How To Make a Galaxy - Speaker Deck

How To Make a Galaxy

by Alison Crocker

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HOW TO MAKE A GALAXY Alison Crocker, Reed College

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HOW TO MAKE A GALAXY SPIRAL ^

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GOAL A SPIRAL GALAXY We live here!

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GOAL A SPIRAL GALAXY Disk Spiral arms

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GOAL A SPIRAL GALAXY Bulge

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GOAL A SPIRAL GALAXY Supermassive blackhole: Sagittarius A*

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GOAL A SPIRAL GALAXY Dark Matter ‘Halo’

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DARK MATTER EASY FOR ASTROPHYSICS! Dark matter: Gravity Electromagnetism Weak Strong Normal matter: Gravity Electromagnetism Weak Strong

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WHERE DO WE START?

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WHERE DO WE START? The Early Universe

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DARK MATTER Density ﬂuctuations. ~0.001% variation

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DARK MATTER Density ﬂuctuations. ~0.001% variation

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DARK MATTER Step 1 Choose an overdense region.

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DARK MATTER Step 2 Turn on gravity! Simulation of dark matter. (Illustris collaboration.) solar masses

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DARK MATTER Step 2 Turn on gravity! Simulation of dark matter. (Illustris collaboration.)

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GOAL DARK MATTER HALO ✔

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NORMAL MATTER Step 3 Wait 380,000 years.

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NORMAL MATTER Step 3 Wait 380,000 years. Too hot.

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NORMAL MATTER Step 3 Wait 380,000 years. Too hot. Cool enough! CMB photon

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NORMAL MATTER Step 4 Let gas fall into your dark matter halo.

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NORMAL MATTER Step 4 Let gas fall into your dark matter halo. Note: must conserve angular momentum.

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NORMAL MATTER Step 4 Let gas fall into your dark matter halo. Note: must conserve angular momentum.

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NORMAL MATTER Step 5 Make stars. Overdense region of gas Star!

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NORMAL MATTER Step 5 Make stars. Overdense regions of gas Stars

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NORMAL MATTER Step 5 Make (some) stars. (Self-regulated star formation.)

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GOAL A SPIRAL GALAXY Disk Spiral arms ✔ ✔

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GOAL A SPIRAL GALAXY Bulge

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NORMAL MATTER Step 6 Merge your galaxy. Arp 87. Typical galaxy “family tree”.

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NORMAL MATTER Step 6 Merge your galaxy. Bulge created!

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GOAL A SPIRAL GALAXY Bulge Disk Spiral arms ✔ ✔ ✔

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SUPERMASSIVE BLACKHOLE Step 7 Add a supermassive black hole.

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SUPERMASSIVE BLACKHOLE Step 7 Add a supermassive black hole… SUPERMASSIVE BLACKHOLE ?

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1. Choose over densities 2. Gravity 3. Wait 4. Add gas 5. Form stars 6. Merge 7. Add supermassive blackhole SPIRAL GALAXY

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Variation: - Choose a small set of small overdensities. - Don’t allow much merging. - Don’t add a supermassive blackhole. IRREGULAR GALAXY

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Variation: - Choose a larger set of larger overdensities. - Vigorously merge. - Use up or expel all star-forming gas.* ELLIPTICAL GALAXY

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GOOD LUCK!