Physical Properties of Tidal Features in Interacting Disk Galaxies

Abstract

We investigate the physical properties of tidal structures in a disk galaxy created by gravitational interactions with a companion using numerical N-body simulations. We consider a simple galaxy model consisting of a rigid halo/bulge and an infinitesimally thin stellar disk with Toomre parameter Q % 2. A perturbing companion is treated as a point mass moving on a prograde parabolic orbit, with varying mass and pericenter distance. Tidal interactions produce welldefined spiral arms and extended tidal features, such as bridge and tail, that are all transient, but distinct in nature. In the extended disks, a strong tidal force is able to lock the perturbed epicycle phases of the near-side particles to the perturber, shaping them into a tidal bridge that corotates with the perturber. A tidal tail develops on the opposite side as strongly perturbed, near-side particles overtake mildly perturbed, far-side particles. The tail is essentially a narrow material arm with a roughly logarithmic shape, dissolving with time because of large velocity dispersions. Inside the disks where the tidal force is relatively weak, on the other hand, a two-armed logarithmic spiral pattern emerges due to the kinematic alignment of perturbed particle orbits. While self-gravity makes the spiral arms a bit stronger, the arms never become fully self-gravitating, wind up progressively with time, and decay almost exponentially after the peak in a timescale of $1 Gyr. The arm pattern speed varying with both radius and time converges to À /2 at late time, suggesting that the pattern speed of tidally driven arms may depend on radius in real galaxies. Here and denote the angular and epicycle frequencies, respectively. We present the parametric dependences of various properties of tidal features on the tidal strength and discuss our findings as applied to tidal spiral arms in grand-design spiral galaxies.

The Origin of Faint Tidal Features around Galaxies in the RESOLVE Survey

“…Tidal tails or arms, in which material from the primary galaxy is pulled out due to an interaction with a companion, are dependent on the primary's rotation (prograde for maximum effect) and thus are expected to come from progenitors with a gas-rich, disc-dominated component (e.g., Byrd & Howard 1992;Oh et al 2008). In contrast, tidal streams consist of stripped material from a lowmass companion orbiting or being consumed by the primary galaxy; these features can be found around a variety of primary morphologies.…”

A multiwavelength study of spiral structure in galaxies. I. General characteristics in the optical

“…Most likely, it is related to the selection effect, as we carefully selected galaxies with a rather traceable spiral pattern and without strong interactions. Also, it should be stressed that determining truly isolated galaxies and those that have not undergone a recent merger event is not a trivial task (Verley et al 2007), taking into account that grand design galaxies should retain their spiral structure for ∼ 1 Gyr after an interaction (Oh et al 2008).…”

Bars and spirals in tidal interactions with an ensemble of galaxy mass models

“…We choose two different interaction strengths; S = 0.1 and 0.05 which represent a strong and weak interaction scenario. While studies find that values of S in the range of 0.01 S 0.25 can produce some sort of arm response, values below S < 0.05 produce only a very weak spiral structure visible in the outer disc or for a very short duration, with values higher than 0.25 causing widespread disruption of the primary's disc structure (Elmegreen et al 1991;Oh et al 2008;Pettitt et al 2016). Determining S from observations is somewhat complicated, due to the impulse dependence, though minimum values for some interacting galaxies have been calculated.…”