Caught in the act: Interaction-driven evolution in the nearby compact galaxy group Robert's Quartet (SCG0018-4854)

Abstract

We present a spatially resolved multiwavelength study of the compact galaxy group Robert's Quartet (RQ; SCG0018-4854), aimed at understanding interaction-driven galaxy evolution in dense environments. The system comprises four galaxies (NGC 87, NGC 88, NGC 89, and NGC 92) that span a range of masses and evolutionary states. Using UV-to-IR data from GALEX, DECaLS, MUSE/VLT (IFU), VISTA/VIRCAM, 2MASS, and WISE, we investigated the interplay between kinematics, star formation, and stellar populations across the group. The spatially resolved analysis reveals disturbed stellar and gas kinematics, enhanced turbulence, and asymmetric structures in all members, consistent with repeated gravitational interactions. The most massive galaxy, NGC 92, exhibits prominent tidal features, a bar, and ring-like star-forming structures, indicative of interaction-driven gas inflows. Another massive member, NGC 89, shows suppressed star formation and signatures of active galactic nucleus-driven feedback. Lower-mass galaxies NGC 88 and the dwarf galaxy NGC 87, by contrast, display enhanced star formation and, in one case, kinematic decoupling between stellar and gaseous components consistent with recent gas accretion. Combining UV-based age estimates with non-parametric star formation histories, we constrain the recent interaction timescale of the group to ≲500 Myr, whereas the crossing timescale is 424 Myr. These results indicate that RQ is a dynamically young system undergoing ongoing assembly, where interactions, gas exchange, and feedback processes are actively shaping galaxy evolution. The dynamical complexity of the group further suggests that its present configuration may involve more than four progenitor components. In this context, RQ provides a valuable nearby analogue of compact, rapidly evolving groups observed at high redshift by recent JWST observations, offering a resolved view of the physical processes governing galaxy assembly in the early Universe.