The SAGA Survey. III. A Census of 101 Satellite Systems around Milky Way-mass Galaxies

Kavli Affiliate: Risa H. Wechsler

| First 5 Authors: Yao-Yuan Mao, Marla Geha, Risa H. Wechsler, Yasmeen Asali, Yunchong Wang

| Summary:

We present Data Release 3 (DR3) of the Satellites Around Galactic Analogs
(SAGA) Survey, a spectroscopic survey characterizing satellite galaxies around
Milky Way (MW)-mass galaxies. The SAGA Survey DR3 includes 378 satellites
identified across 101 MW-mass systems in the distance range of 25-40.75 Mpc,
and an accompanying redshift catalog of background galaxies (including about
46,000 taken by SAGA) in the SAGA footprint of 84.7 sq. deg. The number of
confirmed satellites per system ranges from zero to 13, in the stellar mass
range of 10^6 to 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. 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’s, and the SAGA quenched fraction below 10^8.5
solar masses is lower than the MW’s, but in both cases, the MW is within 1
sigma of SAGA system-to-system scatter. SAGA satellites do not exhibit a clear
corotating signal as has been suggested in the MW/M31 satellite systems.
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.

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