utu.spectrum.ions#

utu.spectrum.ions(wavelength_min=None, wavelength_max=None, abundance_min=1e-05, **kwargs)[source]#

Find the ions worth computing over a range of wavelengths.

An ion is worth computing if its element is abundant enough to contribute and if it has a line in the range at all. Reading the line list of an ion is cheap; solving its level populations is not, and this is how the second is avoided for ions which cannot matter.

Parameters:

  • wavelength_min (None | Quantity | AbstractScalar) – The shortest wavelength worth looking at. If None (the default), there is no lower bound.

  • wavelength_max (None | Quantity | AbstractScalar) – The longest wavelength worth looking at. If None (the default), there is no upper bound.

  • abundance_min (float) – The abundance, relative to hydrogen, below which an element is not worth including.

  • kwargs (object) – Additional arguments passed to fiasco.Ion.

Return type:

list[str]

Notes

Which ions come back is a statement about the database as much as about the wavelengths: an ion the database does not describe cannot be returned, and the databases built for a documentation page or a test suite describe only a few.

The database is read on the first call and remembered afterwards, so the first call takes a few seconds and the rest take none. What is remembered is the wavelengths of the lines of the ions abundant enough to pass abundance_min, a few megabytes.

Examples

The line ESIS was built to observe is a line of \(\mathrm{O\,V}\).

import astropy.units as u
import utu

"O 5" in utu.spectrum.ions(
    wavelength_min=629 * u.AA,
    wavelength_max=630 * u.AA,
)

True
On this page
Show Source