Vapor growth/evaporation of Mg-silicate under protoplanetary

Transcription

1 CPS seminar 3/6/2013 原始惑星系円盤でのマグネシウムケイ酸塩気相成 長と蒸発 Vapor growth/evaporation of Mg-silicate under protoplanetary disk conditions: Experimental study Shogo Tachibana Dept. of Natural History Sciences, Hokkaido Univ. HOKKAIDO UNIVERSITY

2 Material Circulation in the Galaxy Dense molecular clouds Blue supergiant Sher 25 Starburst cluster Giant pillars Proplyds NGC3603

3 Material Circulation in the Galaxy log MSun [kpc y ] 10 Stars AGB(M) AGB(S) SNe II SNe Ia AGBs AGB(C) OB Interstellar Medium PP disks RSG LBV WCL Molecular Clouds Journey of Dust Dust in the interstellar medium medium 2.1 Dust in the interstellar -1-1 Novae SN AGBs AGB(M (M) ) AGB(S (S) ) AGB(C (C) ) OB OB RSG RSG LBV LBV gas WCL WCL carbon dust carbon dust Novae ae Nov gas silicate dust silicate dust peculiar dust peculiar dust SN SNe types in solar nt stellar return rate by di ere Fig Dust production and gas mass Gail & Hoppe (2010) types in solar stellar nt ce di ere by rate return mass tion andatgas Dust produc Fig. mainly produ Stars cycle. solar the galaxy the in kpc masses per year and 2 e mainly produc cycle.ialstars solarmater at the the galaxy in and kpc year per masses, formed is dust of kind nt di ere a cases some in only dust; silicate or carbon al is formed, materi of dust kind nt a di ere some cases indust). only dust; carbon or silicate nents compo dust onal additi Many iar (pecul alloy iron some or probably iron components nal sdust additio Many dust). iar (pecul iron alloy or some ly iron probab 1999; Tielen from (Data cases most in formed are ance abund r smalle with much dance are formed in most cases (Data from Tielens 1999;

4 Material Circulation in the Galaxy SNe II Stars SNe Ia AGBs Interstellar Medium Molecular Clouds PP disks Material Supply Rate Acceleration Mass-loss wind Dust formation Evolved star Dust: Key for the Galactic Chemical Evolution

5 Material Circulation in the Galaxy Stars Interstellar Medium PP disks SNe II SNe Ia AGBs Molecular Clouds Dust: Building block of planets

6 Infrared Spectroscopy Presence of crystalline Mg-silicates Astromineralogy MAC * B(100K) MAC * B(100K) M.A.C. * B(100 K) Flux Flux (Jy) M.A.C. * B(100 K) Enstatite Enstatite Forsterite λ (μm) wavelength (micron) Forsterite AFGL4106 Jäger+ (1998)

7 Infrared Spectroscopy 0.08 Bouwman+ (2010) REX5 RECX5 Presence of crystalline Mg-silicates Astromineralogy Flux (Jy) Forsterite Hale-Bopp Forsterite λ (μm) wavelength (micron)

8 How did dust particles form in space? Grain size, number density, mineral assemblages Dust formation from gas Nucleation and Growth Krot+ (2004)

9 How did dust particles form in space? Grain size, number density, mineral assemblages Dust formation from gas If all the colliding gas condense, If only a fraction of gas condense, Krot+ (2004) slower growth less amount of dust diversity of dust species

10 Growth kinetics of dust from vapor Fe(g) Fe(s) Jnet = Jin Jout Fe Jnet = αc pfe αe pfe(eq) 2π mfekt Jin Jout αc : Condensation coefficient (Sticking probability of impinging atoms/molecules) αe : Evaporation coefficient Laboratory Studies!

11 Evaporation experiments of minerals

12 Evaporation experiments at low pressures - Forsterite (Mg2SiO4): Hashimoto, 1990; Nagahara & Ozawa, 1996; Tsuchiyama+, 1999; Wang+, 1999; Kuroda & Hashimoto, 2002; Yamada+, 2006; Takigawa+, 2009; Ozawa+, Olivine ((Mg0.9 Fe0.1)2SiO4): Ozawa & Nagahara, Enstatite (MgSiO3): Tachibana+, Silica (SiO2): Young+, Silicate melts: e.g., Hashimoto, 1983; Nagahara & Ozawa, 1996; Wang+, 2001; Yu+, 2003; Richter+, 2002, 2007

13 Evaporation experiments at low pressures - Forsterite (Mg2SiO4): Hashimoto, 1990; Nagahara & Ozawa, 1996; Tsuchiyama+, 1999; Wang+, 1999; Kuroda & Hashimoto, 2002; Yamada+, 2006; Takigawa+, 2009; Ozawa+, Metallic iron : Tsuchiyama & Fujimoto, 1995; Tachibana+, Troilite (FeS): Tachibana & Tsuchiyama, Corundum (Al2O3): Takigawa, 2012, Ph.D. thesis

14 Evaporation experiments at low pressures H2 gas thermocouple vacuum gauge Weight loss of sample due to isothermal heating in vacuum or at low hydrogen pressures heater sample electrode Evaporation rate continuous evacuation

15 Evaporation of Fe metal in vacuum Tachibana+ (2011) ApJ 1718 K 1347 K Ideal evaporation αe =1

16 Evaporation of forsterite at low hydrogen pressures circle: along the a-axis square: along the b-axis triangle: along the c-axis Evaporation rate [m/s] (a) (b) (c) (d) 1930 K 1803 K 1600 K 1430 K αe =0.1 αe =0.01 αe =0.1 αe =0.01 αe =0.1 αe =0.1 Anisotropic evaporation w/ kinetic hindrance P(H2) [Pa] Takigawa+ (2009) ApJL

17 Evaporation coefficients mineral αe references corundum Takigawa (2012, PhD thesis) forsterite e.g., Tsuchiyama+ (1998); Yamada+ (2006); Takigawa+ (2009) enstatite 0.1 (as Fo) Tachibana+ (2002) Metallic Fe Tsuchiyama & Fujimoto (1995) Tachibana+ (2011) troilite Tachibana & Tsuchiyama (1998)

18 Condensation experiments of minerals Growth at low pressures - good for understanding kinetics if experimental conditions are controlled

19 Condensation of metallic iron in vacuum (Tachibana+, 2011) substrate 1340 K vacuum gauge Growth of metallic iron at controlled T and PFe heater gas source (Fe) electrode continuous evacuation

20 Condensation of metallic iron in vacuum weight change (g) weight gain of substrate due to condensation weight loss of gas source due to evaporation T sub =1235 K T source =1630 K hour Tachibana+ (2011)

21 Condensates Tachibana+ (2011) Photo: Growth steps on Fe metal condensed from vapor at 1235 K for 48 hr 1 micron

22 Condensates Tachibana+ (2011) 1235 K, 48 hr Photo: Growth steps on Fe metal condensed from vapor at 1235 K for 48 hr 1 micron

23 K 1337 K Tachibana+ (2011) T gas :1580 K J cond / J id evap (0) K 1680 K αc= K 1580 K 1510 K 1630 K Ideal condensation!=1!=0.8!=0.6!=0.4 0!= Supersaturation ratio, S (=p/p eq )

24 Evaporation & Condensation coefficients mineral αe αc corundum ~0.05 (Takigawa, 2012) forsterite enstatite 0.1 (as Fo) Metallic Fe ~1 (Tachibana+, 2011) troilite ~0.02

25 Condensation of forsterite in low-pressure H2-H2O gas

26 Evaporation of forsterite Mg2SiO4(s) = 2Mg(g) + SiO(g) + 3O(g) Free evaporation regime Hashimoto (1990); Wang+ (1999); Yamada+ (2006); Takigawa+(1999); Ozawa+ (2012) (FED) Mg2SiO4(s) + 3H2(g) = 2Mg(g) + SiO(g) + 3H2O(g) Hydrogen-reaction dominated regime (HRD) Jevap proportional to ph2 1/2 Nagahara & Ozawa (1996); Tsuchiyama+ (1998); Kuroda & Hashimoto (2002); Takigawa+ (2009) ph2o/ph2-buffer dominated regime (HBD) Jevap proportional to ph2o/ph2

27 Evaporation of forsterite solar composition α = K 1973 K 1873 K 1773 K 1673 K FED HRD 1573 K 1473 K 1373 K HBD 1273 K 1173 K Tsuchiyama, Tachibana, Takahashi (1999)

28 Evaporation of forsterite in low-pressure H2-H2O gas Infrared vacuum furnace H2+H2O silica tube gold mirror Pt mesh halogen lamp Forsterite vacuum gauge QMS continuous evacuation TMP+RP

29 Evaporation of forsterite in low-pressure H2-H2O gas ptotal=4x10-5 atm, T~1150 C (1423 K) H2O/H2=0.016 H2O/H2=0.0015

30 Evaporation of forsterite in low-pressure H2-H2O gas ptotal=4x10-5 atm, T~1150 C (1423 K) HRD HBD αe=1 αe=0.1 αe=0.01

31 Evaporation of forsterite Mg2SiO4(s) = 2Mg(g) + SiO(g) + 3O(g) Free evaporation regime Hashimoto (1990); Wang+ (1999); Yamada+ (2006); Takigawa+(1999); Ozawa+ (2012) (FED) Mg2SiO4(s) + 3H2(g) = 2Mg(g) + SiO(g) + 3H2O(g) Hydrogen-reaction dominated regime (HRD) Jevap proportional to ph2 1/2 Nagahara & Ozawa (1996); Tsuchiyama+ (1998); Kuroda & Hashimoto (2002); Takigawa+ (2009) ph2o/ph2-buffer dominated regime (HBD) Jevap proportional to ph2o/ph2 confirmed for the first time

32 Evaporation of forsterite in low-pressure H2-H2O gas

33 Condensation of forsterite in low-pressure H2-H2O gas Pressure: 4 Pa Pt mesh gas source: Forsterite ~1900 K H2O/H2=0.016 ~25 mm substrate: Forsterite ~1% of gas evaporated from the gas source

34 Condensation coefficient Flux hitting the substrate surface αc Flux condensed on the substrate Tcond = ~1350 K SiO/H2 = ~0.15 solar H2O/H2 = ~16 solar S = ~5 #1 #2 #3 # min 1250 min 790 min 1530 min

35 Evaporation & Condensation coefficients mineral αe αc corundum ~0.05 (Takigawa, 2012) spinel ~0.02 forsterite ~0.1? enstatite 0.1 (as Fo) Metallic Fe ~1 (Tachibana+, 2011) troilite ~0.02 Growth (and evaporation) of forsterite dust occurs less efficiently than Fe metal

36 Application to cosmochemistry AOA Formation Grain size, number density, mineral assemblages Krot+ (2004)

37 Application to infrared spectroscopy Anisotropy: Probe for high-t history of dust MAC (cm 2 /g) 1.2x10 4 8x10 3 4x10 3 evap. Takigawa & Tachibana, 2012 cond. CDE LDE 1 LDE 2 LDE wavelength ( m) 25% LDE1 + 75% CDE laboratory DHS HD (Juhász et al. 2010)

38 Summary & Conclusions Understanding of dust formation kinetics is a key to understand dust forming environments experiments at controlled low-pressure realistic conditions combined with observation and modeling Evaporation of forsterite controlled by ph2o/ph2 is confirmed; Kinetics is likely to be the same Growth experiments of forsterite under controlled protosolar disk-like conditions are now being made; The growth efficiency is not as good as metallic iron