Single Object Slitless Spectroscopy Simulations Loïc Albert (with help from Étienne, David and Jason) Science Team Meeting UdeM, October 20 2015

Simulation Objectives Test different trace extraction scenarios to devise an optimal extraction method and calibration strategy. Investigate our sensitivity to instrumental artifacts such as intra-pixel response, flat-fielding and wheel repeatability. Provide simulated transit data sets to the community on our web page.

Main Difficulties Want to limit digitization artifacts to <1 ppm therefore need PSF oversampling by x10 in simulations. ~1 day per order on Mac Pro using IDL. Contamination by order 2 for λ>2.0 μm at a level of ~1% (10000 ppm). How to extract traces in this overlap region? Wheel repeatability is ~0.15 degrees, perhaps quantized position (-0.15, 0.00,+0.15), perhaps a normal distribution? Impacts multi-epoch targets and calibrations (to a lesser extent). Spatial axis tilted by a few degrees relative to the detector pixels (by design to oversample spectral lines). Can not simply assume constant wavelengths to be along detector rows.

2nd and 1st orders cross contamination

Table interpolation (and extrapolation...) Trace Position λ x y 0.7 30 0.8 40 200 ... 2.5 220 1700 2.6 225 1900 JWST Cryo indices for ZnS and ZnSe CodeV Table interpolation (and extrapolation...)

Monochromatic Wavelength PSFs

x10 oversampled

Stellar + Planetary Atmosphere Model "Delta Function" Trace Oversampled x10

"Delta Function" Trace Delta function trace convolution by PSF kernel for ~30 wavelengths + Interpolation for in-between wavelengths Monochro- matic PSF 80x80 256x2048 + padding ... 30 monochromatic convoluted traces Interpolate traces between existing traces

Trace examples x10 oversampled Order 1 Order 2

Zodiacal Light

Simulated background components Modelled zodiacal light background Modelled 1/f noise Scattering on optics (10-3 and uniform, ref. Rohrbach simulations) OTE thermal emission?

Spectrum extraction Baseline spectral extraction: 2D trace extracted and drizzled on a 1D, constant dispersion, oversampled spectrum. (See next slide) Currently being implemented and tested as the baseline in our pipeline. Other extraction ideas: Traditionnal aperture extraction  λ-dependent transit modelling 1-D drizzle (like baseline) with mask to mitigate contamination  λ-dependent transit modelling White-light transit modelling 2-D image subtraction of median  spectral extraction (any method) Somehow feed information from order 1 to extract order 2 where traces overlap.

Spectrum extraction: Drizzle the 2D trace to a 1D oversampled spectrum Still have to define an extraction aperture. Assumes a lambda+tilt vs. pixel calibration.

Background Subtraction Spectral Traces Stack Subtracted Assumes the existence of a deep stack Needs a "threshold" parameter to establish pixels to reject from fit (good pixel > threshold) Currently use mean of un-masked pixel, column by column. Can think of more fancy fits and quantify them. Masked Corrected

Schedule Milestone Time Line Handling limb darkening appropriately to generate realistic transit sequences now-Oct 31 Generate a ~5hr simulated transit and make available on the web Nov 7 Experiment extraction with 1D drizzle on time-series Nov 1 and on Test how wheel repeatability affects extracted planet spectra Nov 7-15 JWST Transiting Workshop (Nov 16-18, STScI) Nov 16-18 Experiment with a few other extraction methods Till X-mas Self wavelength calibration using the science target model Spring 2016 Generate fake calibration data (A0 star for flat-fielding and trace profile) Compare extracted planet spectra when including intra-pixel sensitivity Could compare dependency on the non-linear coefficient maps. Add red noise to the time-series and study