Milky Way Analogues in MaNGA: Multi-Parameter Homogeneity and Comparison to the Milky Way

TL;DR

This study analyzes Milky Way analogs from the MaNGA survey, examining their stellar populations, kinematics, and metallicity gradients to compare their properties with those of the Milky Way, revealing insights into galaxy evolution.

Contribution

The paper introduces a sample of Milky Way analogs from MaNGA and compares their properties to the Milky Way, highlighting the importance of scale and perspective in galaxy characterization.

Findings

Milky Way analogs show diverse central stellar ages.

Metallicity gradients are flatter in physical units but align better when scaled by disc length.

Differences in metallicity gradients are partly due to galaxy compactness and observational perspective.

Abstract

The Milky Way provides an ideal laboratory to test our understanding of galaxy evolution, owing to our ability to observe our Galaxy over fine scales. However, connecting the Galaxy to the wider galaxy population remains difficult, due to the challenges posed by our internal perspective and to the different observational techniques employed. Here, we present a sample of galaxies identified as Milky Way Analogs (MWAs) on the basis of their stellar masses and bulge-to-total ratios, observed as part of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We analyse the galaxies in terms of their stellar kinematics and populations as well as their ionised gas contents. We find our sample to contain generally young stellar populations in their outskirts. However, we find a wide range of stellar ages in their central regions, and we detect central AGN-like or composite-like activity in roughly half of the sample galaxies, with the other half consisting of galaxies with central star-forming emission or emission consistent with old stars. We measure gradients in gas metallicity and stellar metallicity that are generally flatter in physical units than those measured for the Milky Way; however, we find far better agreement with the Milky Way when scaling gradients by galaxies' disc scale lengths. From this, we argue much of the discrepancy in metallicity gradients to be due to the relative compactness of the Milky Way, with differences in observing perspective also likely to be a factor.