Improved Constraints on the Total Stellar Mass, Color, and Luminosity of the Milky Way

Determining the global properties of the Milky Way presents unique challenges. Our position within the disk of the Galaxy yields a distorted view of its overall light emission; interstellar dust alters the spectral energy density we would otherwise measure in complex ways. For this reason, measurements of the global properties of the Milky Way, such as its star formation rate and total stellar mass, have proven to be historically difficult and remain sparsely studied within the literature. Here, we utilize updated models of the components of the Milky Way and constraints from similar galaxies to determine improved estimates of its total stellar mass. We model the stellar composition of the Galaxy as an exponential disk, both thin and thick components, combined with additional mass contributions from a central bulge, pseudo-bulge, and/or bar (halo contributions are negligible compared to current uncertainties). We constrain this model with a variety of measurements from the literature, taking into account the uncertainties in these estimates. With conservative assumptions we find that the total stellar mass of the Milky Way is 4.6 (median) +2.0/-1.3 (68% limit) ×10₁₀ M^sun (or +8.2/-2.0 ×10₁₀ M^sun at 95% confidence). We then employ a random selection process that yields a sample of SDSS galaxies whose distribution in stellar mass and star formation rate matches what we know about the Milky Way’s (incorporating all uncertainties). By analyzing the properties of these Milky Way analog galaxies, after correcting for inclination effects and Eddington bias, we find that the color of our Galaxy is g-r = 0.671 +0.061/-0.073 mag, and its absolute magnitude is M^r = -20.87 +0.33/-0.44 mag. We therefore find that the Milky Way most likely lies in the saddle of the bimodal distribution of red and blue galaxies.