On the characteristics of tidal structures of interacting galaxies

TL;DR

This study analyzes the geometrical properties of tidal tails in interacting galaxies, revealing differences between nearby and distant galaxies and proposing models to explain their observed characteristics.

Contribution

It provides a comprehensive analysis of tidal tail lengths and thicknesses across a large sample of galaxies, introducing models to interpret their geometrical and evolutionary features.

Findings

Distant galaxy tidal tails are shorter than those in nearby galaxies.

The upper envelope of the tail length vs. luminosity follows l ∝ √L.

Angular lengths of tidal tails typically exceed 180 degrees.

Abstract

We present the results of our analysis of the geometrical tidal tail characteristics for nearby and distant interacting galaxies. The sample includes more than two hundred nearby galaxies and about seven hundred distant ones. The distant galaxies have been selected in several deep fields of the Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS) and they are at mean redshift z=0.65. We analyze the distributions of lengths and thicknesses for the tidal structures and show that the tails in distant galaxies are shorter than those in nearby ones. This effect can be partly attributed to observational selection effects, but, on the other hand, it may result from the general evolution of the sizes of spiral galaxies wih z. The location of interacting galaxies on the galaxy luminosity ($L$) -- tidal tail length ($l$) plane are shown to be explained by a simple geometrical model, with the upper envelope of the observed distribution being $l \propto \sqrt{L}$. We have solved the problem on the relationship between the observed distribution of tail flattening and the tail length in angular measure by assuming the tidal tails to be arcs of circumferences visible at arbitrary angles to the line of sight. We conclude that the angular length of the tidal tails visually distinguished in nearby and distant galaxies, on average, exceeds 180 degrees.