Unveiling the kinematics of a central region in the triple-AGN host NGC 7733-7734 interacting group

¹ Indian Institute of Astrophysics, Kormangala II Block, Bengaluru 560034, India
² Department of Physics, Pondicherry University, R.V. Nagar, Kalapet, 605014 Puducherry, India
³ Observatoire de Paris, LERMA, Collège de France, CNRS, PSL University, Sorbonne University, F-75014 Paris, France

^⋆ Corresponding author; saili.keshri@iiap.res.in

Received: 4 July 2024
Accepted: 14 January 2025

Abstract

We present a detailed study of the interacting triple active galactic nuclear system, NGC 7733-34, focusing on stellar kinematics, ionised gas characteristics, and star formation within the central region and stellar bars of both galaxies. We performed a comprehensive analysis using archival data from MUSE, HST/ACS, and DECaLS, complemented with observations from UVIT and IRSF. We identified a disc-like bulge in both NGC 7733 and NGC 7734 through a 2D decomposition. A central nuclear structure, with a semi-major axis of ∼1.113 kpc, was detected in NGC 7733 via a photometric and kinematic analysis, confirmed by the strong anti-correlation between V/σ and h₃, indicative of circular orbits in the centre. NGC 7734 lacks a distinct nuclear structure. The presence of a disc-like bulge results in an anti-correlation between V/σ and h₃, along with diffuse light. However, it does show higher central velocity dispersion, possibly attributed to an interaction with a smaller clump, which is likely a fourth galaxy within the system. Both galaxies demonstrate ongoing star formation, evidenced by FUV and Hα observations. NGC 7734 shows recent star formation along its bar, while NGC 7733 experiences bar quenching. The star formation rate (SFR) analysis of NGC 7734 reveals that the bar region’s SFR dominates the galaxy’s overall SFR. Conversely, in NGC 7733, the lack of star formation along the bar and the presence of a Seyfert 2 active galactic nucleus (AGN) at the galaxy centre suggest the possibility of link among both. However, this would not affect the galaxy’s overall star formation. Our findings provide valuable insights into the stellar and gas kinematics, star formation processes, and AGN feedback mechanisms in interacting galaxies hosting stellar bars.