Review to be published in "Tidal effects in Astronomy
and Astrophysics", Lecture Notes in Physics.
astro-ph/1112.1922
For a PDF version of the article, click here.
TIDES IN COLLIDING GALAXIES
Pierre-Alain Duc 1 and
Florent Renaud 2
1 AIM Paris-Saclay, CNRS/INSU, CEA/Irfu,
Université Paris-Diderot,
Service d'astrophysique, Orme des Merisiers, 91191 Gif sur Yvette cedex,
France; paduc@cea.fr
2 Observatoire de Strasbourg, CNRS UMR 7550 and AIM
Paris-Saclay, CEA/Irfu, CNRS/INSU,
Université Paris-Diderot,
Service d'astrophysique,
Orme des Merisiers, 91191 Gif sur Yvette cedex, France;
florent.renaud@cea.fr
Abstract: Long tails and streams of stars are the most noticeable
upshots of galaxy collisions. Their origin as gravitational, tidal,
disturbances has however been recognized only less than fifty years ago
and more than ten years after their first observations. This Review
describes how the idea of galactic tides emerged, in particular thanks
to the advances in numerical simulations, from the first ones that
included tens of particles to the most sophisticated ones with tens of
millions of them and state-of-the-art hydrodynamical
prescriptions. Theoretical aspects pertaining to the formation of tidal
tails are then presented. The third part of the review turns to
observations and underlines the need for collecting deep
multi-wavelength data to tackle the variety of physical processes
exhibited by collisional debris. Tidal tails are not just stellar
structures, but turn out to contain all the components usually found in
galactic disks, in particular atomic / molecular gas and dust. They host
star-forming complexes and are able to form star-clusters or even
second-generation dwarf galaxies. The final part of the review
discusses what tidal tails can tell us (or not) about the structure and
content of present-day galaxies, including their dark components, and
explains how tidal tails may be used to probe the past evolution of
galaxies and their mass assembly history. On-going deep wide-field
surveys disclose many new low-surface brightness structures in the
nearby Universe, offering great opportunities for attempting galactic
archeology with tidal tails.
Table of Contents
PRELIMINARY REMARKS
- HISTORICAL CONTEXT
- Discovery of peculiarities
- A controversial scenario
- Tidal origin
- Forty years of numerical simulations
- THEORY OF THE TIDAL TAIL FORMATION IN INTERACTING
GALAXIES
- Gravitational potential and tidal tensor
- Compressive tides
- Formation of tidal tails and bridges
- Gas dynamics
- Influence of the internal and orbital parameters
- Spin-orbit coupling
- Mass ratio
- Impact parameter
- Dark matter halo
- Rings, ripples, shells and warps
- Differences with tides at other scales
- MULTI-WAVELENGTH OBSERVATIONS OF TIDAL TAILS
- Where the mass is: atomic hydrogen in tidal tails
- When components are missing: H i without optical
counterparts; stellar tails without gas
- Sparse components: molecular clouds, dust and
heavy elements
- STRUCTURE FORMATION IN TIDAL TAILS
- Star formation
- Star cluster formation
- Formation of Tidal Dwarf Galaxies
- TIDAL STRUCTURES AS PROBES OF GALAXY EVOLUTION
- Determining the merger rate evolution with tidal
tails
- Determining the mass assembly history of galaxies
with tidal tails
- Constraining the distribution of dark matter with
tidal tails
- CONCLUSIONS
- REFERENCES
