Prof. Niranjan Thatte

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.

Abstract:

In this and a companion paper (Eisenhauer et al. 2003b), we discuss some of the scientific results obtained during the SPIFFI guest instrument runs at the VLT in March and April 2003. This paper concentrates on results for the Galactic Center. Section I discusses the stellar population of the Galactic Center, in which we clearly detect, for the first time, an early, hot WN star, as well as a large number of WC stars. Analysis of the stellar population indicates that the young stars in the Galactic Center originated in a high metalicity starburst about 5 Myr ago. A surprising result is that essentially all young stars in the central 10" belong to one of two well defined, rotating stellar rings/disks. Section 2 outlines a new determination of the distance to the Galactic Center which is essentially free of systematic uncertainties in the astrophysical modelling, and gives R. as 7.94 +/- 0.42 kpc.

Abstract:

This is the second of two papers (I: Horrobin et al. 2003) on the first scientific results from the SPIFFI integral field spectrometer at the VLT. Here we discuss the observations and properties of the prototypical luminous infrared galaxy NGC 6240 and the luminous sub-millimeter galaxy SMMJ 14011+0252. Taking full advantage of the excellent seeing conditions of 0.27", our integral field spectroscopy data allow us for the first time to study in detail the stellar and gas dynamics in NGC 6240 on scales of 125 pc, and to establish a galactic shock as the origin of the strong emission from molecular hydrogen. Our observations of SMMJ 14011+0252 provide us with deep, spatially resolved near infrared spectra of the SCUBA selected luminous submillimeter galaxy at a redshift of z=2.565, revealing a remarkably old, massive and metal-rich starburst galaxy for the early epoch at which it is observed.

Abstract:

SPIFFI (SPectrometer for Infrared Faint Field Imaging) is a fully cryogenic, near-infrared imaging spectrograph built at the Max-Planck-Institute for Extraterrestrial Physics (MPE) and upgraded with a new detector and spectrograph camera by ASTRON/NOVA, ESO and MPE. The upgraded instrument will become a facility instrument for the ESO VLT in summer 2004 as part of the SINFONI (SINgle Faint Object Near-IR Investigation) project, which is the combination of SPIFFI and ESOs adaptive optics module MACAO (Multiple Application Curvature Adaptive Optics), at the Cassegrain focus of Yepun (UT4). In spring 2003 we had the opportunity to observe with SPIFFI as a guest instrument without the AO-module at the Cassegrain focus of UT2 of the VLT. In this paper we discuss the performance of SPIFFI during the guest-instrument phase. First we summarize the technical performance of SPIFFI like the spatial and spectral resolution, the detector performance and the instruments throughput. Afterwards we illustrate the power of integral field spectroscopy by presenting data and results of the Galactic Center.