Our Milky Way

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Our Milky Way

• Astro 174 Majors Seminar
• Gail Zasowski
• 4/21/09

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The Ancient Milky Way

• Egypt

Bat
Narmer Palette, c. 3000 BCE
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The Ancient Milky Way
Greece/Rome
Greek Galaxias from gala (?a?a),
milk Latin Via Lactea
Jacopo Tintoretto c. 1575
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Galileo Galilei, 1610 A.D.
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Greg Martin
William Herschel, 1785
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Island Universes?
Hubble Ultra Deep Field, 2004
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To make a Milky Way
3 main components

• Bulge
• Disk
• Halo

? Not to scale!
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The (Hidden) Bulge
Christopher Picking
2MASS
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Galactic Center
Orbits of stars around supermassive black hole
Galactic Center region at ? 1 m
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The Milky Ways Disk(Around and around we go!)
M31 - Matthew T. Russell
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(No Transcript)
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NGC 4565
M104
NGC 5866
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NGC 3185
NGC 4622
M74
NGC 1365
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Spiral Arms

• Definitely pretty, but also full of physics

NGC 7793
M51
Grand design
Flocculent
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Disk Stability
Q parameter

• ? pattern wavevector
• vs local sound speed
• S0 unperturbed surface density

If Q gt 1 gas is stable If Q lt 1 self-gravity
may collapse gas
Wave Amplification

• Resonances in disk
• Q-barriers
• Swing amplification

Noise rotation only!
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Other Spiral Arm Theories

• Flocculents
• Star formation smearing by differential
  rotation
• Chaotic and incoherent
• Tidal Interactions
• Internal and external arms observed
• Driven by central bar

M51
M33
NGC 1300
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The Halo (and Beyond!)
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M31 Robert Gendler
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Tidal Streams
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And hows the neighborhood?
B. Bingelli