Retrievals of Dayside Emission Spectra: Trends in Chemistry
Michael Line, Aaron Wolf, Xi Zhang,Yuk YungCaltech
Thermo. Eq.
Vertically Mixed
Photochemistry
Ions
CO
CH4
CO quenched
CH4 quenched
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fH2O fCH4fCO fH2
3 P 2=Keq
H2O + CH4 = CO + 3H2
Synthetic Study
S/N~3.5Δλ=0.0075 μm
Spitzer Broadband Spitzer Broadband+IRS+NICMOS
FINESSE
MCMC
Optimal Est.
HD189733Moses et al. 2011
WASP12Kopparapu et al. 2012
GJ436Line et al. 2011
GJ436
HD189733
TRES2
HD149026
WASP19 WASP12
HD189733Moses et al. 2011
WASP12Kopparapu et al. 2012
GJ436Line et al. 2011
GJ436
HD189733
TRES2
HD149026
WASP19 WASP12
MCMC
OPT. EST.
Dis-eq. Models
HD189733Moses et al. 2011
WASP12Kopparapu et al. 2012
GJ436Line et al. 2011
Conclusions
• Opt est and MCMC agree for “quality” data
• Most planets seem out of equilibrium (to within “1-sigma”)
• Errors large on current gas estimations
• Need dedicated space based spectroscopic instrument
• Can maybe constrain Kzz
Goals
• Look at the ensemble of planetary atmospheres. Indentify trends in composition—equilibrium vs. disequilibrium
• First must robustly determine temperatures and compositions of exoplanet atmosphere
Two Bayesian Retrieval Approaches
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P(T,f |Data)∝ P(Data |T,f) × P(T,f)Optimal Estimation
(Lee et al. 2011 , Line et al. 2012)
This Parameter
That
Par
amet
er
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χ 2
-Levenberg-Marquardt to find best solution
-Assumes Gaussian posterior
- Fast—not slowed down by additional parameters or more sophisticated forward models
This Parameter
That
Par
amet
er
€
χ 2
- Randomly explore’s all of parameter space
- Accounts for non-Gaussian posteriors
- Slow—many parameters and more sophisticated forward models unwieldy
Markov Chain Monte Carlo(Madhusudhan et al. 2011 , Benneke & Seager 2012)
Forward Model: [T, fH2O, fCH4, fCO ,fCO2]
Guillot 2010 [γv1, γv2, κIR, α, β]
Synthetic StudySpitzer Broadband Spitzer Broadband+IRS+NICMOS
FINESSE
MCMCOpt. Est.True
Synthetic StudySpitzer Broadband Spitzer Broadband+IRS+NICMOS
FINESSE
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