Astronomical instrumentation

Abstract:

Spectropolarimetry of the 3.4 μm aliphatic C-H stretch feature, generally attributed to carbonaceous dust in the diffuse interstellar medium, has been carried out in the line of sight from the Galactic center source Sagittarius A IRS 7. The feature is unpolarized (Δp/Δτ < 0.2): the upper limit for polarization is well below that expected on the basis of a model in which the carrier molecules are associated with the aligned silicate component of interstellar dust, for example, as an organic or carbonaceous mantle on a silicate core. The simplest explanation is that the 3.4 μm carrier resides in a population of small, non-polarizing carbonaceous grains, physically separate from the silicates and sharing many characteristics with the carriers of the 217.5 nm extinction bump.

Abstract:

The technique of integral field spectroscopy,: which provides simultaneous spectra for each pixel of a contiguous two-dimensional field of view, holds tremendous promise for improving our ability to study circumstellar environments. The technique becomes especially important at near infrared wavelengths, where rapid changes in the night sky background level limit the use of standard scanning techniques. In addition, combining the capabilities of adaptive optics systems with near infrared integral field spectrographs provides an unique way to enhance-spatial resolution for ground based observations. We present the technique of integral field spectroscopy, with special emphasis on the near infrared, and illustrate future developments by describing SINFONI, an adaptive optics assisted near infrared integral field spectrometer for the ESO VLT.