Browsing by Author "Ocran, E. F."

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    Cosmic evolution of star-forming galaxies to z 1.8 in the faint low-frequency radio source population
    (Oxford University Press, 2019) Ocran, E. F.; Taylor, A. R.; Vaccari, M.
    We study the properties of star-forming galaxies selected at 610 MHz with the GMRT in a survey covering ∼1.86 deg2 down to a noise of ∼7.1 μJy beam−1. These were identified by combining multiple classification diagnostics: optical, X-ray, infrared, and radio data. Of the 1685 SFGs from the GMRT sample, 496 have spectroscopic redshifts whereas 1189 have photometric redshifts. We find that the IRRC of star-forming galaxies, quantified by the infrared-to-1.4 GHz radio luminosity ratio qIR⁠, decreases with increasing redshift: qIR=2.86±0.04(1+z)−0.20±0.02 out to z ∼ 1.8. We use the V/Vmax statistic to quantify the evolution of the comoving space density of the SFG sample. Averaged over luminosity our results indicate ⟨V/Vmax⟩ to be 0.51±0.06⁠, which is consistent with no evolution in overall space density. However, we find V/Vmax to be a function of radio luminosity, indicating strong luminosity evolution with redshift.
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    Deep GMRT 610 MHz observations of the ELAIS N1 field: Catalogue and source counts
    (Oxford University Press, 2019) Taylor, A. R.; Ocran, E. F.; Vaccari, M.
    This is the first of a series of papers based on sensitive 610 MHz observations of the ELAIS N1 field, using the Giant Metrewave Radio Telescope. We describe the observations, processing and source catalogue extraction from a deep image with area of 1.86 deg2 and minimum noise of ∼7.1 μJy beam−1. We compile a catalogue of 4290 sources with flux densities in the range of 28.9 μJy– 0.503 Jy and derive the Euclidean-normalized differential source counts for sources with flux densities brighter than 35.5μJy⁠.
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    The evolution of the low-frequency radio AGN population to z 1.5 in the ELAIS N1 field
    (Oxford University Press, 2021) Ocran, E. F.; Taylor, A. R.; Vaccari, M.
    We study the cosmic evolution of radio sources out to z ≃ 1.5 using a GMRT 610 MHz survey covering ∼1.86 deg2 of the ELAIS N1 field with a minimum/median rms noise 7.1/19.5 μJy beam−1 and an angular resolution of 6 arcsec. We classify sources as star forming galaxies (SFGs), radio-quiet (RQ) and radio-loud (RL) Active Galactic Nuclei (AGNs) using a combination of multiwavelength diagnostics and find evidence in support of the radio emission in SFGs and RQ AGN arising from star formation, rather than AGN-related processes. At high luminosities, however, both SFGs and RQ AGN display a radio excess when comparing radio and infrared star formation rates.