Dust grids

A dust grid describes what dust does to light, worked out over a range of parameters. Synthesizer uses them in its dust models. They come in two kinds:

Attenuation

How much light the dust absorbs and scatters, as a function of wavelength.

Emission

The infrared spectrum the dust gives off as it re-emits that energy.

What’s in the file

A dust grid has the same axes as a grid: an axes attribute naming them, and an axes/<name> dataset for each, with its Units. Over those axes it holds one of:

extinction_curves/

Attenuation curves, and the wavelength they cover.

spectra/

Dust emission spectra, and their wavelength.

Naming

Name a dust grid after its model, include dust, and say which kind it is:

draine-li-dust-extcurve-mrn

Draine and Li attenuation curves, for an MRN grain size distribution.

draine-li-dust-emission-mw-3p1

Draine and Li (2007) dust emission for the Milky Way, with \(R_V = 3.1\).

Checks

A dust grid is checked like any other grid, axis warnings included. The one difference is how it is recognised.

An extinction_curves group is unmistakable, so attenuation grids are recognised by their contents. A spectra group, though, looks the same in a dust emission grid as in an SPS grid, so for emission grids the filename decides.

Important

A dust emission grid’s filename must contain dust. Without it, the file is treated as an ordinary grid and refused for not saying what kind of grid it is.