Astr 222 Feb 14, 2005

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Classifying Galaxies via Spectra

Stellar Spectra

Elliptical Galaxy Spectrum

Question: What will the spectrum of a spiral look like?

Different Hubble type spectra

Dark Matter:

Dark matter in galaxies

Distribution of mass via rotation curves

Milky Way rotation curve

Some well-observed rotation curves

NGC 3198 -- HI extends much further than stars

Mass inside R as function of circular velocity

Flat rotation curves -- huh?

How do we go from L to M?

We postulate existence of dark matter

Dark matter candidates

Wait a minute!