The Nature of the Double Nuclei in the Barred S0 Galaxy IC 676

Abstract

The lenticular galaxy IC 676 is a barred galaxy with double nuclei and active star formation in the central region. In this work we present the long-slit spectroscopy and archival multiwavelength images to investigate the nature and origin of the double nuclei in IC 676. Through photometric 1D brightness profiles and 2D image decomposition, we show that this galaxy consists of a stellar bar with the length of ∼2.5 kpc and two Sérsic disks both of which with Sérsic index n  ∼ 1.3. There is probably little or no bulge component assembled in IC 676. The luminosities of the double nuclei are primarily dominated by young stellar populations within the ages of 1–10 Myr. The northern nucleus has stronger star formation activity than the southern one. The surface densities of the star formation rate in the double nuclei are similar to those in starburst galaxies or the circumnuclear star-forming regions in spiral galaxies. Each of the double nuclei in IC 676 likely consists of young massive star clusters, which can be resolved as bright knots in the Hubble Space Telescope high-resolution image. Our results suggest that IC 676 likely has a complex formation and evolutionary history. The secular processes driven by the stellar bar and external accretion may dominate the formation and evolution of its double nuclei. This indicates that the secular evolution involving the internal and external drivers may have an important contribution for the evolution of lenticular galaxies.