Multi-unit spectroscopic explorer

The Multi-Unit Spectroscopic Explorer (MUSE) is an integral field spectrograph installed at the Very Large Telescope (VLT) of the European Southern Observatory (ESO).

The high spatial resolution and sampling will enable MUSE to simultaneously observe the spectra of thousands of stars in one shot in dense regions such as globular clusters.

A common way to study such sources is to use narrow-band imaging,[8] but this technique can only survey a very narrow redshift range at a time – set by the width of the filter.

It is expected that the instrument will be used for exposures of up to 100 hours, in which case it should reach a limiting flux of 3x10−19 erg/s/cm2 which is an order of magnitude fainter than current narrow-band imaging surveys.

MUSE will be a powerful instrument for studying the dynamical properties of galaxies from the nearby Universe out to at least a redshift of 1.4, after which the [O II] forbidden emission line at 372.7 nm disappears off the red end of the spectrograph.

Combining this with environmental information due to the wide field of view (1 arcminute corresponds to 430 kilo-parsec at a redshift of 0.7) it will be possible to study how the properties of galaxies are affected by the environment they find themselves in a very powerful, and mostly new, way.

To meet the scientific aims of the instrument, MUSE has had to fulfill a number of requirements: To achieve the latter two points, the spectrograph consists of 24 identical integral field units (IFU), hence reducing cost by replication.

The spectrograph design has achieved an excellent image quality across the spectral bandwidth of MUSE with the tilt of the detector compensating for axial chromaticism.

In order to achieve the required boost in spatial resolution across the celestial sphere, MUSE makes use of the GALACSI[12] interface which is part of the Adaptive Optics Facility[13] on UT4 at VLT.

Armed with the AO system, it is expected that MUSE will achieve a median spatial resolution of 0.46 arcseconds, or ~3 kpc at a redshift >3, across the 1'x1' field-of-view of the wide-field mode.

MUSE mounted on the VLT Yepun (UT4)
MUSE at the Lyon Observatory : The ESO director general, two local politicians, the university president, and the instrument's principal investigator [ 6 ]
A simulation of how MUSE will see the globular cluster NGC 2808 . This colour image has been created by first creating a simulated MUSE observation of the globular cluster and then extract three spectral regions from this data cube. Thus for each source in this image there is in truth an entire spectrum.
MUSE views the strange galaxy NGC 4650A [ 9 ]
Intricate network of pipes surrounding the 24 spectrographs of the MUSE instrument. [ 10 ]
Neptune from the VLT with MUSE/GALACSI Narrow Field Mode adaptive optics. [ 11 ]
Deep observations made with the MUSE spectrograph. [ 14 ]