Development of the MUSE Integral-Field Spectrograph

The Multi Unit Spectroscopic Explorer (MUSE) is a 3D-spectrograph for the Very Large Telescope (VLT) of the European Southern Observatory at Paranal (Chile). MUSE features a complex optical system with the capacity to split and slice a field that measures one square arcminute on the sky into 90,000 spatial elements. For each point a spectrum is created, covering the optical and near infrared wavelength region of 465-930nm. The large number of spatial and spectral resolution elements is realized through a modular layout of the instrument, featuring a total of 24 identical integral field units (IFU), each consisting of an image slicer, a spectrograph, and a detector system.

The major science case for MUSE is to discover distant, high-redshift galaxies and to measure their properties. Further interests of AIP astronomers are the spectroscopic analyses of individual objects in nearby galaxies and to study galaxy mergers.

In order to obtain spectra of these faint or crowded targets, long integration times, high instrumental throughput, and very good opto-mechanical stability are required. Equally important is the Data Reduction Software (DRS) which is needed to extract the scientific signal from the noise and to subtract the instrumental and sky background accurately. The software needs to be able to calibrate the 24 sub-fields individually, then to combine multiple exposures to one output datacube and to reconstruct global images or specific maps. To extensively test the software in advance, both laboratory exposures taken with the MUSE spectrographs as well as simulated data, created by an instrument numerical model (INM) are fed into the pipeline.

MUSE is a project of a European consortium of 7 partners, led by the Observatoire de Lyon. AIPs develops the data reduction pipeline, has designed and built the MUSE calibration unit, and performed the acceptance tests of the 24 detectors. All sub-systems have been built and shipped to the leading institute at Lyon, where MUSE is being assembled and globally tested. After acceptance in Europe, the instrument is scheduled for commissioning at the Paranel observatory in early 2014. In exchange for the development of MUSE, the partners obtain guaranteed observing nights at the VLT.