The SAGA Survey. I. Satellite Galaxy Populations around Eight Milky Way Analogs

Marla Geha, Risa H. Wechsler, Yao Yuan Mao, Erik J. Tollerud, Benjamin Weiner, Rebecca Bernstein, Ben Hoyle, Sebastian Marchi, Phil J. Marshall, Ricardo Muñoz, Yu Lu

Research output: Contribution to journalArticlepeer-review

102 Scopus citations


We present the survey strategy and early results of the "Satellites Around Galactic Analogs" (SAGA) Survey. The SAGA Surveys goal is to measure the distribution of satellite galaxies around 100 systems analogous to the Milky Way down to the luminosity of the Leo I dwarf galaxy (Mr > -12.3). We define a Milky Way analog based on K-band luminosity and local environment. Here, we present satellite luminosity functions for eight Milky-Wayanalog galaxies between 20 and 40 Mpc. These systems have nearly complete spectroscopic coverage of candidate satellites within the projected host virial radius down to ro > 20.75 using low-redshift gri color criteria. We have discovered a total of 25 new satellite galaxies: 14 new satellite galaxies meet our formal criteria around our complete host systems, plus 11 additional satellites in either incompletely surveyed hosts or below our formal magnitude limit. Combined with 13 previously known satellites, there are a total of 27 satellites around 8 complete Milky-Way-analog hosts. We find a wide distribution in the number of satellites per host, from 1 to 9, in the luminosity range for which there are 5 Milky Way satellites. Standard abundance matching extrapolated from higher luminosities predicts less scatter between hosts and a steeper luminosity function slope than observed. We find that the majority of satellites (26 of 27) are star-forming. These early results indicate that the Milky Way has a different satellite population than typical in our sample, potentially changing the physical interpretation of measurements based only on the Milky Ways satellite galaxies.

Original languageEnglish (US)
Article number4
JournalAstrophysical Journal
Issue number1
StatePublished - Sep 20 2017


  • galaxies: dwarf
  • galaxies: halos
  • galaxies: luminosity function, mass function
  • galaxies: structure
  • Local Group

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The SAGA Survey. I. Satellite Galaxy Populations around Eight Milky Way Analogs'. Together they form a unique fingerprint.

Cite this