Imaging neutral hydrogen on large scales during the Epoch of Reionization with LOFAR

S. Zaroubi, A. G. de Bruyn, G. Harker, R. M. Thomas, P. Labropolous, V. Jelić, L. V.E. Koopmans, M. A. Brentjens, G. Bernardi, B. Ciardi, S. Daiboo, S. Kazemi, O. Martinez-Rubi, G. Mellema, A. R. Offringa, V. N. Pandey, J. Schaye, V. Veligatla, H. Vedantham, S. Yatawatta

Research output: Contribution to journalArticlepeer-review


The first generation of redshifted 21 cm detection experiments, carried out with arrays like Low Frequency Array (LOFAR), Murchison Widefield Array (MWA) and Giant Metrewave Telescope (GMRT), will have a very low signal-to-noise ratio (S/N) per resolution element (≲0.2). In addition, whereas the variance of the cosmological signal decreases on scales larger than the typical size of ionization bubbles, the variance of the formidable galactic foregrounds increases, making it hard to disentangle the two on such large scales. The poor sensitivity on small scales, on the one hand, and the foregrounds effect on large scales, on the other hand, make direct imaging of the Epoch of Reionization of the Universe very difficult, and detection of the signal therefore is expected to be statistical. Despite these hurdles, in this paper we argue that for many reionization scenarios low-resolution images could be obtained from the expected data. This is because at the later stages of the process one still finds very large pockets of neutral regions in the intergalactic medium, reflecting the clustering of the large-scale structure, which stays strong up to scales of ≈120 h-1 comovingMpc (≈1°). The coherence of the emission on those scales allows us to reach sufficient S/N (≳3) so as to obtain reionization 21 cm images. Such images will be extremely valuable for answering many cosmological questions but above all they will be a very powerful tool to test our control of the systematics in the data. The existence of this typical scale (≈120 h-1 comovingMpc) also argues for designing future EoR experiments, e.g. with Square Kilometre Array, with a field of view of at least 4°.

Original languageEnglish
Pages (from-to)2964-2973
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 1 Oct 2012
Externally publishedYes

Bibliographical note

Funding Information:
SZ would like to thank the Lady Davis Foundation and The Netherlands Organization for Scientific Research (NWO) VICI grant for financial support. LVEK thanks the European Research Council Starting Grant for support. GH is a member of the LUNAR consortium, which is funded by the NASA Lunar Science Institute (via Cooperative Agreement NNA09DB30A) to investigate concepts for astrophysical observatories on the Moon.

Publisher Copyright:
© 2012 The Authors.


  • Cosmology: observations
  • Cosmology: theory
  • Diffuse radiation
  • Large-scale structure of Universe
  • Methods: statistical
  • Radio lines: general


Dive into the research topics of 'Imaging neutral hydrogen on large scales during the Epoch of Reionization with LOFAR'. Together they form a unique fingerprint.

Cite this