1 / 27

Massive Stars in the UV Spectra of Galaxies Claus Leitherer (STScI)

Massive Stars in the UV Spectra of Galaxies Claus Leitherer (STScI). Morton & Spitzer (1965). Average spectra of 16 local SF galaxies ( STIS ) vs. 811 LBGs ( LRIS ) Schwartz et al. (2006). Outline. Galaxy Properties Stellar Population Neutral and Ionized Gas Lyman- α Lyman continuum.

salma
Télécharger la présentation

Massive Stars in the UV Spectra of Galaxies Claus Leitherer (STScI)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Massive Stars in the UV Spectra of GalaxiesClaus Leitherer (STScI) Claus Leitherer: UV Spectra of Galaxies

  2. Morton & Spitzer (1965) Claus Leitherer: UV Spectra of Galaxies

  3. Claus Leitherer: UV Spectra of Galaxies

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

  5. Outline • Galaxy Properties • Stellar Population • Neutral and Ionized Gas • Lyman-α • Lyman continuum Claus Leitherer: UV Spectra of Galaxies

  6. Galaxy Properties • UV-bright local star-forming galaxies are of late Hubble type, include Irr, BCDs, SB,….. • Stellar masses of order 108 – 109 M • Absolute magnitudes MB in the range –16 to –19 • Oxygen abundances from 1/20 Z to Z Claus Leitherer: UV Spectra of Galaxies

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

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

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

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

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

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

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

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

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

  16. Grimes et al. (2008) • FUSE UV profiles of selected IS lines • All lines are blue-shifted and asymmetric • Outflows with velocities of order ~102 km s–1 • Galactic superwinds Claus Leitherer: UV Spectra of Galaxies

  17. LIR + LUV = SFR; LK = Mass • Outflow velocity shows trend with SFR/Mass • Outflows expected to be more signifcant at high z • Pollution of the IGM and leakage of radiation Claus Leitherer: UV Spectra of Galaxies

  18. Lyman-α • Leitherer (2007) • Predicted Ly-α strength for a standard population • W(Ly-α) ≈ 102 Å • Almost never observed in the local universe Claus Leitherer: UV Spectra of Galaxies

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

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

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

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

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

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

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

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

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

More Related