Niranjan A. Thatte

SINFONI: integral field spectroscopy at 50-milli-arcsecond resolution with the ESO VLT

SINFONI is an adaptive optics assisted near-infrared integral field spectrometer for the ESO VLT. The Adaptive OPtics Module (built by the ESO Adaptive Optics Group) is a 60-elements curvature-sensor based system, designed for operations with natural or sodium laser guide stars. The near-infrared integral field spectrometer SPIFFI (built by the Infrared Group of MPE) provides simultaneous spectroscopy of 32 x 32 spatial pixels, and a spectral resolving power of up to 3300. The adaptive optics module is in the phase of integration; the spectrometer is presented tested in the laboratory. We provide an overview of the project, with particular emphasis on the problems encountered in designing and building an adaptive optics assisted spectrometer.

Seyfert Activity and Nuclear Star Formation in the Circinus Galaxy

We present high angular resolution (015-05) near-infrared images and spectroscopy of the Circinus galaxy, the closest Seyfert 2 galaxy known. The data reveal a nonstellar nuclear source at 2.2 μm whose radius is smaller than 1.5 pc. The coronal line region and the hot molecular gas emission extend for 20-50 pc in the ionization cone. The data do not show evidence for a pointlike concentration of dark mass; we set an upper limit of 4 × 106 M☉ to the mass of a putative black hole. We find evidence for a young, nuclear stellar population, with typical ages between 4 × 107 and 1.5 × 108 yr. The luminosity of the starburst inside a few hundred parsecs is comparable to the intrinsic luminosity of the Seyfert nucleus, and together the two account for most of the observed bolometric luminosity of the galaxy. Within the central 12 pc, the starburst has an age of about 7 × 107 yr and radiates ~2% of the luminosity of the active nucleus. We discuss the implications of these results for models that have been proposed for the starburst-active galactic nucleus connection.

LUCIFER : a multi-mode NIR instrument for the LBT

LUCIFER (LBT NIR-Spectroscopic Utility with Camera and Integral-Field Unit for Extragalactic Research) is a NIR spectrograph and imager for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona. It is built by a consortium of five German institutes and will be one of the first light instruments for the LBT. Later, a second copy for the second mirror of the telescope will follow. Both instruments will be mounted at the bent Gregorian foci of the two individual telescope mirrors. The final design of the instrument is presently in progress. LUCIFER will work at cryogenic temperature in the wavelength range from 0.9 μm to 2.5 μm. It is equipped with three exchangeable cameras for imaging and spectroscopy: two of them are optimized for seeing-limited conditions, the third camera for the diffraction-limited case with the LBT adaptive secondary mirror working. The spectral resolution will allow for OH suppression. Up to 33 exchangeable masks will be available for longslit and multi-object spectroscopy (MOS) over the full field of view (FOV). The detector will be a Rockwell HAWAII-2 HgCdTe-array.

Near-Infrared Integral Field Spectroscopy of Markarian 231

The ultraluminous infrared Seyfert 1 galaxy Mrk 231 has been spectrally imaged in the K band with the new three-dimensional MPE integral field spectrometer. The combined images of the H2 emission lines show, for the first time in an ultraluminous infrared galaxy, the presence of an extended circumnuclear structure of hot molecular gas. The H2 emitting region has a size of ~2.4 kpc and a hot molecular gas mass M ~2 × 104 M☉. The H2 emission-line ratios indicate that the gas is most likely thermally excited. If as in NGC 7469 star formation is associated with the H2 emission, the starburst would have a far-IR luminosity LFIR ~ 1 × 1012 L☉. This value represents an upper limit, since a fraction of the hot molecular gas may be excited by the radiation field emerging from the nucleus. The K-band three-dimensional data cube also shows for the first time the presence of extended narrow Paα emission blueshifted by ~1400 km s-1 with respect to the systemic velocity, and located ~0.6 kpc northwest of the nucleus. The detection of CO absorption bands with a spatial distribution peaking on the K-band continuum provides evidence for a central stellar concentration. The low CO spectroscopic index indicates, however, dilution by hot dust emission or by a nonthermal active galactic nucleus. The Paα/Hα ratio confirms previous extinction measurements based on Balmer line ratios, i.e., visual extinction of AV ~ 2.0-6.6 mag. The quasar-type nucleus of Mrk 231 should then be transparent at 2 μm and also in hard X-rays. A weak nuclear He I λ2.058 μm (He I/Paα = 0.032) is detected, and no detection of [Si VI] λ1.962 μm is made, placing an upper limit of 4 × 10-18 Wm-2 for the coronal gas emission. The ionizing source could either be a far-UV and X-ray quiet quasar or else a nuclear starburst with an upper mass limit ≥60 M☉.

Kinematics of galaxies in the Hubble Deep Field-South: Discovery of a very massive spiral galaxy at z=0.6

We report the first results from a study of the internal kinematics, based on spatially resolved Hvelocity profiles, of three galaxies at redshift z � 0:6 and one at redshift z � 0:8, detected by ISOCAM in the Hubble Deep Field-South. The kinematics are derived from high-resolution near-IR Very Large Telescope spectros- copy. One of the galaxies is a massive spiral that possesses a very large rotational velocity of 460 km s � 1 and contains a mass of 10 12 M� (within 20 kpc), significantly higher than the dynamical masses measured in most other local and high-redshift spiral galaxies. Two of the galaxies comprise a counterrotating interacting sys- tem, while the fourth is also a large spiral. The observed galaxies are representative examples of the morphol- ogies encountered among ISOCAM galaxies. The mass-to-light (M=Lbol) ratios of ISOCAM galaxies lie between those of local luminous IR galaxies and massive spiral galaxies. We measure an offset of 1:6 � 0:3 mag in the rest-frame B band and of 0:7 � 0:3 mag in the rest-frame I band when we compare the four ISO- CAM galaxies with the local Tully-Fisher B- and I-band relations. We conclude that the large IR luminosity of the ISOCAM population results from a combination of large mass and efficient triggering of star forma- tion. Since ISOCAM galaxies contribute significantly to the cosmic infrared background, our results imply that a relatively small number of very massive and IR-luminous objects contribute significantly to the IR background and star-formation activity near z � 0:7. Subject headings: cosmology: observations — galaxies: evolution — galaxies: starburst

Imaging the universe in 3D with the VLT: the next-generation field spectrometer SPIFFI

We present SPIFFI, the integral field spectrometer for the VLT. This instrument allows simultaneous observation of IR spectra in more than 1000 image points of a 2D 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.

LUCIFER: a NIR spectrograph and imager for the LBT

LUCIFER is a full cryogenic NIR spectrograph and imager to be built by a consortium of fiber institutes, Max Planck Institut fuer Astronomie in Heidelberg, Max Planck Institut fuer Extraterrestrische Physik in Garching, Astronomisches Institut der Ruhr Universitaet Bochum and Fachhochschule fuer Technik und Gestaltung in Mannheim. The instrument has been selected as one of three first-light instruments for the Large Binocular Telescope 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 months later. Both LUCIFER instruments will be mounted dat the bent Gregorian foci of the two individual LBT-mirrors and include six observing six observing modes: seeing and diffraction limited imaging, seeing and diffraction limited longslit spectroscopy, seeing limited multi-object spectroscopy and integral-field spectroscopy. The detector will be a Rockwell HAWAII-2 HgCdTe-array with a pixel-size of 18(mu) .

SINFONI: a near-infrared AO-assisted integral field spectrometer for the VLT

SINFONI, the SINgle Faint Object Near-IR Investigation, is an instrument for the very large telescope, designed to provide spectroscopy at the telescope diffraction limit in the near-IR. This unique capability is achieved by combining two state-of-the-art developments, an integral field spectrometer and a curvature sensor based adaptive optics system. SINFONI is a collaborative effort by the Max-Planck- Institut fuer extraterrsetrische Physik and the European Southern Observatory.

SPIFFI: A High-Resolution Near-Infrared Imaging Spectrometer

SPIFFI is an integral field spectrograph with an HAWAII array that enables us to simultaneously take near IR spectra of 1024 spatial pixels in a hexagonal field of view on the sky. It can be used on 4 to 8 meter class telescopes with a maximum pixel scale of 0.5 arcsec and with adaptive optics pixel scales, Nyquist sampling the point spread function of the telescope. A fiber bundle of 1024 silica/silica fibers rearranges the 2D field of view into the 1D entrance slit of the spectrometer. A novel technique involving flared fibers is used to achieve a high filling factor and coupling efficiency. Each fiber tip in the bundle is flared to increase the fiber core diameter by a factor of 15. The tapered end is polished to form a spherical micro-lens with a hexagonal cross-section to couple light into the fiber core. Apart from yielding a high coupling efficiency and a high geometrical filling factor, the monolithic micro- lens/fiber system can be used at a working temperature of 77K without loosing positioning accuracy. The spectrometer optics is achromatic from 1.1 to 2.5 microns and use four reflection gratings on a wheel as dispersing elements with a resolving power from 2000 to 4500. The fore-optics includes the filter wheel, the cold pupil stop and a scale changing mechanism to switch between three different image scales according to observing and seeing conditions. The spectrometer collimator is a f/4.3 three lens achromat, the spectrometer camera is a f/1.2 folded Schmidt camera. The optical design of the spectrometer is distortion free to get straight, equidistant spectra that match the columns of the detector, thus minimizing cross-talk form adjacent spectra to less than 5 percent.

SPIFFI image slicer: high-precision optics at cryogenic temperatures

SPIFFI is the near-infrared integral field spectrograph of the SINFONI VLT instrument. SPIFFI uses an image slicer with plane mirrors as its integral field unit. The integral field unit consists of two stacks of mirrors, each with 32 mirrors, rearranging a two-dimensional field-of-view of 32 x 32 pixels into a one-dimensional pseudo slit, which is fed into a long-slit spectrograph. The image slicer is constructed solely from Zerodur and is operated at a cryogenic temperature of 77 Kelvin. Only optical contacting is used for the assembly of the individual slicer mirrors and the image slicer on its base-plate. The special slicer mount holds the image slicer stress-free and compensates for the different thermal coefficients of expansion of the Zerodur image slicer and the Aluminium mount. Tests at room and cryogenic temperatures show the performance of the image slicer, the durability of the optical contacting technique, and the accuracy of the slicer mount.