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

**Authors:** Yao-Yuan Mao, Marla Geha, Risa H. Wechsler, Yasmeen Asali, Yunchong Wang, Erin Kado-Fong, Nitya Kallivayalil, Ethan O. Nadler, Erik J. Tollerud, Benjamin Weiner, Mithi A. C. de los Reyes, John F. Wu  
**arXiv:** [2404.14498](https://arxiv.org/abs/2404.14498)  
**Date:** 2024-04-22  
**Summary page:** https://www.summarizepaper.com/en/paper/2404.14498v1/

## Key points

- The SAGA Survey's third Data Release (DR3) provides a census of satellite galaxies around Milky Way (MW)-mass galaxies.
- 378 satellites identified across 101 MW-mass systems within a distance range of 25-40.75 Mpc.
- Redshift catalog of background galaxies with approximately 46,000 entries covering an impressive footprint of 84.7 sq. deg.
- Sample accounts for an impressive 94% completeness down to a stellar mass of 10^7.5 solar masses.
- Most massive satellite in SAGA systems is the strongest predictor of satellite abundance.
- One-third of SAGA systems contain Large Magellanic Cloud (LMC)-mass satellites and tend to host more satellites compared to the MW itself.
- Radial distribution of SAGA satellites appears less concentrated than that of the MW's satellites.
- Quenched fraction below 10^8.5 solar masses is lower in SAGA systems compared to the MW, but both show similar system-to-system scatter within one sigma.
- Contrary to previous suggestions, there is no clear corotating signal in SAGA satellites compared to MW/M31 satellite systems.
- Differences between the MW and typical SAGA systems can be reconciled by considering the age and mass differences, as well as recent accretion history.

## Summary

The SAGA Survey has released its third Data Release (DR3), providing a comprehensive census of satellite galaxies around Milky Way (MW)-mass galaxies. The latest release includes 378 identified satellites across 101 MW-mass systems within a distance range of 25-40.75 Mpc. Along with this, the survey also features a redshift catalog of background galaxies with approximately 46,000 entries taken by SAGA and covering an impressive footprint of 84.7 sq. deg. Through a detailed completeness model, the sample accounts for an impressive 94% of the true satellite population down to a stellar mass of 10^7.5 solar masses. Interestingly, the most massive satellite in SAGA systems emerges as the strongest predictor of satellite abundance. One-third of the SAGA systems contain Large Magellanic Cloud (LMC)-mass satellites and tend to host more satellites compared to the MW itself. The radial distribution of SAGA satellites appears less concentrated than that of the MW's satellites. Additionally, the quenched fraction below 10^8.5 solar masses is lower in SAGA systems than in the MW; however, both cases show that the MW is within one sigma of SAGA's system-to-system scatter. Contrary to previous suggestions regarding corotating signals in MW/M31 satellite systems, SAGA satellites do not exhibit a clear pattern in this regard. These differences between the MW and typical SAGA systems can be reconciled if we consider that the MW is an older host with slightly less mass and recently accreted LMC/SMC system. In conclusion, this latest data release from the SAGA Survey provides valuable insights into satellite galaxy populations around Milky Way-mass galaxies and sheds light on key factors influencing their abundance and distribution within galactic systems.