Spectral study of faint radio sources in ELAIS N1 field

Abstract

Understanding the spectral properties of sources is crucial for the characterization of the radio source population. In this work, we have extensively studied the ELAIS N1 field using various low-frequency radio observations. For the first time, we presented the 1250 MHz observations of the field using the upgraded Giant Meterwave Radio Telescope (uGMRT) that reach a central off-source RMS noise of \(\sim \)12 \(\upmu \)Jy beam\(^{-1}\). A source catalog of 1086 sources is compiled at \(5\sigma \) threshold (>60 \(\upmu \)Jy) to derive the normalized differential source counts at this frequency, which is consistent with existing observations and simulations. We presented the spectral indices derived in two ways: two-point spectral indices and by fitting a power-law. The latter yielded a median \(\alpha = -0.57\pm 0.14\), and we identified nine ultra-steep spectrum sources using these spectral indices. Further, using a radio color diagram, we identified the three mega-hertz peaked spectrum (MPS) sources, while three other MPS sources are identified from the visual inspection of the spectra, the properties of which are discussed. In our study of the classified sources in the ELAIS N1 field, we presented the relationship between \(\alpha \) and z. We found no evidence of an inverse correlation between these two quantities and suggested that the nature of the radio spectrum remains independent of the large-scale properties of the galaxies that vary with redshifts.