PSF Photometry for Kepler and K2 Data

Talk given at the PSF Photometry and Software Workshop, Space Telescope Science Institute, Baltimore, 2017.

Transcript

1. PSF Photometry for Kepler/K2 data Geert Barentsen Z´ e Vin´ ıcius http://keplerscience.arc.nasa.gov Space Telescope Science Institute, Baltimore November 6, 2017
2. K2 Guest Observer Office + Ben Montet Geert Barentsen Michael Gully Ann Marie Cody Christina Hedges Z´ e Vin´ ıcius Ben Montet 1
3. PSF Photometry of Multiple Overlapping Stars 2
4. PSF Photometry of Multiple Overlapping Stars • Data: single image, time-series of images, etc... 2
5. PSF Photometry of Multiple Overlapping Stars • Data: single image, time-series of images, etc... • Parameters: θ(1) = x(1) 0 , y(1) 0 , F(1), B ... θ(K) = x(K) 0 , y(K) 0 , F(K), B That’s a total of 3K + 1 parameters! 2
6. PSF Photometry of Multiple Overlapping Stars • Data: single image, time-series of images, etc... • Parameters: θ(1) = x(1) 0 , y(1) 0 , F(1), B ... θ(K) = x(K) 0 , y(K) 0 , F(K), B That’s a total of 3K + 1 parameters! • Model: PSF x, y, θ(k) = F(k)h x − x(k), y − y(k) + B K 2
7. PSF Photometry of Multiple Overlapping Stars • Data: single image, time-series of images, etc... • Parameters: θ(1) = x(1) 0 , y(1) 0 , F(1), B ... θ(K) = x(K) 0 , y(K) 0 , F(K), B That’s a total of 3K + 1 parameters! • Model: PSF x, y, θ(k) = F(k)h x − x(k), y − y(k) + B K • Objective: θ = arg min θ∈Θ x,y dataxy − k PSF x, y, θ(k) 2 2
8. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND 3
9. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND while len(stars) > 0: groups = group(stars) // DBSCAN 3
10. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND while len(stars) > 0: groups = group(stars) // DBSCAN fitted_groups = fit(groups, model) 3
11. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND while len(stars) > 0: groups = group(stars) // DBSCAN fitted_groups = fit(groups, model) residual = subtract(image, fitted_groups) 3
12. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND while len(stars) > 0: groups = group(stars) // DBSCAN fitted_groups = fit(groups, model) residual = subtract(image, fitted_groups) stars = find(residual) 3
13. DAOPHOT-like PSF Photometry stars = find(image) // DAOFIND while len(stars) > 0: groups = group(stars) // DBSCAN fitted_groups = fit(groups, model) residual = subtract(image, fitted_groups) stars = find(residual) 3
14. How are we doing PSF Photometry? K2 data looks like: 4
15. How are we doing PSF Photometry? K2 data looks like: 4
16. The Kepler Pixel Response Function Our module looks like: 5
17. Our tools: PyKE and oktopus PyKE: KeplerPRF, KeplerTargetPixelFile, KeplerPRFPhotometry (work in progress) pyke.keplerscience.org 6
18. Our tools: PyKE and oktopus oktopus: Likelihood, Prior, Posterior keplergo.github.io/oktopus 7
19. Fitting K2 data 8