1. Stellar Kinematics of the Faintest Dwarf Galaxies Josh Simon Carnegie Observatories Marla Geha Beth Willman Louie Strigari Evan Kirby James Bullock Manoj Kaplinghat Erik Tollerud Joe Wolf...

2. What Can Dwarf Galaxies Do For You? © Wei-Hao Wang© Johannes Schedler 2006 Dwarf irregularDwarf elliptical/spheroidal

3. What Can Dwarf Galaxies Do For You? Dwarf galaxies are nearby –Can be studied in great detail Dwarf galaxies are dark matter- dominated –Perhaps they can be useful laboratories for studying dark matter Dwarf galaxies are astrophysically simple systems

4. What Can Dwarf Galaxies Do For You? Dwarf galaxies are nearby –Can be studied in great detail Dwarf galaxies are dark matter- dominated –Perhaps they can be useful laboratories for studying dark matter Dwarf galaxies are astrophysically simple systems not as #%@#$ complicated as bigger galaxies

5. What Can Dwarf Galaxies Do For You? Dwarf galaxies are nearby –Can be studied in great detail Dwarf galaxies are dark matter- dominated –Perhaps they can be useful laboratories for studying dark matter Dwarf galaxies are astrophysically simple systems not as #%@#$ complicated as bigger galaxies Cave man version: dwarf galaxies good. Big galaxies bad.

6. Despite claims to the contrary, no Can You Measure Cusps in Dwarfs?

7. Dwarf Galaxies Five Years Ago SDSS Luminosity: ~10 5 -10 6 L  Distance: ~100 kpc Mass-to-light ratio: ~10-100 M  /L  Mean density: <0.1 M  pc -3 (5 GeV/c 2 cm -3 ) Leo II e.g., Mateo (1998), Gilmore et al. (2007)

8. Dwarf Galaxies Today SDSS Luminosity: ~10 3 -10 5 L  Distance: ~20-200 kpc Mass-to-light ratio: ~100-10 3 M  /L  Mean density: <0.5 M  pc -3 (20 GeV/c 2 cm -3 ) Willman 1 e.g., Simon & Geha (2007), Geha et al. (2008)

9. Masses of the Ultra-Faint Dwarfs Strigari et al. (2008) Measure the velocities of individual stars Calculate mass from: –Virial arguments –Maximum-likelihood method with CDM prior

10. Masses of the Ultra-Faint Dwarfs Strigari et al. (2008) Even the tiniest dwarfs have 10 7 M  of dark matter! These dwarfs are also very nearby (<50 kpc)

11. Masses of the Ultra-Faint Dwarfs Nailing down the masses of the least luminous dwarfs Segue 1 (d=23 kpc) Bootes II (d=42 kpc)

12. Masses of the Ultra-Faint Dwarfs New Segue 1 data! Geha et al. (2008)

13. Masses of the Ultra-Faint Dwarfs New data! Segue 1 ???

14. Masses of the Ultra-Faint Dwarfs Nailing down the masses of the least luminous dwarfs

15. Dwarf Galaxies Are Cool Nearby + dark matter-dominated = good laboratories for studying DM Cusps vs. cores has to wait for future instruments Smallest, closest, densest dwarfs are good indirect detection targets... No star formation = no astrophysical foregrounds