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Towards 21-cm intensity mapping at z = 2.28 with uGMRT using the tapered gridded estimator - III. Foreground removal

Elahi, KMA and Bharadwaj, S and Pal, S and Ghosh, A and Ali, SS and Choudhuri, S and Chakraborty, A and Datta, A and Roy, N and Choudhury, M and Dutta, P (2023) Towards 21-cm intensity mapping at z = 2.28 with uGMRT using the tapered gridded estimator - III. Foreground removal. In: Monthly Notices of the Royal Astronomical Society, 525 (3). pp. 3439-3454.

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Official URL: https://doi.org/10.1093/mnras/stad2495


Neutral hydrogen () 21-cm intensity mapping (IM) is a promising probe of the large-scale structures in the Universe. However, a few orders of magnitude brighter foregrounds obscure the IM signal. Here, we use the tapered gridded estimator to estimate the multifrequency angular power spectrum C(Δν) from a bandwidth upgraded Giant Metrewave Radio Telescope Band 3 data at. In C(Δν) foregrounds remain correlated across the entire Δν range, whereas the 21-cm signal is localized within Δν ≤ [Δν] (typically, 0.5-1 MHz). Assuming the range Δν > [Δν] to have minimal 21-cm signal, we use C(Δν) in this range to model the foregrounds. This foreground model is extrapolated to Δν ≤ [Δν], and subtracted from the measured C(Δν). The residual [C(Δν)]res in the range Δν ≤ [Δν] is used to constrain the 21-cm signal, compensating for the signal loss from foreground subtraction. [C(Δν)]res is found to be noise-dominated without any trace of foregrounds. Using [C(Δν)]res, we constrain the 21-cm brightness temperature fluctuations Δ2(k), and obtain the 2σ upper limit at. We further obtain the 2σ upper limit, where and are the comoving density and bias parameters, respectively. Although the upper limit is nearly 10 times larger than the expected 21-cm signal, it is 3 times tighter over previous works using foreground avoidance on the same data. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

Item Type: Journal Article
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Oxford University Press
Additional Information: The copyright for this article belongs to the Author.
Keywords: Diffuse radiation; Intensity mapping; Large scale structure of universe; Large-scale structure; Methods. Data analysis; Methods:statistical; Neutral hydrogen; Orders of magnitude; Technique: interferometric; Upper limits, Mapping
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 14 Dec 2023 03:46
Last Modified: 14 Dec 2023 03:46
URI: https://eprints.iisc.ac.in/id/eprint/83380

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