Conceptual design of IR multi-IFU spectrograph with MOAO

To study properties of cold dark matter (CDM), which can only be observed through its gravitational interaction with galaxies, spatially resolved spectra at least to the K-band are desirable. We started designing a spectrograph which observes multiple targets spatially resolved in a telescope eld of view fed with multi-object adaptive optics (MOAO). The current design either places eld lenses on the telescope eld of view to image the pupil onto steering mirrors, or uses a single set of eld lens to deliver beams to pick-o arms. The steering mirror on the pupil image tilts and selects a sub-eld from each of the telescope eld of view physically split by the eld lenses. This allows cheaper and more robust construction of a method to select the target elds with a limitation in selections of the target elds. On the other hand, the pick-o arm implementation allows more exibility in assigning targets to elds of the integral eld units (IFUs) especially when targets are clustered. The IFU arranges spatial elements of each of sub-eld of view to be fed into the spectrograph. If enough pixels are aorded, using microlens arrays, which image pupils of spatial elements onto the object plane of the spectrograph is ideal in robustness. Otherwise, an image slicer is to be located to arrange the sub-eld of view onto the entrance slit. The instrument should be built as modules to allow expeditious scientic results