Photometric redshift for clusters through A1689 andsimulation 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 :
http://www.cfht.hawaii.edu/~arnouts/LEPHARE/cfht_lephare/lephare.html
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 PhareCOSMOS : 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 +0.02 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 : LePhare & BPZ
Massimo's simulations : LePhare & BPZ
Massimo's simulations : lenses
Contamination by galaxy cluster members :Photometry extraction problems
Between Le Phare and BPZ we will probablyBe 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. 2010 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. 2009
Why in one sentence
Improve photoz fit through error budget
+0.02
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 +0.02 in quadrature to r,i,z HST filters photometric errors