Prof. Niranjan Thatte

Abstract:

We present SPIFFI, the integral field spectrometer for the VLT. This instrument allows simultaneous observation of infrared spectra in more than 1000 image points of a two dimensional field. With its set of four gratings and a pixel scale that can be varied by a factor of ten, SPIFFI provides high flexibility, and at the same time offers the unique possibility of diffraction limited imaging spectroscopy at an 8m-class telescope, when fed by the adaptive optics system MACAO. We outline the scientific drivers for building such an instrument, the concept of image slicing, the optical design, and the implementation of SPIFFI.

Abstract:

We present multi-wavelength imaging observations of three nearby and famous active galaxies obtained with of NICMOS, ISOCAM and the MPE near-In integral held spectrometer. The data reveal a variety of features and properties that are missed in optical studies and in traditional IR monodimensional spectroscopy.

Abstract:

LUCIFER (LBT NIR-Spectroscopic Utility with Camera and Integral-Field Unit for Extragalactic Research) is a full cryogenic NIR spectrograph and imager (lambda 0.9 mu - 2.5 mu, zJHK-bands) to be built by a consortium of five institutes (Landessternwarte Heidelberg (LSW), Max Planck Institut fur Astronomie in Heidelberg (MPIA), Max Planck Institut fur Extraterrestrische Physik (MPE) in Garching, Astronomisches Institut der Ruhr Universitat Bochum (AIRUB) and Fachhochschule fur Technik und Gestaltung (FHTG) in Mannheim). The instrument has been selected as one of three first-light instruments for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona which first mirror becomes available to the community in early 2003. The second mirror and a second more or less identical spectrograph/imager follows 18 month later. Both LUCIFER instruments will be mounted at the bent Gregorian foci of the two individual LET-mirrors and include six observing modes: seeing and diffraction limited imaging, seeing and diffraction Limited longslit spectroscopy, seeing limited multi-object spectroscopy (MOS) and integral-field spectroscopy (IFU). The detector will be a Rockwell HAWAII-2 HgCdTe-array with a pixel-size of 18 mu.

Abstract:

LUCIFER-MOS is a liquid nitrogen cooled near infrared multi object spectrograph imaging 20 freely selectable sub-fields of about 2.2" x 1.8" and 6 x 4 image elements each on the entrance slit of the LUCIFER spectrograph. The image elements are re-arranged by 480 fused silica fibers of 50 mu m core diameter and 100 mu m total diameter with integrated, hexagonal lenslets of 0.6 mm width corresponding to a 0.3" field. The pre-optics magnifies the telescope image by a factor 3.3, thus adapting the telescope plate scale to the lenslet scale, and additionally providing a cold stop. The post-optics converts the f/3 fiber output beam to the f/15 beam accepted by the spectrograph. Each of the 20 6 x 4 fiber arrays together with its pre-optics is mounted in a spider arm which can be freely positioned within the 200 mm diameter field of view by a cryogenic robot. The robot performs three rotational movements to position the spider arms and is driven by cold stepper motors. The spider arms are locked in their positions by two permanent magnets each. Their magnetic field can be compensated by coils to unlock the arms and move them across the field of view.

Abstract:

Integral field spectroscopy, in conjunction with adaptive optics systems, has the unique potential of providing spectra at spatial resolutions close to the diffraction limit of the telescope. We present first results from integral field spectroscopy in conjunction with an adaptive optics system, achieving diffraction limited images and spectra at the Calar Alto 3.5 meter telescope. SINFONI, an adaptive optics assisted integral field spectrometer currently being built for the VLT, is one of the few adaptive optics optimized integral field instruments. We present a brief summary of its features, together with a brief description of the image slicer employed in SINFONI.