| Author(s) and Co-Author(s) with Affiliation: Prerana Biswas(Indian Institute of Astrophysics, Bangalore, India), Mousumi Das(Indian Institute of Astrophysics, Bangalore, India), Sudhanshu Barway(Indian Institute of Astrophysics, Bangalore, India) |
| Abstract: We present a spectroscopic study of galaxies hosting multiple nuclei, dominated by dual-nucleus systems, based on a visually confirmed sample identified using GOTHIC algorithm applied to SDSS-DR16 data. From 949 candidates, we analyse 915 nuclei with high-quality spectra (SNR > 10), obtained through stellar continuum and emission-line fitting using pPXF. This represents one of the largest homogeneous samples of spectroscopically confirmed multi-nucleus galaxies, primarily probing dual-nucleus phase across star-forming, Composite, AGN–Seyfert, and AGN–LINER classes.
For each nucleus, we derive stellar velocity dispersion, stellar mass, stellar-age, metallicity, mass-to-light ratio, black hole mass and Eddington luminosity. While overall distributions of these properties broadly resemble those in single-nucleus galaxies, clear differences emerge in their scaling relations. M_BH-M_star relation is preserved overall but shows class-dependent slopes, with steeper trends for AGN–LINERs and shallower ones for Seyferts. Importantly, supermassive black holes in dual AGN systems are systematically more massive than those in single AGN at fixed stellar mass, indicating enhanced black hole growth during galaxy interactions, even before SMBH coalescence. Stellar mass–velocity dispersion relation follows expected virial scaling for massive Composite and AGN hosts, suggesting that global dynamical equilibrium is largely maintained despite presence of dual nuclei.
In contrast, mass–metallicity and age-metallicity relations exhibit significant departures from classical single-nucleus trends. Dual-nucleus systems show elevated metallicities at low stellar masses and suppressed metallicities at high masses, along with structured age-metallicity behaviour, particularly in Composite and AGN hosts. These features point to merger-driven gas inflows, metal redistribution, and AGN feedback influencing chemical evolution during close interactions. Analysis of confirmed dual-nucleus pairs further reveals correlated black hole growth but diverse stellar population properties between companions. Overall, our results demonstrate that dual-nucleus galaxies retain global scaling relations while exhibiting distinct internal growth and chemical evolution shaped by interactions, making them valuable laboratories for studying galaxy and black hole co-evolution.
|
