Deep far-UV observations of the ELAIS N1 field using AstroSat: source catalogue, spectral energy distribution modelling, and star formation

Abstract

We present a far-ultraviolet (FUV) photometric study of the ELAIS N1 (European Large-Area ISO Survey-North 1) deep field using the UVIT (Ultra-Violet Imaging Telescope) onboard AstroSat, observed in the F154W filter ((Formula presented) Å) with a total on-source exposure time of 30 ks. Level 1 data were reduced using ccdlab v3.0, yielding source catalogues of 1637 objects at (Formula presented) and 458 objects at (Formula presented), with limiting magnitudes of (Formula presented) and (Formula presented), respectively. FUV positions are cross-matched against multiwavelength catalogues spanning optical and infrared wavelengths, with redshifts drawn from spectroscopic and photometric sources. Active galactic nuclei (AGNs) are identified and excluded via established multiwavelength criteria, leaving a clean sample of star-forming galaxies. Spectral energy distribution modelling is performed using cigale, employing a delayed star formation history with an optional late burst, Bruzual & Charlot stellar population synthesis, Calzetti dust attenuation, and the skirtor AGN module. From the best-fitting models, we derive star formation rates (SFRs), total stellar masses, and young stellar masses as a function of redshift. The SFR increases monotonically with redshift, consistent with the evolution of the star formation main sequence. The ratio of young-to-total stellar mass remains approximately constant across (Formula presented), confirming that the sample consists predominantly of secularly evolving systems undergoing steady, self-regulated star formation rather than starburst-driven episodes. © The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.