Astronomical instrumentation

Abstract:

We present the optical and mechanical design of the KMOS spectrograph module together with a detailed analysis of its performance. KMOS is a cryogenic near-infrared multi-object spectrograph being developed as a second-generation instrument for the VLT by a consortium of UK and German institutes. Three identical spectrograph modules provide Nyquist sampled spectra in the wavelength range covering the atmospheric bands z, J, H, and K with a resolving power exceeding 3200. The spectrographs are fully achromatic over the bands and the single mirror collimator and six-element camera, together with six high efficiency gratings provide high throughput. The optical performance analysis includes amongst others the spectral resolving power and variation of the PSF as a function of the pupil illumination.

Abstract:

We describe the build phase of the UK FMOS spectrograph, a 200 fibre cooled OH Suppression infrared spectrograph being constructed as part of Subaru's Fibre Multi Object Spectroscopy facility. Here we describe recent UK activities within the FMOS programme and the likely schedule for commissioning at Subaru.

Abstract:

We describe the integration and test phase of the construction of the VISTA Infrared Camera, a 64 Megapixel, 1.65 degree field of view 0.9-2.4 micron camera which will soon be operating at the cassegrain focus of the 4m VISTA telescope. The camera incorporates sixteen IR detectors and six CCD detectors which are used to provide autoguiding and wavefront sensing information to the VISTA telescope control system.

Abstract:

The science case for the next generation of Extremely Large Telescopes (ELTs) covers a huge range of astronomical topics and requires a wide range of capabilities. Here we describe top-level requirements on an ELT, which were derived from some of the key science cases identified by European astronomers. After a brief summary of these science cases we discuss the requirements on the ELT system in terms of several parameters, including wavelength range, field of view, image quality etc. We discuss the science driver that sets the limits on each parameter. We also discuss specific requirements on instrumentation, site and adaptive optics. In several cases, detailed simulated observations will be required in order to set the requirements. While the example science cases provide a useful guide, we also note that an important goal is to develop a facility that covers a broad parameter space, and maintains flexibility in order to adapt to new scientific directions.

Abstract:

We present the fundamental plane (FP) in the z = 0.28 cluster of galaxies RX J0142.0+2131. There is no evidence for a difference in the slope of the FP when compared with the Coma Cluster, although the internal scatter is larger. On average, stellar populations in RX J0142.0+2131 have rest-frame V-band mass-to-light ratios (MILv) 0.29 ± 0.03 dex lower than in Coma. This is significantly lower than expected for a passively evolving cluster formed at zf = 2. Lenticular galaxies have lower average M/L v and a distribution of M/Lv with larger scatter than ellipticals. Lower mass-to-light ratios are not due to recent star formation: our previous spectroscopic observations of RX J0142.0+2131 E/S0 galaxies showed no evidence for significant star formation within the past ∼4 Gyr. However, cluster members have enhanced α-element abundance ratios, which may act to decrease M/Lv. The increased scatter in the RX J0142.0+2131 FP reflects a large scatter in M/Lv implying that galaxies have undergone bursts of star formation over a range of epochs. The seven easternmost cluster galaxies, including the second brightest member, have M/Lv consistent with passive evolution and zf = 2. We speculate that RX J0142.0+2131 is a cluster-cluster merger where the galaxies to the east are yet to fall into the main cluster body or have not experienced star formation as a result of the merger. © 2006. The American Astronomical Society. All rights reserved.