Chemical composition of cosmic dust in the solar vicinity

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1 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

2 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

3 Solar neighbourhood

4 Chemical composition of ISM dust - presence of dust in cold/warm (<10 4 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: N(X) e(x) = log + 12 N(H)

5 Chemical composition of ISM dust - presence of dust in cold/warm (<10 4 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators indirect methods our previous work (Nieva & Przybilla 2012) (X/H) dust = (X/H) ref (X/H) gas [ppm] astrophysical notation for elemental abundances: e(x) = log + 12 N(X) N(H)

6 Chemical composition of ISM dust - presence of dust in cold/warm (<10 4 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators indirect methods our previous work (Nieva & Przybilla 2012) (X/H) dust = (X/H) ref (X/H) gas [ppm] new work (Heuschneider, Nieva et al. in prep.) astrophysical notation for elemental abundances: N(X) e(x) = log + 12 N(H)

7 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 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

Early B-type stars objects considered: - spectral type: B0 B2 - LC V III (ZAMS to TAMS) - masses: 8.

8 Early B-type stars objects considered: - spectral type: B0 B2 - LC V III (ZAMS to TAMS) - masses: M 8 lifetime of up to few tens of Myr - T eff : K - luminosity: L 8 constraints on elemental present day

9 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 d< 1 kpc

10 We have to model their atmospheres

11 (Restricted) Non-LTE transfer equation Non-Local Thermodynamic Equilibrium statistical equilibrium: radiative rates: non-local collisional rates: local excitation, ionization, charge exchange, dielectronic recombination, etc. MgII Przybilla et al. (2001) model atoms

Atomic data Example: collisional excitation by e - -impact what we CII have replacing approximations by experimental or ab-initio data Schrödinger equation W=1 what

12 Atomic data Example: collisional excitation by e - -impact what we CII have replacing approximations by experimental or ab-initio data Schrödinger equation W=1 what Van we Regemorter need Formula LS-coupling: low-z Breit-Pauli Hamiltonian huge amounts of atomic data: OP/IRON Project & own Methods: R-matrix/CC approximation MCHF CCC

13 Non-LTE Diagnostics: Stellar Parameters & Abundances using hybrid non-lte approach, robust analysis methodology & comprehensive model atoms - ionization equilibria T eff /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 minimising systematics! DT eff / T eff ~ 1 2% usually: 5 10% - Stark broadened hydrogen lines log g/t eff D log g ~ (cgs) usually: microturbulence, helium abundance, metallicity + other constraints, where available: SED s, near-ir, - abundances: Dloge ~ dex (1s-stat.) usually: factor ~2 Dloge ~ dex (1s-sys.) usually:???

14 Non-LTE Diagnostics: Stellar Parameters & Abundances minimising systematics! Nieva & Przybilla (2012)

15 Non-LTE Diagnostics: Tests & Additional Constraints Distances: right log g SEDs: right Teff C N No abundance trends O Ne Mg nuclear path of CN cycle: right abundances Si Fe Nieva & Przybilla (2012)

16 Quantitative Spectroscopy Nieva & Przybilla (2012) observations: 2.2m, 2.2m, 1.93m high S/N, high resolution R ~

17 Quantitative Spectroscopy Nieva & Przybilla (2012) telluric lines several 10 4 lines: ~30 elements, 60+ ionization stages complete spectrum synthesis in visual (& near-ir) ~95% in NLTE

18 Chemical composition of solar present day 1s ~ 0.05 dex chemical homogeneity Cosmic Abundance Standard X=0.715 Y=0.271 Z=0.014 black: OB stars literature red: Nieva & Przybilla (2012)

19 Dust Depletion - similar abundance distributions in gas & stars Nieva & Przybilla (2012)

20 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

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

21 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).

22 Chemical composition of ISM dust - presence of dust in cold/warm (<10 4 K) ISM: reddening & extinction - chemical composition difficult to be determind directly: lack of spectroscopic indicators indirect methods our previous work (Nieva & Przybilla 2012) (X/H) dust = (X/H) ref (X/H) gas [ppm] new work (Heuschneider, Nieva et al. in prep.) astrophysical notation for elemental abundances: N(X) e(x) = log + 12 N(H)

23 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

24 Chemical composition of ISM gas #1 - determination of hydrogen column density: via IS Lya damping wings e.g. continuum reconstruction technique (Bohlin 1975) multiplication of flux by e t(l) = e s(l) N(HI) to correct for damping Diplas & Savage (1994) s(l) = cm 2 l 0 = Å ( l - l 0 ) 2 hydrogen column density: N(H) = N(HI) + N(H 2 )

25 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 W l ~ 0.2 må Sofia (2004) - metal column density via W l ~ N(X) f ij s(l) - chemical homogeneity of gas-phase in solar neighbourhood from many sightlines: C, O, Mg, Si, S, Fe, Zr, Kr,...

26 ISM gas: observational data UV: solar Neighbourhood OB star ISM Jenkins (2012) Thomas Heuschneider, Veronika Schaffenroth (Innsbruck) IUE International Ultraviolet Explorer Hubble Space Telescope

27 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 VLT (Chile) ESO Calar Alto (Spain) This work NOT (La Palma) Spain

29 RESULTS: this is what you expect from us (spectroscopists) Normal single OB dwarfs and giants vs. detached eclipsing binaries Nieva & Przybilla (2014)

30 Credit: M. Shultz/BinaMIcS Credit: NASA Credit: ESO/L. Calçada The massive star zoo

31 The massive star zoo Non-radial pulsations Chemical abundance spots Strong magnetic field Credit: O. Kochukhov

32 The massive star zoo Fast rotators/classical Be stars See review by Rivinius et al. (2013)

33 When your favorite star is actually a team... Nieva & Przybilla (2012)

34 Gonzales et al. (in prep) a triple system Identifying the individual component contributions to the spectra in different phases

35 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

The radial metallicity gradient from. OB star and HII region studies. Norbert Przybilla

The radial metallicity gradient from OB star and HII region studies Norbert Przybilla HII regions Intro emission-line spectra: He, C, N, O, Ne, S, Ar excited by OB stars present-day abundances T e ~ 10