The Milky Way and other spiral galaxies

TL;DR

This paper compares the properties of the Milky Way with other spiral galaxies from SDSS, revealing it is atypical and exploring implications for galaxy formation and history.

Contribution

It provides a comparative analysis of the Milky Way's properties against SDSS galaxies, highlighting its uniqueness and potential evolutionary history.

Findings

Milky Way is offset from fundamental scaling relations by ~2 sigma.

Only 1.2% of SDSS spirals are like the Milky Way.

Milky Way's quiescent history suggests a direct link to distant z=2-3 galaxies.

Abstract

Cosmologists have often considered the Milky Way as a typical spiral galaxy, and its properties have considerably influenced the current scheme of galaxy formation. Here we compare the general properties of the Milky Way disk and halo with those of galaxies selected from the SDSS. Assuming the recent measurements of its circular velocity results in the Milky Way being offset by ~2 sigma from the fundamental scaling relations. On the basis of their location in the (M_K, R_d, V_flat) volume, the fraction of SDSS spirals like the MilkyWay is only 1.2% in sharp contrast with M31, which appears to be quite typical. Comparison of the Milky Way with M31 and with other spirals is also discussed to investigate whether or not there is a fundamental discrepancy between their mass assembly histories. Possibly the Milky Way is one of the very few local galaxies that could be a direct descendant of very distant, z=2-3 galaxies, thanks to its quiescent history since thick disk formation.