Does the Milky Way Obey Spiral Galaxy Scaling Relations?
  It is crucial to understand how the Milky Way, the galaxy we can study in the
most intimate detail, fits in amongst other galaxies. Key examples include the
Tully-Fisher relation (TFR) --- i.e., the tight correlation between luminosity
($L$) and rotational velocity ($V_\textrm{rot}$) --- and the 3-dimensional
luminosity-velocity-radius ($LVR$) scaling relation. Several past studies have
characterized the MW as a 1--1.5$\sigma$ outlier to the TFR. This study
reexamines such comparisons using new estimates of MW properties that are
robust to many of the systematic uncertainties that have been a problem in the
past and are based on assumptions consistent with those used for other spiral
galaxies. Comparing to scaling relations derived from modern extragalactic
data, we find that our Galaxy's properties are in excellent agreement with TFRs
defined using any SDSS-filter absolute magnitude, stellar mass, or baryonic
mass as the $L$ proxy. We next utilize disk scale length ($R_\textrm{d}$)
measurements to extend this investigation to the $LVR$ relation. Here we find
that our Galaxy lies farther from the relation than $\sim$90\% of other spiral
galaxies, yielding $\sim$9.5$\sigma$ evidence that it is unusually compact for
its $L$ and $V_\textrm{rot}$ (based on MW errors alone), a result that holds
for all of the $L$ proxies considered. The expected $R_\textrm{d}$ for the MW
from the $LVR$ relation is $\sim$5 kpc, nearly twice as large as the observed
value, with error estimates placing the two in tension at the $\sim$1.4$\sigma$
level. The compact scale length of the Galactic disk could be related to other
ways in which the MW has been found to be anomalous.
