Home doc page for eblur/dust

The eblur/dust set of python modules calculate scattering absorption and scattering efficiencies for dust from the infrared to the X-ray. This code can also be used to calculate dust scattering halo images in the X-ray, in both interstellar and intergalactic (cosmological) contexts.

First published version of this code (released with Corrales & Paerels, 2015) http://dx.doi.org/10.5281/zenodo.15991

Source code: github.com/eblur/dust

Support: If you are having issues, please contact lia@space.mit.edu

Features

A number of dust grain size distributions and optical constants are provided, but they can be fully customized by the user by invoking custom objects of the approporiate class. Provided dust models include:

Installation

As of yet there is no static install version. I recommend cloning the github repo into a directory in your python path.:

cd /path/to/python/libraries/
git clone https://github.com/eblur/dust.git dust

Then be sure to add to your python path:

export PYTHONPATH=$PYTHONPATH:/path/to/python/libraries/dust/

Dependencies

I recommend using Anaconda to manage python distributions and packages

Modules

astrodust.distlib

This module is for setting up dust grain populations.

sizedist

Classes
Functions

composition.cmindex

This module contains built-in complex indices of refraction typically used for astrophysical dust.

API for CmIndex classes

class CmIndex (object)

ATTRIBUTES
cmtype : string (‘Drude’, ‘Graphite’, or ‘Silicate’)
citation : A string containing citation to original source of optical constants
rp : either a function or scipy.interp1d object that can called,
e.g. rp(E) where E is in [keV]
ip : same as above, ip(E) where E is in [keV]
Class Library
Functions

composition.minerals

astrodust.extinction

This module contains libraries for calculating scattering and extinction properties of dust grains.

sigma_scat

This module combines the complex index of refraction (cmindex) and scattering algorithm (scatmodels) to calculate the total or differential cross-sections for a particular dust grain size distribution (dust).

Classes

The ScatModel object specifies what type of scattering physics will be used both through the complex index of refraction and the scattering physics algorithm.

The remaining classes contain cross-sections that are integrated over a particular dust grain size distribution.

Functions

The makeScatmodel function is a short-cut for creating a Scatmodel object based on two input strings (which become the stype and cmtype).

scatmodels

This module contains built-in algorithms for Mie scattering and the Rayleigh-Gans approximation.

API for Scattering classes

class Scattering (object)

FUNCTIONS
Qsca with inputs
( E : scalar or np.array [keV]
cm : cmtype object cmindex.py
a : scalar [grain size, micron] )
returns scalar or np.array [scattering efficiency, unitless]

Diff with inputs
( cm : cmtype object from cmindex.py
theta : scalar or np.array [angle, arcsec]
a : scalar [grain size, micron]
E : scalar or np.array [energy, keV]
** if len(E) > 1 and len(theta) > 1, then len(E) must equal len(theta)
returns dsigma/dOmega of values (E0,theta0), (E1,theta1) etc...

(optional)
Qext with inputs
( E : scalar or np.array [keV]
cm : cmtype object cmindex.py
a : scalar [grain size, micron] )
returns scalar or np.array [extinction efficiency, unitless]
Class Library

astrodust.halos

This module is for calculating X-ray surface brightness profiles for dust scattering halos from both Galactic and cosmological (z > 0) point sources.

Halo class

The Halo class is used for both Galactic and extragalactic sources and contains the attribute htype, which can be filled with one of two objects: either CosmHalo (for extragalactic sources) or GalHalo (for Galactic sources, see galhalo).

Halo types (htype)

CosmHalo

GalHalo

Sub-modules

galhalo

This module is for calculating X-ray scattering halos from Galactic (z=0) point sources.

One must import the Halo object from astrodust.halos. The Halo object is used for both Galactic and extragalactic sources and contains the attribute htype, which can be filled with one of two objects: either CosmHalo (for extragalactic sources) or GalHalo (for Galactic sources). See astrodust.halos for a description of these halo types.

Functions

Functions within this module take a Halo object as input and modifies it by updating the htype, intensity, and any other related attributes.

Intensities are calculated using numerical integration (trapezoidal method). For the semi-analytic solutions, see analytic.

cosmhalo

This module is for calculating X-ray scattering halos from Galactic (z=0) point sources.

One must import the Halo object from astrodust.halos. The Halo object is used for both Galactic and extragalactic sources and contains the attribute htype, which can be filled with one of two objects: either CosmHalo (for extragalactic sources) or GalHalo (for Galactic sources). See astrodust.halos for a description of these halo types.

Functions

Functions within this module take a Halo object as input and modifies it by updating the htype, intensity, and any other related attributes.

cosmology

This module contains functions for calculating cosmological distances and other relevant values for the cosmhalo module.

Classes
Functions
halodict

This module is for creating and manipulating HaloDict objects (a dictionary of Halo objects, see astrodust.halos). The keys of the HaloDict objects are energy values.

Classes
Functions

Some somewhat useful functions for reading and writing HaloDict objects

analytic

This module contains semi-analytic functions for calculating X-ray scattering halo intensities from a power-law distribution of dust grain sizes (see Appendix of Corrales & Paerels, 2015).

When creating a Halo object, one must import from halo. The functions in this module are for Galactic sources only. (Note that galhalo contains functions for numerically integrated solutions).

Functions

Functions within this module modify the Halo object by updating the htype and intensity.

model_halo

This module is for modeling scattering halos for Galactic sources (see galhalo) from a dust grain size distribution (astrodust.distlib) and apparent flux spectrum of a point source. It uses HaloDict objects from the halodict module.

Functions

The following two functions are helpers for integrating up the total intensity from a HaloDict object.

The following functions take inputs that will allow us to simulate a scattering halo intensity profile from a set of basic starting parameters.

Indices and tables