Line-of-Sight Anisotropies in the Cosmic Dawn and Epoch of Reionization 21-cm Power Spectrum

  • Suman MajumdarEmail author
  • Kanan K. Datta
  • Raghunath Ghara
  • Rajesh Mondal
  • T. Roy Choudhury
  • Somnath Bharadwaj
  • Sk. Saiyad Ali
  • Abhirup Datta


The line-of-sight direction in the redshifted 21-cm signal coming from the cosmic dawn and the epoch of reionization is quite unique in many ways compared to any other cosmological signal. Different unique effects, such as the evolution history of the signal, non-linear peculiar velocities of the matter etc. will imprint their signature along the line-of-sight axis of the observed signal. One of the major goals of the future SKA-LOW radio interferometer is to observe the cosmic dawn and the epoch of reionization through this 21-cm signal. It is thus important to understand how these various effects affect the signal for its actual detection and proper interpretation. For more than one and half decades, various groups in India have been actively trying to understand and quantify the different line-of-sight effects that are present in this signal through analytical models and simulations. In many ways the importance of this sub-field under 21-cm cosmology have been identified, highlighted and pushed forward by the Indian community. In this article, we briefly describe their contribution and implication of these effects in the context of the future surveys of the cosmic dawn and the epoch of reionization that will be conducted by the SKA-LOW.


Methods: statistical—cosmology: theory—dark ages, reionization, first stars—diffuse radiation. 



The first author (SM) would like to acknowledge financial support from the European Research Council under the ERC grant number 638743-FIRSTDAWN and from the European Unions Seventh Framework Programme FP7-PEOPLE-2012-CIG, Grant No. 321933-21ALPHA. The second author (KKD) would like to thank University Grants Commission (UGC), India for support through UGC-Faculty Recharge Scheme (UGC-FRP) vide ref. no. F.4-5(137-FRP)/2014(BSR).


  1. Alcock, C., Paczynski, B. 1979, Nature, 281, 358.ADSCrossRefGoogle Scholar
  2. Ali, S. S., Bharadwaj, S., Pandey, B. 2005, MNRAS, 363, 251.ADSCrossRefGoogle Scholar
  3. Ali, Z. S. et al. 2015, ApJ, 809, 61.ADSCrossRefGoogle Scholar
  4. Barkana, R., Loeb, A. 2005, ApJL, 624, L65.ADSCrossRefGoogle Scholar
  5. Barkana, R., Loeb, A. 2006, MNRAS, 372, L43.ADSCrossRefGoogle Scholar
  6. Becker, R. H. et al. 2001, Astron. J., 122, 2850.ADSCrossRefGoogle Scholar
  7. Becker, G. D., Bolton, J. S., Madau, P., Pettini, M., Ryan-Weber, E. V., Venemans, B. P. 2015, MNRAS, 447, 3402.ADSCrossRefGoogle Scholar
  8. Bharadwaj, S., Ali, S. S. 2004, MNRAS, 352, 142.ADSCrossRefGoogle Scholar
  9. Bharadwaj, S., Ali, S. S. 2005, MNRAS, 356, 1519.ADSCrossRefGoogle Scholar
  10. Bharadwaj, S., Pandey, S. K. 2005, MNRAS, 358, 968.ADSCrossRefGoogle Scholar
  11. Bharadwaj, S., Nath, B. B., Sethi, S. K. 2001, J. Astrophys. Astr., 22, 21.ADSCrossRefGoogle Scholar
  12. Bouwens, R. 2016, in: Astrophysics and Space Science Library, edited by A. Mesinger, vol. 423, Astrophysics and Space Science Library. p. 111 (arXiv:1511.01133), doi:  10.1007/978-3-319-21957-8_4.
  13. Bowman, J. D. et al. 2013, Publ. Astron. Soc. Australia, 30, 31.Google Scholar
  14. Choudhuri, S., Bharadwaj, S., Ghosh, A., Ali, S. S. 2014, MNRAS, 445, 4351.Google Scholar
  15. Choudhuri, S., Bharadwaj, S., Roy, N., Ghosh, A., Ali, S. S., MNRAS (2016)Google Scholar
  16. Choudhury, T. R., Haehnelt, M. G., Regan, J. 2009, MNRAS, 394, 960.ADSCrossRefGoogle Scholar
  17. Cole, S., Fisher, K. B., Weinberg, D. H. 1995, MNRAS, 275, 515.ADSGoogle Scholar
  18. Datta, K. K., Choudhury, T. R., Bharadwaj, S. 2007, MNRAS, 378, 119.ADSCrossRefGoogle Scholar
  19. Datta, A., Bowman, J. D., Carilli, C. L. 2010, ApJ, 724, 526.ADSCrossRefGoogle Scholar
  20. Datta, K. K., Mellema, G., Mao, Y., Iliev, I. T., Shapiro, P. R., Ahn, K. 2012, MNRAS, 424, 1877.ADSCrossRefGoogle Scholar
  21. Datta, K. K., Jensen, H., Majumdar, S., Mellema, G., Iliev, I. T., Mao, Y., Shapiro, P. R., Ahn, K. 2014, MNRAS, 442, 1491.ADSCrossRefGoogle Scholar
  22. Dillon, J. S. et al. 2014, Phys. Rev. D, 89, 023002.Google Scholar
  23. Fan, X. et al. 2003, Astron. J., 125, 1649.Google Scholar
  24. Fialkov, A., Barkana, R., Cohen, A. 2015, Phys. Rev. Lett., 114, 101303.ADSCrossRefGoogle Scholar
  25. Ghara, R., Choudhury, T. R., Datta, K. K. 2015a, MNRAS, 447, 1806.Google Scholar
  26. Ghara, R., Datta, K. K., Choudhury, T. R. 2015b, MNRAS, 453, 3143.ADSCrossRefGoogle Scholar
  27. Greig, B., Mesinger, A., Koopmans, L. V. E. 2015, preprint (arXiv:1509.03312).
  28. Hamilton, A. J. S. 1992, ApJL, 385, L5.ADSCrossRefGoogle Scholar
  29. Hamilton, A. J. S. 1998, in: Astrophysics and Space Science Library, edited by D. Hamilton, vol. 231, The Evolving Universe, p. 185 (arXiv:astro-ph/9708102).
  30. Jacobs, D. C. et al. 2015, ApJ, 801, 51.ADSCrossRefGoogle Scholar
  31. Jensen, H. et al. 2013, MNRAS, 435, 460.ADSCrossRefGoogle Scholar
  32. Jensen, H., Majumdar, S., Mellema, G., Lidz, A., Iliev, I. T., Dixon, K. L. 2016, MNRAS, 456, 66.ADSCrossRefGoogle Scholar
  33. Komatsu, E. et al. 2011, ApJS, 192, 18.Google Scholar
  34. Koopmans, L. et al. 2015, Advancing Astrophysics with the Square Kilometre Array (AASKA14), p. 1.Google Scholar
  35. La Plante, P., Battaglia, N., Natarajan, A., Peterson, J. B., Trac, H., Cen, R., Loeb, A. 2014, ApJ, 789, 31.ADSCrossRefGoogle Scholar
  36. Lidz, A., Zahn, O., McQuinn, M., Zaldarriaga, M., Dutta, S., Hernquist, L. 2007, ApJ, 659, 865.ADSCrossRefGoogle Scholar
  37. Lidz, A., Zahn, O., McQuinn, M., Zaldarriaga, M., Hernquist, L. 2008, ApJ, 680, 962.ADSCrossRefGoogle Scholar
  38. Majumdar, S., Bharadwaj, S., Datta, K. K., Choudhury, T. R. 2011, MNRAS, 413, 1409.ADSCrossRefGoogle Scholar
  39. Majumdar, S., Bharadwaj, S., Choudhury, T. R. 2012, MNRAS, 426, 3178.ADSCrossRefGoogle Scholar
  40. Majumdar, S., Bharadwaj, S., Choudhury, T. R. 2013, MNRAS, 434, 1978.ADSCrossRefGoogle Scholar
  41. Majumdar, S., Mellema, G., Datta, K. K., Jensen, H., Choudhury, T. R., Bharadwaj, S., Friedrich, M. M. 2014, MNRAS, 443, 2843.ADSCrossRefGoogle Scholar
  42. Majumdar, S. et al. 2016, MNRAS, 456, 2080.Google Scholar
  43. Mao, Y., Shapiro, P. R., Mellema, G., Iliev, I. T., Koda, J., Ahn, K. 2012, MNRAS, 422, 926.ADSCrossRefGoogle Scholar
  44. Mellema, G. et al. 2013, Experimental Astron., 36, 235.ADSCrossRefGoogle Scholar
  45. Mellema, G., Koopmans, L., Shukla, H., Datta, K. K., Mesinger, A., Majumdar, S. 2015, Advancing Astrophysics with the Square Kilometre Array (AASKA14), p. 10.Google Scholar
  46. Mesinger, A., Furlanetto, S., Cen, R. 2011, MNRAS, 411, 955.ADSCrossRefGoogle Scholar
  47. Mesinger, A., Ewall-Wice, A., Hewitt, J. 2014, MNRAS, 439, 3262.ADSCrossRefGoogle Scholar
  48. Mondal, R., Bharadwaj, S., Majumdar, S., Bera, A., Acharyya, A. 2015, MNRAS, 449, L41.ADSCrossRefGoogle Scholar
  49. Mondal, R., Bharadwaj, S., Majumdar, S. 2016a, preprint, (arXiv:1606.03874).
  50. Mondal, R., Bharadwaj, S., Majumdar, S. 2016b, MNRAS, 456, 1936.ADSCrossRefGoogle Scholar
  51. Ouchi, M. et al. 2010, ApJ, 723, 869.ADSCrossRefGoogle Scholar
  52. Paciga, G. et al. 2013, MNRAS, 433, 639.Google Scholar
  53. Parsons, A. R. et al. 2014, ApJ, 788, 106.ADSCrossRefGoogle Scholar
  54. Planck Collaboration 2015, preprint (arXiv:1502.01589).
  55. Pober, J. C. 2015, MNRAS, 447, 1705.ADSCrossRefGoogle Scholar
  56. Pober, J. C. et al. 2014, ApJ, 782, 66.ADSCrossRefGoogle Scholar
  57. Pritchard, J. R., Loeb, A. 2008, Phys. Rev. D, 78, 103511.ADSCrossRefGoogle Scholar
  58. Sethi, S., Haiman, Z. 2008, ApJ, 673, 1.ADSCrossRefGoogle Scholar
  59. Shapiro, P. R., Mao, Y., Iliev, I. T., Mellema, G., Datta, K. K., Ahn, K., Koda, J. 2013, Phys. Rev. Lett., 110, 151301.ADSCrossRefGoogle Scholar
  60. Tingay, S. J. et al. 2013, Publ. Astron. Soc. Australia, 30, 7.Google Scholar
  61. Trenti, M., Stiavelli, M., Bouwens, R. J., Oesch, P., Shull, J. M., Illingworth, G. D., Bradley, L. D., Carollo, C. M. 2010, ApJL, 714, L202.ADSCrossRefGoogle Scholar
  62. Trott, C. M., Wayth, R. B., Tingay, S. J. 2012, ApJ, 757, 101.ADSCrossRefGoogle Scholar
  63. Tseliakhovich, D., Hirata, C. 2010, Phys. Rev. D, 82, 083520.ADSCrossRefGoogle Scholar
  64. van Haarlem, M. P. et al. 2013, A&A, 556, A2.Google Scholar
  65. Wyithe, J. S. B., Loeb, A., Barnes, D. G. 2005, ApJ, 634, 715.ADSCrossRefGoogle Scholar
  66. Yatawatta, S. et al. 2013, A&A, 550, A136.ADSCrossRefGoogle Scholar
  67. Yu, Q. 2005, ApJ, 623, 683.ADSCrossRefGoogle Scholar

Copyright information

© Indian Academy of Sciences 2016

Authors and Affiliations

  1. 1.Department of Physics, Blackett LaboratoryImperial CollegeLondonUK
  2. 2.Department of PhysicsPresidency UniversityKolkataIndia
  3. 3.National Centre for Radio AstrophysicsTata Institute of Fundamental ResearchPuneIndia
  4. 4.Department of Physics & Centre for Theoretical StudiesIndian Institute of Technology KharagpurKharagpurIndia
  5. 5.Department of PhysicsJadavpur UniversityKolkataIndia
  6. 6.Centre for AstronomyIndian Institute of Technology IndoreIndoreIndia

Personalised recommendations