Characterizing EoR foregrounds: a study of the Lockman Hole region at 325 MHz. Issue 4 (13th May 2020)

• Record Type: Journal Article
• Authors: Mazumder, Aishrila; Chakraborty, Arnab; Datta, Abhirup; Choudhuri, Samir; Roy, Nirupam; Wadadekar, Yogesh; Ishwara-Chandra, C H
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 495:Issue 4(2020)
• Page Start: 4071
• Page End: 4084
• Publication Date: 2020-05-13
• Subjects: techniques: interferometric -- surveys -- galaxies: general -- diffuse radiation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1317
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: One of the key science goals for the most sensitive telescopes, both current and upcoming, is the detection of the redshifted 21-cm signal from the Cosmic Dawn and Epoch of Reionization. The success of detection relies on accurate foreground modelling for their removal from data sets. This paper presents the characterization of astrophysical sources in the Lockman Hole region. Using 325-MHz data obtained from the Giant Metrewave Radio Telescope, a 6° × 6° mosaiced map is produced with an rms reaching 50 μ Jy per beam. A source catalogue containing 6186 sources is created, and the Euclidean normalized differential source counts have been derived from it, consistent with previous observations as well as simulations. A detailed comparison of the source catalogue is also made with previous findings – at both lower and higher frequencies. The angular power spectrum (APS) of the diffuse Galactic synchrotron emission is determined for three different Galactic latitudes using the tapered gridded estimator. The values of the APS lie between ∼1 and ∼100 mK 2 . Fitting a power law of the form A ℓ −β gives values of A and β varying across the latitudes considered. This paper demonstrates, for the first time, the variation of the power-law index for diffuse emission at very high Galactic locations. It follows the same trend that is seen at locations near the Galactic plane, thus emphasizing the need for low-frequency observations for developing better models of the diffuse emission.