AstroSat/UVIT Far- and Near-UV Deep Field Around IC 4329A

Abstract

We present high-resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) deep imaging of the field around the Seyfert galaxy IC 4329A based on five observations performed with the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat. The long exposures of 82.9 ks in the NUV (N245M; λ_mean = 2447 Å; Δλ = 270 Å) and 92.2 ks in the FUV (F154W; λ_mean = 1541 Å; Δλ = 380 Å) bands constitute the deepest observations with 5σ detection limits of AB magnitudes m_NUV = 26.2 and m_FUV = 25.7. Leveraging UVIT's excellent angular resolution (FWHM ∼ 1.2″-1.8″, we performed a detailed analysis of the IC 4329A field and detected (above the 5σ significance level) a total of 4437 and 456 sources in the NUV and FUV bands, respectively. A large number of these detected sources were previously unknown. We performed astrometry and photometry on all detected sources. By cross-matching our catalog with the Gaia-DR3 and XMM-Newton DR12 catalogs, we found 651 optical and 97 X-ray counterparts of our sources. Additionally, we explored the UV variability of point sources, identifying 28 NUV sources as variable with a significance above the 2.5σ level. Of these, only three sources exhibited variability in the FUV band. Utilizing the NUV and Gaia fluxes, we determined that two previously cataloged white dwarf candidates are misclassified. Furthermore, we highlight galaxies with atypical morphology, including ring-like structures, multiple compact central sources, bifurcating spiral arms, and so on. Follow-up optical spectroscopy and multiwavelength observations are imperative to further investigate the nature of the sources within this field.