Prof. Niranjan Thatte

Abstract:

VLT J- to M'-band adaptive optics observations of the Circinus galaxy on parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9 ± 0.6 pc. This source is only visible at wavelengths longward of 1.6 μm and coincides in position with the peak of the [Si VII] 2.48 μm coronal line emission. With respect to the peak of the central optical emission, the source is shifted by ∼0″15 (2.8 pc) to the southeast. Indeed, the Ks-band source defines the vertex of a fairly collimated beam that extends for ∼10 pc and is seen in both continuum light shortward of 1.6 μm and in Hα line emission. The source also lies at the center of a ∼19 pc size [Si VII] ionization bicone. Identifying this source as the nucleus of Circinus, its size is compatible with a putative parsec-scale torus. Its spectral energy distribution, characterized by a prominent narrow peak, is compatible with a dust temperature of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The active galactic nucleus (AGN) luminosity required to heat this dust is in the range of X-ray luminosities that have been measured toward the central source. This in turn supports the existence of highly obscuring material, with column densities of 10²⁴ cm ². that must be located within 1 pc of the core.

Abstract:

VLT J- to M\p-band adaptive optics observations of the Circinus Galaxy on parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9 $\pm$ 0.6 pc. This source is only visible at wavelengths longward of 1.6 $\mu$m and coincides in position with the peak of the [Si VII]~2.48 $\mu$m coronal line emission. With respect to the peak of the central optical emission, the source is shifted by $\sim$ 0.15\arcsec (2.8 pc) to the south-east. Indeed, it defines the vertex of a fairly collimated beam which extends for $\sim$ 10 pc, and which is seen in both continuum light shortward of 1.6 $\mu$m and in H$\alpha$ line emission. The source also lies at the center of a $\sim$ 19 pc size [Si VII] ionization {\it bicone}. Identifying this source as the nucleus of Circinus, its size is compatible with a putative parsec-scale torus. Its spectral energy distribution, characterized by a prominent narrow peak, is compatible with a dust temperature of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The AGN luminosity required to heat this dust is in the range of X-ray luminosities that have been measured toward the central source. This in turn supports the existence of highly obscuring material, with column densities of $10^{24}$ cm$^{-2}$, that must be located within 1 pc of the core.

Abstract:

A data reduction software package is developed to reduce data of the near-IR integral field spectrometer SPIFFI built at MPE. The basic data reduction routines are coded in ANSI C. The high level scripting language Python is used to connect the C-routines allowing fast prototyping. Several Python scripts are written to produce the needed calibration data and to generate the final result, a wavelength calibrated data cube with the instrumental signatures removed.

Abstract:

We present the results of a design study for the spectrograph module for KMOS - 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. KMOS will consist of 24 deployable integral field units feeding three identical spectrograph units via image slicers. The spectrographs are designed to provide a resolving power greater than 3000, so as to provide adequate OH avoidance, whilst covering one of the J, H or K bands within a single exposure. We present the opto-mechanical layout of the spectrographs, together with an analysis of the impact of the image quality (and PSF uniformity) on the accuracy of sky background subtraction within each IFU's field of view.