Description

Classes:

romancal.flux.FluxStep

Alias:

flux

This step will apply the flux scale factor, as defined in the meta of the input ImageModel. The step will check units and not re-apply the correction, simply returning the original data.

The flux step can take:

  • a single 2D input image (in the format of either a string with the full path and filename of an ASDF file or a Roman Datamodel/ModelContainer);

  • an association table (in JSON format).

This step takes no other parameters than the standard stpipe parameters.

The output product are ImageModels, but with the flux scale applied to all the data and variance arrays.

Flux Application

If the input data is in \(DN / second\), the flux scale factor, as found in the meta meta.photometry.conversion_megajanskys, is simply multiplied to the data and err arrays. The square of the scale factor is multiplied to all the variance arrays. The resultant units is in \(MJy/sr\).

\[ \begin{align}\begin{aligned}DATA &= DATA * SCALE\\ERR &= ERR * SCALE\\VAR_{rnoise} &= VAR_{rnoise} * SCALE ^ 2\\VAR_{poisson} &= VAR_{poisson} * SCALE ^2\\VAR_{flat} &= VAR_{flat} * SCALE ^2\end{aligned}\end{align} \]