HII regions and massive stars are very valuable tools to measure present-day oxygen abundances across the Universe.

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3 Take away messages HII regions and massive stars are very valuable tools to measure present-day oxygen abundances across the Universe. We have improved A LOT in the last decades on the reliability of oxygen abudances as derived from B-type stars and BA supergiants. Possible sources of uncertainties and systematics are now controlled. From the comparison of oxygen abundances from massive stars and HII regions one might conclude that abundaces derived from CEL might need a correction (at least at solar metallicities) Is this correction dependent of metallicity/element? Time will say...

4 Previously on this conference... Massive stars (MS) are of definite importance to have access to information about the chemical properties of galaxies across the Universe Ionizing fluxes HII regions Understanding nebular emission in far distant galaxies requires knowledge of High mass end of the IMF Physical properties of MS MS evolution MS ionizing fluxes

5 Motivation of this talk Massive stars and HII regions are alternative/complementary astrophysical tools to obtain present-day abundances of the ISM in the galactic region where they are located Unique opportunity to check the reliability of abundances derived by means of two independent methodologies For the moment, only possible in the Local Universe (up to a few Mpc)

6 Abundances in HII regions and massive stars: key aspects HII regions (HII-r) * ISM gas-phase abundances Dust depletion ( ISM dust) * He, C, N, O, Ne, S, Fe, Ar, Cl * Methods: generally straightforward * Atomic data: a few quantities Massive stars (MS) * Photospheric abundances No dust depletion ( ISM) * He, C, N, O, Si, Mg, Ne, S, Fe * Methods: Complex modelling * Complex atomic models [OIII]λ4363 (+ faint ORL) detection Flux calibration, scattered light [...] Ionizing correction factors CEL/ORL discrepancy + Reliability of strong line methods + Metal rich regime Early-B stars + BA supergiants SNR, resolution, vsini < 100 km/s Stellar parameter determination Microturbulence + Photospheric contamination + Undetected binarity

7 (Massive) OB-type stars: Quantitative spectroscopy Stellar atmosphere code vsini T eff, logg, Y(He), ζ t, logq ε(x) Rotation Spectroscopic parameters Abundances

8 (Massive) OB-type stars: Quantitative spectroscopy OBSERVED SPECTRUM Observed line profiles and EWs PHOTOMETRIC DATA STELLAR PARAMETER DETERMINATION T eff, logg, ε(he), (wind param.) Stellar atmosphere model for the studied star T eff, logg,... ε(x i ), ζ t ABUNDANCE ANALYSIS GRID OF MODELS Synthetic line profiles EWs Global SED STELLAR ATMOSPHERE CODE T eff, logg, ε(he), Z, (wind param.) + ε(x i ), ζ t

9 (Massive) OB-type stars: Quantitative spectroscopy Stellar parameter determination: O-type stars diagnostic lines H I, He I, He II Teff = 40000, logg = 3.6, logq = -12.1

10 (Massive) OB-type stars: Quantitative spectroscopy Stellar parameter determination: O-type stars diagnostic lines H I, He I, He II Teff = 34000, logg = 4.0, logq < -13.5

11 (Massive) OB-type stars: Quantitative spectroscopy Stellar parameter determination: B-type stars diagnostic lines H I, Si IV, Si III, Si II Depending of the star, different Si line ratios must be used as T eff indicators: Si IV/III, Si II/III

12 (Massive) OB-type stars: Quantitative spectroscopy Stellar abundance determination: the curve of growth method For a fixed set of stellar parameters T eff, logg, ε(he), (wind param.) i.e. a given atmosphere structure Grid of EWs of diagnostic lines (line formation code) for different [ε(x), ζ t ] pairs

13 (Massive) OB-type stars: Quantitative spectroscopy A final word of caution: things were not always as smooth are they are now Stellar atmosphere code State-of-the-art codes Stellar atmosphere model Stellar atm. structure: Te(τ), Ne(τ) Global SED -- LTE/NLTE, line blanketing -- + Line formation code Level populations: N ij (τ) Line profiles + EWs -- LTE/NLTE -- ATLAS (Kurucz) TLUSTY (Hubeny & Lanz) CMFGEN (Hillier) FASTWIND (Puls et al.) DETAIL/SURFACE (Buttler & Giddings) Stellar parameter determination Use of photometric calibrations vs. Self-consistent spectroscopic approach e.g. Lester, Gray & Kurucz (1986) [c 1 ] = c (b-y) = f(t eff, logg) Based on Kurucz s (1979) models T eff, logg,... are determined by using synthetic lines resulting from the same stellar atmosphere code that will be used for the abundance analysis

14 Abundances from Massive Stars and HII regions Do they agree?

15 Massive star vs. HII region abundances Best element to compare: oxygen No ICFs needed in the case of HII regions Oxygen abundances from CEL and ORL sometimes accessible Photospheres of massive stars are only contaminated by oxygen produced in the stellar interior in late evolutionary phases Global approach gradients in spiral galaxies Local approach comparison of abundances in a given star-forming region

16 Oxygen abundances from Massive Stars and HII regions Do they agree? Abundance gradients in spiral galaxies --- M33 ---

17 The present-day oxygen abundance gradient in M33 HII regions: Vilchez et al. (1998) B Supergiants: Urbaneja et al. (2005) HII: CEL + direct method

18 The present-day oxygen abundance gradient in M33 HII regions: Rosolowsky & Simon (2008) B Supergiants: Urbaneja et al. (2005) HII: CEL + direct method Scatter!!!!

19 The present-day oxygen abundance gradient in M33 HII regions: Rosolowsky & Simon (2008), Bresolin (2011) B Supergiants: Urbaneja et al. (2005) HII: CEL + direct method Scatter???

20 Oxygen abundances from Massive Stars and HII regions Do they agree? Abundance gradients in spiral galaxies --- NGC

21 The present-day oxygen abundance gradient in NGC300 Bresolin et al. (2009) HII (CEL + direct method) vs. BA supergiants

22 Oxygen abundances from Massive Stars and HII regions Do they agree? Abundance gradients in spiral galaxies --- Milky Way (as for 2007) ---

23 The present-day oxygen abundance gradient in the Milky Way HII regions: García-Rojas & Esteban (2007) CEL (direct method) & ORL

24 The present-day oxygen abundance gradient in the Milky Way HII regions: García-Rojas & Esteban (2007) CEL (direct method) & ORL B-type stars: Rolleston et al. (2000), Daflon & Cunha (2004), Gummersbach et al. (1998)

25 The present-day oxygen abundance gradient in the Milky Way B-type stars: Rolleston et al. (2000), Daflon & Cunha (2004), Gummersbach et al. (1998)

26 Oxygen abundances from Massive Stars and HII regions Do they agree? Oxygen abundance in the same site --- Orion OB1 ---

27 Oxygen abundance in the Orion OB1 star forming region (One of) The closest star forming region Orion OB1 association: Four subgroups of OB stars with different ages and location in the sky (Blaauw 1964, Brown et al. 1994) Signatures of several SN events + The Orion nebula (M42) the closest and most studied HII region

28 Oxygen abundance in the Orion OB1 star forming region B-type stars: Cunha & Lambert (1994) Highest values of oxygen abundance found for stars in the youngest groups Contamination of the new generation of stars by SNe type-ii ejecta (O, Si, Mg...)

29 Oxygen abundance in the Orion OB1 star forming region B-type stars: Cunha & Lambert (1994) Orion nebula: Esteban et al. (2004)

30 Oxygen abundance in the Orion OB1 star forming region B-type stars: Cunha & Lambert (1994), Simón-Díaz (2010) Orion nebula: Esteban et al. (2004) Simón-Díaz (2010) Homogeneous set of stellar abundances In fair good agreement (though a bit larger) with ORL abundances Dust???

31 Oxygen abundance in the Orion OB1 star forming region B-type stars: Simón-Díaz (2010) vs. Cunha & Lambert (1994) What is making the difference? - Improvements in stellar atmosphere models - Better observations - Careful selection of diagnostic lines - Stellar parameter determination (self-consistent spectroscopic approach [1] ) [1] T eff, logg,... are determined by using synthetic lines resulting from the same stellar atmosphere code that will be used for the abundance analysis

32 Abundances in B-type stars are nowadays much more reliable! B-type stars in the Solar vicinity: Nieva & Przybilla (2012)

33 Oxygen abundance in the Orion OB1 star forming region B-type stars: Cunha & Lambert (1994), Simón-Díaz (2010) Orion nebula: Esteban et al. (2004) Simón-Díaz (2010) Homogeneous set of stellar abundances In fair good agreement (though a bit larger) with ORL abundances Dust???

34 Oxygen abundance in the Orion OB1 star forming region Extending the study by Simón-Díaz (2010) to other elements Simón-Díaz (2010) * O and Si abundances * Spectroscopic approach: FASTWIND * Curve of growth * To investigate oxygen depletion onto dust grains: Mg and Fe abundances are also needed Nieva & Simón-Díaz (2011) * C, N, O, Ne, Si, Mg, Fe abundances * Spectroscopic approach: ATLAS+DETAIL+SURFACE * Spectral synthesis Perfect agreement in the derived O and Si abundances!!!

35 Oxygen abundance in the Orion OB1 star forming region Taking care of dust Simón-Díaz & Stasinska (2011) Draine (2003) B-type stars: ε(si) = / ε(mg) = / ε(fe) = / Orion nebula: ε(si) = / ε(mg) = 6.50 :: ε(fe) = 6.0 +/- 0.3 ε(o) = /.0.04 Dust correction (oxygen) ~ dex Refs (B-type): Simón-Díaz (2010), Nieva & Simón-Diaz (2011) Refs (HII-r): Esteban et al. (2004), Rubin et al. (1993), Baldwin et al. (1991), Rodriguez & Rubin (2005)

36 Oxygen abundances from Massive Stars and HII regions Do they agree? Oxygen abundance in the Magellanic Clouds

37 Present-day oxygen abundances in the MW and MCs + Tsamis et al. (2003) find ADF(O 2+ ) > 0.3 dex in the SMC and LMC

38 Take away messages HII regions and massive stars are very valuable tools to measure present-day oxygen abundances across the Universe. We have improved A LOT in the last decades on the reliability of oxygen abudances as derived from B-type stars and BA supergiants. Possible sources of uncertainties and systematics are now controlled. From the comparison of oxygen abundances from massive stars and HII regions one might conclude that abundaces derived from CEL might need a correction (at least at solar metallicities) Is this correction dependent of metallicity/element? Time will say...