The MW is an exceptionnally quiet galaxy: implications for spiral formation

TL;DR

The paper compares the Milky Way and M31 to similar galaxies, revealing the Milky Way's unique deficiency in stellar mass, angular momentum, and metallicity, likely due to its quiet merger history over the past 10-11 billion years.

Contribution

It provides a comparative analysis showing the Milky Way's distinct properties and links these to its lack of recent major mergers, offering insights into spiral galaxy formation.

Findings

Milky Way is offset in key galaxy relations, indicating lower stellar mass and angular momentum.

The Milky Way's outskirts are less metal-rich compared to similar galaxies.

Most local spirals show evidence of recent mergers, unlike the Milky Way.

Abstract

We compare both the Milky Way and M31 to local external disk galaxies within the same mass range, using their relative locations in the planes formed by Vflat vs. MK (the Tully-Fisher relation), j_disk (specific angular momentum) and the average Fe abundance of stars in the galaxy outskirts. We find, for all relationships, that the MW is systematically offset by 1 sigma or more, showing a significant deficiency in stellar mass, angular momentum, disk radius and [Fe/H] in the stars in its outskirts at a given Vflat. Our Galaxy appears to have escaped any significant merger over the last 10-11 Gyr which may explain its peculiar properties. As with M31, most local spirals show evidence for a history shaped mainly by relatively recent merging.