skymap-overlap 0.1.6

Compute overlap between two skymaps

# skymap-overlap

Compute the overlap between two skymaps

## Requirements

• scipy-stack (numpy, scipy, matplotlib, pandas)

• astropy

• healpy

• ligo.skymap (only supports Python3.X)

• ligo-gracedb (for batch downloading skymaps)

• pycondor

## Installation This package is available on PyPI. To install, simply run `bash pip install skymap-overlap `

## Usage ### Computing the overlap between two skymaps To compute the overlap between two skymaps $`p(Omega)`$ and $`q(Omega)`$, one can use compute_overlap to compute the overlap. Currently the script computes three overlap statistics:

1. Posterior overlap, which is defined as `math \displaystyle\int_{\rm all sky} p(\Omega)q(\Omega) \; d\Omega `

2. Normalized posterior overlap, which is defined as `math \frac{\displaystyle\int_{\rm all sky} p(\Omega)q(\Omega) \; d\Omega}{\sqrt{\displaystyle\int_{\rm all sky} p(\Omega)p(\Omega) \; d\Omega}\sqrt{\displaystyle\int_{\rm all sky} q(\Omega)q(\Omega) \; d\Omega}} `

3. 90% credible region (CR) overlap, which is defined as `math \frac{\displaystyle\int \mathbf{1}_{\rm 90\% CR} \left[ p(\Omega)\right] \mathbf{1}_{\rm 90\% CR} \left[ q(\Omega) \right] d\Omega}{{\rm min} (\displaystyle\int \mathbf{1}_{\rm 90\% CR} \left[ p(\Omega) \right] \; d\Omega , \displaystyle\int \mathbf{1}_{\rm 90\% CR} \left[ q(\Omega) \right] \; d\Omega)}, ` where $`mathbf{1}`$ is the indicator function.

4. Cross-highest posterior density (HPD) `math \max \left\{ 1 - \mathcal{H}(p, q), 1 - \mathcal{H}(q, p) \right\} ` where `math \mathcal{H}(p, q) = \int \mathbf{1} \left[ q(\Omega) > q(\Omega_{p, \mathrm{MAP}}) \right] q(\Omega) d\Omega \,, ` $`mathbf{1}`$ is the indicator function, $`Omega_{p,mathrm{MAP}}`$ is the maximum a posteriori estimate of the sky location $`Omega`$ for $`p`$.

Given two FITS skymaps, the simplest usage is ` compute_overlap --skymap SKYMAP1.fits.gz --skymap SKYMAP2.fits.gz `

### Computing the pairwise overlap between a batch of skymaps To compute the pairwise overlap between a batch of skymaps, you can use compute_overlap_from_skymaps_pipe which generates a DAG file for you to submit to a HTCondor-compatible cluster to calculate the overlap. The simplest usage is ` compute_overlap_from_skymaps_pipe --skymap SKYMAP1.fits.gz --skymap SKYMAP2.fits.gz --skymap SKYMAP3.fits.gz ` so on and so forth. There are also other options for example the accounting tag (if you are running on LDG).

### Batch downloading skymaps from GraceDB You can use download_skymap to download skymaps from GraceDB given the GID or SID. The simplest usage is ` download_skymap GID_or_SID ` By default it will download LALInference skymaps whenever possible. There is also an option –bayestar to only use skymaps generated by bayestar.

### Joint sky localization This package provides a command-line-interface tool combine_skymaps that is identical to ligo-skymap-combine [here](https://lscsoft.docs.ligo.org/ligo.skymap/tool/ligo_skymap_combine.html), except all distance information stored in the given maps will be discarded. The simplest usage is ` combine_skymaps INPUT1.fits INPUT2.fits OUTPUT.fits `

## Author Rico K. L. Lo @ka-lok.lo