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V. Lebouteiller, D. Kunth

Metal abundances in star-forming regions The puzzle. V. Lebouteiller, D. Kunth. Mixing in the ISM. Fate of the metals produced in stars ? Dispersion + mixing timescales Starburst regions context. The Blue Compact Dwarf Galaxy IZw 18. 1/18. From the IR. Optical, IR :

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V. Lebouteiller, D. Kunth

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  1. Metal abundances in star-forming regionsThe puzzle V. Lebouteiller, D. Kunth

  2. Mixing in the ISM • Fate of the metals produced in stars ? • Dispersion + mixing timescales • Starburst regions context The Blue Compact Dwarf Galaxy IZw 18 1/18

  3. From the IR... • Optical, IR : emission line spectrum • Kunth & Sargent (1986) : lack of extremely metal-poor galaxies in surveys Self–pollution ? by fresh released metals in situ by SNe, providing rapid (few Myrs) cooling of the hot gas during the lifetime of the starburst 2/18

  4. ...to the UV Absorption line spectrum FUSE(NASA-CNES-ASC) + (HST/STIS, HST/GHRS, IUE, Copernicus, HUT) 900 Å • Res: ~0.07 Å • Resonant lines of : HI, OI, NI, FeII, SiII, ArI, ... 1200 Å 3/18

  5. Probing the neutral gas + clouds of the Milky Way 4/18

  6. Absorption Spectra analysis • Profile fitting procedure Owens (M. Lemoine, IAP) • returns most likely values • Owens derives an estimation of the errors • (including uncertainties on the LSF, the continuum,...) N , b, T • One single absorption line system • Deriving abundances from the column densities • ionization structure H N O Si P Ar Fe H I (13.60 eV) N I (14.53 eV) O I (13.62 eV) SiII (16.34 eV) P II (19.72 eV) Ar I (15.76 eV) FeII (16.18 eV) 5/18

  7. Blue Compact Dwarfs HII region (opt. +IR em. lines) HI region (UV abs. lines) [N/H] [O/H] NGC1705 NGC253 IZw18 IZw36 Markarian59 SBS0335-052 [Si/H] [P/H] [Ar/H] [Fe/H] Refs :Lebouteiller et al. (2003), Lecavelier et al. (2003), Aloisi et al. (2003), Thuan et al. (2005), Thuan et al. (2002), Lee et al. (2003) 6/18

  8. Individual HII regions in spiral galaxies M33 • Single HII region • Stellar population can be resolved Avoid possible systematic errors, study the effects of the multiple sightlines, ... Opportunity to model the ionization stucture, etc... 1’ 7/18

  9. Far-UV spectra FUSE MDRS FUSE LWRS IUE FUSE LWRS HST/STIS HST/ STIS FUSE MDRS 20 pc Fig. : HST/STIS image at 2000 Å of NGC604, in M33 8/18

  10. ISM analysis Pcygni CIII Pcygni OVI Wavelength (Å) Metals in NGC604 HI in NGC604 9/18

  11. HIcontent • Radio, 21cm emission  log N(HI)=21.1 • UV, 10 IUE spectra Lya • UV, STIS spectra towards ind. stars Lya • UV, STIS global spectrum Lya • UV, FUSE spectra Lyb HI in absorption (UV resonance lines) HI in emission (21cm, radio) 10/18

  12. HI content • Radio, 21cm emission  log N(HI)=21.1 • UV, 10 IUE spectra Lya 21.07±0.20 • UV, STIS spectra towards ind. stars Lya • UV, STIS global spectrum Lya • UV, FUSE spectra Lyb 11/18

  13. HI content • Radio, 21cm emission  log N(HI)=21.1 • UV, 10 IUE spectra Lya 21.07±0.20 • UV, STIS spectra towards ind. stars Lya • UV, STIS global spectrum Lya • UV, FUSE spectra Lyb 12/18

  14. HI HI with STIS • Mean value = 20.84±0.23 • Flux-weighted mean = 20.77±0.27 selection effects  no significant systematic errors Lyman a

  15. HI content • Radio, 21cm emission  log N(HI)=21.1 • UV, 10 IUE spectra Lya 21.07±0.20 • UV, STIS spectra towards ind. stars Lya 20.84±0.23 • UV, STIS global spectrum Lya 20.67±0.20 • UV, FUSE spectra Lyb 14/18

  16. HI content • Radio, 21cm emission  log N(HI)=21.1 • UV, 10 IUE spectra Lya 21.07±0.20 • UV, STIS spectra towards ind. stars Lya 20.84±0.23 • UV, STIS global spectrum Lya 20.67±0.20 • UV, FUSE spectra Lyb 20.75±0.20 15/18

  17. Ionization effects CLOUDYphotoionization code Estimate column densities in the HII gas + dominant ionization state in the neutral gas 16/18

  18. Comparison with ionized gas results Abundances consistent with O Global underabundance of N and the α-elements / solar (X/H neutral < X/H ionized) except Fe (depletion HII gas ?) O, Si, Ar in solar proportions N/O, Ar/O consistent HII/HI No depletion and ionization corrections for N, O, Si, and Ar 17/18

  19. Discussion Confirmation on more solid grounds of the BCDs results • Local enrichment by a previous burst ? (timescale !) • Dilution by lower metallicity gas ? • Infalling halo or extragalactic gas • Photodissociation of H2 • HI in form of baryionic dark matter (dense cold clumps of primordial material) 18/18

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