ner_tags: O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O B-Wavelength I-Wavelength B-Survey I-Survey I-Survey I-Survey B-Survey O O O O O B-Dataset O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O B-CelestialRegion I-CelestialRegion I-CelestialRegion I-CelestialRegion I-CelestialRegion I-CelestialRegion O O O O O O O O O O O O O O O O O O O O O B-CelestialRegion I-CelestialRegion I-CelestialRegion I-CelestialRegion O O O O O O O O O O O O B-CelestialRegion I-CelestialRegion I-CelestialRegion O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O B-CelestialObject I-CelestialObject B-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O B-Survey O O O O O O O O O B-Survey O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Dataset O O O O O O O O O O O O B-Wavelength O O O O O O O B-Software I-Software O O O O O B-Survey O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Software B-Software I-Software I-Software I-Software O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: fields to search for weak diffuse emission from the targets (e.g. Cook et al. 2020 ). For this work, we have used data from the 150 MHz TIFR GMRT Sky Survey (TGSS). The first alternative data release (TGSS-ADR1) of this survey (Intema et al. 2017 ) provides the continuum Stokes I images of 99.5 per cent of the sky area north of declination δ = −53° (i.e. ∼90 per cent of the full sky), at a resolution of 25 × 25 arcsec 2 for fields that are north of 19° declination, and 25 × 25 arcsec 2 /cos (δ − 19°) for fields south of 19°. The median value of RMS noise is 3.5 mJy beam −1 for the survey. Out of around 65 dSph galaxies of Milky way and Local Group (McConnachie 2012 ; Drlica-Wagner et al. 2020 ), 23 are found to be within the TGSS footprint. There were five more targets observed in the TGSS, but are not included in this analysis due to presence of image artifacts in those fields. The target coordinates, their half-light radius and distance (McConnachie 2012 ; Koposov et al. 2015 ; Laevens et al. 2015 ; Martin et al. 2015 ; Martínez-Vázquez et al. 2019 ; Cook et al. 2020 ) are tabulated in Table 1 , and the half-light radius distribution is shown in Fig. 1 . Note that the unique hybrid array configuration of the GMRT implies that the telescope has sensitivity to both small-scale compact structures as well as large-scale diffuse emission, with the largest detectable structure (corresponding to the shortest baselines) being 68 arcmin. If the diffuse emission from these targets have angular extent ∼few × r h , there will not be any significant missing flux issue in this analysis. Figure 1. Histogram of the half-light radii, r h of the sample of 23 dSph galaxies used in this study. Table 1. List of the dSph galaxies used in this analysis, with their J2000.0 coordinates, half-light radius ( r h ), and distance ( D ). 3 DATA ANALYSIS For the 23 dSph galaxies, we have used the TGSS-ADR image archive to extract the image of a region centred around the optical position of each of the galaxies in FITS format combining data from multiple overlapping TGSS pointing. For the first part of our analysis, we have extracted 1° × 1° region for each of the target dSph galaxies. Further analysis was done using the casa (Common Astronomy Software Applications) package. We have visually inspected each field to identify and blank all the compact sources (unresolved and marginally resolved) using a 5 σ cut off. These compact sources are unrelated to the expected faint diffuse emission (originating from processes directly involving the DM annihilation/decay) at the galaxy-wide scale, that is of our interest. This will also filter out any plausible unidentified imaging artefact present in the field. We then shift the central coordinate of all the fields, regrid and convolve the data to exactly same pixel size and same synthesized beam before combining to create a stacked image from all 23 dSph target field. We have also selected 23 ‘control’ regions, located close to