# Star formation and ISM morphology in tidally induced spiral structures

## TL;DR

This paper uses high-resolution simulations to study how tidal encounters induce spiral structures in galaxies, revealing unique morphological features, star formation patterns, and gas-stellar offsets that differ from other spiral formation theories.

## Contribution

The study provides detailed simulation-based insights into the morphology, star formation, and gas-stellar offsets in tidally induced spiral arms, highlighting differences from density wave models.

## Key findings

- Tidal interactions produce distinct spiral features with active star formation.
- Gaseous arms tend to be on the convex side of stellar arms.
- Offsets between gas and stars are time-dependent and vary across the galaxy.

## Abstract

Tidal encounters are believed to be one of the key drivers of galactic spiral structure in the Universe. Such spirals are expected to produce different morphological and kinematic features compared to density wave and dynamic spiral arms. In this work we present high resolution simulations of a tidal encounter of a small mass companion with a disc galaxy. Included are the effects of gas cooling and heating, star formation and stellar feedback. The structure of the perturbed disc differs greatly from the isolated galaxy, showing clear spiral features that act as sites of new star formation, and displaying interarm spurs. The two arms of the galaxy, the bridge and tail, appear to behave differently; with different star formation histories and structure. Specific attention is focused on offsets between gas and stellar spiral features which can be directly compared to observations. We find some offsets do exist between different media, with gaseous arms appearing mostly on the convex side of the stellar arms, though the exact locations appear highly time dependent. These results further highlight the differences between tidal spirals and other theories of arm structure.