... PyGILDAS)¹

Weeds requires Python version $\ge$ 2.6 or newer.

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... database²

The use command, as well as the select and insert commands that we use later on, are part of the linedb\ language. Please type help linedb\ for the full documentation of this language.

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... survey³

The spectrum used in this tutorial is included in the Gildas distribution (courtesy of Emmanuel Caux), and can be copied in the current directory with the following CLASS command: sic copy gag_demo:demo-weeds-1.30m demo-weeds-1.30m.

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... spectrum⁴

This frequency interval can be changed with the /delta option.

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... equilibrium⁵

See Maret, Hily-Blant, Pety et al., Astronomy & Astrophysics 526, A47 (2011) for the formula used.

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... command⁶

Alternatively, one may retrieve the predicted spectrum with retrieve TB_MODEL, and plot it over the observed spectrum with spectrum. However, it is important to fix the y-axis range; if the axis is set to auto, then the predicted and modeled spectrum will not be on the same scale, and the comparison will be meaningless. The modshow command ensures that both the observed and predicted spectra are on the same scale.

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... modeled⁷

Additional details on spectrum modelling with absorbing components can be found in Belloche, Muüller, Menten, Schilke and Comito , Astronomy & Astrophysics 559, A47 (2013)

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