ABSTRACT.Results of the commissioning of the first Gemini Multi-Object Spectrograph (GMOS) are described. GMOS and the Gemini-North telescope act as a complete system to exploit a large 8 m aperture with improved image quality. Key GMOS design features such as the on-instrument wave-front sensor (OIWFS) and active flexure compensation system maintain very high image quality and stability, allowing precision observations of many targets simultaneously while reducing the need for frequent recalibration and reacquisition of targets. In this paper, example observations in imaging, long-slit, and multiobject spectroscopic modes are presented and verified by comparison with data from the literature. The expected high throughput of GMOS is confirmed from standard star observations; it peaks at about 60% when imaging in the and bands, and at 45%-50% in r i spectroscopic mode at 6300 Å . Deep GMOS photometry in the , , and filters is compared to data from the g r i literature, and the uniformity of this photometry across the GMOS field is verified. The multiobject spectroscopic mode is demonstrated by observations of the galaxy cluster A383. Centering of objects in the multislit mask was achieved to an rms accuracy of 80 mas across the 5Ј .5 field, and an optimized setup procedure (now in regular use) improves this to better than 50 mas. Stability during these observations was high, as expected: the average shift between object and slit positions was 5.3 mas hr Ϫ1 , and the wavelength scale drifted by only 0.1 Å hr Ϫ1 (in a setup with spectral resolution of 6 Å ). Finally, the current status of GMOS on Gemini-North is summarized, and future plans are outlined.

A new integral‐field spectrograph, SAURON, is described. It is based on the TIGER principle, and uses a lenslet array. SAURON has a large field of view and high throughput, and allows simultaneous sky subtraction. Its design is optimized for studies of the stellar kinematics, gas kinematics, and line‐strength distributions of nearby early‐type galaxies. The instrument design and specifications are described, as well as the extensive analysis software which was developed to obtain fully calibrated spectra, and the associated kinematic and line‐strength measurements. A companion paper will report on the first results obtained with SAURON on the William Herschel Telescope.

The Gemini Multiobject Spectrograph (GMOS) installed on the Gemini-North telescope has a facility for integral field spectroscopy over the wavelength range 0.4-1.0 mm. GMOS is converted to this mode by the remote insertion of an integral field unit (IFU) into the beam in place of the masks used for the multiobject mode. With the IFU deployed, integral field spectroscopy is available over a fully filled contiguous field of with a sampling of 0Љ .2. A separate field of half the area, but otherwise identical, is also provided to 5 # 7 improve background subtraction. The IFU contains 1500 lenslet-coupled fibers and is the first facility of any type for integral field spectroscopy employed on an 8-10 m telescope. We describe the design, construction, and testing of the GMOS IFU and present measurements of the throughput both in the laboratory and at the telescope. We compare these with a theoretical prediction made before construction started. All are in good agreement with each other, with the on-telescope throughput exceeding 60% (averaged over wavelength). A second paper will verify the scientific performance by comparison with existing one-and two-dimensional data sets.

Using the multislit LDSS-2 spectrograph on the William Herschel Telescope we have completed a redshift survey in the magnitude range 22:5 < B < 24 which has produced 73 redshifts representing a 73% complete sample uniformly-selected from four deep elds at high Galactic latitude. The survey extends out to z > 1 and includes the highest redshift galaxy (z = 1:108) yet discovered in a eld sample. The median redshift, z MED = 0:46, and form of the redshift distribution constitute compelling evidence against simple luminosity evolution as an explanation of the large excess of faint galaxies (' 2{4 no-evolution) seen in this magnitude range. Rather we identify the excess population as blue objects with z 0:4 and B luminosities similar to local L galaxies indicating a dramatic decrease in the density of such objects over the last Hubble time, con rming the trends found in brighter redshift surveys. We also nd a marked absence of very low redshift galaxies (z <0.1) at faint limits, severely constraining any signi cant steepening of the local eld galaxy luminosity function at low luminosities.

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Using ultrafast laser inscription, we report the fabrication of a prototype three-dimensional 121-waveguide fan-out device capable of reformatting the output of a 120-core multicore fiber (MCF) into a one-dimensional linear array. When used in conjunction with an actual MCF, we demonstrate that the reformatting function using this prototype would result in an overall through put loss of ≈7.0  dB. However, if perfect coupling from the MCF into the fan-out could be achieved, the reformatting function would result in an overall loss of only ≈1.7  dB. With adequate development, similar devices could efficiently reformat the output of so-called "photonic lanterns" fabricated using highly multicore fibers.

Abstract:The application of photonics to astronomy offers major advantages in the area of highly-multiplexed spectroscopy, especially when applied to extremely large telescopes. These include the suppression of the near-infrared night-sky spectrum [J.