Multiple-object and integral field near-infrared spectroscopy using fibers

We describe a new system for multiple-object spectroscopy and integral fiel d spectroscopy at near-infrared wavelengths using optical fibers. Both mode s of the SMIRFS instrument have been tested at the UK Infrared Telescope wi th the CGS4 infrared spectrograph. The modular system includes a common opt ical system to image the fiber slit onto the cold slit inside the CGS4 cryo stat. The multiobject mode consists of 14 interchangeable fused silica or z irconium fluoride fibers each with a field of 4 ". The integral field mode consists of 72 fused silica fibers coupled with a lenslet array to give a c ontiguous held of 6 " x 4 " with 0 ".6 sampling. We describe the performance of both modes. For the multiobject mode, the fe asibility and desirability of using fluoride fibers to extend the wavelengt h range into the K band is discussed. For the integral field mode, the perf ormance is compared with theoretical expectation with particular attention to the effect of focal ratio degradation in the fibers. These results demonstrate the feasibility of multiobject and integral field spectroscopy in the near-infrared using lenslet-coupled fiber systems. Alt hough SMIRFS in an experimental system working with a spectrograph not desi gned for this purpose, the throughput and uniformity of response are good. SMIRFS points the way forward to systems with much larger numbers of elemen ts.