Flux calibration

\label{sec:fcalib}

The FLOYDS spectra are flux calibrated using the IRAF task standard, sensfunction and calibrate. The standard frames are automatically identified from the coordinates and compared with their tabulated values. The FLOYDS spectrograph sensitivity functions have a specific shape in the second order with two deep absorptions around 3800 Å and 4400 Å (see Figs. \ref{fig:sensblue} and \ref{fig:sensblue2}). In order to reproduce this specific shape, the FLOYDS pipeline computes the sensitivity function in two steps: a first step with the full second order range (3000-6000 Å) is fitted with a low order function (usually 10-12), and a second step is focused on a smaller window with a higher order in order to reproduce the two deep absorptions. The two blue sensitivity functions are then merged into a single sensitivity function. Because of this, specific standards with a dense and wide coverage of tabulated flux are required. The standard stars that are usually used for FLOYDS are reported in Table \ref{tab:specphotstandards}.

The 2D frames (2df) after being flux and wavelength calibrated have the following units: \(10^{-20}\) erg cm\(^{-2}\) s\(^{-1}\) Å\(^{-1}\)