Does the Milky Way lie on the Tully-Fisher Relation?

Using new estimates of the optical properties of the Milky Way, we can for the first time place it accurately on the Tully-Fisher relation (TFR) and other scaling relations for spiral galaxies. We make use of improved measurements of both the stellar mass and luminosity of our Galaxy from our recent work. We find that the properties of the Milky Way are in excellent agreement with the best-fit optical, stellar-mass, and baryonic TFRs followed by other spiral galaxies, contrary to prior claims in the literature. We also investigate our Galaxy's position in the 3D luminosity-velocity-size (LVS) parameter space, incorporating measurements of the disk scale length for both the Milky Way and external galaxies. Using updated measurements of the stellar light distribution of the Galactic disk, we find that the Milky Way is typical compared the best-fit LVS scaling relation derived via Principal Component Analysis. However, when using the best-to-date, dynamically-measured distribution of stellar mass in the Galactic disk, we find the Milky Way is off the LVS relation at the ~2σ level. Since scale lengths for external galaxies are measured using starlight, the former should be the more appropriate comparison. Overall, given this level of consistency, our ability to study the Milky Way in more intimate detail than other galaxies may ultimately help us to decipher the origins of the Tully-Fisher relation.