presented by Vianney Lebouteiller (IAP) coll. with Daniel Kunth

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Team / Collaborators Thesis of Vianney Lebouteiller Team of the Institut d’Astrophysique de Paris (IAP) french team (A. Lecavelier des Etangs, J.-M. Désert, G. Hébrard, R. Ferlet, A. Vidal-Madjar) & LERMA - Obs. de Paris : J. Lequeux & JHU Baltimore : A. Aloisi

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Outline Problematic : self-enrichment of the H II regions ? A new approach: study of the neutral gas FUSE FUSE method and analysis method and analysis Results on Blue Compact Dwarfs The next step: Giant H II regions the example of NGC 604 the example of NGC 604 Results on NGC 604 neutral gas homogeneity neutral gas homogeneity abundances ratio abundances ratio modelling modelling Conclusions & Perspectives

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Origin of the problem The problem of mixing in the ISM is a genenal one Moreover, Kunth & Sargent (1986) pointed out the lack of extremely metal-poor galaxies in emission-line surveys hence proposed : Self-enrichment hypothesis : Self–pollution by fresh released metals in situ by SNe, providing rapid cooling of the hot gas during the lifetime of the starburst. Pristine gas in the outer regions ? IZw18

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Small scale abundances inhomogenities suspected in a few objects:  NGC5253 (Walsh & Roy, 1989; Kobulnicky et al. 1997)  local pollution in IIZw40 (Walsh & Roy, 1993)  and Mkn 996 (Thuan et al. 1996) : N/H overabundances  attributed to WR winds. But not true in all young starburts (Kobulnicky, 1999; Oey & Schield, 2000) Abundances are similar to those of young stars Evidences against/for abundances discontinuities  IZw18, SBS , SMC: 6 regions: log O/H=8.13 ±0.08 LMC: 4 regions: log O/H=8.37 ±0.25 (Russel & Dopita 1990)  α-elements in hot gas is often over solar e.g. in the LMC (Dennerl et al. 2001)  Delayed mixing ? IZw18

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Two models … Tenorio-Tagle 1996 Recchi et al SNe expell the gas, creating a superbubble evolving in a low density spherical halo: disperse and mix ejecta and winds carry out metals but gas immediately cools down and enrich the ISM no discontinuities discontinuities few 10 9 yrs few 10 6 yrs Mixing timescale

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 FUSE Å H I, O I, N I, Fe II, Si II, Ar I,...

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Studying the H I metal composition

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Abundances determination Profile fitting procedure Owens (M. Lemoine)  returns most likely values (N, b, T,...) Owens derives an estimation of the errors (including uncertainties on the LSF, the continuum,...) One homogeneous cloud Deriving abundances from the column densities  ionization structure assumed a priori Fig: Example of fitted lines HNOSiPArFe 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)

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Results : Blue Compact Dwarfs Refs : Lebouteiller et al. (2003) for IZw36, Lecavelier et al. (2003) and Aloisi et al. ( 2003) for IZw18 Thuan et al. (in preparation) for SBS , Thuan et al. (2002) for Markarian 59 H I region (UV abs. lines) H II region (opt. em. lines) log (X/H) (+NGC1705 poster n°3 A. Aloisi and NGC253 poster n°14 J. Cannon)

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Kunth/Lebouteiller - The Neutral Gas Cambridge 04  Observations of individual H II regions in spiral galaxies 1’ Relatively high S/N, sightlines less complex Avoid possible systematic errors, study the effects of the multiple sightlines,... Unique possibility to model, to know the ionization stucture, etc... M33

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 The case of NGC604 FUSEMDRSFUSELWRSHST/STIS 20 pc 3-5 Myrs (Hunter et al. 1996), 4-5 (Wilson & Matthews 1995) ~200 pc H II region size ~2 ksec~7 ksec~13 ksec Exp. time ~2 Å ~0.07 Å Resolution G140L 52’’x2’’4’’x20’’30’’x30’’ ModeHST/STIS (H I, ) (H I, 2D )FUSE(metals)FUSE(metals)

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 C III Pcygni feature NGC 604 spectrum O VI Pcygni feature Metals from M33H I from M33

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 HI column density determination  log N(H I) = 21.01±0.05 Profiles before convolution Profiles after convolution Red: total profile

20.52 ±0.19 star O4, V= ±0.18 star O4 Iab, V= ±0.15 star O4 Ia, V= /18 H I with STIS (fig. of Bruhweiler at al. 2001) Lyman α

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Mimic FUSE data Do we overestimate H I column density ?  N(H I )=20.96 Construction of the global spectrum ≡ mean, weighted by the stars magnitudes

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Consistent determinations Global underabundance in the neutral gas, even for Fe Less enriched gas in the sightlines vs. enrichment of the H II gas X/H Results: abundances X/H Diffuse neutral gas (FUSE LWRS & MDRS) Ionized gas (optical emission-lines) log (X/H)

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Results: abundances X/Y N/O same as H II region  N primary, no ionization correction Ar/O  little ionization correction may be needed log (X/Y) X/Y

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 PDR H II region H I region => Modelling of NGC604 Coupling with HI

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Conclusions & perspectives Difficult interpretation for BCDs needs to be validated  Giant H II Regions Evidence for pockets of metal deficient neutral gas in NGC604  less chemically evolved gas in the sight lines ?  are dustier regions invisible in far-UV more metallic ? Is the neutral gas associated to the H II region ?  v(H I ) always  v(H II ) Future work on other giant H II regions in M33 Investigate hidden saturated lines (...resolution effects) See poster n°41 for more details

end of the presentation

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Column densities LWRSMDRS HIHIHIHI 21.00±0.03? NINININI 15.21± ±0.05 OIOIOIOI 16.47± ±0.80 Si II 15.52± ±0.12 P II 13.83± ±0.10 Ar I 13.86± ±0.10 Fe II 14.94± ±0.04

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 HST/STIS LWRSMDRS NGC 604 NGC 604 : MDRS and LWRS observations  test λ (Å) Total broadening/3 (px) The derived broadenings are consistent with the size of the cluster with the size of the cluster 15’’ 4’’

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 HI stellar contamination ? Stellar vs. interstellar HI ? O stars dominate  No significant stellar contamination is expected for Lyβ in hot stars stellar population (Robert et al. 2003) Observations Synth Mod Spec Theo model

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 V -246 km s -1 (Melnick) D 840 kpc(Freedman, Wilson & Madore 1991 Size ~10 comp. of ~10 pc in the halo 190 pc core(Viallefond & Gross 1986) 220 pc core(Israel et al. 1981) 450 pc halo(Aller 1984) d center 3 kpc(Wilson & Scoville 1992) M(H I ) M  (Wilson & Scoville 1992) (Viallefond & Gross 1986) (Deul & Van der Hulst 1986) M(H II ) (Viallefond & Gross 1986) (Churchwell & Goss 1999) (Israel et al. 1981) M(H 2 ) (Wilson & Scoville 1992) NGC 604, some facts

Kunth/Lebouteiller - The Neutral Gas Cambridge 04

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Stellar contamination evidences C III N V Si IV C IV Synthetic model spectra (Starburst 99) 0.5 Z  IMF=-2.35 Instantaneous burst Uses a stellar library from observations Synthetic model spectra (Robert et al. 2003) 2003) 0.5 Z  IMF=-2.35 Instantaneous burst Uses a stellar library from observations

Kunth/Lebouteiller - The Neutral Gas Cambridge 04 Modelling of NGC604 Cd fit LWRS independent compare with HIIR cd: To come : PDR modelling NEUTRAL REGION PDR H II region