1. Characterizing atmospheres with JWST: Optimizing multi-instrument observations via simulations and retrievals Tom Greene (NASA ARC) Michael Line (UCSC / Hubble Fellow / ARC), Jonathan Fortney (UCSC) November 16, 2015 Also see the poster By Everett Schlawin

2. Planet transmission / emission spectra 16 Nov 2015JWST Transit Characterization2

3. Some progress from transit (spectroscopy) 16 Nov 20153JWST Transit Characterization Molecules & atoms identified in exoplanet atmospheres – H2O, CO (CH4, CO2), Na, other alkali, HI, CII, OI,… Measured temperature-pressure profiles from hot Jupiter emission spectra – Few with high confidence T inversions Some Neptune-sized planets have been diagnosed – HAT-P-11 (Fraine+ 2014) and GJ 436b (Knutson+, etc.) Sub-Neptunes and super-Earths have been difficult – GJ 1214b: flat absorption, no sec. eclipse (many people…) – Promise of cooler planets like K2-3 (Crossfield+ 2015) and K2- 18b (Montet+ 2015): T = 300 – 500K, different clouds?

4. Questions about exoplanet atmospheres What are their compositions? – Elemental abundances C/O and [Fe/H]: Both are formation diagnostics – Molecular components and chemical processes Identify equilibrium & disequilibrium chemistry: – Vertical mixing, photochemistry, ion chemistry… – 3-D effects: spatial variations Energy budget and transport –1-D structure: measure profiles, inversions present? –Dynamical transport: day/night differences Clouds –Cloud composition, particle sizes, vertical & spatial distribution –Remove cloud effects to determine bulk properties Anything about low mass / small r< ~2R e planet atmospheres Trends with bulk parameters (mass, insolation, host stars, …) – Requires a population of diverse planets 16 Nov 2015JWST Transit Characterization 4

5. 16 Nov 20155JWST Transit Characterization We clearly can use all ~10 years of JWST time to observe transiting planets! But what should we do if that doesn’t happen?

6. New JWST Simulation / Retrieval Assessment 16 Nov 20156JWST Transit Characterization Model some known planet types, simulate spectra, assess information & constraints Select archetypal planets from known system parameters – Hot Jupiter, warm Neptune, warm sub-Neptune, cool super-Earth Create model transmission and emission spectra (M. Line) Simulate JWST spectra using performance models (TG) – Simulate slitless modes with large bandpasses & good bright limits: NIRISS SOSS, NIRCam grisms, MIRI LRS slitless 1 – 11  m – Code based on instrument models & data, detector parameters, JWST background models, random & systematic noise – 1 transit or eclipse per spectrum Perform atmospheric retrievals (M. Line) to assess uncertainties in molecules, abundances, T-P profiles – Focus on uncertainties, not absolute parameters Identify what wavelengths give most useful information for what planets

7. Use 1-D forward models – Emission: Line+(2013a), Diamond-Lowe+(2014), Stevenson+(2014) – Transmission: Line+(2013b) Swain+(2014), Kreidberg+(2014, 2015) Transmission model has 11 free parameters – T(SH), R(P=10b),hard clouds (Pc,  ,  ), H 2 O, CH 4, CO, CO 2, NH 3, N 2 absorbers, constant with altitude Emission model has 1D T-P profile & 10 free params – H 2 O, CH 4, CO, CO 2, NH 3, 5 gray atm parameters for T-P (Line+ 2013a) CHIMERA Bayesian retrieval suite (Line+ 2013a,b) – Updated with emcee MCMC – Uniform & Jeffreys priors 16 Nov 20157JWST Transit Characterization Forward models & retrievals

8. Simulated Planet Signals (S ) & Noise (N ) 16 Nov 20158JWST Transit Characterization (  m) Noise floor 1.0 – 2.520 ppm 2.5 – 5.030 ppm 5.0 - 1250 ppm NIRISS NIRCam MIRI LRS

9. Selected Model Systems 16 Nov 20159JWST Transit Characterization

10. Model Transmission Spectra 16 Nov 201510 JWST Transit Characterization

11. Simulated JWST Trans Spectra (1 transit) 16 Nov 201511 JWST Transit Characterization

12. Model Emission Spectra 16 Nov 201512 JWST Transit Characterization

13. Simulated JWST Emission Spectra (1 eclipse) 16 Nov 201513 JWST Transit Characterization

14. Retrieval Birds & Bees 16 Nov 201514JWST Transit Characterization Benneke & Seager (2012)

15. Retrieval Results: Hot Jupiter Gasses 16 Nov 201515 JWST Transit Characterization Priors

16. Retrieval Results: Warm Neptune Gasses 16 Nov 201516 JWST Transit Characterization Priors

17. Retrieval: Warm Sub-Neptune Gasses 16 Nov 201517 JWST Transit Characterization Priors

18. Retrieval Result: Cool Super-Earth Gasses 16 Nov 201518 JWST Transit Characterization Priors

19. Emission retrievals: T-P Profiles 16 Nov 201519 JWST Transit Characterization Dashed: True value Solid line: Retrieved mean value Shaded: 1 sigma Detect inversion at 4 sigma with NIRISS only (red)

20. 16 Nov 201520 JWST Transit Characterization

21. Constraining C/O from H 2 O + T eq 16 Nov 201521 JWST Transit Characterization Transmission spectra

22. Mass - Metallicity 16 Nov 201522 JWST Transit Characterization Transmission spectra Adapted from Kreidberg+ 2014b

23. Dis-equilibrium Chemistry (v mixing) 16 Nov 201523 JWST Transit Characterization Emission spectra

24. Summary / Conclusions (1) NIRISS (1 – 2.5  m) transmission spectra alone sometimes constrain mixing ratios of dominant molecules in clear solar atmosphere planets (H 2 O, CH 4, NH 3 ) – C/O and [Fe/H] sometimes constrained with only NIRISS – ≥ 5  m spectra needed in a number of cases Cloudy solar atmospheres are often constrained (~ 1 dex or better mixing ratios) with = 1 - 11  m spectra – Transmission is better than emission for warm sub-Neptune – Hot Jupiter and warm Neptune do better with emission Need sufficient F p and high F p /F * for useful emission spectra High MMW atmospheres can be identified by high [Fe/H] C/O is constrained to 0.2 dex for hot Jupiters with = 1 – 5+  m spectra. Also: C/O for hot planets with H 2 O + Teq  [Fe/H] < 0.5 dex for warm, clear planets ( = 1-5+  m tr) 16 Nov 2015JWST Transit Characterization24

25. Summary / Conclusions (2) Non-equilibrium vertical mixing cannot be detected via molecular mixing ratios – Photochemistry could show unexpected spectral features Observing 5 planets from Uranus to Jupiter mass should measure [Fe/H] vs. Log (M) slope to 1  = 0.13 – = 1-5+  m transmission spectra – More than adequate (~20  ) for detecting Solar System slope These results are for observations of single transits or eclipses. We will not know the actual JWST data quality – and how noise will decrease with co-adding – until after launch Many more retrieval issues to be explored (binning, Bayesian estimators, priors, 3D, parameterization), but will largely be driven by future data 16 Nov 2015JWST Transit Characterization25

26. The End 16 Nov 2015JWST Transit Characterization26