Imaging the redshifted 21 cm pattern around the first sources during the cosmic dawn using the SKA. Issue 2 (30th September 2016)

• Record Type: Journal Article
• Authors: Ghara, Raghunath; Choudhury, T. Roy; Datta, Kanan K.; Choudhuri, Samir
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 464:Issue 2(2017)
• Page Start: 2234
• Page End: 2248
• Publication Date: 2016-09-30
• Subjects: radiative transfer -- galaxies: formation -- intergalactic medium -- cosmology: theory -- dark ages, reionization, first stars -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stw2494
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: Understanding properties of the first sources in the Universe using the redshifted H i 21 cm signal is one of the major aims of present and upcoming low-frequency experiments. We investigate the possibility of imaging the redshifted 21 cm pattern around the first sources during the cosmic dawn using the SKA1-low. We model the H i 21 cm image maps, appropriate for the SKA1-low, around the first sources consisting of stars and X-ray sources within galaxies. In addition to the system noise, we also account for the astrophysical foregrounds by adding them to the signal maps. We find that after subtracting the foregrounds using a polynomial fit and suppressing the noise by smoothing the maps over 10–30 arcmin angular scale, the isolated sources at z ∼ 15 are detectable with the ∼4σ–9σ confidence level in 2000 h of observation with the SKA1-low. Although the 21 cm profiles around the sources get altered because of the Gaussian smoothing, the images can still be used to extract some of the source properties. We account for overlaps in the patterns of the individual sources by generating realistic H i 21 cm maps of the cosmic dawn that are based on N -body simulations and a one-dimensional radiative transfer code. We find that these sources should be detectable in the SKA1-low images at z = 15 with a signal-to-noise ratio (SNR) of ∼14(4) in 2000 (200) h of observations. One possible observational strategy thus could be to observe multiple fields for shorter observation times, identify fields with SNR ≳ 3 and observe these fields for much longer duration. Such observations are expected to be useful in constraining the parameters related to the first sources.