1. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 1 Massive Stars in the UV Spectra of Galaxies Claus Leitherer (STScI)

2. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 2 Morton & Spitzer (1965)

3. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 3

4. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 4 o Average spectra of 16 local SF galaxies (STIS) vs. 811 LBGs (LRIS) o Schwartz et al. (2006)

5. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 5 Outline o Galaxy Properties o Stellar Population o Neutral and Ionized Gas o Lyman-α o Lyman continuum

6. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 6 Galaxy Properties o UV-bright local star-forming galaxies are of late Hubble type, include Irr, BCDs, SB,….. o Stellar masses of order 10 8 – 10 9 M  o Absolute magnitudes M B in the range –16 to –19 o Oxygen abundances from 1/20 Z  to Z 

7. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 7 o Gil de Paz et al. (2007): GALEX FUV+NUV composite vs. SDSS image of NGC 5253

8. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 8 o Goldader et al. (2002) o VV 114 (d = 83 Mpc; log L = 11.7) o Interacting pair o UV vs. IR view

9. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 9 Stellar Population o Satellite UV is sensitive to stars with masses of ~10 M  and above o Continuum: late-O/early-B o Spectral lines: O stars of all types o Most prominent lines: O VI 1035, N V 1240, Si IV 1400, C IV 1550

10. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 10 o Chandar et al. (2004) o UV line profiles suggest universal Salpeter IMF o N V: 77 eV; C IV: 49 eV; Si IV: 33 eV o Confirmed independently by modeling of optical emission lines (González Delgado et al. 2002)

11. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 11 o Beware of selection effects! o HST slit sizes are small (0.2 ʺ for STIS) o Massive stars form in clusters

12. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 12 o Chandar et al. (2005) o Compare cluster and inter-cluster spectra o Inter-cluster spectra are softer o IMF or age? o Field population due to dissolving clusters

13. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 13 Direct comparison with high-z galaxies may be misleading → Direct comparison with high-z galaxies may be misleading → need large- or multi-aperture spectroscopy

14. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 14 Neutral and Ionized Gas o UV spectral region displays plethora of interstellar lines o Spectral region below 1200 Å in particular is dominated by IS lines o Well-suited for observations with FUSE because of wavelength coverage and spectral resolution (R ≈ 20,000)

15. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 15 o Grimes et al. (2008): FUSE survey of local starburst galaxies

16. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 16 o Grimes et al. (2008) o FUSE UV profiles of selected IS lines o All lines are blue- shifted and asymmetric o Outflows with velocities of order ~10 2 km s –1 o Galactic superwinds

17. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 17 o L IR + LUV = SFR; L K = Mass o Outflow velocity shows trend with SFR/Mass o Outflows expected to be more signifcant at high z o Pollution of the IGM and leakage of radiation

18. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 18 Lyman-α o Leitherer (2007) o Predicted Ly-α strength for a standard population o W(Ly-α) ≈ 10 2 Å o Almost never observed in the local universe

19. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 19 o Spectroscopy can cover only a small solid angle of the Lyman-α emission o HST/ACS Lyman-α imaging survey of local SF galaxies (PI: D. Kunth) o Haro 11: M B = ̶ 20.5; log O/H = 7.9 o Local analog of a Lyman-break galaxy

20. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 20 o Östlin et al. (2007) o Fields: 20’’  20’’ or 8 kpc  8 kpc o Small W(Ly-α) in the center o Large W(Ly-α) where flux levels are small o Correlates with velocity field but not with E(B-V) o 2.7% Ly-α escapes

21. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 21 o Deharveng et al. (2008) o GALEX survey of Ly- α emitters at z ≈ 0.3 o Equivalent width distribution consistent with observation at high z o Ly-α/UV luminosity function suggests increase of Ly-α escape with redshift

22. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 22 Lyman Continuum o Leitherer et al. (1999) o ~10% of the total luminosity emitted as ionizing radiation o Observationally verified via recombination lines o Leakage?

23. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 23 o Grimes et al. (2008): FUSE survey; 9 galaxies have sufficiently high z to permit Lyman continuum observations

24. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 24 o Bergvall et al. (2006): detection of Lyman continuum in Haro 11 using the same data; 5 – 10% escape fraction

25. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 25 o Alternatively: use opacity of interstellar lines as proxy for H I opacity o C II 1036 o Upper limits of a few % for escape fraction o Local galaxies are opaque o Reionization?

26. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 26 Main Points o Restframe UV spectra of local and distant star- forming galaxies are superficially similar but suggest rather significant differences o Beware of selection effects introduced by aperture sizes o Mechanical energy input by newly formed stars is significant and increases with redshift o Growing importance of galactic winds, escape of Ly-α, and Lyman continuum leakage

27. 10/14/08 Claus Leitherer: UV Spectra of Galaxies 27 UV spectroscopy with HST during C17 and later UV spectroscopy with HST during C17 and later