The radial metallicity gradient from OB star and HII region studies

Norbert Przybilla

GREATESF Workshop Bologna – 30.05.2012 Intro HII regions

• emissionline spectra: He , C, N, O, Ne, S, Ar • excited by OB stars presentday abundances

4 2 4 3 •Te ~ 10 K, n e ~ 10 10 cm abundance determination from Recombination Li nes ( RL ) or Collisionally Excited Lines ( CEL ) via direct method/requires measurement of weak [OIII] 4363 Å line strongline methods/calibration needed photoionisation models

complications : dust depletion & ICF‘s GREATESF Workshop temperature fluctuations? Bologna – 30.05.2012 Intro

OB Stars M ~ 8...30 MÍ • dominate energy and momentum budget of ISM in galaxies • key drivers for cosmic cycle of matter • highly luminous abundance indicators over large distances CNO/ αelements/irongroup • shortlived presentday abundances • simple atmospheres: radiative envelopes weak winds no diffusion NLTE treatment required

GREATESF Workshop Bologna – 30.05.2012 Overview Metallicity gradient from HII regions • oxygen as metallicity substitute for HII regions and OB stars

Stasinska et al. (2012)

-0.03 ... -0.07 azimuthal variation 5-22 133 Balser et al. (2011)

• ‘steep‘ and ‘shallow‘ solutions for abundance gradient • wide variation of (extrapolated) central oxygen abundance

GREATGREATESF Workshop Workshop Bologna Bologna – 30.05.2012 Overview Metallicity gradient from OB stars Stasinska et al. (2012)

• ‘zero ‘, ‘ steep‘ and ‘shallow‘ solutions for abundance gradient • wide variation of (extrapolated) central oxygen abundance

GREATESF Workshop Bologna – 30.05.2012 Overview Metallicity gradient from OB stars data from 3 most recent studies Stasinska et al. (2012)

• large scatter > 0.5dex within single clusters/associations

• large scatter > 1dex for clusters @ similar R g ... effect of 12+Gyr GCE GREATESF Workshop Bologna – 30.05.2012 Overview Metallicity gradient from different indicators

OB stars Cepheids Stasinska et Stasinska al. (2012) steep gradient, shallow gradient high abundances, low abundances

what to adopt for GCE modelling ?

HII regions PNe

GREATESF Workshop Bologna – 30.05.2012 Diagnostics

HII region and stellar analyses from interpretation of observation (spectro)photometry, spectroscopy

• plasma parameters: Te, n e • fundamental stellar parameter: L, M, R ξ • elemental abundances • atmospheric parameters: Teff , log g , , Y, Z, etc. • elemental abundances

quantitative spectroscopy

direct method (T e) model atmospheres strong line methods photoionization models

GREATESF Workshop Bologna – 30.05.2012 Diagnostics 6 BSGs Urbaneja et al. (2005)

Zaritsky et al. (1994) NGC300: abundance gradient from strongline method

• HII regions vs. BSGs

Kobulnicky et al. (1999) • different trends for HIIregions from 3 different

R23 calibrations βββ R23 =([OII] λλλ3727 +[OIII] λλλ4959,5007 )/H

• independent verification Pilyugin (2001) and extension via stellar analyses • systematic bias in published gradients!?

GREATESF Workshop Bologna – 30.05.2012 Diagnostics

HII regions: RL/CEL dichotomy Stasinska et al. (2012) SimonDiaz & Stasinska (2011) effect on gradient

revolution in progressMaxwellBoltzmann ? distribution ? κκκdistribution

stellar and nebular abundances in Orion Nicholls, Dopita & Sutherland (2012) RL/CEL dichotomy characteristic for Milky Way GREATESF Workshop Bologna – 30.05.2012 Diagnostics (Restricted) NLTE problem

•transfer equation

•statistical equilibrium:

• radiative rates: nonlocal • collisional rates: MgII: Przybilla et al. (2001) local • excitation, ionization, charge exchange, dielectronic recombination, etc. model atoms ... required for many elements/ions

GREATESF Workshop Bologna – 30.05.2012 Diagnostics Atomic data

Example: collisional excitation by e impact replacing approximations CII by experimental or abinitio data

Schrödinger equation

LScoupling: ΩΩΩ=1 Allen Formula

lowZ BreitPauli Hamiltonian

Methods: huge amounts of • Rmatrix/CC approximation atomic data: • MCHF OP/IRON Project & own • CCC GREATESF Workshop Bologna – 30.05.2012 Quantitative Spectroscopy without Systematics ... Diagnostics Nieva & Przybilla (2012)

4 • several 10 lines: ~30 elements, 60+ ionization stages GREATESF Workshop • complete spectrum synthesis in visual (& nearIR) ~7090% in NLTE Bologna – 30.05.2012 ... Realisation of a Stellar Astrophysicists‘s Dream Diagnostics Nieva & Przybilla (2012)

telluric lines

4 • several 10 lines: ~30 elements, 60+ ionization stages GREATESF Workshop • complete spectrum synthesis in visual (& nearIR) ~7090% in NLTE Bologna – 30.05.2012 Diagnostics NLTE Diagnostics: Stellar Parameters using robust analysis methodology & minimising comprehensive model atoms systematics !

• ionization equilibria Teff elements: e.g. He I/II,C I/II, N I/II, O I/II, Ne I/II, Mg I/II, Si III/IV, S II/III, Fe II/III

∆ Teff / Teff ~ 1…2% usually: 5…10% • Stark broadened hydrogen lines log g ∆ log g ~ 0.05…0.10 (cgs) usually: 0.2 • microturbulence, helium abundance, metallicity + other constraints, where available: SED’s, nearIR, … • absolute ∆∆∆log εεε ~ 0.05...0.10 dex (1 σ−stat.) usually: factor ~2 abundances : ∆∆∆log εεε ~ 0.07...0.12 dex (1 σ−sys.) usually: ???

fine ruler IAU Symposium 224:GREATESF The AStar Workshop Puzzle Poprad – July 10, 2004 Bologna – 30.05.2012 Diagnostics

Elemental Abundances Przybilla et al. (2006) • NLTE: absolute abundances reduced uncertainties artifact log ε:ε:ε: ~ 0.05 0.10 dex (1 σσσstat.) ~ 0.10 dex (1 σσσsyst.) artifact reduced systematics

• typical uncertainties in literature: factor ~2 (1 σstat.) + unknown syst. errors

artifact NLTE /LTE neutral

ionized

GREATESF Workshop Bologna – 30.05.2012 Diagnostics Elemental Abundances Przybilla et al. (2006)

HD87737 (A0 Ib)

absolute abundances relative to Cosmic Abundance Standard Nieva & Przybilla (2012)

NLTE /LTE neutral

ionized

• LTE: abundance pattern? large uncertainties GREATESF Workshop Bologna – 30.05.2012 Diagnostics Elemental Abundances Przybilla et al. (2006)

HD87737 (A0 Ib)

absolute abundances relative to Cosmic Abundance Standard Nieva & Przybilla (2012)

NLTE /LTE neutral

ionized

no NLTE abundance “corrections“

• NLTE: consistency & reduced uncertainties GREATESF Workshop Bologna – 30.05.2012 Results Chemical composition of the solar neighborhood @ present day σσσ 1 ~ 0.05 dex Nieva & Przybilla (2012) He C N O

Ne Mg Si Fe

Red: our work 29 stars black: OB stars literature Chemical homogeneity cosmic abundance standard

X=0.715 Y=0.271 Z=0.014 GREATESF Workshop Bologna – 30.05.2012 Results Milky Way: Oxygen Abundance Gradient

Literature: HII regions & Bstars Przybilla (2008)

calibrated to Sun

HII Regions: Models: BStars (NLTE): ○ Rudolph et al. (2006) Chiappini et al. (2001) ■ Gummersbach et al. (1998) □ Esteban et al. (2005) ♦ Daflon & Cunha (2004)

• large scatter @ every R • complex picture from “simple“ analysis

GREATESF Workshop Bologna – 30.05.2012 Results

Some slides on work in progress removed

GREATESF Workshop Bologna – 30.05.2012 Conclusions Quote, insted of conclusions

“It is also a good rule not to put overmuch confidence in the observational results that are put forward until they are confirmed by theory.“ A.S. Eddington

GREATESF Workshop Bologna – 30.05.2012