Faint Fuzzies and the Formation of Lenticular Galaxies

Abstract

We investigate the dynamical state of a new class of extended star clusters known as ``faint fuzzies,'' which were discovered in two nearby S0 galaxies, NGC 1023 and NGC 3384. It is shown that the faint fuzzies of NGC 1023 lie in a fast-rotating ringlike structure within the galactic disk with mean radius of 5 kpc, rotational velocity of 200 km s^-1, and velocity dispersion of 115 km s^-1. We propose a scenario for the origin of faint fuzzies that is connected to the origin of S0 galaxies as a result of galaxy-galaxy interactions in dense environments. As is apparent in the Cartwheel galaxy and confirmed by numerical simulations, the passage of a small galaxy through, or close to, the center of a disk galaxy can form a ring of clumpy star formation with a radius comparable to the faint fuzzy ring radius in NGC 1023. In this case, the faint fuzzies are signposts for the transformation of spiral galaxies into lenticulars via such interactions.