1. USM Photometric Redshifts for Astro-wise
R. Bender, A. Gabasch, M. Neeser, R. Saglia, J. Snigula
Universitätssternwarte München
Ludwig-Maximillians-Universität
18/11/2003
Groningen Workshop (M. Neeser)

2. Groningen Workshop (M. Neeser)
Introduction
Photometric Redshifts:
deducing redshifts from multiple-band optical and near
infrared imaging (poor man´s spectroscopy)
Scientific drivers:
Source identifications and redshifts
Luminosity functions
Star formation histories
Large scale structures
Cluster searches
An obvious scientific product for the database catalogues
18/11/2003
Groningen Workshop (M. Neeser)

3. Spectral Energy Distributions (model input)
Galaxies
Stars
20 SED´s
18/11/2003
Groningen Workshop (M. Neeser)

4. Groningen Workshop (M. Neeser)
Method:
Filter curves
convolved with
detectors
Observed flux
for each source
SEDs:
convolved with
filters
stepped in redshift
18/11/2003
Groningen Workshop (M. Neeser)

5. Assigning a redshift and SED to each source
18/11/2003
Groningen Workshop (M. Neeser)

6. Groningen Workshop (M. Neeser)
Final SED/redshift fit
FDF 2893
18/11/2003
Groningen Workshop (M. Neeser)

7. Groningen Workshop (M. Neeser)
FDF 2367
18/11/2003
Groningen Workshop (M. Neeser)

8. Groningen Workshop (M. Neeser)
FDF 914
18/11/2003
Groningen Workshop (M. Neeser)

9. Groningen Workshop (M. Neeser)
Comparison with zspec
200 FDF spectra
18/11/2003
Groningen Workshop (M. Neeser)

10. Limitations of this method
Requires adequate spectral coverage (ie. at least 4 filters)
Existence of degeneracies in SEDs at some redshifts
SED input library inadequate to accurately map the coolest stars
Id´s and redshifts for AGN‘s must be done separately from
galaxies
18/11/2003
Groningen Workshop (M. Neeser)

11. Groningen Workshop (M. Neeser)
FDF 4940
18/11/2003
Groningen Workshop (M. Neeser)

12. Groningen Workshop (M. Neeser)
FDF 2497
18/11/2003
Groningen Workshop (M. Neeser)

13. Integration into Astro-Wise Pipeline
Envision two modes of operation:
automatic redshifts and source identification from catalogue
colours assuming given default settings (filters, SED´s) and
with output: zphot, SED, probability, and errors.
interactive mode with user defined parameters (SED´s,
zrange, Mrange ) with simple plotting facilities and filter
convolution routines.
18/11/2003
Groningen Workshop (M. Neeser)

14. Integration into Astro-Wise Pipeline
Class Photred
Persistent class PhotredConfig()
persistent SED models
“ model errors
“ filter convolution
“ seeing factors
“ filter weight (SED error in given filter / bad filter value)
==> each object assigned: z1, z2, MB
(persistent) Dz1, Dz2
P1, P2
C1, C2
model1, model2
18/11/2003
Groningen Workshop (M. Neeser)

15. Integration into Astro-Wise Pipeline
Open crucial issues:
1/ class definitions
2/ reliable, consistent photometric redshifts can only be achieved
with photometric and PSF uniformity across filter sets.
(ie. PSF homogenization across all filters).
18/11/2003
Groningen Workshop (M. Neeser)

16. Present Implementation of Photometric Redshift Routine
fortran routines to compute chi-square minimization and
redshift probability function
super mongo routines to display output, with a large
number of user defined parameters
Munics interactive source selection
18/11/2003
Groningen Workshop (M. Neeser)