Unveiling the Milky Way: A New Technique for Determining the Optical Color and Luminosity of our Galaxy

• Main Authors: Licquia, Timothy C, Newman, Jeffrey A, Brinchmann, Jarle
• Format: Journal Article
• Language: English
• Published: 18-08-2015
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.1508.04446

2015 ApJ 809, 96 We demonstrate a new statistical method of determining the global photometric
properties of the Milky Way (MW) to an unprecedented degree of accuracy,
allowing our Galaxy to be compared directly to objects measured in
extragalactic surveys. Capitalizing on the high-quality imaging and
spectroscopy dataset from the Sloan Digital Sky Survey (SDSS), we exploit the
inherent dependence of galaxies' luminosities and colors on their total stellar
mass, $\mathrm{M}_\star$, and star formation rate (SFR),
$\mathrm{\dot{M}}_\star$, by selecting a sample of $Milky$ $Way$ $analog$
$galaxies$ designed to reproduce the best Galactic $\mathrm{M}_\star$ and
$\mathrm{\dot{M}}_\star$ measurements, including all measurement uncertainties.
Making the Copernican assumption that the MW is not extraordinary amongst
galaxies of similar stellar mass and SFR, we then analyze the photometric
properties of this matched sample, constraining the characteristics of our
Galaxy without suffering interference from interstellar dust. We explore a
variety of potential systematic errors that could affect this method, and find
that they are subdominant to random uncertainties. We present both SDSS $ugriz$
absolute magnitudes and colors in both rest-frame $z$=0 and $z$=0.1 passbands
for the MW, which are in agreement with previous estimates but can have up to
$\sim$3$\times$ lower errors. We find the MW to have absolute magnitude
$^0\!M_r-5\log h=-21.00_{-0.37}^{+0.38}$ and integrated color
$^0(g-r)=0.682_{-0.056}^{+0.066}$, indicating that it may belong to the
green-valley region in color-magnitude space and ranking it amongst the
brightest and reddest of spiral galaxies. We also present new estimates of
global stellar mass-to-light ratios for our Galaxy. This work will help relate
our in-depth understanding of the Galaxy to studies of more distant objects.