Modeling Molecular Line Emission from Protoplanetary Disks€¦ · –chemical composition disk gas...

Modeling of Protoplanetary Disks • Schloß Ringberg • April 13–17 2004

Modeling Molecular LineModeling Molecular LineEmission fromEmission from

Protoplanetary Protoplanetary DisksDisks

Michiel HogerheijdeMichiel Hogerheijde, , Leiden Leiden ObservatoryObservatory

Collaborations with: Collaborations with: Floris Floris van van der Takder Tak, Charlie , Charlie QiQi, Geoff Blake,, Geoff Blake,AdwinAdwin BoogertBoogert, Cecilia , Cecilia CeccarelliCeccarelli, , EwineEwine van van DishoeckDishoeck, , GerdGerd-Jan van-Jan van

ZadelhoffZadelhoff


OverviewOverview•• IntroductionIntroduction•• The The radiative radiative transfer problemtransfer problem•• ……and solution methodsand solution methods•• Examples:Examples:

–– TW TW HyaHya–– L1489 IRSL1489 IRS–– High-J CO from superheated disk surfaceHigh-J CO from superheated disk surface–– CN/HCN as a probe of the stellar spectrumCN/HCN as a probe of the stellar spectrum

•• Conclusions and further workConclusions and further work


IntroductionIntroduction•• Molecular lines excellent tools to studyMolecular lines excellent tools to study

–– chemical composition disk gaschemical composition disk gas–– motions in the diskmotions in the disk–– temperature and density of the gas contenttemperature and density of the gas content

•• Many molecules freeze out in cold & denseMany molecules freeze out in cold & densemidplanemidplane–– Molecular lines trace inner disk and intermediate heightsMolecular lines trace inner disk and intermediate heights

•• Line opacities often high and excitation Line opacities often high and excitation ≠≠ LTE LTE–– Accurate simulation of line strengths and profiles trickyAccurate simulation of line strengths and profiles tricky


The The radiative radiative transfer problemtransfer problem

•• For NLTE & For NLTE & tt>1:>1:–– Excitation non-local problemExcitation non-local problem

•• Line emission from one location affects excitation inLine emission from one location affects excitation inanotheranother

•• Propagation of line photons from one region affectedPropagation of line photons from one region affectedby conditions in other regionsby conditions in other regions

–– The resulting The resulting ‘‘integrointegro-differential-differential’’ equations equationscan only be solved through iterative methodscan only be solved through iterative methods

–– Inefficient in presence of large opacitiesInefficient in presence of large opacities•• Updates only spread over Updates only spread over tt~1 per iteration step~1 per iteration step•• May be mistaken for convergenceMay be mistaken for convergence


……and solution methodsand solution methods•• Acceleration methods existAcceleration methods exist

–– developed originally for stellar atmospheresdeveloped originally for stellar atmospheres–– Accelerated Lambda IterationAccelerated Lambda Iteration

•• Technique rests on separating Technique rests on separating locallocal and global and globalcontributions to the radiation fieldcontributions to the radiation field

•• Implemented in Monte Carlo methods (Implemented in Monte Carlo methods (Hogerheijde Hogerheijde &&van van der Tak der Tak 2000)2000)


(Hog

erhe

ijde

& va

n de

r Ta

k 20

00)

……and solution methodsand solution methods


……and solution methodsand solution methods•• Radiative Radiative transfer & molecular excitation codestransfer & molecular excitation codes

have been benchmarkedhave been benchmarked–– van van Zadelhoff Zadelhoff et al. (2002)et al. (2002)–– Including the water molecule (March 2004)Including the water molecule (March 2004)

•• Reliability of results rests on Reliability of results rests on input modelsinput models (this (thisworkshop!) and on workshop!) and on molecular datamolecular data (collision rates) (collision rates)

•• (Almost) standard practice to produce (Almost) standard practice to produce syntheticsyntheticdatadata from modeling, to compare with observations from modeling, to compare with observations–– cc22 in image- or (u,v)-plane in image- or (u,v)-plane


Examples: TWExamples: TW Hya Hya(Q

i et

al. 2

004)

CO J=2CO J=2––1 and 31 and 3––2 at 22 at 2”–”–44”” using the SMA using the SMA

obsobs

mdlmdl


Examples: TWExamples: TW Hya Hya•• Lines and continuumLines and continuum

agree with agree with Calvet Calvet etetal. modelal. model–– R~200 AUR~200 AU

•• CO optically thickCO optically thick–– TTkinkin~20 K~20 K

•• DDvvturbturb~0.05 km s~0.05 km s-1-1

•• Keplerian Keplerian rotationrotation•• Inclination 7Inclination 7˚±˚±11˚̊

–– sin(i) sin(i) ±± 30% 30%

(Qi et al. 2004)


Examples: L1489 IRSExamples: L1489 IRS•• HCOHCO++ 1-0, 3-2; HCN 1-0; 1-0, 3-2; HCN 1-0; 1313CO 1-0; CCO 1-0; C1818O 1-0 O 1-0 interferometryinterferometry•• 3-2 and 4-3 single-dish lines + isotopes3-2 and 4-3 single-dish lines + isotopes

(Hogerheijde 2001)

2000 AU


Examples: L1489 IRSExamples: L1489 IRS•• Keplerian Keplerian rotationrotation•• Radial flow?Radial flow?

(Hogerheijde 2001)


Examples: L1489 IRSExamples: L1489 IRS

•• Flared density profile + Flared density profile + Keplerian Keplerian rotationrotation•• Possible radial motionsPossible radial motions•• NLTE excitation andNLTE excitation and radiative radiative transfertransfer•• cc22 minimization w.r.t. position-velocity diagram minimization w.r.t. position-velocity diagram


Examples: L1489 IRSExamples: L1489 IRS

•• 10% of |v| directed inward10% of |v| directed inward•• Continues to within 0.1 AU from starContinues to within 0.1 AU from star•• DDt~2x10t~2x1044 yr: transitional stage? yr: transitional stage?

(Hogerheijde 2001)

(Boo

gert

et

al. 2

002)

Ro-virbrational absorption lines at 4.5 µm


Examples: High-J CO from SHLExamples: High-J CO from SHL

•• Elias 29Elias 29–– face-on disk + outflow + foreground cloudsface-on disk + outflow + foreground clouds

((Boogert Boogert et al. 2002)et al. 2002)

•• ISO detected CO emission up to J=19ISO detected CO emission up to J=19––1818–– 170170––250 K; ~10250 K; ~10-3-3 M Mùù; >10; >1066 cm cm-3-3; ; ∅∅ 550 AU550 AU

•• Material shocked by outflowMaterial shocked by outflow•• Or superheated disk surface?Or superheated disk surface?•• Ceccarelli Ceccarelli et al. (2002)et al. (2002)


Examples: High-J CO from SHLExamples: High-J CO from SHL(C

ecca

relli

et

al. 2

002)


Examples: High-J CO from SHLExamples: High-J CO from SHL•• NLTE + simple flared diskNLTE + simple flared disk

modelmodel–– Adjust depth of SHL Adjust depth of SHL ´́

higher densities in warmhigher densities in warmgasgas

•• Can reproduce high-J COCan reproduce high-J COline fluxes only for higherline fluxes only for higherdensities than standarddensities than standardmodel predictsmodel predicts–– Need self-consistentNeed self-consistent

modelingmodeling


Examples: CN/HCNExamples: CN/HCN•• Increase in CN abundance due to Increase in CN abundance due to photoionizationphotoionization

by accretion UVby accretion UV•• Flared diskFlared disk

–– 2D UV propagation2D UV propagation

(van Zadelhoff et al. 2003)


Examples: CN/HCNExamples: CN/HCN

(van Zadelhoff et al. 2003)

Spectrum B = with UVSpectrum B = with UVSpectrum C = without UVSpectrum C = without UV

CN 3CN 3––2/HCN 42/HCN 4––33


ConclusionConclusion•• Modeling techniques to simulate molecularModeling techniques to simulate molecular

line data from line data from protoplanetary protoplanetary disks aredisks arematuringmaturing

•• Current observations can be reproducedCurrent observations can be reproduced(at limited spatial resolution)(at limited spatial resolution)

•• Convergence is and remains a problemConvergence is and remains a problem•• Molecular lines form a valuable probe ofMolecular lines form a valuable probe of

conditions in gas-rich disks, when combinedconditions in gas-rich disks, when combinedwith the existing modeling techniqueswith the existing modeling techniques


Further work: the 3 RFurther work: the 3 R’’ss•• RapidRapid

–– Continued work on efficient codesContinued work on efficient codes–– ‘‘DownsizingDownsizing’’ of theoretical models may be required to of theoretical models may be required to

save computing timesave computing time

•• ReliableReliable–– Use the best modeling methods availableUse the best modeling methods available

•• LTE only when applicable!LTE only when applicable!–– ConvergenceConvergence

•• RealisticRealistic–– 2D, 3D disk models2D, 3D disk models–– Parameterized versions are most suitable for Parameterized versions are most suitable for cc22

Modeling Molecular Line Emission from Protoplanetary Disks€¦ · –chemical composition disk gas...

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