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

  • Kanan K. DattaEmail author
  • Raghunath Ghara
  • Suman Majumdar
  • T. Roy Choudhury
  • Somnath Bharadwaj
  • Himadri Roy
  • Abhirup Datta


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 \(R_{\mathrm {b}} \gtrsim 10\) Mpc with ∼100 h of observations at redshift z∼8 provided that the mean outside neutral hydrogen fraction \(\mathrm {x}_{\text {HI}} \gtrsim 0.5\). We also investigate the possibility of detecting HII regions around known bright QSOs such as around ULASJ1120+0641 discovered by Mortlock et al. (Nature 474, 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.


Cosmology: cosmic reionization 21-cm signal square kilometre array 



The first author, KKD would like to thank University Grant Commission (UGC), India for support through UGC-Faculty Recharge Scheme (UGC-FRP) vide ref. no. F.4-5(137- FRP)/2014(BSR).


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Copyright information

© Indian Academy of Sciences 2016

Authors and Affiliations

  1. 1.Department of PhysicsPresidency UniversityKolkataIndia
  2. 2.National Centre for Radio Astrophysics, TIFRPuneIndia
  3. 3.Department of Physics, Blackett LaboratoryImperial CollegeLondonUK
  4. 4.Department of Physics & Centre for Theoretical StudiesIndian Institute of Technology KharagpurKharagpurIndia
  5. 5.Centre for AstronomyIndian Institute of Technology IndoreIndoreIndia

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