About p3d

p3d is a general data-reduction tool that is intended to be used with data of fiber-fed integral field spectrographs (IFSs). This tool can be useful for people who have access to astronomical data of such an instrument. Data-reduction tasks, which are performed by p3d, convert raw data of CCD detectors into extracted spectra that can thereafter be used for scientific purposes.

Version 2.1.2 was released 23.4.2012.
Versions 2.1.1 (6.2.2012), 2.1 (16.1.2012).

The aim with p3d has been to write a user-friendly tool that will reduce the time that is spent performing repetitive tasks in IFS data-reduction. p3d can combine several images (exposures) into one image, can extract spectra using three different methods, does full error propagation through all steps, and provides graphical tools for inspection of both intermediate and final results. Release 2.1 of p3d contains tools to handle the following tasks:

• Creation of a master-bias image – prescan and overscan regions can also be used to estimate the bias level.
• Cleaning of raw data of cosmic-ray hits.
• Automatic finding and tracing of spectra on the detector.
• Creation of a dispersion mask for wavelength calibration.
• Creation of a dataset that is used to normalize (flat field) extracted spectra.
• Extraction of science-object data, using different extraction methods.
• Combination of extracted images of separate detectors to one image (VIMOS).
• Correction of data for effects of differential atmospheric refraction (DAR; PMAS/Larr, Spiral, VIMOS, FLAMES, and MPFS).
• Conversion of RSS-formated output of p3d to data cubes – for PMAS/Larr, Spiral, VIMOS, FLAMES, MPFS, and ERA2 – or the E3d-format (all instruments).
• Combination of several extracted images using different exposure times, where all exposures target the same region.

p3d also provides several graphical tools to inspect the raw data and the outcome of the different tasks. One task that is important when calculating scientific spectra is flux calibration; this task is nearly, but not yet completely, included in p3d. It will be included in the next release (2.2). However, the flux calibration can be easily performed on output data; using, for example, IRAF (instructions on necessary steps are available at the documentation WIKI).

Have a look at the presentation of p3d – for use with the ESO instruments VIMOS and FLAMES – in the June 2011 issue of The Messenger; "p3d – A Data Reduction Tool for the Integral-field Modes of VIMOS and FLAMES" Sandin C., Weilbacher P., Streicher O., Walcher J., and Roth M.M. 2011, The Messenger, 144, 13–16.
In October 2010, at the STScI-workshop "IFUs in the era of JWST", Christer Sandin gave a presentation with the title "Integral-Field Spectroscopy Data Reduction Made Easy with p3d". You can watch the presentation if you follow this link.

p3d is written in the IDL language of EXELIS Visual Information Solutions. While p3d is licensed under GPLv3 and can be used freely with the help of provided tools, IDL is in itself a proprietary program.

We refer to p3d as a general tool since it has been developed to work with any fiber-fed integral field unit (IFU) of any IFS. Currently the software has been configured and tested with the following instruments:

• PMAS – that is mounted on the 3.5m telescope at the Calar Alto Observatory in southern Spain. p3d supports data of both the old 2kx4k CCD and the new 4kx4k CCD.
• VIRUS-P – that is mounted on the 2.7m Harlan J. Smith telescope at the McDonald Observatory in western Texas.
• SPIRAL of the AAOMEGA spectrograph – that is mounted on the 3.9m telescope at the Anglo Australian Observatory.
• VIMOS – that is mounted on the third unit telescope (UT3) at the VLT in Chile. p3d supports data using the medium- and the high-resolution (MR and HR) gratings. Data sampled both before and after the instrument refurbish about October 2010 are supported.
• FLAMES – that is mounted on the second unit telescope (UT2) at the VLT in Chile. p3d supports data using the ARGUS IFU as well as the two mini-IFU configurations. Data sampled both before and after the instrument refurbish in 2007 are supported.
• MPFS – that is mounted on the 6m SAO Big Telescope Alt-azimuth (BTA) near Mount Pastukhov in the Caucasus Mountains in Russia. p3d has been setup to work with the newer CCD.
• GMOS-N and GMOS-S – that are mounted on the Gemini North telescope on top of Mauna Kea on the Big Island of Hawaií, and the Gemini South telescope on top of Cerro Pachon in Chile; both telescopes belong to the Gemini Observatory. p3d supports data using the two one-slit modes; i.e. the red and the blue slits. The two-slit mode is (logistically) more complex to handle, which is why it is not (yet) supported.
• INTEGRAL, which is a set of IFUs that are connected to the WYFFOS spectrograph at the 4.2m William Herschel Telescope (WHT) (of the Isaac Newton Group of Telescopes) at the Roque de los Muchachos Observatory on the island of La Palma. p3d, currently supports the older single-detector configuration.
• ERA2, which is an integral-field spectrograph in development at AIP.

A tool as complex as p3d is never finished. There are several parts of p3d, which could be extended and improved upon. Additional tools could be written in order to optimize the control and analysis of the outcome. p3d can also, if required, be configured for more instruments. If and how this will happen at large depends on the interest of the community. Please, tell us if there is some functionality missing, in your opinion, or if you need support for another instrument. We are scientists with limited resources, but we will do what we can to help you out. We do consider taking on people with a suitable expertise in our development team.

The p3d team
fifth version, for release 2.1.2: 23.4.2012
fourth version, for release 2.1: 24.11.2011
third version, for release 2.0: 20.6.2011
second version, for release 2.0a: 26.1.2011
first version: 4.2.2010