X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope

TL;DR

X-shooter is a versatile, wide-band spectrograph at the ESO VLT that covers 300-2500 nm in a single exposure, offering intermediate spectral resolution and innovative features for efficient astronomical observations.

Contribution

This paper introduces X-shooter, the first second-generation VLT instrument, highlighting its unique wide spectral coverage, high efficiency, and integrated data reduction capabilities.

Findings

Achieved broad spectral coverage from 300 to 2500 nm in one exposure

Demonstrated intermediate spectral resolution (R~4,000 - 17,000)

Validated instrument performance during commissioning and initial science operations

Abstract

X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope(VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R~4,000 - 17,000, depending on wavelength and slit width) with fixed echelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8"x4" Integral Field Unit as an alternative to the 11" long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.