centre for Theoretical Studies, Kharagpur, 721 302, India , Kharagpur (India)
  • 5 Indian Institute of Technology Indore, Centre for Astronomy, Indore, 452 020, India , Indore (India)
Published Article
Journal of Astrophysics and Astronomy
Springer India
Publication Date
Nov 04, 2016
DOI: 10.1007/s12036-016-9405-x
Springer Nature


Detection of individual luminous sources during the reionization epoch and cosmic dawn through their signatures in the HI 21-cm signal is one of the direct approaches to probe the epoch. Here, we summarize our previous works on this and present preliminary results on the prospects of detecting such sources using the SKA1-low experiment. We first discuss the expected HI 21-cm signal around luminous sources at different stages of reionization and cosmic dawn. We then introduce two visibility based estimators for detecting such signals: one based on the matched filtering technique and the other relies on simply combing the visibility signal from different baselines and frequency channels. We find that the SKA1-low should be able to detect ionized bubbles of radius Rb≳10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$R_{\mathrm {b}} \gtrsim 10$\end{document} Mpc with ∼100 h of observations at redshift z∼8 provided that the mean outside neutral hydrogen fraction xHI≳0.5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mathrm {x}_{\text {HI}} \gtrsim 0.5$\end{document}. We also investigate the possibility of detecting HII regions around known bright QSOs such as around ULASJ1120+0641 discovered by Mortlock et al. (Nature474, 7353 (2011)). We find that a 5σ detection is possible with 600 h of SKA1-low observations if the QSO age and the outside xHI are at least ∼2×107 Myr and ∼0.2 respectively. Finally, we investigate the possibility of detecting the very first X-ray and Ly- α sources during the cosmic dawn. We consider mini-QSOs like sources which emits in X-ray frequency band. We find that with a total ∼ 1000 h of observations, SKA1-low should be able to detect those sources individually with a ∼ 9σ significance at redshift z=15. We summarize how the SNR changes with various parameters related to the source properties.

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