Astronomical instrumentation

Abstract:

Although most of the luminosity of Seyfert galaxy nuclei is emitted in the IR, the relative amounts of thermal dust and non-thermal emission are uncertain. Seyfert galaxies generally have smooth and featureless IR spectra, in contrast to the prominent dust emission features seen in galaxies whose nuclei resemble giant H II regions - the star burst nuclei1,2. Nevertheless, in type 2 Seyferts, the general form of the energy distribution and lack of marked variability suggest that here too thermal dust emission is dominant 3-5, and in NGC1068 this supposition is supported by the resolved size of its nucleus6. Dust is observed in absorption at 10 m (refs 7,8) and in emission near 20 m (ref. 9). Polarization has been detected from the UV to 10 m, and attributed to scattering and absorption at short wavelengths10 with a possible non-thermal component11,12, to scattering and non-thermal radiation in the near IR9, and to either absorption or non-thermal emission in the 10 m region13. We present here spectropolarimetric measurements of NGC1068, between 8 and 13 m, which show that the polarized flux at these wavelengths is intrinsic to the emission mechanism and not due to absorption by aligned grains. © 1984 Nature Publishing Group.

Abstract:

Four 8 - 13 μm spectra of the dust emission from Nova Aquilae 1982 are presented. The data, obtained between 140 and 280 days after outburst, show a prominent silicate emission feature superposed on a smooth warm continuum. The presence of the silicate grain signature, which is similar to laboratory emissivity curves of amorphous olivine smoke, indicates that these grains originated in an oxygen-rich environment where graphite or other carbon-rich grains are unlikely to have formed.

Abstract:

The infrared spectra of the type II OH/IR source OH 32.8 - 0.3 are presented, showing evidence for absorption bands near 12 and 3.1 microns. The 12 micron absorption feature is similar to that seen in OH 231.8 + 4.2 and is attributed to relatively pure water ice formed in the outflow from an evolved star.