CLASH Photometric redshifts for galaxies in cluster field
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Transcript of CLASH Photometric redshifts for galaxies in cluster field
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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
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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
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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
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Stephanie Jouvel 4
Lensed background galaxies z>zcluster+0.2
London sept 2013
Very good accuracy of NMAD~3%
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Stephanie Jouvel 5
Foreground+cluster galaxies z<zcluster+0.2
London sept 2013
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Stephanie Jouvel 6
Photo-z scatter for full spec-z sample
London sept 2013
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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
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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
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Stephanie Jouvel 9
MACS1206 System 1
London sept 2013
Zs=1.03: Balmer & Lyman break=> Good photoz
Lyman break
Balmer break
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Stephanie Jouvel 10
MACS1206 System 2
London sept 2013
Zs=3.03: Balmer break outside the CLASH filters
Lyman break
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Stephanie Jouvel 11
MACS1206 System 3
London sept 2013
Zs=3.03: Balmer break outside the CLASH filters
Lyman break
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Stephanie Jouvel 12
MACS1206 System 4
London sept 2013
Zs=2.54: Balmer & Lyman break=> Good photoz
Lyman break
Balmer break
Cluster light contamination
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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
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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
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Stephanie Jouvel 15
BPZ and Le Phare
London sept 2013
Some work needed to understandthe discrepancy at low z between BPZ and Le Phare
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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
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Stephanie Jouvel 17
Some ideas
London sept 2013
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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