Welcome to Institute for Astronomy


Research Groups

Extragalactic Astrophysics
(Lead: Prof. Carollo)
Observational Cosmology
(Lead: Prof. Lilly)
Star and Planet Formation
(Lead: Prof. Meyer)
(Lead: Prof. Refregier)
Black Holes
(Lead: Prof. Schawinski)

The Zurich Extragalactic Bayesian Redshift Analyzer


ZEBRA is a free and open-source software distributed under the GNU General Public License 3 and can be downloaded here.


ZEBRA combines and extends several of the classical approaches to produce accurate photometric redshifts down to faint magnitudes. In particular, ZEBRA uses the template-fitting approach to produce Maximum Likelihood and Bayesian redshift estimates based on:


The workflow of ZEBRA. The input files are indicated on the top. The resulting output data on the bottom. A typical ZEBRA session would take the following route: 1) Check & correction of the photometric catalog; 2) Optimization of the spectral energy distributions (templates); 3) Maximum-Likelihood fit or Bayesian estimation of the probability distribution in template type - redshift space.


The user can choose from, or has otherwise to provide, an initial set of templates and filter transmission curves. In addition a catalog is needed which provides ZEBRA with the magnitudes of the galaxies in question in the various filter bands.



In Feldmann et al. 2006 we have demonstrated ZEBRA's performance using the Subaru, CFHT and NOAO groundbased photometry (Capak et al. 2006; Taniguchi et al. 2006; ApJ COSMOS Special issue) on a sample of ~50,000 COSMOS galaxies and, as a training set, zCOSMOS spectroscopic redshifts that were available for 1.8% of the sample under study.

A simple Maximum-Likelihood estimate of redshifts without template optimization; (top) spectroscopic vs. photometric redshifts; (bottom) the error in the redshift estimation as function of redshift for different template types.
ZEBRA's Maximum-Likelihood estimate of redshifts with template optimization. Top and bottom panel as in a).

ZEBRA's Bayesian estimate of redshifts with template optimization. Top and bottom panels as in a).
standard deviation of dz/1+z ~ 0.043
outlier fraction ~ 2.1 %
standard deviation of dz/1+z ~ 0.027
outlier fraction ~ 1.1 %
standard deviation of dz/1+z ~ 0.027
outlier fraction ~ 0.8 %


In order to run ZEBRA on your machine you may try to download an appropriate, precompiled ZEBRA binary. Alternatively you can download the ZEBRA package and compile the code yourself. Please refer to the ZEBRA user manual on how to install ZEBRA properly. The ZEBRA package includes: the source code, examples on how to use ZEBRA, wrapper scripts and the user manual.

Latest stable version - v1.10 - 09.02.2013
Target Platform
File Remarks
Binary Linux 64 bit - x86 zebra gsl statically linked
Binary Mac OS X 10.8 - Intel
gsl statically linked
Unix / Linux / Mac OS
incl. source code, examples, wrapper scripts, manual

A note about binaries: We recommend the installation of ZEBRA from source as described in the user manual. Installation from source requires lapack and the GNU Scientific Library (gsl).


Previous Versions

Change Log

Please report any bugs or problems you encounter with the code to:
If you are intending to extend / improve ZEBRA it would be kind to let us know as well.

It is kindly requested that the use of ZEBRA should be acknowledged with an explicit reference to Feldmann, Carollo, Porciani, Lilly et al., MNRAS 372, 564 (2006) in the bibliographic list of any resulting publication.


A new version of ZEBRA (ZEBRA+) is currently being built in order to:

Stay tuned!


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© 2014 ETH Zurich | Imprint | Disclaimer | 19 March 2013