aurelio-amerio/gPCS: v1.0.2
Creators
Description
gPCS: Gamma-ray Photon-Counts Statistics
This repository contains the code for the paper Deepening gamma-ray point-source catalogues with sub-threshold information.
We provide our results in the form of a precomputed FITS, as well as python package which can be used to read the data as numpy
arrays, as well as export a similar FITS table.
Installation
This package can easily be installed through pip:
pip install gPCS
Example usage
These examples can be run online on colab.
This package can be used to obtain the firing pixels, either given a chosen TS_star or by fixing a quality factor (QF) and significance level (alpha).
import numpy as np
from gPCS import gPCS
# specify manually a TS_star
TS_star = 36
pixel_firing = gPCS.get_firing_pixels(TS_star, filter=False)
print(len(pixel_firing))
# Compute the TS_star from a chosen QF and alpha
QF = 0.5
alpha = 0.05
TS_star = gPCS.get_TS_from_QF(QF, alpha=alpha)
pixel_firing = gPCS.get_firing_pixels(TS_star, filter=False)
print(len(pixel_firing))
We can get the TS of the firing pixels:
TS_star=36
firing_pixels = gPCS.get_firing_pixels(TS_star, filter=False)
TS_ranking = gPCS.TS_map_Fermi[firing_pixels]
It is easy to obtain the galactic coordinates of the firing pixels using healpy:
import healpy as hp
lon, lat = hp.pix2ang(NSIDE, firing_pixels, lonlat=True) # lon lat in degrees
And we can compute the QF and QF range of the firing pixels, given alpha:
# obtain the QF using all the simulations
QF = gPCS.get_QF_from_TS(TS_ranking, alpha=alpha)
# compute the mean and std of the QF using batches of simulations
mean_QF, std_QF = gPCS.get_QF_ranges_from_TS(TS_ranking, alpha=alpha,
batches=100, batch_size=3000)
# we can obtain the QF range for the firing pixels using the mean and std
QF_min = mean_QF - std_QF
QF_max = mean_QF + std_QF
If desired, we provide some simple functions to filter the firing pixels, for example by removing pixels that are firing for the simulated 4FGL K map (see paper):
# filter out the firing pixels for the 4FGL K map
pixel_firing = gPCS.get_firing_pixels(TS_star, filter=True)
# If conservative is True, after filtering the pixels in K,
# the routine will also filter the pixels in the 1 pixel neighborhood of the pixels in K.
pixel_firing = gPCS.get_firing_pixels(TS_star, filter=True, conservative=True)
# If deg is specified, the routine will also filter the pixels
# in the disc of radius deg centered on the centroid of the 4FGL catalog sources.
pixel_firing = gPCS.get_firing_pixels(TS_star, filter=True, conservative=True, deg=0.5)
For ease of use, we provide the TS maps both for Fermi and the simualted 4FGL map (numpy
attays. The maps are computed at nside=512
and are stored in the following variables:
gPCS.TS_map_Fermi
gPCS.TS_map_4FGL
In order to compute the 4FGL gll_psc_v30
catalog, available from the Fermi LAT colalboration website.
Exporting the results
We provide a simple function to export the results in the form of a FITS table, which can be used to reproduce the results of the paper.
export_fits_table(filename, QF, alpha, overwrite=False, **kwargs)
export_fits_table
accepts the following arguments:
- filename : name of the output FITS file
- QF : quality factor
- alpha : significance level (can be an array, and the supported values are 0.01, 0.05, 0.1)
- overwrite : if True, the routine will overwrite the output file if it already exists
- **kwargs : additional arguments to be passed to
get_firing_pixels
.
export_fits_table
will create a FITS table with the following columns:
- pixel : pixel index
- TS : TS value
- QF_best : QF value obtained by considering all the simulations
- QF_min : lower bound of the QF range
- QF_max : upper bound of the QF range
In order to export the FITS table available in the examples folder, we can run the command:
gPCS.export_fits_table(filename="firing_pixels.fits", QF=0.50, alpha=[0.01, 0.05, 0.1])
List of functions
-
get_QF_from_TS(TS, alpha)
: computes the quality factor from a given TS and alpha -
get_QF_ranges_from_TS(TS, alpha, batches=100, batch_size=3000)
: computes the mean and std of the QF from a given TS and alpha, using batches of simulations -
get_TS_from_QF(QF, alpha)
: computes the TS from a given QF and alpha -
get_firing_pixels(TS_lim, filter=False, conservative=False, deg=None)
: computes the firing pixels for a given TS_lim. -
export_fits_table(filename, QF, alpha, overwrite=False, **kwargs)
: exports the results in the form of a FITS table.
For more information about what each function does, please refer to the docstrings and help of each function.
License
This code is released under the Zlib license. See the LICENSE file for more information.
Files
aurelio-amerio/gPCS-v1.0.2.zip
Files
(38.3 MB)
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Additional details
Related works
- Is supplement to
- https://github.com/aurelio-amerio/gPCS/tree/v1.0.2 (URL)