Estimate H0 from GW measurements and galaxy catalogs.

This code estimates a posterior probability for the Hubble constant using a skymap from LIGO and a galaxy catalog. The formalism is similar to the one described in Del Pozzo et al. 2012, Chen et al. 2017. It can be run on data, or it can rotate skymaps on galaxies or higher density peaks for simulations.

Note: At the moment this is running in the close distances approximation, with no deceleration parameter!

Contributors: Antonella Palmese, Jim Annis, Marcelle Soares-Santos, Maria E. Pereira, Alyssa Garcia, Zoheyr Doctor and DES collaborators.

1. Uncompress the skymaps in the skymaps folder before running. skymap.fits is the LAL inference map for GW170814, skymapGW170817.fits is for GW170817.

2. Create a "catalogs" folder with the necessary catalogs. Flask simulations and DES/2MASS catalogs for the GW1708 events can be found at /data/des60.b/data/palmese/Dark_sirens/catalogs

3. run make in the source directory.

From inside the "source" directory, run:

python prepare_galaxy_catalog.py
python rotate_skymap_on_galaxies.py
python H0_nevents.py

Step 1: prepare_galaxy_catalog.py adds healpix pixel information for each galaxy in the catalog, and makes it quicker to match catalogs to skymaps later on for hundreds of events.

Step 2: rotate_skymap_on_galaxies.py rotates the peak of the skymap to the position of galaxies which are found to be the closest to the redshift computed from the peak of the skymap luminosity distance and some input H0 provided by the user. The map can be rotated to nevents different galaxies.

Step 3: H0_nevents_flask.py computes a posterior for N events, provided the skymaps from Step 2 and a galaxy catalog.

See the codes for a full list of user defined inputs (e.g. H0, redshift range considered...), or type

python code.py --help

H0_nevents.py : reads in a single file for the catalog, can be used for multiple events (posteriors are multiplied)

H0_onevent_hpix_search.py : Reads in a catalog in healpix pixel files (as in the usual DES format) and a skymap, and produces a posterior. The default version uses the GW170814 skymap and a value added DES catalog, that can be downloaded from the DES machines. There are a bunch of keywords.

H0_onevent_GW170817.py : Reads in a catalog in the GW170817 area, and compares the H0 posterior to the one computed when considering NGC 4993 only.

taud_onevent_hpix_search.py : Reads in a galaxy catalog with SFHs and computes a time delay posterior assuming a cosmology.

See the codes for a full list of user defined inputs (e.g. H0, redshift range considered...), or type

python code.py --help

H0_nevents.py and H0_onevent_hpix_search.py can be run using a Gaussian pdf for galaxies' redshifts (key --zerr_use True) instead of a delta function, and a Flat LambdaCDM cosmology (--cosmo_use True) instead of a simple Hubble law. Both of these options will make the code much slower, especially the p(z).

Check the beginning of these .py files if you want to change paths, binnings, etc. This will soon be implemented in a params.py input file.