(Nanowerk Information) Is our residence galaxy, the Milky Method Galaxy, a particular place? A workforce of scientists began a journey to reply this query greater than a decade in the past. Commenced in 2013, the Satellites Round Galactic Analogs (SAGA) Survey research galaxy techniques just like the Milky Method. Now, the SAGA Survey simply printed three new analysis articles that present us with new insights into the individuality of our personal Milky Method Galaxy after finishing the census of 101 satellite tv for pc techniques just like the Milky Method’s.
These “satellites” are smaller galaxies in each mass and dimension that orbit a bigger galaxy, normally known as the host galaxy. Simply as with smaller satellites that orbit the Earth, these satellite tv for pc galaxies are captured by the gravitational pull of the huge host galaxy and its surrounding darkish matter. The Milky Method Galaxy is the host galaxy of a number of satellite tv for pc galaxies, of which the 2 largest are the Giant and Small Magellanic Clouds (LMC and SMC). Whereas LMC and SMC are seen to the bare eye from the Southern Hemisphere, there are a lot of different fainter satellite tv for pc galaxies orbiting across the Milky Method Galaxy that may solely be noticed with a big telescope.
The purpose of the SAGA Survey is to characterize satellite tv for pc techniques round different host galaxies which have related stellar lots because the Milky Method Galaxy. Yao-Yuan Mao, a College of Utah college member within the Division of Physics and Astronomy, is co-leading the SAGA Survey with Marla Geha at Yale College and Risa Wechsler at Stanford College. Mao is the lead writer of the primary article within the collection of three which have all been accepted by the Astrophysical Journal and have been posted forward of publication on ArXiv. This collection of articles experiences on the SAGA Survey’s newest findings and makes the survey knowledge accessible to different researchers worldwide.
A picture of a Milky Method-like galaxy and its system of satellite tv for pc galaxies. The SAGA survey recognized six small satellite tv for pc galaxies in orbit round this Milky Method analog. (Picture: Yasmeen Asali (Yale), with pictures from the DESI Legacy Surveys Sky Viewer)
An outlier galaxy?
Within the first research led by Mao (“The SAGA Survey. III. A Census of 101 Satellite Systems around Milky Way-mass Galaxies”), the researchers highlighted 378 satellite tv for pc galaxies recognized throughout 101 Milky Method-mass techniques. The variety of confirmed satellites per system ranged from zero to 13—in comparison with 4 satellites for the Milky Method. Whereas the variety of satellite tv for pc galaxies within the Milky Method system is on par with the opposite Milky Method-mass techniques, “The Milky Way appears to host fewer satellites if you consider the existence of the LMC,” Mao stated. The SAGA Survey has discovered that techniques with a large satellite tv for pc just like the LMC are inclined to have the next whole quantity ofsatellites, and our Milky Method appears to be an outlier on this regard.
A proof for this obvious distinction between the Milky Method and the SAGA techniques is the truth that the Milky Method has solely acquired the LMC and SMC fairly lately, in contrast with the age of the universe. The SAGA article explains that if the Milky Method Galaxy is an older, barely much less huge host with the lately added LMC and SMC, one would then count on a decrease variety of satellites within the Milky Method system not counting different smaller satellites that LMC/SMC might need introduced in.
This end result demonstrates the significance of understanding the interplay between the host galaxy and the satellite tv for pc galaxies, particularly when deciphering what we study from observing the Milky Method. Ekta Patel, a NASA Hubble Postdoctoral Fellow on the U however not a part of the SAGA workforce, research the orbital histories of Milky Method satellites. After studying concerning the SAGA outcomes, Patel stated, “Though we cannot yet study the orbital histories of satellites around SAGA hosts, the latest SAGA data release includes a factor of ten more Milky Way-like systems that host an LMC-like companion than previously known. This huge advancement provides more than 30 galaxy ecosystems to compare with our own, and will be especially useful in understanding the impact of a massive satellite analogous to the LMC on the systems they reside in.”
A mosaic of the photographs of 378 satellites throughout 101 Milky Method-like techniques that the SAGA workforce has surveyed. The satellite tv for pc pictures are sorted by their luminosity from left to proper. (Picture: Yao-Yuan Mao (Utah), with pictures from the DESI Legacy Surveys Sky Viewer) (click on on picture to enlarge)
Why do galaxies cease forming stars?
The second SAGA research of the collection is led by Geha (“The SAGA Survey. IV. The Star Formation Properties of 101 Satellite Systems around Milky Way-mass Galaxies”), and it explores whether or not these satellite tv for pc galaxies are nonetheless forming stars. Understanding the mechanisms that might cease the star formation in these small galaxies is a vital query within the discipline of galaxy evolution. The researchers discovered, for instance, that satellite tv for pc galaxies positioned nearer to their host galaxy have been extra prone to have their star formation “quenched,” or suppressed. This implies that environmental elements assist form the life cycle of small satellite tv for pc galaxies.
The third new research is led by Yunchong (Richie) Wang (“The SAGA Survey. V. Modeling Satellite Systems around Milky Way-mass Galaxies with Updated UniverseMachine”), who obtained his doctorate with Wechsler. This research makes use of the SAGA Survey outcomes to enhance current theoretical fashions of galaxy formation. Based mostly on the variety of quenched satellites in these Milky Method-mass techniques, this mannequin predicts quenched galaxies also needs to exist in additional remoted environments—a prediction that must be attainable to check within the coming years with different astronomical surveys such because the Darkish Power Spectroscopic Instrument Survey.
Present to the astronomy neighborhood
Along with these thrilling outcomes that can improve our understanding of galaxy evolution, the SAGA Survey workforce additionally brings a present to the astronomy neighborhood. As a part of this collection of research, the SAGA Survey workforce printed new distance measurements, or redshifts, for about 46,000 galaxies. “Finding these satellite galaxies is like finding needles in a haystack. We had to measure the redshifts for hundreds of galaxies to just identify one satellite galaxy,” Mao stated. “These new galaxy redshifts will enable the astronomy community to study a wide range of topics beyond the satellite galaxies.”
