P3D: a general data-reduction tool for fiber-fed integral-field spectrographs

Abstract

The reduction of integral-field spectrograph (IFS) data is demanding work. Many repetitive operations are required to convert raw data into, typically, a large number of spectra. This effort can be markedly simplified through the use of a tool or pipeline, which is designed to complete many of the repetitive operations without human interaction. Here we present our semi-automatic data-reduction tool p3d, which is designed to be used with fiber-fed IFSs. Important components of p3d include a novel algorithm for automatic finding and tracing of spectra on the detector and two methods of optimal spectrum extraction in addition to standard aperture extraction. p3d also provides tools to combine several images, perform wavelength calibration and flat field data. p3d is at the moment configured for four IFSs. To evaluate its performance, we tested the different components of the tool. For these tests we used both simulated and observational data. We demonstrate that a correction for so-called cross-talk due to overlapping spectra on the detector is required for three of the IFSs. Without such a correction, spectra will be inaccurate, in particular if there is a significant intensity gradient across the object. Our tests showed that p3d is able to produce accurate results. p3d is a highly general and freely available tool. It is easily extended to include improved algorithms, new visualization tools, and support for additional instruments. The program code can be downloaded from the p3d-project web site http://p3d.sourceforge.net.

The Lyman alpha reference sample

“…To reduced the raw data we employed the p3d 3 -pipeline (Sandin et al 2010(Sandin et al , 2011, which covers all the important steps in the reduction of fiber-fed integral field spectroscopic data: bias subtraction, flat fielding, cosmic-ray removal, tracing, and extraction of spectra. The final data products resulting from p3d are flux-calibrated data cubes and the associated pipelinepropagated variances for all on-target and sky exposures.…”

The jet-ISM interaction in the outer filament of Centaurus A

“…For flux calibration purposes, we used standard star calibration exposures taken during the same night. The data reduction is carried out using P3D, a data reduction tool optimized for IFU data (Sandin et al 2010). The reduction mainly involves five relevant steps: 1) the creation of a trace mask in order to locate the spectra on the CCD; 2) the extraction of a flat-field mask, to take into account the sensitivity variations of the detector; 3) the creation of a dispersion mask to perform the wavelength calibration; 4) spectra extraction; and 5) the creation of an overall sensitivity function to flux calibrate the scientific exposures.…”

THE DATA REDUCTION PIPELINE FOR THE SDSS-IV MaNGA IFU GALAXY SURVEY

“…Similarly, the various IFUs at the Very Large Telescope (VLT) can all be reduced with software from a common ISO C-based pipeline library, although some other packages (e.g., GIRBLDRS, Blecha et al 2000) are also capable of reducing data from some VLT IFUs. Substantial effort has been invested in the P3D (Sandin et al 2010) and R3D (Sánchez 2006) packages as well, which together are capable of reducing data from a wide variety of fiber-fed instruments (including PPAK/LARR, VIRUS-P, SPIRAL, GMOS, VIMOS, INTEGRAL, and SparsePak) for which similar extraction and calibration algorithms are generally possible. For survey-style operations, the SAMI survey has adopted a two-stage approach, combining a general-purpose spectroscopic pipeline 2DFDR (Hopkins et al 2013) with a custom 3D stage to assemble IFU data cubes from individual fiber spectra (Sharp et al 2015).…”