This project aims to compute how many quasars could be detected by an astronomical survey. For any filter of interest, this code will produce a plot of # quasar detections vs. limiting magnitude with curves showing how many quasars will be found above specified redshift cutoffs.

The code uses simulated quasar lightcurves to calculate the expected magnitude of quasars at many redshifts. It then integrates, over redshift and over absolute quasar magnitude, the number density of quasars as given by a parameterized quasar luminosity function.

1. Python 2 or 3 (see below for which to choose)
2. numpy, scipy, matplotlib
3. sims_photUtils from the LSST stack

If you don't already have the LSST software stack on your machine, getting sims_photUtils may be difficult. If possible, you should install the stack from source, since the simulations stack no longer supports conda. In this case, you should use Python 3, since the LSST stack is mostly moving to Python 3.

However, in practice, installing the LSST stack from source is very difficult to do. Instead, you can install an old version of sims_photUtils using conda by running the following commands:

conda update conda
conda config --add channels http://conda.lsst.codes/sims
conda install lsst-sims-photutils

This will add the lsst sims conda distribution channel and then install sims_photUtils along with all of its dependencies. In this case, I think you may need to use Python 2, but I'm not entirely sure.

Note that installing an old version in this way may downgrade packages pip and astropy. I recommend installing lsst-sims-photutils in a conda virtual environment.

Before running code in this repository, you need to set up the sims_photUtils package. First, source the correct loadLSST file for your terminal. This should be located in the bin directory for your conda virtual environment if you installed with conda, or in the root directory of your stack install if you installed from source. You might be able to get the path by running setup with no arguments.

source path/to/conda/env/or/stack/root/loadLSST.myshell

Then set up the sims_photUtils package:

setup sims_photUtils

The code has many configuration options located in countQuasars.conf. The parameters are documented in the file.

When run without any options, the countQuasars.py script will show the output plot but will not save any results to disk. When the --saveOutput argument is present, it will save the output plot and tables respectively to config.outputDir/<current git revision>/config.outFilenamePlt(Tbl). Because the output filenames are formatted with only the survey, filter, and reddening (as documented in the config file), it is important to commit any changes you make to the config file or the code between output-saving runs unless the changes are made exclusively to config.survey, config.f, and config.reddening, since those parameters are saved in the filenames themselves.

The config file currently in use is also saved to config.outputDir/<current git revision>