From the outside looking in: what can Milky Way analogues tell us about the star formation rate of our own galaxy?

The Milky Way has been described as an anaemic spiral, but is its star formation rate (SFR) unusually low when compared to its peers? To answer this question, we define a sample of Milky Way analogues (MWAs) based on stringent cuts on the best literature estimates of non-transient structural features for the Milky Way. This selection yields only 176 galaxies from the whole of the SDSS DR7 spectroscopic sample which have morphological classifications in Galaxy Zoo 2, from which we infer SFRs from two separate indicators. The mean SFRs found are log(SFR_SED/M⊙ yr⁻¹) = 0.53 with a standard deviation of 0.23 dex from SED fits, and log(SFR_W4/M⊙ yr⁻¹) = 0.68 with a standard deviation of 0.41 dex from a mid-infrared calibration. The most recent estimate for the Milky Way’s SFR of log(SFR_MW/M⊙ yr⁻¹) = 0.22 fits well within 2σ of these values, where σ is the standard deviation of each of the SFR indicator distributions. We infer that the Milky Way, while being a galaxy with a somewhat low SFR, is not unusual when compared to similar galaxies.