| Sep 26, 2024 |
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(Nanowerk Information) Is our residence galaxy, the Milky Method Galaxy, a particular place? A group 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 programs just like the Milky Method. Now, the SAGA Survey simply printed three new analysis articles that present us with new insights into the distinctiveness of our personal Milky Method Galaxy after finishing the census of 101 satellite tv for pc programs much like the Milky Method’s.
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These “satellites” are smaller galaxies in each mass and measurement that orbit a bigger galaxy, often 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 large 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 Massive and Small Magellanic Clouds (LMC and SMC). Whereas LMC and SMC are seen to the bare eye from the Southern Hemisphere, there are numerous different fainter satellite tv for pc galaxies orbiting across the Milky Method Galaxy that may solely be noticed with a big telescope.
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The aim of the SAGA Survey is to characterize satellite tv for pc programs round different host galaxies which have related stellar plenty 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 creator of the primary article within the sequence of three which have all been accepted by the Astrophysical Journal and have been posted forward of publication on ArXiv. This sequence of articles studies on the SAGA Survey’s newest findings and makes the survey knowledge obtainable to different researchers worldwide.
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| 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 photographs from the DESI Legacy Surveys Sky Viewer)
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An outlier galaxy?
Within the first examine led by Mao (“The SAGA Survey. III. A Census of 101 Satellite tv for pc Techniques round Milky Method-mass Galaxies”), the researchers highlighted 378 satellite tv for pc galaxies recognized throughout 101 Milky Method-mass programs. 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 programs, “The Milky Method seems to host fewer satellites if you happen to take into account the existence of the LMC,” Mao mentioned. The SAGA Survey has discovered that programs with an enormous satellite tv for pc just like the LMC are inclined to have a better complete quantity ofsatellites, and our Milky Method appears to be an outlier on this regard.
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A proof for this obvious distinction between the Milky Method and the SAGA programs is the truth that the Milky Method has solely acquired the LMC and SMC fairly just 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 just lately added LMC and SMC, one would then anticipate a decrease variety of satellites within the Milky Method system not counting different smaller satellites that LMC/SMC may need introduced in.
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This consequence demonstrates the significance of understanding the interplay between the host galaxy and the satellite tv for pc galaxies, particularly when decoding 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 group, research the orbital histories of Milky Method satellites. After studying concerning the SAGA outcomes, Patel mentioned, “Although we can not but examine the orbital histories of satellites round SAGA hosts, the newest SAGA knowledge launch features a issue of ten extra Milky Method-like programs that host an LMC-like companion than beforehand recognized. This big development supplies greater than 30 galaxy ecosystems to match with our personal, and can be particularly helpful in understanding the impression of an enormous satellite tv for pc analogous to the LMC on the programs they reside in.”
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| A mosaic of the photographs of 378 satellites throughout 101 Milky Method-like programs that the SAGA group has surveyed. The satellite tv for pc photographs are sorted by their luminosity from left to proper. (Picture: Yao-Yuan Mao (Utah), with photographs from the DESI Legacy Surveys Sky Viewer) (click on on picture to enlarge)
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Why do galaxies cease forming stars?
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The second SAGA examine of the sequence is led by Geha (“The SAGA Survey. IV. The Star Formation Properties of 101 Satellite tv for pc Techniques round Milky Method-mass Galaxies”), and it explores whether or not these satellite tv for pc galaxies are nonetheless forming stars. Understanding the mechanisms that may cease the star formation in these small galaxies is a vital query within the subject of galaxy evolution. The researchers discovered, for instance, that satellite tv for pc galaxies situated nearer to their host galaxy had been extra more likely 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.
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The third new examine is led by Yunchong (Richie) Wang (“The SAGA Survey. V. Modeling Satellite tv for pc Techniques round Milky Method-mass Galaxies with Up to date UniverseMachine”), who obtained his doctorate with Wechsler. This examine makes use of the SAGA Survey outcomes to enhance present theoretical fashions of galaxy formation. Primarily based on the variety of quenched satellites in these Milky Method-mass programs, this mannequin predicts quenched galaxies must also exist in additional remoted environments—a prediction that needs to be potential to check within the coming years with different astronomical surveys such because the Darkish Power Spectroscopic Instrument Survey.
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Present to the astronomy neighborhood
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Along with these thrilling outcomes that may improve our understanding of galaxy evolution, the SAGA Survey group additionally brings a present to the astronomy neighborhood. As a part of this sequence of research, the SAGA Survey group printed new distance measurements, or redshifts, for about 46,000 galaxies. “Discovering these satellite tv for pc galaxies is like discovering needles in a haystack. We needed to measure the redshifts for lots of of galaxies to only determine one satellite tv for pc galaxy,” Mao mentioned. “These new galaxy redshifts will allow the astronomy neighborhood to review a variety of subjects past the satellite tv for pc galaxies.”
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