the milky way galaxy and the formation of spiral galaxies prof. ata sarajedini university of florida...
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![Page 1: The Milky Way Galaxy and the Formation of Spiral Galaxies Prof. Ata Sarajedini University of Florida Department of Astronomy](https://reader035.vdocuments.us/reader035/viewer/2022062515/56649f4d5503460f94c6dd77/html5/thumbnails/1.jpg)
The Milky Way Galaxy and the Formation of
Spiral Galaxies
Prof. Ata SarajediniUniversity of Florida
Department of Astronomy
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The Milky Way Galaxy - Our HomePole-On View
Edge-On View
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The Andromeda Galaxy - Our Nearest Large Neighbor
M32
NGC 205
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• What is the significance of these satellite galaxies?
• Since the late 1970s, theories of galaxy formation have suggested that disrupted satellite galaxies formed the Milky Way’s halo.
They are remnants from the formation of the Milky Way’s halo!
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Satellite Galaxies of the Milky Way and Andromeda
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FgFg
Fg
How do dwarf galaxies get disrupted?
Tidal Effects
€
gravityF ∝1
2
Distance
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The problem was that there was no concrete evidence for the buildup of spiral galaxies via the disruption and accretion of dwarf galaxies until 1994!
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The “Smoking Gun” - the Sagittarius Dwarf Galaxy (Discovered in 1994)
Blue Red
Velocity along the line-of-sight for
stars toward
the Galaxy’s
Bulge
Bulge stars with an average velocity of 0 km/s
Sagittarius dwarf galaxy
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M55 turns out to be a M55 turns out to be a foreground cluster!foreground cluster!
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Observations of stars known to be a part of the Sagittarius dwarf galaxy and its tidal tails.
Theoretical model of how the Sagittarius dwarf galaxy should be disrupted by the Milky Way.
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Canis Major Dwarf Galaxy
• In 2003, another disrupted and digested dwarf galaxy was found…
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• Globular clusters are also disrupted and accreted to form the Galaxy’s halo.
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• We have even detected tidal streams and tidal tails composed of stars in the halo of the Andromeda galaxy.
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• The halos of the Milky Way and Andromeda do indeed show evidence of having been formed via the disruption and accretion of dwarf satellite galaxies.
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Conclusion
The halo of a spiral galaxy is like a bowl of spaghetti!
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Today, NASA and the Space Telescope Science Institute released images of the Hubble Ultra Deep Field - the result of 11.3 days of total exposure time with the Advanced Camera for Surveys instrument.
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Satellite Galaxies of the Milky Way and Andromeda
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• Similar searches for tidally disrupted dwarf galaxies around the spiral galaxy M33 have turned up nothing significant.
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