45) From the Outside Looking in: What can Milky Way Analogues Tell us About the Star Formation Rate of Our Own Galaxy?

Abstract: In order to place our Galaxy in the context of the Universe, it is imperative that we first are able to place it amongst its peers. Defining analogues to the Milky Way (MW) is challenging, in part because we know so much about our home galaxy. Selecting a sample of Milky Way analogues (MWAs) based on all of the physical parameters observed for the MW (e.g. mass, size, bulge fraction, star formation rate (SFR), number of close neighbours) would result in a vanishing number of galaxies with which to compare it to. In this work, we take four well-known non-transient structural features of the MW - its stellar mass, bulge size, and the presence of spiral arms and a stellar bar - to define a robust sample of MWAs. Using these four criteria, we find just 176 MWAs in the whole of the SDSS DR7 spectroscopic sample. The MW has long been described as an anaemic spiral, so we use our MWA sample to determine whether this is the case. The SFR of the MW from literature is ~log[SFR(M_sol/yr)] = 0.22, which is within 2σ of the mean SFR of the MWA sample at log[SFR(M_sol/yr)] = 0.53. In fact, the MW lies on or slightly above the star formation main sequence line for local-Universe galaxies. We reiterate the importance of defining a sample of MWAs suitable for the science being performed and infer that the MW, while being a galaxy with a somewhat low SFR, is not unusual when compared to its cousins.

Bio: I am an observational extragalactic astronomer working to understand galaxy evolution via large-scale integral field spectroscopic surveys. My particular interest is understanding the influence of galaxy morphology (including bulges, bars, spiral arms etc) on the overall evolution of a galaxy. I examine the effects of morphology using both stellar population and kinematic analyses. Also of interest to me is linking the Milky Way to its extragalactic cousins.