the Empirical

Galaxy Generator

Builds your own Universe during the coffee break.

Project maintained by Corentin Schreiber (cschreib) Hosted on GitHub Pages — Theme by mattgraham


EGG is a suite of tools that can generate mock galaxy catalogs with realistic positions, morphologies and fluxes from the far-ultraviolet to the far-infrared.

The process is based exclusively on empirical relations that are carefully calibrated on state-of-art observations from the deep CANDELS fields, in particular using data from the Hubble-WFC3 camera and Herschel-PACS and SPIRE. The "root" element of the simulation process is the stellar mass of each galaxy, which is used to derive statistically the dust content, star formation rate, optical colors and morphology. The full panchromatic spectrum of the galaxy is generated from this set of parameters, and by construction the resulting flux distributions reproduce accurately the observed ones.

The generated catalogs can be used to produce realistic maps and mock observations to test source extraction codes, or to evaluate the reliability of any map-based science (stacking, dropout identification, ...).

Legend. Example of a cosmological deep field simulated with EGG. The image on the left is a false color image built from the Hubble B (blue), z (green) and H (red) bands. The image on the right is a false color image of the Herschel 100┬Ám band. In the center, the two images overlap and are artificially blended with one another. You can click the image for a larger version.

How to get it?

Simply download the code using the link provided at the top of this page, which will give you the latest stable version. You will then need to follow the installation instructions to compile the program before you start using it. Alternatively, you can download a Bash install script that will take care of most of this dirty work for you: (usage instructions are given at the beginning of the file, be sure to read them before executing the script). In all cases, please refer to the documentation for in depth instructions.

If you wish, you can also obtain the very latest development version by cloning the git repository:

git clone

This will give you access to the latest features, but may not be as stable and well tested.


C. Schreiber and the ASTRODEEP collaboration, EGG: hatching a mock Universe from empirical prescriptions, A&A, 906, 96.

EGG is written with the vif C++ library for numerical analysis.