Clues on the origin of galactic angular momentum from looking at galaxy pairs

TL;DR

This study investigates the origin of galactic angular momentum by analyzing galaxy pairs, finding weak correlations in spin magnitude but no orientation alignment, highlighting the impact of interactions on spin evolution.

Contribution

It provides new insights into how tidal torques and galaxy interactions influence the angular momentum of spiral galaxies, using SDSS data.

Findings

Weak correlation in spin magnitudes of galaxy pairs

No significant alignment in galaxy orientations

Interactions reduce the spin parameter λ, depending on neighbor morphology

Abstract

We search for correlations between the spin in pairs of spiral galaxies, to study if the angular momentum gain for each galaxy was the result of tidal torques imprint by the same tidal field. To perform our study we made use of a sample of galaxy pairs identified using the Sloan Digital Sky Survey. We find a weak, but statistically significant correlation between the spin magnitude of neighbouring galaxies, but no clear alignment between their orientation. We show that events such as interactions with close neighbours play an important role in the value of the spin for the final configuration, as we find these interactions tend to reduce the value of the $\lambda$ spin parameter of late-type galaxies considerably, with dependence on the morphology of the neighbour. This implies that the original tidal field for each pair could have been similar, but the redistribution of angular momentum at later stages of evolution is important.