1. Metal Loss from Dwarf Galaxies
Evan Kirby
Hubble Fellow
Caltech (for now)
CGE Fellow
UC Irvine (starting August 2012)
Kawata & Rauch 2007, ApJ, 663, 38

2. The Wide Applicability of Medium-Resolution, Multi-Object Stellar Spectroscopy
Method for measuring
metallicities
Gas removal from
dwarf galaxies
The pollution of the IGM

3. Detailed abundances may be measured from med-res spectra.
EK et al. 2009, ApJ, 705, 328
Frebel, EK, & Simon 2010, Nature, 464, 72

4. Med-res [Fe/H] is accurate when compared to high-res [Fe/H].
[Fe/H]MRS
[Fe/H]HRS
EK et al. 2010, ApJS, 191, 352

5. A catalog of multi-element abundances in MW dSphs
texp (hours)
Fornax
675
4.1
Leo I
827
15.5
Sculptor
376
3.3
Leo II
258
5.3
Sextans
141
5.8
Draco
298
6.0
Canes Venatici I
174
6.2
Ursa Minor
212
5.1
Total
2961
51.2
EK et al. 2010, ApJS, 191, 352

6. Galaxies obey a one-parameter mass-metallicity relationship.
á[Fe/H]ñ
log (Ltot/L⊙)
EK et al. 2008, ApJL, 685, L43
EK et al. 2011a, ApJ, 727, 78

7. Galaxies obey a one-parameter mass-metallicity relationship.
á[Fe/H]ñ
log (Ltot/L⊙)
Gallazzi et al. 2005, MNRAS, 362, 41
EK et al. 2008, ApJL, 685, L43
EK et al. 2011a, ApJ, 727, 78

8. The metallicity distributions of dwarf galaxies evolve with luminosity.
df / d[Fe/H]
[Fe/H]
EK et al. 2011a, ApJ, 727, 78

9. The metallicity distributions of dwarf galaxies evolve with luminosity.

10. The metallicity distributions of dwarf galaxies evolve with luminosity.
df / d[Fe/H]
[Fe/H]
EK et al. 2011a, ApJ, 727, 78

11. Dwarf galaxies lose almost all of their metals in outflows.
Chandra: C. Martin, H. Kobulnicky,
T. Heckman
HST+WIYN: M. Westmoquette

12. The amount of metals lost is a strong function of stellar mass.
log Mejected (M⊙)
log Mretained (M⊙)
[X/H]stellar
log M* (M⊙)
EK, Martin, & Finlator 2011, ApJL, 742, L25

13. The amount of metals lost is a strong function of stellar mass.
No metals lost
90% of metals lost
99% of metals lost
log fretained
log fretained
99.9% of metals lost
log M* (M⊙)
log M* (M⊙)
EK, Martin, & Finlator 2011, ApJL, 742, L25

14. Smaller dSphs contribute negligibly to the IGM.
log M* (M⊙)
log (Mejected dN/d log M*)
EK, Martin, & Finlator 2011, ApJL, 742, L25

15. The shapes of some metallicity distributions suggest ram pressure stripping.
df / d[Fe/H]
[Fe/H]
EK et al. 2011a, ApJ, 727, 78

16. Conclusions
Medium-resolution spectroscopy is an efficient way to measure elemental abundances in nearby galaxies.
The mass-metallicity relation holds for 8 Orders of magnitude in stellar mass or luminosity.
Dwarf galaxies lost >96% of their metals to galactic outflows and/or gas stripping.
But only the most massive dwarf galaxies could contribute a significant amount of metals to the IGM.