Galaxy formation and evolution

Abstract:

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 μm. 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 5″ × 7″ with a sampling of 0″.2. A separate field of half the area, but otherwise identical, is also provided to 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.

Abstract:

We describe MUSE (Multi Unit Spectroscopic Explorer), a second-generation integral-field spectrograph for the VLT, operating in the visible and near IR wavelength range. It combines a 1' × 1' Field of View with the improved spatial resolution (0.2″) provided by adaptive optics and covers a large simultaneous spectral range (0.48-1 μm). With this unique combination of capabilities, MUSE has a wide domain of application, and a large discovery potential. It will provide ultra deep fields with a limiting magnitude for spectroscopy of R = 28. After a brief presentation of the scientific case and the derived instrument requirements, we will focus on the MUSE optical design, including the overall architecture, the major trade-off that were conducted in order to optimize the cost and performance, and a provisional implementation scheme of the instrument on the VLT Nasmyth platform. Then the most important optical subsystems (as the 3 × 8 Field-splitter, the Image Slicers and the Spectrometers) are described. One of MUSE special feature is the impressive number of Image Slicer and Spectrometer modules which must be manufactured, that is 24. The realization of such series has been studied in collaboration with an industrial company. Finally, a preliminary estimation of the expected performance and a technological development program in order to secure the realization of the critical optical subsystems will be presented.

Abstract:

We present new techniques to perform adaptive spatial binning of two-dimensional (2D) data to reach a chosen constant signal-to-noise ratio per bin. These methods are required particularly for the proper analysis of Integral Field Spectrograph (IFS) observations, but can also be used for standard photometric imagery. Various schemes axe tested and compared using data obtained with the panoramic IFS SAURON.

Abstract:

We discuss a cryogenic, multi-object near-infrared spectrometer as a second generation instrument for the VLT. The spectrometer combines 20 to 40 independent integral field units (IFUs), which can be positioned by a cryogenic robot over the entire unvignetted field of the VLT (similar to 7'). Each IFU consists of a contiguous cluster of 20 to 30 pixels (0.15 to 0.25" per pixel). The individual IFUs have cold fore-optics and couple into the spectrograph with integrated fibers-microlenses. The spectrometer has resolving power of lambda/Deltalambdasimilar to4000 and simultaneously covers the J-, H-, and K-bands with three HAWAII 2 detectors. The system is designed for operation both in seeing limited and MCAO modes. Its speed is approximately 3500 times greater than that of ISAAC and 60 times greater than NIRMOS (in H-band). The proposed instrument aims at a wide range of science, ranging from studies of galaxies/clusters in the high-z Universe (dynamics and star formation in z>1 galaxies, evolution of ellipticals, properties of distant, obscured far-IR and X-ray sources), to investigations of nearby starbursts, star clusters and properties of young low mass stars and brown dwarfs.