Python bindings for the YMW16, NE2001 and YT2020 electron density models
This package is a Python interface to the YMW16 and NE2001 electron density models, and YT2020 halo model.
The Yao, Manchester and Wang (2017, Astrophys. J., 835, 29;
arXiv:1610.09448) YMW16 electron density model, is written in C++, and the Cordes and Lazio
(2001, arXiv:0207156) NE2001 model is written in FORTRAN. This package, PyGEDM, wraps these
two codes using pybind11 to make them usable from Python. Here, we have converted NE2001 to C++ using
We provide a web app at https://apps.datacentral.org.au/pygedm/
The pygedm web app is kindly hosted by Data Central.
Some usage examples can be found in the examples directory.
import pygedm # calculate DM at a given distance DM, tau_sc = pygedm.dist_to_dm(204.0, -6.5, 200, method='ne2001') DM, tau_sc = pygedm.dist_to_dm(204.0, -6.5, 200, method='ymw16') # calculate distance for a given sky position and DM dist, tau_sc = pygedm.dm_to_dist(123.4, 4.0, 200) # calculate N_e density at xyz galactocentric coordinates ne = pygedm.calculate_electron_density_xyz(1.0, 2.0, 3.0) # calculate N_e density at Galactic lat/long/distance coords ne = pygedm.calculate_electron_density_lbr(204.0, -6.5, 3000.0) # Calculate halo DM contribution dm_halo = pygedm.calculate_halo_dm(gl=0, gb=30)
import pygedm import astropy.units as u import astropy.coordinates as c DM = u.Quantity(10.0, unit='pc cm^-3') ra, dec = c.Angle(23.0, unit='hourangle'), c.Angle('-43:00:02', unit='degree') sky_coords = c.SkyCoord(ra, dec, frame='icrs') dist, tau_sc = pygedm.dm_to_dist(sky_coords.galactic.l, sky_coords.galactic.b, DM) print(dist.to('lyr')) >> 3362.16343117 lyr print(tau_sc.to('ns')) >> 7.758686138 ns
scipy, a newish C compiler with C++11 support (Ubuntu 16.04+ default gcc will work), plus
Pre-compiled wheels are generated for linux, meaning you can skip the
f2c install step. Alternatively you can install via
apt-get f2c in Ubuntu, or via
conda install -c conda-forge f2c if you use conda.
For MacOS, you are best off using
conda and getting
conda install -c conda-forge f2c. Windows is not currently supported.
You should be able to install with:
pip install pygedm
pip install git+https://github.com/telegraphic/pygedm
to install the latest version from github. Alternatively, download this repository and install via
pip install .
To run unit tests, run
python setup.py test. Note that these tests only check the Python bindings,
not the underlying C/FORTRAN source code (which is not supplied with unit tests).
If using PyGEDM in a journal article, please remember to cite the underlying electron density models:
Cordes, J. M., & Lazio, T. J. W. (2002),
NE2001.I. A New Model for the Galactic Distribution of Free Electrons and its Fluctuations, arXiv e-prints, astro-ph/0207156.
Cordes, J. M., & Lazio, T. J. W. (2003),
NE2001. II. Using Radio Propagation Data to Construct a Model for the Galactic Distribution of Free Electrons, arXiv e-prints, astro-ph/0301598.
Yao, J. M., Manchester, R. N., & Wang, N. (2017),
A New Electron-density Model for Estimation of Pulsar and FRB Distances, The Astrophysical Journal, Volume 888, Issue 2, id.105, Colume 835, id.29
Yamasaki, S., & Totani, T. (2020),
The Galactic Halo Contribution to the Dispersion Measure of Extragalactic Fast Radio Bursts, The Astrophysical Journal, Volume 888, Issue 2, id.105
YMW16 C README
YMW16 is a model for the distribution of free electrons in the Galaxy, the Magellanic Clouds and the inter-galactic medium, that can be used to estimate distances for real or simulated pulsars and fast radio bursts (FRBs) based on their position and dispersion measure.
The Galactic model is based on 189 pulsars that have independently determined distances as well as dispersion measures, whereas simpler models are used for the electron density in the MC and the IGM. It is estimated that the 95% of predicted Galactic pulsar distances will have a relative error of less than a factor of 0.9. Pulse broadening due to scattering in the Galactic interstellar medium, the Magellanic Clouds, the intergalactic medium and FRB host galaxies is estimated.
As well as the ymw16 dm-distance program, we also provide a program, ymw16_ne, which gives the electron density at any point in the Galaxy or Magellanic Clouds.
A paper (Yao, Manchester and Wang, 2017, Astrophys. J., 835, 29; arXiv:1610.09448) describes the model and compares its predictions with those of earlier Galactic electron density models. YMW16 is the first electron-density model to estimate extragalactic pulsar distances and FRB distances.
To make a command-line executable version of the program, download and unpack the latest version of the program. Then run "make_ymw16" to create the executable. The environment variable YMW16_DIR may be set up to point at a directory containing ymw16par.txt and spiral.txt. Access to these files is needed at runtime.
Websites allowing interactive access to the YMW16 distance model and download of the latest program version are available at:
- http://www.atnf.csiro.au/research/pulsar/ymw16/ and
Please report any issues or bugs at https://bitbucket.org/psrsoft/ymw16/issues/new/ or directly to the authors. Please provide an example illustrating the problem.
YMW16 C LICENSE
Copyright (C) 2016, 2017 J. M. Yao, R. N. Manchester, N. Wang. YMW16 is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. YMW16 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, available at http://www.gnu.org/licenses/, for more details. Jumei Yao (yaojumei _@_ xao.ac.cn), Richard N Manchester (dick.manchester _@_ csiro.au), Na Wang (na.wang _@_ xao.ac.cn)
07 July 2002 To compile and execute the code, see code.pdf.