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Chemical composition of cosmic dust in the solar vicinity Derived indirectly from massive stars María Fernanda Nieva* Norbert Przybilla Institute for Astro- and Particle Physics * Lise-Meitner Fellow AUSTRIA Other collaborators in current work New work in the UV: Veronika Schaffenroth (stars), Thomas Heuschneider (gas) More observations in the optical (besides ours): Sergio Simon-Diaz Sepctroscopic binaries: Andreas Irrgang Edward Jenkins, Miguel Urbaneja, Marilyn Latour, David Wessmeyer Institute for Astro- and Particle Physics AUSTRIA Solar neighbourhood Chemical composition of ISM dust - presence of dust in cold/warm (<104 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators ► indirect methods (X/H)dust = (X/H)ref – (X/H)gas [ppm] astrophysical notation for elemental abundances: e(X) = log N(X) + 12 N(H) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Chemical composition of ISM dust - presence of dust in cold/warm (<104 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators our previous work (Nieva & Przybilla 2012) ► indirect methods (X/H)dust = (X/H)ref – (X/H)gas [ppm] astrophysical notation for elemental abundances: e(X) = log N(X) + 12 N(H) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Chemical composition of ISM dust - presence of dust in cold/warm (<104 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators our previous work (Nieva & Przybilla 2012) ► indirect methods (X/H)dust = (X/H)ref – (X/H)gas [ppm] new work (Heuschneider, Nieva et al. in prep.) astrophysical notation for elemental abundances: e(X) = log N(X) + 12 N(H) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Quest for a Suitable Abundance Reference abundance reference: Sun, local F & G stars, B stars Sun: + star that can be studied best + independent abundances from different indicators - 4.56 Gyr old, representative for present-day ISM? - formed 2 kpc away from current position F&G stars: + differential abundances relative to Sun + increased number statistics - difficult age determination - non-LTE & 3D-corrections (convection) not considered early B stars: + short-lived: formed out of presen-day ISM + simple atmospheric physics - non-LTE dominated Sofia & Meyer (2001): recommendation of Sun and F&G stars since then: revision of solar abundances, new work on early B stars Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Early B-type stars objects considered: - spectral type: B0 – B2 - LC V – III (ZAMS to TAMS) - masses: 8 ... 18 M8 ► lifetime of up to few tens of Myr - Teff: 18000 ... 32000 K - luminosity: 104 ... 105 L8 ► constraints on elemental abundances @ present day Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Spatial Distribution of Sample Stars solar neighbourhood d ≤ 400 pc associations: - Sco-Cen - Ori OB1 - Per OB2 - Lac OB1 - Cas-Tau + field stars + Ori OB1 Ia-Id sample of Nieva & Simon-Diaz (2011) Nieva & Przybilla (2012) New sample: > 250 stars @ d< 1 kpc Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 We have to model their atmospheres Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 (Restricted) Non-LTE Non-Local Thermodynamic Equilibrium •transfer equation •statistical equilibrium: • radiative rates: non-local • collisional rates: local MgII Przybilla et al. (2001) • excitation, ionization, charge exchange, dielectronic recombination, etc. model atoms Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Atomic data Example: collisional excitation by e--impact replacing approximations by experimental or ab-initio data what we CII have Schrödinger equation LS-coupling: W=1 what we Van Regemorter need Formula low-Z Breit-Pauli Hamiltonian huge amounts of atomic data: OP/IRON Project & own Methods: • R-matrix/CC approximation • MCHF • CCC Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Non-LTE Diagnostics: Stellar Parameters & Abundances using hybrid non-LTE approach, robust analysis methodology & comprehensive model atoms minimising systematics ! - ionization equilibria ► Teff/log g elements: e.g. He I/II, C II/III/IV, O I/II, Ne I/II, Si II/III/IV, S II/III, Fe II/III DTeff / Teff ~ 1…2% usually: 5…10% - Stark broadened hydrogen lines ► log g/Teff D log g ~ 0.05…0.10 (cgs) usually: 0.2 - microturbulence, helium abundance, metallicity + other constraints, where available: SED’s, near-IR, … - abundances: Dloge ~ 0.05...0.10 dex (1s-stat.) Dloge ~ 0.07...0.12 dex (1s-sys.) usually: factor ~2 usually: ??? Non-LTE Diagnostics: Stellar Parameters & Abundances minimising systematics ! Nieva & Przybilla (2012) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Non-LTE Diagnostics: Tests & Additional Constraints SEDs: right Teff Distances: right log g C No abundance trends N O Ne Mg nuclear path of CN cycle: right abundances Si Fe Nieva & Przybilla (2012) Quantitative Spectroscopy Nieva & Przybilla (2012) • observations: FEROS@ESO 2.2m, FOCES@CA 2.2m, ELODIE@OHP 1.93m • high S/N, high resolution R ~ 40 - 48000 Quantitative Spectroscopy Nieva & Przybilla (2012) telluric lines • several 104 lines: ~30 elements, 60+ ionization stages • complete spectrum synthesis in visual (& near-IR) ~95% in NLTE Chemical composition of solar neighbourhood @ present day 1s ~ 0.05 dex black: OB stars literature red: Nieva & Przybilla (2012) chemical homogeneity ► Cosmic Abundance Standard X=0.715 Y=0.271 Z=0.014 Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Dust Depletion - similar abundance distributions in gas & stars Nieva & Przybilla (2012) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 CAS & Consequences for Dust Composition Nieva & Przybilla (2012) - Dust in diffuse ISM: relatively carbon poor & silicate-rich - checksum Mg+Si+Fe vs. O match (some extra O may be in unidentified constituent) - comparison with Orion dust: graphite minor species ► C in PAHs - homogeneity over hundreds of parsecs: highly efficient mixing Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Interstellar dust at Saturn Credit: ESA / NASA / JPL / Space Science Institute The Cosmic Dust Analyser on the Cassini spacecraft has detected the faint but distinct signature of dust coming from outside our Solar System, from the local interstellar cloud. Altobelli et al. (2016): “It can be verified that Mg/Si, Fe/Si, Mg/Fe, and Ca/Fe ratios are on average CI chondritic (carbonaceous chondrite of type Ivuna whose composition is considered as a proxy of solar or cosmic element abundances) and similar to a composition inferred for LIC-ISM dust (Przybilla et al. 2008, Nieva & Przybilla 2012). Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Chemical composition of ISM dust - presence of dust in cold/warm (<104 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators our previous work (Nieva & Przybilla 2012) ► indirect methods (X/H)dust = (X/H)ref – (X/H)gas [ppm] new work (Heuschneider, Nieva et al. in prep.) astrophysical notation for elemental abundances: e(X) = log N(X) + 12 N(H) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Current study Self-consistent study of spatial distribution and chemical composition of massive (OB) stars, gas and dust for ~250 lines-of-sight within ~1 kpc distance from the Sun Chemical composition of ISM gas #1 - determination of hydrogen column density: via IS Lya damping wings ► e.g. continuum reconstruction technique (Bohlin 1975) Diplas & Savage (1994) multiplication of flux by et(l) = e s(l) N(HI) to correct for damping s(l) = hydrogen column density: 4.26· 10-20 cm2 6.04· 10-10 + ( l - l0 )2 N(H) = N(HI) + N(H2) l0 = 1215.67Å Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Chemical composition of ISM gas #2 - metal abundances from unsaturated lines from ground states e.g. semi-forbidden CII] l2325Å HST GHRS: S/N~850 Wl ~ 0.2 mÅ Sofia (2004) - metal column density via Wl ~ N(X)· fij· s(l) - chemical homogeneity of gas-phase in solar neighbourhood from many sightlines: C, O, Mg, Si, S, Fe, Zr, Kr, ... Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 ISM gas: observational data UV: solar Neighbourhood OB star ISM Thomas Heuschneider, Veronika Schaffenroth (Innsbruck) Jenkins (2012) IUE International Ultraviolet Explorer Hubble Space Telescope Own observational database in the optical:~ 300 high resolution spectra of background sources PIs: Nieva, Przybilla (collected along ~10 years + additional data) FEROS in La Silla (Chile) ESO FOCES @ Calar Alto (Spain) UVES @ VLT (Chile) ESO This work FIES @ NOT (La Palma) Spain RESULTS: this is what you expect from us (spectroscopists) Normal single OB dwarfs and giants vs. detached eclipsing binaries Nieva & Przybilla (2014) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Credit: M. Shultz/BinaMIcS Credit: NASA Credit: ESO/L. Calçada The massive star zoo Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 The massive star zoo Non-radial pulsations Chemical abundance spots Strong magnetic field Credit: O. Kochukhov http://www.astro.uu.se/~oleg/ Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 The massive star zoo http://lasp.colorado.edu/~cranmer/cranmer_st_hot.html Fast rotators/Classical Be stars See review by Rivinius et al. (2013) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 When your favorite star is actually a team... Nieva & Przybilla (2012) Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Gonzales et al. (in prep) a triple system Identifying the individual component contributions to the spectra in different phases Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 Gonzales et al. (in prep) After solving the orbital parameters and individual stellar parameters of the system: check for reproduction of observed time-series spectra Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016