Dynamics of Galaxy Interactions

Abstract

Abstract. Interacting galaxies are a natural arena for studies of nonequilibrium stellar dynamics, gas dynamics, and thermodynamics. Only galaxy formation itself is as deeply concerned with as many different aspects of dynamics, and the connection between interactions and the formation of galaxies is probably no coincidence. This review discusses tidal interactions, halos and orbit decay, dissipative effects in galaxy interactions, properties of merger remnants, and origins of starbursts.

The Development of Gas/Star Offsets in Tidal Tails

“…This has particularly important ramiÐcations for the frequent exercise of modeling speciÐc galaxies based on H I or Ha velocity Ðelds. Because of the increased computational cost of running hydrodynamic simulations, collisionless N-body models typically are used to match the observed (gas phase) velocities (see, e.g., Stanford & Balcells 1991 ;Mihos et al 1993 ;Hibbard & Mihos 1995 ;Yun 1999 ;Barnes 1998). If severe kinematic segregation exists in the tidal debris, models derived from matching collisionless kinematics to gas velocities may be in serious error.…”

“…This coevolutionary status of tidal gas and stars permits detailed matching between the theoretical predictions of stellar-dynamical models and the observed morphology and kinematics of the gas. Several investigators have taken advantage of this fact to produce dynamical models of speciÐc merging systems (see, e.g., Stanford & Balcells 1991 ;Mihos, Bothun, & Richstone 1993 ;Hibbard & Mihos 1995 ;Yun 1999 ;Barnes 1998).…”

Interactions as a driver of galaxy evolution

“…Barnes 1998). Major mergers clearly do wreck disks and can form giant ellipticals, as first proposed by TT.…”

Kinematics of Planetary Nebulae in M51's Tidal Debris

“…In the Toomre & Toomre (1972) study, many of the tidal features of the M51 system were explained by a parabolic encounter of two galaxies with mass ratio of 3 : 1 viewed shortly after the initial collision. Since then, in response to the ever-increasing amount of observational data on the system, a number of alternate scenarios have been proposed (Toomre 1978;Howard & Byrd 1990;Hernquist 1990, hereafter H90;Barnes 1998;Salo & Laurikainen 2000, hereafter SL00). Despite M51's long history of dynamical modeling, significant uncertainties in the basic description of the system remain.…”

“…As a result, these models have not followed the full dynamical response of the system (SL00). Consequently, no single scenario satisfactorily explains all of the system's observational data (see the discussion in Barnes 1998).…”