Astronomical instrumentation

Abstract:

A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, ’dirty’ silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.

Abstract:

The proposed 15m NNTT offers a gain in collecting area over a 4m telescope of 14 and a gain in speed of up to 200. In this paper the types of problem where the gain in limiting flux is inversely proportional to area (D2-problems) and those in which the gain goes only as the diameter (D-problems) are identified. The performance of the NNTT is compared to a 4m telescope and to the Space Telescope in three configurations. The NNTT isshown to have a small advantage over the Space Telescope for spectroscopy of point sources even at low resolutions. For work on sources of diameter one arcsecond or greater the gains are (formula omitted) a factor of 15. Even for the direct imaging of point sources the NNTT is only a little slower than the Space Telescope when there is no confusion. Three areas of astronomical investigation, studies of star formation, the Galactic halo and high redshift galaxies, are used to illustrate the impact a 15m telescope would make scientifically. These astronomical problems make substantial demands on the telescope performance and instrumentation. If these can be met the NNTT will lead to considerable advancement in the understanding of current problems and, given the order of magnitude improvement in infrared performance and spectroscopic capability, is likely to lead to the discovery of new phenomena. © 1983 SPIE.

Abstract:

Spectrophotometry at 8 - 13 μm of Mkn 231 confirms that the 10 μm minimum is due to large columns of silicate dust in the line-of-sight to the nucleus. Fits to the detailed spectral shape demonstrate that the cool absorbing grains are at the emission (z = 0.042) rather than the absorption (z \equiv 0.025) redshift and are located within the nuclear region.