the spectral mlty transition: the role of convection in cloud formation
DESCRIPTION
The spectral MLTY transition: the role of convection in cloud formation. F. Allard (CRAL-ENS, Lyon, France). MLT Spectral Sequence optical to red spectral range Burgasser CS13 2003. Burgasser et al. (2001). Kirkpatrick et al. ‘99. VO. CrH,FeH . TiO, VO . H . FeH. NaID,K - PowerPoint PPT PresentationTRANSCRIPT
F. AllardF. Allard
(CRAL-ENS, Lyon, France)(CRAL-ENS, Lyon, France)
The spectral MLTY The spectral MLTY transition:transition:
the role of convection in cloud the role of convection in cloud formationformation
CaH
CrH
Cs
K
Li
Rb
H2O
FeH
VO
H
Martín et al ‘99Martín et al ‘99wraps in L4-L8wraps in L4-L8in only 2 extrain only 2 extrasubtypes (to L6)subtypes (to L6)
1/3 of 2MASS field L dwarfs but ZERO T dwarfs show Li 1/3 of 2MASS field L dwarfs but ZERO T dwarfs show Li 6708Å 6708Å Hundreds of L dwarfs and at least 30 T dwarfs knownHundreds of L dwarfs and at least 30 T dwarfs known
Kirkpatrick et al. ‘99 Burgasser et al. (2001)
TiO, VO
Hyd, alk
NaID,KH2O
Rb,Cs
CrH,FeH
CH4
MLT Spectral SequenceMLT Spectral Sequenceoptical to red spectral rangeoptical to red spectral range
Burgasser CS13 2003Burgasser CS13 2003
Changes in HChanges in H22O bands behavior due to dust DO NOT define M-L transitionO bands behavior due to dust DO NOT define M-L transition
L-T transition defined by onset of CHL-T transition defined by onset of CH44 in H and K bandpasses in H and K bandpasses
HH22
H2,CH4 CO KI no FeH
MLT Spectral SequenceMLT Spectral Sequencenear-IR spectral rangenear-IR spectral rangeBurgasser, CS12, 2003Burgasser, CS12, 2003
Grain extinction cross-section (Mie) per particle as a function of wavelength for species we include. The monoatomiques monomers such as the metals only contribute as diffusion (dotted lines) in the UV to visual, while corundum, magnesium spinel, CaTiO3, silicates absorb (full, dashed and dotted bleue lines) in the IR.
Extinction profile for a grain size distribution of 1, 2, 10, and 100 times that of the ISM, for conditions prevailing in the photospheric layers (T1300K) of our AMES-Dusty model at Teff = 1800K. Spectral features seen above 8.5 m are due to Mg2SiO3 and MgAl2O4.
Al203Mg2Si04 Mg2Si04
name dust handling referencename dust handling reference
NextGen NextGen nonenone Allard et al. Allard et al. (1996)(1996) DustyDusty/Cond/Cond EquilibriumEquilibrium Allard et al. Allard et al. (2001)(2001)
Model GridsModel Grids
2 models to bracket de 2 models to bracket de solutionsolution
Allard et al. (2001)
General PrinciplePhenomenological Model:
• Chemical equilibrium• Dust monomers in equilibrium with gas phase• Cloud bottom set to its hottest CE condensation level• Cloud extension controlled by convective turbulent
updraft refueling cloud layers with refractory material
A. Hydrostatic equilibrium T, Pgas (done independently
before) We solve layer by layer outwards:
1) Grain diffusion (cond., sed., mix.) Ngrain , rgrain
2) Revised elemental abundances3) Chemical equilibrium4) Go back to 1) and repeat until no more grain forms
B. Radiative transfer, spectrum, model iteration, and back to A) till model converged
Refractory Elements
Quasi-Static Cloud Model
Microphysical and convective characteristic time scales as a function of mean particle radius
Grain growth:• Convection transports
condensable gas up• Sedimentation (rain)
brings dust particles down• Condensation increases
radii of small particles• Coalescence brings large
particles togetherLast 3 timescales estimated
using Rossow (1978)
Surface convection in late M dwarfLudwig, Allard, Hauschildt, ApJ 2002
• RHD simulation
• Teff =2800K, logg=5.0
• Vertically: timescale=100 sec velocities=240 m/s
• Horizontally: cell size = 80 km contrast 1.1%
3 4 5 6 7 8log10 P [dyn/cm 2]
-4.0
-3.5
-3.0
-2.5
-2.0
Mass exchange frequency as a function of Pressure for various degrees of
subsonic filtering
Considered Mixing Options
• Phenomenological model i.e.with NO free parameter
mix conv Hp / inside the convection zone.
mix parabola of same opening above
the convection zone.
name dust handling referencename dust handling reference NextGen NextGen nonenone Allard et al. Allard et al. (1996)(1996) Dusty/Cond Equilibrium Allard et al. (2001)
Settl Cloud Model Allard et al. (2003) to replace Dusty Rainout Full Sedimentation to replace Cond
New alkali line profiles for NaI D & KI by Allard N. F. et al. (2003, 2005)New solar abundances by Asplund, Grevesse & Sauval (2005, astro-ph/04102v2)New cloud model by Allard et al. (2003, IAU 211, ASP, p.325)New line data for CaH & VO C-X systems (B. Plez GRAAL)Update on QTiO ( X 3 or 0.5 dex too large!) X 3 larger TiO opacity! weaker contrast to lines!
New Model GridsNew Model Grids
Tsuji et al. (1999, 2002) TcrAckerman & Marley (2001) frainCooper et al. (2002) Smax
Metals’ Depletion
O Na Mg Al Si K Ca Ti V Cr Fe
2300 80
100
100
0
100
100
0
100
100
0
100
100
0
100
100
100
100
100
0
100
100
0
100
100
0
100
100
10
100
100
0
100
100
2000 80
80
100
0
0
100
0
99
100
0
0
100
0
99
100
100
100
100
0
60
100
0
0
100
0
0
100
0
100
100
0
80
100
1700 80
80
100
0
0
100
0
10
100
0
0
100
0
80
100
100
100
100
0
0
100
0
0
100
0
0
100
0
100
100
0
100
100
1400 80
80
100
0
0
100
0
0
100
0
0
100
0
0
100
100
100
100
0
0
100
0
0
100
0
0
100
0
0
100
0
0
100
1100 80
80
100
0
0
100
0
0
99
0
0
0
0
0
50
100
100
100
0
0
0
0
0
0
0
0
100
0
0
100
0
0
30
““Parabolic” Cloud Parabolic” Cloud ModelModel
Allard, Guillot, Ludwig et al. (2003)
TTmixmix & N & Ngrains grains vs Tauvs Tau1,21,2
Ludwig, Allard, Hauschildt (2002)
Ngrains
Tmix
OUTOUT
ININ
LAH02 ModelLAH02 Model Constant gravity locus: logg=5.0
ConclusionsConclusionsMLT and perhaps Y transition is highly sensitive to
turbulence ! 3D RHD convection simulations needed to
study the range and type of turbulence dependence upon optical depth, Teff, and surface gravity.
Project for the next 3 yrs: modeling cloud formation with 3D RHD COBOLD models in BDs
import Phoenix’s opacities and CE into COBOLD
import cloud model into COBOLD
Gravity Effect?Gravity Effect?Constant gravity locii: 5.0 & 5.5
Évolution de Phoenixpériode 2005 - 2015
• Transfert radiatif 3D vs 1D en symétrie sphérique PHH• Diffusion géométrique vs isotropie JP • Croissance des grains vs taux de condensation (Rossow ‘78) CH • Diffusion des grains vs solution linéaire au 1er ordre FA • Photochimie vs équilibre chimique de gaz idéal FS • Chimie non-idéale (SC) vs équilibre chimique de gaz idéal FA • Profiles de raies unifiés vs profiles de Lorentz NFA • Extension de nos calculs d’équilibre chimique jusqu’à 10K FA • Complétion de nos bases d’opacités moléculaires jusqu’à 10K JF
PHH= P. H. Hauschildt (Obs. de Hamburg); NFA= Nicole F. Allard (IAP) JP = Jimmy Paillet (CRAL, PhD ss ma dir.); CH= C. Helling (Univ. T. de Berlin) FS = Franck Selsis (CRAL, CR2 ss ma dir.); JF= Jason Ferguson (WSU)