Searching for the earliest galaxies in the 21 cm forest

Abstract

We use a model developed by Xu et al. (2010) to compute the 21 cm line absorption signatures imprinted by star-forming dwarf galaxies (DGs) and starless minihalos (MHs). The method, based on a statistical comparison of the equivalent width (W_ν) distribution and flux correlation function, allows us to derive a simple selection criteria for candidate DGs at very high (z >= 8) redshift. We find that ~ 18% of the total number of DGs along a line of sight to a target radio source (GRB or quasar) can be identified by the condition W_ν< 0; these objects correspond to the high-mass tail of the DG distribution at high redshift, and are embedded in large HII regions. The criterion W_ν> 0.37 kHz instead selects ~ 11% of MHs. Selected candidate DGs could later be re-observed in the near-IR by the JWST with high efficiency, thus providing a direct probe of the most likely reionization sources.

8 pages, 3 figures. Accepted for publication in Science in China Series G

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• The Tianlai project: a 21cm cosmology experiment
• The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history
• Deep learning-driven likelihood-free parameter inference for 21-cm forest observations
• Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21-cm Forest Observations
• Prospects for measuring neutrino mass with 21-cm forest
• Analytical modeling of the one-dimensional power spectrum of 21-cm forest based on a halo model method