The Satellites Around Galactic Analogs (SAGA) Survey is a decade-long research project that aims to study galaxy systems similar to the Milky Way. The survey recently published three new research articles that provide insights into the uniqueness of the Milky Way Galaxy after completing a census of 101 satellite systems akin to the Milky Way. Satellite galaxies, smaller galaxies that orbit a larger host galaxy, are captured by the gravitational pull of the host galaxy and its surrounding dark matter. The Milky Way has several satellite galaxies, with the Large and Small Magellanic Clouds being the largest visible from the Southern Hemisphere.
Led by Yao-Yuan Mao, the SAGA Survey aims to characterize satellite systems around host galaxies similar in mass to the Milky Way. The first study highlighted 378 satellite galaxies across 101 Milky Way-mass systems, with the Milky Way having a lower number of satellites when considering the presence of the LMC and SMC. This anomaly is attributed to the recent acquisition of LMC and SMC by the Milky Way in cosmic time, indicating the importance of understanding the interaction between the host galaxy and satellite galaxies for interpretation purposes.
Another study led by Ekta Patel explores the orbital histories of Milky Way satellites, emphasizing the influence of massive satellites on the systems they reside in. The second study led by Marla Geha investigates whether satellite galaxies are still forming stars, with environmental factors near the host galaxy affecting the star formation in these small galaxies. The third study led by Yunchong (Richie) Wang uses the SAGA Survey results to enhance existing theoretical models of galaxy formation, predicting the existence of quenched galaxies in more isolated environments.
The SAGA Survey also provided new distance measurements for about 46,000 galaxies, enabling the astronomy community to study a wide range of topics beyond satellite galaxies. The survey’s results shed light on galaxy evolution and the impact of environmental factors on star formation in satellite galaxies. Supported by the National Science Foundation and the Heising-Simons Foundation, the SAGA Survey is a valuable contribution to the astronomical community and will continue to inform future research in the field.