SAGA Survey: A Census of 101 Satellite Systems around Milky Way-like Galaxies

Abstract: I will present the main findings of the third Data Release (DR3) of the Satellites Around Galactic Analogs (SAGA) Survey, a spectroscopic survey characterizing satellite galaxies around Milky Way (MW)-mass galaxies. SAGA DR3 includes 378 satellites identified across 101 MW-mass systems in the distance range 25-40.75 Mpc, and an accompanying redshift catalog of background galaxies (including 46,000 taken by SAGA). The number of confirmed satellites per system ranges from zero to 13, in the stellar mass range 10^6-10^10 solar masses. Based on a detailed completeness model, this sample accounts for 94% of the true satellite population down to a stellar mass of 10^7.5 solar masses. Below 10^7.5 solar masses, we identified 135 satellites with confirmed redshifts, of which 98 are star forming. We find that the mass of the most massive satellite in SAGA systems is the strongest predictor of satellite abundance; one-third of the SAGA systems contain LMC-mass satellites, and they tend to have more satellites than the MW. The SAGA satellite radial distribution is less concentrated than the MW, and the SAGA quenched fraction below 10^8.5 solar masses is lower than the MW, but in both cases, the MW is within 1-sigma of SAGA system-to-system scatter. We do not find a signal for corotation of SAGA satellites. Although the MW differs in many respects from the typical SAGA system, these differences can be reconciled if the MW is an older, slightly less massive host with a recently accreted LMC/SMC system.