here - Institute for Astronomy Umleitung

Title: Science Case
Reference: MUSE-MEM-SCI-052
Issue: 1.3
Date: 04/02/2004
Page: 48/100
Fig. 2-25: Simulated MUSE deep field from GalIcs simulation. Galaxies are coloured
according to their apparent redshift. Galaxies detected by their continuum (I AB < 26.7 )
and/or by their Ly α emission (Flux > 3.9 10 -19 erg.s -1 .cm -2 ) are shown.
For surveys, as opposed to studies of previously identified objects, the power of an integral
field spectrograph relative to a multi-slit spectrograph observing previously identified (i.e.
continuum-selected) objects, is to survey "blank fields". Especially for objects with strong
emission lines, such as expected for young star-forming galaxies, a survey for emission lines
with an integral field spectrograph reaches to extremely faint continuum levels. An emission
line galaxy with line flux 3.9×10 -19 erg s -1 cm -2 at 9200 Å and an equivalent width of 200 Å
(as seen in a good fraction of emission line objects at this wavelength, from Hα at z ~ 0.4,
[OII] 3727 at z ~ 1.4 and Lyman α at z ~ 6.5) has a continuum Z AB ~ 30.0, far below the point
where systematic spectroscopy of continuum-selected galaxies is feasible or attractive
(because most such galaxies would not have detectable lines).
Thus the integral field approach is most attractive (relative to the others) at faint levels and a
MUSE survey should seek to survey down to the faintest possible levels, i.e. well below the
current depth of narrow band surveys (~10 -17 erg s -1 cm -2 ). One consequence of this is that
complementary data to the MUSE data cubes (e.g. imaging and photometry outside of the
MUSE wavelength interval or very high resolution imaging within it) must be
correspondingly deep (AB ~ 30 magnitude) if at all possible.