Detailed study of the Boötes field using 300–500 MHz uGMRT observations: source properties and radio–infrared correlations

Abstract

ABSTRACT The dominant source of radio continuum emissions at low frequencies is synchrotron radiation, which originates from star-forming regions in disc galaxies and from powerful jets produced by active galactic nuclei (AGNs). We studied the Boötes field using the upgraded Giant Meterwave Radio Telescope at 400 MHz, achieving a central minimum off-source rms noise of 35 μJy beam−1 and a catalogue of 3782 sources in ∼6 deg2 of the sky. The resulting catalogue was compared to other radio frequency catalogues, and the corrected normalized differential source counts were derived. We use standard multiwavelength techniques to classify the sources in star-forming galaxies (SFGs), radio-loud AGNs, and radio-quiet (RQ) AGNs that confirm a boost in the SFG and RQ AGN populations at lower flux levels. For the first time, we investigated the properties of the radio–infrared (IR) relations at 400 MHz in this field. The $L_{\rm 400\, MHz}$–LTIR relations for SFGs were found to show a strong correlation with non-linear slope values of 1.10 ± 0.01, and variation of qTIR with z is given as qTIR = (2.19 ± 0.07) (1 + z)−0.15 ± 0.08. This indicates that the non-linearity of the radio–IR relations can be attributed to the mild variation of qTIR values with z. The derived relationships exhibit similar behaviour when applied to Low-Frequency Array at 150 MHz and also at 1.4 GHz. This emphasizes the fact that other parameters like magnetic field evolution with z or the number densities of cosmic ray electrons can play a vital role in the mild evolution of q values.