Photometric redshift for clusters through A1689 and simulation studies Stephanie Jouvel, Ofer Lahav, Ole Host

Outline - Presentation of Le Phare code - A1689 photoz results : BPZ (Dan Coe) & Le Phare - Massimo Neghetti’s simulation : photoz results

Le Phare photoz code Stephane Arnouts & Olivier Ilbert : Interesting features and new developments include : - A prior on the redshift distribution using the VVDS spectroscopic redshift survey - Emission lines fluxes included in the library of templates. This is calculated using the relation between UV absolute magnitude – OII fluxes (Kennicutt et al. 1998). Other lines are derived from emission line ratios. - Possibility of including several extinction laws and E(B-V) values. - FIR scaling

Le Phare photoz code COSMOS photoz : Ilbert et al. 2009

A1689 photometric bands

A1689 : photoz BPZ & Le Phare COSMOS : 31 templates – Bruzual & Charlot 03 (Ext,NoEm) + Nz priori (VVDS)

Photoz results for A1689 Adding prior on the redshift distribution Error budget for HST filters probably underestimated : Filter calibration, source extraction Sextractor, photometry accuracy => High constraints on the fitting procedure We release it in adding in quadrature to r,i,z HST filters photometric errors

Photoz results for A1689 : BPZ and Le Phare

A1689 photoz distribution Need to carefully select the filters to calculate photoz

Massimo's simulations : LePhare & BPZ

Massimo's simulations : lenses Contamination by galaxy cluster members : Photometry extraction problems Between Le Phare and BPZ we will probably Be able to remove catastrophic redshit

Conclusion - Validate the 0.02*(1+z) photoz accuracy - Remove catastrophic redshift using pdz information of several photoz codes - Need careful work on the photometry extraction - Do a proper analysis of the photometry error budget to improve the photoz accuracy - Optimize the observation strategy to get good photometry in the key filters - Do a pre-selection of cluster members from background galaxies following Umetsu et al paper

Massimo's simulations : LePhare & BPZ

A1689 : 85 zpsec

Photoz results for A1689

Le Phare parameters

Photoz results for A1689 : dz

Massimo's simulations : LePhare vs BPZ

Massimo's simulations : LePhare & BPZ

Photoz results for A1689

Le Phare photoz code Jouvel et al Why in one sentence

Improve photoz fit through error budget Error budget for HST filters probably underestimated : Filter calibration, source extraction Sextractor, photometry accuracy => High constraints on the fitting procedure We release it in adding in quadrature to r,i,z HST filters photometric errors