Recent developments for the SINFONI pipeline

Abstract

The SINFONI data reduction pipeline, as part of the ESO-VLT Data Flow System, includes recipes for Paranal Science Operations, and for Data Flow Operations at Garching headquarters. At Paranal, it is used for the quicklook data evaluation. The pipeline is available to the science community for reprocessing data with personalised reduction strategies and parameters. The recipes are implemented with the ESO Common Pipeline Library (CPL). SINFONI is the Spectrograph for INtegral Field Observations in the Near Infrared (1.1-2.45 um) at the ESO-VLT, and was developed and built by ESO and MPE in collaboration with NOVA. It consists of the SPIFFI (SPectrometer for Infrared Faint Field Imaging) integral field spectrograph and an adaptive optics module which allows point spread functions very close to the diffraction limit. The image slicer of SPIFFI chops the SINFONI field of view on the sky into 32 slices which are re-arranged to a pseudo slit. The latter is then dispersed by one of four possible gratings (J, H, K, and H+K). The instrument thus produces a two-dimensional (2D) raw image that contains both spatial (along the pseudo-slit) and spectral information. The ultimate task of the SINFONI pipeline is to reconstruct this frame into a three-dimensional (3D) data cube, with the x and y axes representing the spatial, on-sky dimension, and the corresponding spectrum of each spatial pixel along the z-axis. In the present article we describe two major improvements to the SINFONI pipeline. The first is a development to monitor instrument efficiency and stellar zero-points using telluric standard stars. The second involves the implementation of a semi-empirical algorithm to calibrate and remove the effects of atmospheric refraction, sometimes visible in the 3D cube reconstruction. The latter improves the positional offsets through the wavelength cube to an r.m.s. shift of better than 0.25 pixels.