How to explain metallicity dependence??

Transcription

1 Winds of massive stars all massive hot stars with L/L sun > 10 4 highly supersonic, strong winds basic properties explained by theory of line driven winds Mv R 1 2 L 1.8 [Z] 0.8 v 3v phot esc [Z] 0.15 v phot esc = {2G M (1 Γ) R } 1 2 Kudritzki & Puls, 2000, ARAA 38, 613 How to explain metallicity dependence??

2 Hydrodynamics of stationary line driven winds Ṁ =4πr 2 ρ(r)v(r) v(r) dv(r) dr =- 1 ρ(r) dp gas (r) dr g(r)+g rad (r) g rad (r) =g Th rad + gbf,ff rad + g lines rad

3 Contribution by one line i at ν i g i rad = photon momentum absorbed by line i time mass = 1 c L ν i (1 e τ i )dν 1 4πr 2 ρdr τ i dν = ν i dv c g Th rad (r) = n eσ e L c4πr 2 ρ g i rad =gth rad 1 c ν i L νi (1 e τ i ) 1 dv L n e σ e dr M i

4 g lines rad = gth rad M(t) line force multiplier M(t) = v th 1 c t P i ν i L νi L (1-e τ i ) τ i (r) =k i t(r) line optical depth k i = χ i(r) n e σ e n lower n e f lu λ i line strength t= n e σ e v th dv/dr optical depth parameter

5 depth dependence of line force M(t) M(t) = v th 1 c t P i ν i L νi L (1-e τ i ) τ i (r) =k i t(r) t= n e σ e v th dv/dr 2 extreme cases: k max = max {k i }, k min = min {k i } t t s = k 1 max M (t) = M max P i ν i L νi L k i = const. t t m = k 1 min M (t) = 1 t 1 n e dv dr optical thickness of lines is crucial!

6 line strength distribution function n(k,ν)dνdk k α 2 dk atomic line lists, NLTE: {k i } for some 10 6 lines power law T eff = K α = 0.65 see Puls et al. 2000, A&AS 141, 23 for detailed discussion

7 depth dependence of line force n(k,ν)dνdk k α 2 dk M(t) 1 t P i ν i L νi L (1-e k it ) M(t) N eff 1 t R kmax 0 {1 e tk }k α 2 dk log n(k) log M(t) slope: α -2 k max ~ 10 8 log k M(t) N eff t α N eff M max k α max t s M max slope: -α log t

8 v(r) dv(r) dr =- 1 ρ(r) t= n e σ e v th dv/dr dp gas (r) dr g(r){1+γm (t α )} non-linear eq. of motion M N 1 α eff L 1 α {M (1 Γ)} 1 1 α v 2.24 α 1 α vphot esc Mv R 1 2 v phot esc = {2G M (1 Γ) R } 1 2 N 1 α eff L 1 α analytic solutions, scaling relations Castor, Abbott, Klein, 1975 Kudritzki et al. 1989, Puls, Kudritzki et al., 1996, Kudritzki & Puls, 2000

9 H α fits with hydrodynamic NLTE models M Variation of by ± 20% Ṁ Kudritzki & Puls, 2000, AARA 38, 613

10 fit of v ± 5% accuracy Kudritzki & Puls, 2000, AARA 38, 613

11 Kudritzki & Puls, 2000, AARA 38, 613 data from Prinja & Massa (1998), Lamers et al., (1995)

12 Stellar wind momenta: O-stars and CSPN Kudritzki & Puls, 2000 Kudritzki et al., 1997

13 New WLR: O-stars and CSPN (blanketing) Repolust, Puls, Herrero, 2004 Markova, Puls, Repolust, Markov, 2004 Kudritzki, Urbaneja, Puls, 2006

14 theoretical wind momenta calculated observed regressions calculations by Kudritzki, 2002, ApJ 577, 389

15 Wind momentum luminosity relationship (WLR) Rome 2005 Mv R 1 2 = const.l 1 α α 2 3 Predicted by wind theory zero point and slope alpha confirmed and calibrated empirically Kudritzki et al., 89 Puls et al., 96 Kudritzki et al., 1999 Kudritzki & Puls, 2000

16 Stellar wind momenta: B and A supergiants Kudritzki & Puls, 2000 Kudritzki et al., 1999

17 Concepcion 2007 WLR for A-supergiants distances Kudritzki et al., 1999 Bresolin et al., 2001

18 metallicity log n(k) Z=Z sun k=k Z Z k max = k max Z Z log M(t) M max Z=Z sun Z<Z sun k max log k M max = M max Z Z t s Z<Z sun log t N eff = N eff { Z Z } 1 α M(t) { Z Z } 1 α t α Ṁ = Ṁ { Z } 1 α α Z Abbot, 1982 Kudritzki et al., 1989 Puls, Kudritzki et al., 1996

19 curvature of line strength distribution function log n(k) α-2 average power law fit real distribution α-2 consequences: log k contribution to M(t) mostly from lines with τ = k t = 1 M(t) t α(k= 1 t ) for lower metallicity weaker winds larger k contribute α smaller k ~ Z/Z sun distribution shifts α smaller v { Z } x Z Ṁ { Z } m Z α smaller! but no unique exponent!

20 Complication: M (t, n e /W) T eff = 50000K, Z = Z_sun n e /W

21 ionization changes through wind: N eff { n e(r) W (r) }δ log n(k) log M(t) n e /W n e /W log k log t M(t) { n e(r) W (r) }δ t α Ṁ N 1 α δ eff L 1 α δ Ṁ { Z } 1 α α δ Z v α 1 α e 2δ v esc δ 0.05 to 0.1 Kudritzki et al., 1989 Puls et al., 1996, Kudritzki & Puls, 2000

22 numerical calculations Kudritzki et al., 1987 Z/Z_sun = M { Z Z } 0.6±0.1 v { Z Z } 0.15 Leitherer et al., 1992 Z/Z_sun = Ṁ { Z Z } 0.8±0.1 v { Z Z } 0.13 Vink et al., 2001 Z/Z_sun = Ṁ { Z Z } 0.69±0.1

23 data from: Puls & Kudritzki, 2000 Crowther et al., 2002 Hillier et al., 2003, Repolust et al., 2004 Markova et al., 2004 Evans et al., 2004 Massey et al., 2004 Massey et al., 2005 Martins et al., 2004 Bouret et al., 2005

24 data from: Puls & Kudritzki, 2000 Crowther et al., 2002 Hillier et al., 2003, Trundle et al., Evans et al., 2004 Massey et al., 2004 Massey et al., 2005

25 O-star wind momenta new: MW, LMC, SMC without wind clumping observed LMC SMC theory Vink et al., 2001 MW Mokiem, dekoter, Puls et al. 2006, A&A 441, 711

26 WLR: theoretical [Z] dependence calculated calculations by Vink et al., 2002 observed SMC regression calculations by Kudritzki, 2002, ApJ 577, 389

27 NGC 300: A supergiants WLR Rome 2005 Wind analysis 6 late B, early A-type supergiants Bresolin, Kudritzki et al., 2003

28 WLR: A supergiants Bresolin, Kudritzki et al., 2001, 2003 Rome 2005 B + A spectral types plot vs M v ignores B.C. need plot vs. M bol NGC 3621 NGC 3621 and NGC 300 objects have lower metallicity Theory (Kudritzki, 2003) predicts shift of WLR to dotted line

29 Winds, ionizing fluxes and spectra of the first generations of very massive stars in the early universe Rolf-Peter Kudritzki Institute for Astronomy, University of Hawaii Kudritzki & Puls, 2000, ARAA 38, 613 Kudritzki et al., 2000, ApJ 536, 19 Bromm, Kudritzki, Loeb, 2001, ApJ 552, 464 Kudritzki, 2002, ApJ 577, Marigo, Chiosi, Kudritzki, 2003, A&A 399, 617 Rix, Pettini, Leitherer, Bresolin, Kudritzki, Steidel, 2004, ApJ 615, 98

30 Introduction evolution of galaxies in early universe heavily influenced by first generations of very massive stars cosmic z=3.5 Springel & Hernquist, 2003 WMAP very massive stars

31 Z/Z sun 10-3 star formation preferably stars with 1000 M sun > M > 100 M sun hydro-simulations: Abel et al., 2000, 2002 Bromm et al., 2000, 2002 contribution to redshift 20 > z > 6 progenitors of GRBs at high redshift Carr et al. 1984, Couchman & Rees 86, Haiman & Loeb 1997, Bennet et al. 2003, Spergel et al. 2003, Becker et al. 2001, Fan et al., 2001, Springel & Hernquist 2003 Bromm & Loeb 2002, Ciardi & Loeb 2001, Kulkarni et al. 2000, Djorgovski et al. 2001, Lamb & Reichart 2000 extreme Ly-α emitters at high redshift Kudritzki et al. 2001, Rhoads & Malhotra 2001 Malhotra & Rhoads 2002, Hu et al. 2003

32 The first stars in the universe - clues from hydrodynamic simulations Hydrodynamic simulations by Davé, Katz, & Weinberg Ly-α cooling radiation (green) Light in Ly-α from forming stars (red, yellow) z=10 z=8 z=6

33 Stars forming at z=10! Observable with a 30m telescope! 1 Mpc (comoving) GSMT Science Working Group Report, 2003, Kudritzki et al. Simulation As observed through 30-meter telescope R=3000, 10 5 seconds, Barton et al., 2004, ApJ 604, L1

34 A possible IMF diagnostic at z=10 HeII (λ1640 Å) Standard IMF HeII (λ1640 Å) Top-Heavy IMF, zero metallicity (IMF + stellar model fluxes from Bromm, Kudritzki, & Loeb 2001, ApJ 552,464)

35 questions evolution? spectra? ionizing fluxes? recombination lines? winds? old work M {Z/Z } for 0.01 Z/Z 3 Kudritzki et al. 1987, Leitherer et al. 1992, Vink et al., 2001

36 g lines rad = gth rad M(t) line force multiplier M(t) = v th 1 c t P i ν i L νi L (1-e τ i ) τ i (r) =k i t(r) line optical depth k i = χ i(r) n e σ e n lower n e f lu λ i line strength t= n e σ e v th dv/dr optical depth parameter

37 for very weak winds t=n e σ e v th dv/dr << 1 M(t) = v th 1 c t P i τ i = k i t(r) < 1, for all lines if t -1 > k max ν i L νi L (1-e τ i ) M max = v th c Pi ν i L νi L k i 2000 Z = 1 (Gayley, 1995) since for metal lines k i = k i Z Z M max = 2000 Z Z + M H,He

38 necessary for wind (at very low metallicity): g(r)-g rad (r) =g(r)[1 Γ{1+M (t)}] 0 Γ = g Th rad (r)/g(r) Γ Γ min = 1 1+M max = { Z Z + M H,He } 1 Z/Z sun Γ min / /6 minimum Γ for existence of line driven winds winds only very close to Eddington-limit!!

39 Winds at very low metallicities a challenge log M(t) Z Z 10 2 saturation of M(t) at high t k max t 1 strong curvature of M(t) n e /W influences curvature n e /W force multipliers α, δ depth dependent log t M(t) { n e W }δ(t, n e W ) t α(t, n e W ) new approach needed!!!

40 M(t,Z) T eff = 50000K α(t,z) M(t), α(t), δ(t) Z/Z sun = δ(t,z) Kudritzki, ApJ 577, 389, 2002 millions of lines in NLTE

41 α (t, n e /W) T eff = 50000K Z/Z sun = 10-4 Kudritzki, ApJ 577, 389, 2002

42 δ (t, n e /W) T eff = 50000K Z/Z sun = 10-4 Kudritzki, ApJ 577, 389, 2002

43 line driven winds with depth dependent line force multipliers v(r) dv(r) dr =- 1 ρ(r) dp gas (r) dr g(r){1+γm } M=M(t α(t,n e/w ), (n e /W ) δ(t,n e/w ) ) t= n e σ e v th dv/dr For details of numerical of numerical solution including singularity and regularity conditions at critical point see Kudritzki, ApJ 577, 389, 2002

44 wind models for evolved very massive stars at very low metallicity 10 4 Z/Z 1 100M M 300M 40000K T eff 60000K winds ionizing fluxes spectra

45 the model grid M/M sun

46 log M dot vs log Z M/M sun not a power law!!!! analytical formula for M dot = f(l,z) given by Kudritzki, 2002 Kudritzki, ApJ 577, 389, 2002

47 v /v esc vs log Z M/M sun Kudritzki, ApJ 577, 389, 2002

48 wind momentum vs log L Z/Z sun Kudritzki, ApJ 577, 389, 2002

49 wind energy vs log Z M/M sun Kudritzki, ApJ 577, 389, 2002

50 Ionizing fluxes: T eff = 60000K, M/M sun = 250 Z = 1.0 Z = 10-4 Kudritzki, ApJ 577, 389, 2002

51 Ionizing fluxes: T eff = 60000K, M/M sun = 250 HeII NeII HeI H CIII OII bound-free edges for ionizing photons Kudritzki, ApJ 577, 389, 2002

52 Number of ionizing photons:t eff = 50000K, M/M sun = 300 Kudritzki, ApJ 577, 389, 2002

53 ionizing fluxes vs. metallicity, luminosity H and He I ionizing photons unaffected O II, Ne II, C III photons moderately affected He II photons strongly affected

54 120 M sun 300 M sun 40000K 40000K 50000K 50000K 60000K 60000K

55 Spectra:T eff = 50000K, M/M sun = 250 Z/Z sun N V O V C IV He II Kudritzki, ApJ 577, 389, 2002

56 Spectra: T eff = 60000K, M/M sun = 250 Z/Z sun N V O V C IV He II Kudritzki, ApJ 577, 389, 2002

57 UV line spectra line diagnostics possible down to Z/Z sun = 10-4 GSMT JWST wind features disappear at Z/Z sun = 10-3

58 Applications evolution of massive Pop III stars low metallicity starburst galaxies at high z the first stars in the re-ionization epoch

59 Applications evolution of massive Pop III stars low metallicity starburst galaxies at high z the first stars in the re-ionization epoch

60 Evolution of massive Pop III stars with mass-loss Marigo, Chiosi, Kudritzki 2003, A&A 399, 617

61 Final stages of massive Pop III stars He & CO cores at C ignition Marigo, Chiosi, Kudritzki 2003, A&A 399, 617 initial mass

62 He enrichment of ISM He enrichment Marigo, Chiosi, Kudritzki 2003, A&A 399, 617 star formation efficiency

63 He vs Z enrichment of ISM He enrichment Marigo, Chiosi, Kudritzki 2003, A&A 399, 617 metallicity enrichment

64 Applications evolution of massive Pop III stars low metallicity starburst galaxies at high z the first stars in the re-ionization epoch

65 Spectral diagnostics of high-z starbursts Starburst models - fully synthetic spectra based on model atmospheres Rix, Pettini, Leitherer, Bresolin, Kudritzki, Steidel, 2004, ApJ 615, 98

66 Spectral diagnostics of high-z starbursts z=2.7 fully synthetic spectra vs. observation Rix, Pettini, Leitherer, Bresolin, Kudritzki, Steidel 2004, ApJ 615, 98

67 Applications evolution of massive Pop III stars low metallicity starburst galaxies at high z the first stars in the re-ionization epoch

68 Main sequence of the first stars Bromm, Kudritzki, Loeb ApJ 552, 464, 2001

69 Spectra and SEDs of the first stars Bromm, Kudritzki,Loeb,ApJ 552, 464, 2001

70 L ν / M is almost constant!!! Bromm, Kudritzki, Loeb ApJ 552, 464, 2001

71 SED of a cluster of 10 6 stars at a redshift of 10 Bromm, Kudritzki, Loeb ApJ 552, 464, 2001

72 First very massive stars - conclusions generic SEDs ~ BB with T 10 5 K rich H and HeII spectra L ν /M independent of stellar mass for M 200 M_sun N phot (H)/M stars factor ten larger than for Salpeter IMF (HeII) hundred H and HeII recombination lines observable with 30m predicted continuum spectra for 10 6 M sun cluster at z=10 - detectable with JWST - SEDs, colors different from Salpeter IMF Bromm, Kudritzki, Loeb ApJ 552, 464, 2001 Schaerer, A&A 397, 527, 2003

73 Stars forming at z=10! Observable with a 30m telescope! 1 Mpc (comoving) GSMT Science Working Group Report, 2003, Kudritzki et al. Simulation As observed through 30-meter telescope R=3000, 10 5 seconds, Barton et al., 2004, ApJ 604, L1

74 A possible IMF diagnostic at z=10 HeII (λ1640 Å) Standard IMF HeII (λ1640 Å) Top-Heavy IMF, zero metallicity (IMF + stellar model fluxes from Bromm, Kudritzki, & Loeb 2001, ApJ 552,464)

75 Instabilities a few extremely low M dot models may suffer from de-coupling of H,He and metals (Kudritzki 2002, Krticka et al. 2003) heating of winds or fallback of material strong increase of force multiplier parameter δ bi-stability of radiative line force pulsational instabilities important for very massive stars, however see Baraffe, Heger & Woosley (2001): much weaker at low Z rotation rotationally induced mass-loss (Maeder,Meynet) close to Γ = 1 Shaviv, Owocki, Gayley porosity??

76 δ (t, n e /W) Kudritzki, ApJ 577, 389, 2002

77 Instabilities a few extremely low M dot models may suffer from de-coupling of H,He and metals (Kudritzki 2002, Krticka et al. 2003) heating of winds or fallback of material strong increase of force multiplier parameter δ bi-stability of radiative line force pulsational instabilities important for very massive stars, however see Baraffe, Heger & Woosley (2001): much weaker at low Z rotation rotationally induced mass-loss (Maeder,Meynet) close to Γ = 1 Shaviv, Owocki, Gayley porosity??