CLASH Photometric redshifts for galaxies in cluster field

Stephanie Jouvel 1

CLASH Photometric redshifts for galaxies in cluster field

Stephanie Jouvel & CLASH photo-z team

London sept 2013

Jouvel et al 2013 submitted

Stephanie Jouvel 2

CLASH/HST Photo-z goals• Accurate photo-z for the SL arcs• Clean cluster/background galaxy selection

London sept 2013

690 galaxies with spec-z covered by HST:584 cluster+foreground106 lensed background

We use BPZ & Le PhareNot enough galaxies to train NN and other training methods

Stephanie Jouvel 3

COSMOS templates library for Le Phare

London sept 2013

Lines are templates colors, dots are CLASH observations for the full specz sample Good agreement between model & the CLASH observations

Stephanie Jouvel 4

Lensed background galaxies z>zcluster+0.2

London sept 2013

Very good accuracy of NMAD~3%

Stephanie Jouvel 5

Foreground+cluster galaxies z<zcluster+0.2

London sept 2013

Stephanie Jouvel 6

Photo-z scatter for full spec-z sample

London sept 2013

Stephanie Jouvel 7

CLASH photoz accuracy with simulations

London sept 2013

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

Stephanie Jouvel 8

MACS1206 strong-lensing arcs

London sept 2013

4 systems with spec-z:

Sys 1: zs=1.03Sys 2: zs=3.03Sys 3: zs=3.03Sys 4: zs=2.54

Stephanie Jouvel 9

MACS1206 System 1

London sept 2013

Zs=1.03: Balmer & Lyman break=> Good photoz

Lyman break

Balmer break

Stephanie Jouvel 10

MACS1206 System 2

London sept 2013

Zs=3.03: Balmer break outside the CLASH filters

Lyman break

Stephanie Jouvel 11

MACS1206 System 3

London sept 2013

Zs=3.03: Balmer break outside the CLASH filters

Lyman break

Stephanie Jouvel 12

MACS1206 System 4

London sept 2013

Zs=2.54: Balmer & Lyman break=> Good photoz

Lyman break

Balmer break

Cluster light contamination

Stephanie Jouvel 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 2013

Stephanie Jouvel 14

Photoz scatter & LSS in lensing

London sept 2013

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

Stephanie Jouvel 15

BPZ and Le Phare

London sept 2013

Some work needed to understandthe discrepancy at low z between BPZ and Le Phare

Stephanie Jouvel 16

BPZ and Le Phare

London sept 2013

Some work needed to understandthe discrepancy at low z between BPZ and Le Phare:

Low odds are lowz for Le Phare and highz for BPZ

Stephanie Jouvel 17

Some ideas

London sept 2013

Stephanie Jouvel 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 2013