1. CLASH Photometric redshifts for galaxies in cluster field Stephanie Jouvel & CLASH photo-z team London sept 20131Stephanie Jouvel Jouvel et al 2013 submitted

2. CLASH/HST Photo-z goals Accurate photo-z for the SL arcs Clean cluster/background galaxy selection London sept 2013Stephanie Jouvel2 690 galaxies with spec-z covered by HST: 584 cluster+foreground 106 lensed background We use BPZ & Le Phare Not enough galaxies to train NN and other training methods

3. COSMOS templates library for Le Phare London sept 2013Stephanie Jouvel3 Lines are templates colors, dots are CLASH observations for the full specz sample Good agreement between model & the CLASH observations

4. Lensed background galaxies z>z cluster +0.2 London sept 2013Stephanie Jouvel4 Very good accuracy of NMAD~3%

5. Foreground+cluster galaxies z<z cluster +0.2 London sept 2013Stephanie Jouvel5

6. Photo-z scatter for full spec-z sample London sept 2013Stephanie Jouvel6

7. CLASH photoz accuracy with simulations London sept 2013Stephanie Jouvel7 Simulation of the CLASH photometry in the 16 HST filters We reach a limit in the photo-z scatter due to the filter resolution => It’ll be hard to beat the 2-3% NMAD using broadband photometry

8. MACS1206 strong-lensing arcs London sept 2013Stephanie Jouvel8 4 systems with spec-z: Sys 1: zs=1.03 Sys 2: zs=3.03 Sys 3: zs=3.03 Sys 4: zs=2.54

9. MACS1206 System 1 London sept 2013Stephanie Jouvel9 Zs=1.03: Balmer & Lyman break => Good photoz Lyman break Balmer break

10. MACS1206 System 2 London sept 2013Stephanie Jouvel10 Zs=3.03: Balmer break outside the CLASH filters Lyman break

11. MACS1206 System 3 London sept 2013Stephanie Jouvel11 Zs=3.03: Balmer break outside the CLASH filters Lyman break

12. MACS1206 System 4 London sept 2013Stephanie Jouvel12 Zs=2.54: Balmer & Lyman break => Good photoz Lyman break Balmer break Cluster light contamination

13. UV filters in the photoz estimation of background lensed galaxies UVIS filters are useful to follow the Lyman break for galaxies 0.7<z<2.5 – At z>2.5 the Lyman break is in F435W and the UVIS filters stop being useful. – At z<0.7 the Lyman break did not reach F225W UVIS filters useful for the photo-z of background galaxies London sept 201313Stephanie Jouvel

14. Photoz scatter & LSS in lensing London sept 2013Stephanie Jouvel14 Translating a 4% photoz error into a SL arcs positional error when deriving gravitational potential on A1689 (cause it has more than 106 arcs). A 4% photoz error is bigger than LSS positional error for 6/106 arcs. => 3% photoz error is ok for SL

15. BPZ and Le Phare London sept 2013Stephanie Jouvel15 Some work needed to understand the discrepancy at low z between BPZ and Le Phare

16. BPZ and Le Phare London sept 2013Stephanie Jouvel16 Some work needed to understand the discrepancy at low z between BPZ and Le Phare: Low odds are lowz for Le Phare and highz for BPZ

17. Some ideas London sept 2013Stephanie Jouvel17

18. Conclusion Good photoz accuracy for the SL arcs from both BPZ and Le Phare of NMAD ~ 3% Progress needed for the background/foreground galaxy selection. BPZ and Le Phare have different estimates for 7% of galaxies in MACS1206 field Use the full P(z) to improve the photoz estimates London sept 2013Stephanie Jouvel18