CLASH Photometric redshifts for galaxies in cluster field
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Transcript of 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