The SAMI galaxy survey: on the importance of applying multiple selection criteria for finding Milky Way analogues

Milky Way analogues (MWAs) provide an alternative insight into the various pathways that lead to the formation of disc galaxies with similar properties to the Milky Way (MW). In this study, we explore different selection techniques for identifying MWAs in the Sydney-AAO (Australian Astronomical Observatory) Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We utilize a nearest neighbours method to define MWAs using four selection parameters including stellar mass (M_*), star formation rate (SFR), bulge-to-total ratio (B/T ), and disc effective radius (R_e). Based on 15 different selection combinations, we find that including M_* and SFR is essential for minimizing biases in the average MWA properties as compared to the MW. Furthermore, given the MW’s smaller than average size, selection combinations without R_e result in MWAs being too large. Lastly, we find that B/T is the least important parameter out of the four tested parameters. Using all four selection criteria, we define the top 10 most MW-like galaxies in the GAMA and Cluster regions of the SAMI survey. These most MW-like galaxies are typically barred spirals, with kinematically cold rotating discs and reside in a wide range of environments. Surprisingly, we find no significant differences between the MWAs selected from the GAMA and Cluster regions. Our work highlights the importance of using multiple selection criteria for finding MWAs and also demonstrates potential biases in previous MWA studies.