Consistent Models of the Expanding Atmospheres of Hot Star
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1 Consistent Models of the Expanding Atmospheres of Hot Star Institute of Astronomy and Astrophysics at the Ludwig-Maximilian University Munich AWAP 05/19/05 1 May 19, 005 Adalbert W.A. Pauldrach Present Collaborators Tadziu L. Hoffmann LMU Department of Physics and Astronomy Daniel Sauer Max-Planck-Institute of Astrophysics, Garching Philip Hultzsch LMU Department of Physics and Astronomy
2 Consistent Models of the Expanding Atmospheres of Hot Star Observations Motivation Theory - Models non-equilibrium thermodynamics (NLTE) radiation hydrodynamics Boltzmann - equation f = t time development of the distribution functions f + v f + 1 t m F vf ic Application Spectral Diagnostics sub-group Low Mass Stars M CSPN (SN Ia) old, luminous, 10 L yr rare, evolution radiation, UV/EUV M v M yr Ring Nebula Hot Stars T eff = K show wind features Expanding Atmospheres characterized by WR14 M1-67 Massive Stars O/B (WR SN II) high radiation energy density 4000 km/s M v sub-group M young, 10 6 yr 6 luminous, 10 L rare,imf radiation, UV/EUV In this talk focus on the status of UV Spectral Diagnostics! AWAP 05/19/05
3 Hot Stars: Observations Emergent UV Spectra of O-type O Stars are Old Fashioned! Walborn, Nichols-Bohlin, Panek, 1985, NASA Ref. Publ. 1155; Morton and Underhill, 1977, Ap. J. Suppl. 33, 83 Typical UV Spectrum of a Massive Star - ζ Pup (O4If) Signatures of P-Cygni lines SVI,CIII,NIII,OVI,PV,NV,OIV,OV,SiIV,CIV,HEII,NIV Hundreds of strongly wind contaminated lines FeV, NiV, FeIV, FeVI, CrV, ArV, ArVI AWAP 05/19/05 3
4 Hot Stars: Old Fashioned or Trendy? Realistic Synthetic UV Spectra of O-type O Stars A Diagnostic Tool with great Astrophysical Potential!? NGC 686 Hot Stars ζ Puppis spectra of O-type CSPN s similar to spectra of massive O-type stars Spectra contain information about stellar and wind parameters and abundances Spectra available for > 5 years but most work done concentrated on qualitative results and arguments Powerful Tool for modeling realistic synthetic spectra for diagnostic issues is still in development! AWAP 05/19/05 4
![The Note relative the contribution characteristic of P-Cygni the ring lines to the CIV, total SiIV H+[NII] Steidelluminosity et al., 1996, Ap.J.L. is 94%!](/docs-images/91/105785498/images/5-4.jpg "46, L17 Distance:~1 Mpc located in the constellation of Coma Berenices. Hubble Space Telescope Section of the Hubble Deep Field (ca.")
5 Motivation: Galaxies and Galaxy Clusters are Trendy! Section of the Hubble Deep Field (ca.3') showing objects up to 8th magnitude Hubble Space Telescope Corresponding Barred-Spiral Spectrum Galaxy of a Starburst NGC 4314 Galaxy at z=3 Keck Showing spectrum a Nuclear of a z > Starburst 3 galaxy, Ring chosen - the to stars illustrate were the created variety within of features the past encountered. 5 million years For comparison diameter a recent of the HST ring: spectrum 300 pc! of the central It starburst is uncommon region to in find the a Wolf-Rayet ring of infant galaxy stars NGC414 so close is to the core also of shown. a galaxy. The Note relative the contribution characteristic of P-Cygni the ring lines to the CIV, total SiIV H+[NII] Steidelluminosity et al., 1996, Ap.J.L. is 94%! 46, L17 Distance:~1 Mpc located in the constellation of Coma Berenices. Hubble Space Telescope Section of the Hubble Deep Field (ca.3') showing objects up to 8th magnitude, giving an impression of the birthplace of galaxies and galaxy clusters (diameter several Mpc). The small blue objects are distant progenitors of nearby galaxies. Hubble Space Telescope Needful Things for diagnostic issues Synthetic UV Spectra of O-type O Stars Starburst Ring Dominated by Massive Stars AWAP 05/19/05 5
6 Motivation: Reionization of the universe End of Cosmic Dark Ages absence of Gunn-Peterson trough in the spectra of high-redshift quasars implies that the universe was reionized at a redshift of z ~ 6 Fan et al., 000, AJ, 10, 1167 Gnedin, 000, ApJ, 535, 530 Population III stars (Z<10-3 ) are important for the reionization Carr et al.,1984,apj 77, 445 but ionization history of the IGM depends crucially on the IMF of the First Stars Bromm et al., 1999, ApJ, 57, L5 AWAP 05/19/05 6 Numerical simulation of the first stars in the universe Davé, Katz, Weinberg, 00, ApJ, 579, 3
7 First generations of Stars: Ionization Efficiency of a Heavy Initial Mass Function In the Early Universe Population III stars favoured the formation of very Massive Stars M > 100 M 1000 M > < 300 M IMF becomes top-heavy Normalized spectral energy distribution in the continuum M Z=0 Per unit mass the spectra attain an universal form for M>300 M Bromm, Kudritzki et al., 001, ApJ, 540, 687 The enormous amount of UV and EUV radiation of these stars can change the status of the universe to become reionized again Two points are missing: observations for starbursting galaxies at high redshift and Synthetic UV Spectra of O-type Stars for metallicities Z >0 Predicted flux from a Population III star cluster at z=10 A flat universe with Ω Λ = 0.7 is assumed. The cutoff is due to complete Gunn-Peterson absorption (1965, ApJ, 14, 1633). Observable flux is larger by an order of magnitude for the case of the heavy IMF Bromm, Kudritzki et al., 001, ApJ, 540, 687 the flux of very massive stars can contribute the decisive part to the unexplained deficit of ionizing photons AWAP 05/19/05 7
8 Motivation: The impact of massive stars on their Environment Hubble Space Telescope Starburst Cluster Dominated by Massive Stars Giant Gaseous Nebula Massive Stars dominate the life cycle of gas and dust Giant Galactic Nebula NGC 3603 various stages of the life cycle of stars are.captured Hubble Space Telescope Near the center of the view is a Starburst Cluster dominated by young, early O-type stars The Interaction of ionizing radiation with cold molecular-hydrogen cloud material results in the giant gaseous nebula structures to the right of the cluster. In the Carina spiral arm of the Galaxy at a distance of about 6 kpc field.5 x.5 arcmin (~ 6 x 6 pc ) Massive stars dominate the life cycle of gas and dust in several types of galaxies Interaction leads to chemical enrichment of the ISM large amount of momentum and energy input into the ISM basis for star formation Realistic Spectral Energy Distributions of massive stars and stellar clusters are required to analyze the excited HII regions AWAP 05/19/05 8
9 Ultimate test: comparison of observed and synthetic UV spectra of hot stars Ionizing flux of ζ Puppis (O4If) small vertical lines indicate the ionization edges for all important ions! UV Spectra of O Stars: test involves hundreds of spectral signatures of different ionization stages ionization stages depend on ionizing radiation influence can be traced by UV spectral lines! AWAP 05/19/05 9
10 Motivation: SNIa as distance indicators SNIa are Standard Candles! surprising result: Distant SNe Ia appear fainter than a standard candle in an empty Friedmann model of the universe! NGC 456 Galaxy in Virgo SNIa-luminosity distances indicate accelerated expansion! SN 1994D Are SNIa Standard Candles independently of age? Or is there some evolution of SNIa-luminosity with age? Observations: 4 High-z Supernovae imaged with HST Are SNIa Standard Candles? Spectroscopy is a powerful tool to search for differences! AWAP 05/19/05 10
11 Motivation: Observed spectra of Supernovae Type Ia at early phases SN 199A at early phases ~ 5 days after B maximum Early epochs ( < weeks after maximum): No hints for H and He lines Prominent absorption features of mainly intermediate mass elements embedded in a non-thermal pseudo continuum (SiII, OI, SII, CaII, MgII...) photospheric epoch Characteristic P-Cygni line profiles blue-shifted absorption red-shifted emission broad lines high ejecta velocities HST spectrum of 4. Jan. 199 from Kirshner et al., 1993, ApJ 415, 589 Are SNe Ia standard candles in a cosmological sense? Required: Realistic Models and Synthetic Spectra of Type Ia Supernovae AWAP 05/19/05 11
12 Motivation: Conclusion Hot Stars play an important role in Astrophysics they dominate the physical conditions of galaxies and the life cycle of gas and dust chemical enrichment of the ISM - significant impact on chemical evolution large amount of momentum and energy input into the ISM - major dynamical role relevance to cosmological issues Realistic Synthetic UV Spectra of Hot Stars are still relevant for current astronomical research research! AWAP 05/19/05 1
13 Concept for consistent models of hot star atmospheres theoretical basis Lucy L. B., Solomon P., 1970, ApJ 159, 879 Castor J.I., Abbott D.C., Klein R.: 1975, ApJ 195, 157 Theory in its present stage key aspects of theoretical activity basic theoretical ideas Milne E.A., 196, MNRAS 86, 459 Sobolev V., 1957, Sov. A&A J. 1, 678 aspects of radiative transfer Rybicki, G.B., 1971, JQSRT 11, 589 Hummer, D.G., Rybicki, G.B., 1985, ApJ 93, 58 X-rays and wind shocks Cassinelli, J., Olson, G., 1979, ApJ 9, 304 Lucy L. B., White,R., 1980, ApJ 41, 300 Owocki S., Castor, J., Rybicki, G. 1988, ApJ 335, 914 Previous fundamental work was essential to elaborate the theory AWAP 05/19/05 13 basis of our theoretical framework Pauldrach, A.W.A., Puls, J., Kudritzki, R.P.,1986, A&A,164,86; Pauldrach, A.W.A., 1987, A&A, 183, 95 Puls, J., Pauldrach, A.W.A., 1990, PASPC 7, 03; Pauldrach, A.W.A. et al., 1994, A&A, 83, 55 Feldmeier, A. et al., 1997, A&A 30, 899; Pauldrach, A.W.A. et al., 1998, ASPCS 131, 58 Pauldrach, A.W.A., Hoffmann, T.L., Lennon, M., 001, A&A, 375, 161
14 Theory: Motivation E=0 Energy in GNs radiative processes are not balanced in detail! thermodynamic equilibrium can not be established! main processes: e - s p x months = E=0 Energy 10-8 s e s p ~ 100 yr bound states levels ev Hydrogen 1s ev Hydrogen 1s 1 T Disadvantage of NLTE: non local problem! dv 1, T 1 dv, T Photons r just ground states are occupied no thermodynamic equilibrium (TE) instead Non-Equilibrium Thermodynamics (NLTE) described by a well defined mixture of macroscopic and microscopic physics Transport Theory Thermodynamics Quantum Mechanics Advantage of TE: In TE state of the gas completely described by macroscopic variables local problem! * n i = n i( ρ, T ) * n i = occupation numbers of bound levels 3 (number of particles per cm ) n i follows from Boltzmann statistics α1k ( ν) n14π J νdν = npneα hν ν 1k R ionization equation 1 r J ν = n1α1k r r J ν ( + η ) the equation of transfer in spherical symmetry ν Integro-Differential Equation AWAP 05/19/05 14
15 Theory: Motivation 0 Energy Transitions in atoms/ions j i j 1 1 bound-bound transitions excitation and de-excitation radiative/collisional rates R ij, C ij bound-free transitions ionization and recombination processes R ik, C ik -E ion de-population n population KiPij nkjpji of level i [ 1 3 ] cm s 0-th moment of distribution function f Ki for each element K, level i + f Ki ( n u ) = d 3 v = n Pji t - ic yields net rate of changes for each Ki, Ki Kj Ki j i j i n P ij : Nonequilibrium thermodynamics is a rather esoteric field of physics that we would do well to avoid! T Disadvantage of NLTE: non local problem! dv 1, T 1 dv, T Photons r Non-Local Thermodynamic Equilibrium (NLTE) described by a well defined mixture of macroscopic and microscopic physics Transport Theory Thermodynamics Quantum Mechanics AWAP 05/19/05 15
16 T eff R log g Z Concept for consistent models of hot star atmospheres M v(r) synthetic spectra AWAP 05/19/05 16
17 Concept for consistent models of hot star atmospheres well-elaborated atomic models are required in order to avoid GIGO Rate Equations NLTE Models require atomic data for lines, collisions, ionization, recombination Essential for occupation numbers, line blocking, line force Accurate atomic models have been included 6 elements 149 ionization stages 5,000 levels ( + 100,000 ) 0,000 diel. rec. transitions b-b line transitions Auger-ionization recently improved models are based on Superstructure Eisner et al., 1974, CPC 8,70 AWAP 05/19/05 17
18 Concept for consistent models of hot star atmospheres SN 199A EUV line blocking and blanketing: drastic effects on ionization excitation and emergent flux ζ Puppis (O4If) P P NP P j I l + Z i Z 1 I r r 1 ϑ ii reason: the velocity field shifts at different radii up to 1000 spectral lines into the line of sight at the observer s frequency Radiative Transfer P NC+1 r 1 =R max r ND =1 core Z Observer R ϑ n P=Rsinϑ P = Rsin ϑ P = R (1 μ ) PdP = R μd μ Numerical integration on this grid: Z i ( r Z i Pj ) Optical depth τ = κ = + dz Emergent intensity I S e d S w Emergent flux H R I P PdP I w i Z 1 τ max i max + τ j = ( τ ) τ = l i τ = 0 i= 1 Rmax NP max = ( ) j = P= 0 j= 1 j AWAP 05/19/05 18
19 Concept for consistent models of hot star atmospheres radiative emission of shock-cooling cooling zones: ζ Puppis (O4If) influence on rate equations and radiative transfer with respect to high ionization stages OVI A semi-empirical approximation for the emission coefficient is used Comparison to ROSAT observations Pauldrach, Hoffmann, Lennon, 001, A&A, 375, 161 AWAP 05/19/05 19
20 Solution of the system Tool for spectrum synthesis O supergiant model T eff = K log g = 3.6 R 18 R = Are the models realistic? Strategy for quantitative spectral UV analysis flux conservation versus Rosseland optical depth and iteration block number flux conservation is on the 1% level AWAP 05/19/05 0
21 Results: Synthetic and observed spectra of Supernovae of Type Ia Comparison to observations verification of explosion models Constraints for Abundances Velocity-structure Density-structure T R Z v L eff = K = 9900 R = Z W7 = 000 km/s = Steps The present towards method realistic is already models on a quantitative level! 9 L SN 199A at early phases ~ 5 days after B maximum Models based on W7 explosion model averaged chemical composition above the photosphere Nomoto et al, 1984, ApJ. 86, 644 Nugent et al., 1997, ApJ. 485, 81 Pauldrach et al., 1996, A&A 31, 55 Sauer and Pauldrach, 00, Nuclear Astrophysics, MPA/P13 AWAP 05/19/05 1
22 Results: Synthetic and observed spectra of Supernovae of Type Ia Diffusion approximation - standard for inner boundary : Problem H I 0 ν max 0 ( B 3μH ) + τ = ν + ν 1 db ν ( R) = 3 κ dr ν ( τ max ) Logarithm of the total opacity versus velocity and wavelength of a SN Ia model Sauer and Pauldrach, 005, A&A Main features of the spectrum are fairly well reproduced especially in the blue and UV range However, Some features are too deep HST spectrum of 4. Jan. 199 from Kirshner et al., 1993, ApJ 415, 589 Model Sauer and Pauldrach, 00, Nuclear Astrophysics, MPA/P13 AWAP 05/19/05
23 AWAP 05/19/05 3 Modified diffusion approximation for Supernovae of Type Ia Modified diffusion approximation for inner boundary : Diffusion approximation - standard for inner boundary : + 0 I τ = ( J ) max ν + 3μH ν ( τ max) + 0 I τ = ( B ) max ν + 3μH ν ( τ max) after some calculation 0 1 db ν * df ν 3τ ν db ν * 0 1 db ν H ν( R) = ( + C ν( τν) ) J ν( + 1) + τ ν( + C ν( τν) 3 κ dr dr R dr ) H ν ( R) = ν κν κν κ 3 κ ν νdr and C ν β ν q f s Modifications to the inner boundary that allow ν ν J ν( τ ν) = Bν( τ ν) + e qf (, ντ) r deviations of the radiation field from thermal equilibrium conditions with is considered. * Bν J ν 3fν 1 dfν C ν β ν q fν s The dominating contribution from ν C ν( τ ν) = ν q fν e f + + β ν rκ ν κ νdr fr Thomson scattering ν is explicitly taken into account and dqf ν( τ) B ν( τ) B ν( τ 0 ν) + j ν( τ 0 ν) P τ = τ tot τ = τ max τ = 0 ds ν Z min Z max τ 0 ν β ν q fνs0 ν C ν = e I + I + I I ( 1 qf ν) τ + j ( 0 0 ) q f ν ν τ ν β ν ν τ = τ max τ = 0 J ν( τ 0 ν) where j ν( τ 0 ν) = H ν( τ 0 ν) Z r 3 fr ( ) 1 with the Eddington factor fν = K ν / J ν and the sphericality factor r q( r) = exp dr rf ( r ) 1 κ ν with the Thomson opacity: κe = n eσe, ηe = κej and βν( τν) = κν + κe and S η κe ηe t = + = S + κ κ + κ κ + κ κ e e e rmax anddsν = qκνdr, sν = qκνdr r moments of the radiation field Th J Z max anddτν = κνdz, τν = κνdz Z th: J = I( μ) dμ J r J H I( μ) μdμ H r H K I( μ) μ dμ K r K, = 1st: = = = =, nd:, μ= 1 μ= 1 μ= 1 Equation of radiative transfer d + ( I + I )( τ) + = ( I + I )( τ) S ν( τ) dτ iterated with moment equation of radiative transfer d ( qfj ) ds 1 = q ( J S)
24 Results: Synthetic and observed spectra of Supernovae of Type Ia Improvement? Sauer and Pauldrach, 005, A&A AWAP 05/19/05 4 Improvement is striking! Sauer and Pauldrach, 00, Nuclear Astrophysics, MPA/P13 Primary objective: search for spectral differences between local and distant SNe Ia! Are SNe Ia standard candles in a cosmological sense?
25 Empirical wind models for the O-supergiantO ζ Puppis dynamical structure, occupation numbers, and temperature structure are assumed approximate treatment of line radiative transfer start to examine the UV-spectrum of ζ Puppis improved treatment of line radiative transfer first: improvements of UV-line fits which followed from stepwise improvements of the method used Hamann, 1980, A&A 84,34 Lamers and Morton, 1976, Ap.J.S. 3, 715 A more consistent treatment of expanding atmospheres is required for a detailed analysis AWAP 05/19/05 5
26 Consistent wind models of the O-supergiantO ζ Puppis line blanketing neglected - approximated temperature structure approximate treatment of line blocking simple treatment of shocks approximate treatment of line blocking no shocks improved treatment of line blocking and shocks OVI CIII Pauldrach, 1987, A&A, 183, 95; Puls, 1987, A&A, 184, 7 Pauldrach et al., 1994, A&A, 83, 55 A more realistic treatment of expanding atmospheres is required for a detailed analysis AWAP 05/19/05 6
27 Detailed analysis of the hot O-supergiantO ζ Puppis final step Values Determined: stellar parameters T eff log g R R v rot (km/s) 10-6 M yr = 40 = 3.40 = 8. = 0. wind parameters v M (km/s) kk. = 13 7 = 10. state of the art models for expanding atmospheres along with spectrum synthesis techniques allow the determination of stellar parameters, wind parameters, and abundances Pauldrach, 003, Reviews in Modern Astronomy, Vol. 16 AWAP 05/19/05 7 abundances C C NN OO Si Si S S Fe Fe Ni Ni = 1.50 = 5.00 = 0.10 = 7.00 = 0.50 =.00 =.00 present method of quantitative spectral UV analyses of hot stars leads to realistic models!
28 Realistic Spectral Energy Distribution of ζ Puppis quantitative spectral UV analyses: ultimate test for the accuracy of theoretical ionizing fluxes Realistic Spectral Energy Distributions AWAP 05/19/05 8
29 Detailed analysis of the cool O-supergiantO α Cam T eff log g RR = 9 kk = 3.00 = M yr v CC NN OO PP SS Fe Fe Ni Ni M (km/s) = 5.0 = = 0.05 = 1.00 = 0.30 = 0.05 = 1.00 = 1.50 = 1.50 Spectrum synthesis technique allows the determination of T eff (within 1000 K ), log g (within 0.05), R (within 1.0), and the abundances (within a range of 0%) Pauldrach, Hoffmann, Lennon, 001, A&A, 375, 161 AWAP 05/19/05 9
30 Wind momentum luminosity relation winds driven by radiation mechanical momentum of wind flow mostly a function of photon momentum M v R 1 3 L M obs (R/R ) 0.5 relation is independent of M! v obs NGC 686 C IV ( λλ1548,1551å) Same physics involved in CSPN winds as in massive O-star winds! λ v o 17Å c H α M = M yr Puls et al., 1996, A&A 305; Kudritzki et al.,1997, IAU Symp. 180 v can be measured directly M M = = M M yr yr independent tool for measuring extragalactic distances up to Virgo and Fornax AWAP 05/19/05 30
31 Wind momentum luminosity relation of massive O-starsO But, Mass is still unknown! However, wind dynamics of spectral analysis yields M and consistently v M, R α-cam ζ-pup observed behaviour of wind momentum is represented by improved models M v R 1 3 L observed values from Puls et al., 1996, A&A 305; Kudritzki et al.,1997, IAU Symp. 180 AWAP 05/19/05 31 Pauldrach, Hoffmann, Mendez, 004, A&A, 419, 1111
32 Wind properties of massive O-starsO ζ-pup v v GM R ( 1 Γ) esc = - 1 α -Cam Realistic models are characterized by quantitative spectral UV analysis calculated along with consistent dynamics α -Cam ζ-pup predicted terminal velocities of improved models agree within 10% with observed values predicted mass-loss-rates of improved models agree within a factor of with observed optical values M L AWAP 05/19/05 3 Pauldrach, Hoffmann, Mendez, 004, A&A, 419, 1111 M, R
33 Conclusions Consistent state of the art models for expanding atmospheres of hot stars a diagnostic tool* with great astrophysical potential?! Massive Stars O/B (SN II) stellar parameters wind parameters abundances ionizing fluxes Low Mass Stars CSPN (SN Ia) comparison of synthetic and observed UV spectra T, M, L, Z eff v, R, M d Analysis of integrated synthetic spectra of galaxies based on population synthesis is feasible stellar content, IMF, SFR, Z, burst age AWAP 05/19/05 33 * download of the program package -including an easy to use interface- is possible from
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