All-sky angular power spectrum – I. Estimating brightness temperature fluctuations using the 150-MHz TGSS survey. Issue 2 (16th April 2020)

• Record Type: Journal Article
• Authors: Choudhuri, Samir; Ghosh, Abhik; Roy, Nirupam; Bharadwaj, Somnath; Intema, Huib T; Ali, Sk Saiyad
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 494:Issue 2(2020)
• Page Start: 1936
• Page End: 1945
• Publication Date: 2020-04-16
• Subjects: methods: data analysis -- methods: statistical -- techniques: interferometric -- dark ages, reionization, first stars -- radio continuum: galaxies -- radio continuum: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa762
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Measurements of the Galactic synchrotron emission are important for the 21-cm studies of the epoch of reionization. The study of synchrotron emission is also useful for quantifying the fluctuations in the magnetic field and the cosmic-ray electron density of the turbulent interstellar medium (ISM) of our Galaxy. Here, we present the all-sky angular power spectrum ( C ℓ ) measurements of the diffuse synchrotron emission obtained using the TIFR GMRT Sky Survey (TGSS) at 150 MHz. We estimate C ℓ using visibility data both before and after subtracting the modelled point sources. The amplitude of the measured C ℓ decreases significantly after subtracting the point sources, and it is slightly higher in the Galactic plane for the residual data. The residual C ℓ is most likely to be dominated by the Galactic synchrotron emission. The amplitude of the residual C ℓ decreases significantly away from the Galactic plane. We find that the measurements are quite symmetric in the Northern and Southern hemispheres except in the latitude range 15°−30°, which is the transition region from the disc-dominated to the diffuse halo-dominated region. A comparison between this interferometric measurement and the scaled version of the Haslam rms map at 150 MHz shows that the correlation coefficient ( r ) is greater than 0.5 for most of the latitude ranges considered here. This indicates that the TGSS is quite sensitive to the diffuse Galactic synchrotron radiation.