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      https://www.ias.ac.in/article/fulltext/joaa/037/04/0027

    • Keywords

       

      Cosmology: cosmic reionization; 21-cm signal; square kilometre array.

    • Abstract

       

      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 $\sim100 \rm h$ of observations at redshift $z\sim8$ 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 $\mathrm {x}_{\text {HI}}$ are at least $\sim2 \times 10^7$ Myr and $\sim0.2$ 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 $\sim 1000 \rm h$ 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.

    • Author Affiliations

       

      Kanan K. Datta1 Raghunath Ghara2 Suman Majumdar3 T. Roy Choudhury2 Somnath Bharadwaj4 Himadri Roy1 Abhirup Datta5

      1. Department of Physics, Presidency University, Kolkata 700 073, India.
      2. National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune 411 007, India.
      3. Department of Physics, Blackett Laboratory, Imperial College, London SW7 2AZ, UK.
      4. Department of Physics & Centre for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India.
      5. Centre for Astronomy, Indian Institute of Technology Indore, Indore 452 020, India.
    • Dates

       
  • Journal of Astrophysics and Astronomy | News

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