Welcome to CAESAR’s documentation!¶
CAESAR is a python-based
yt extension package for analyzing
the outputs from cosmological simulations.
CAESAR takes as
input a single snapshot from a simulation, and outputs a portable
HDF5 catalog containing a host of galaxy and halo properties
that can be read in and explored without the original simulation
CAESAR thus provides a simple and intuitive interface
for exploring object data within your outputs.
CAESAR provides further functionality such as identifying the
most massive progenitors or descendants across snapshots (see
Progenitors), and generating FSPS photometry and spectra for
Photometry). Also, the
contains particle ID lists for each galaxy/halo, enabling you
to quickly grab the relevant particle data in the original snapshot
in order to compute any other galaxy/halo quantity you want.
CAESAR is OpenMP-parallelized using
joblib. It enjoys decent scaling with the (user-specifiable)
number of cores. Catalog generation does, however, have substantial
memory requirements – e.g. a run with two billion particles requires a
machine with 512 GB to generate the catalog, and this scales with the
number of particles. The resulting
CAESAR catalog typically has
a filesize of less than 1% of the original snapshot, so once this is
generated, using it is not memory-intensive.
CAESAR generates a catalog as follows:
Identify halos (or import a halo membership list)
Compute halo physical properties
Within each halo, identify galaxies using 6-D friends-of-friends
Compute galaxy physical properties
Optionally, compute galaxy photometry including line-of-sight extinction
Create particle lists for each galaxy and halo
Link galaxies and halos, identify centrals+satellites, quantify environment
Output all information into a stand-alone
CAESAR catalog has been generated, it can be loaded
and the data easily accessed using simple python commands.
CAESAR builds upon the yt project,
which provides support for a number of simulation codes and
All meaningful quantities stored within a
CAESAR catalog have
units attached, reducing ambiguity when working with your data.
This tight connection enables you to use both
functionality straightforwardly within a single analysis package.
CAESAR currently supports the following codes/formats:
In principle, any
yt-supported simulation snapshot could be
CAESAR, but some aspects may not work out-of-the-box owing
to different conventions for e.g. metallicity arrays.
CAESAR has been tested on Mufasa, Simba, Illustris/TNG, and EAGLE
We happily accept pull requests for further functionality and bug fixes.
To get started, follow the
Getting Started link below!
- Getting Started
- Running CAESAR
- Loading CAESAR files
- Using CAESAR
- Catalog Quantities
- Aperture Quantities