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Stellar Kinematics of the Faintest Dwarf Galaxies Josh Simon Carnegie Observatories Marla Geha Beth Willman Louie Strigari Evan Kirby James Bullock Manoj.

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Presentation on theme: "Stellar Kinematics of the Faintest Dwarf Galaxies Josh Simon Carnegie Observatories Marla Geha Beth Willman Louie Strigari Evan Kirby James Bullock Manoj."— Presentation transcript:

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: ~ L  Distance: ~100 kpc Mass-to-light ratio: ~ 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: ~ L  Distance: ~ kpc Mass-to-light ratio: ~ 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


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