Galaxy formation and evolution

Abstract:

With the advent of ISO, mid-infrared spectroscopy has become sensitive enough for detailed analyses of sizeable samples of galaxies. Mid-infrared aromatic emission features are detected strong and ubiquitously in star forming galaxies. They are absent close to an active galactic nucleus but can be strong on larger scales of the AGN host, in particular if there is intense circumnuclear star formation. Through their nebular emission, hot star populations can be studied in dusty environments like starburst galaxies. Starbursts seem to be normal in their hot star initial mass function but short lived due to strong negative feedback. The rich fine structure and coronal line spectrum of active galaxies can be used to reconstruct the otherwise unobservable extreme ultraviolet emission of the AGN. We find evidence for 'big blue bump' emission from the accretion disk but also for neutral absorbers located inside the narrow line region. Mid-infrared emission lines and continuum features provide new diagnostics to discriminate between starburst and AGN activity in obscured galaxies. Using these tools, we find that most ultraluminous infrared galaxies are predominantly starburst powered. Our total sample of about 75 ULIRGs allows to search for trends within the class of ULIRGs: The fraction of AGNs increases with luminosity above similar to 3 x 10(12)L(circle dot) but there is no obvious trend for ULIRGs to be more AGN-like with more advanced merger phase.

Abstract:

Conducting resolved spectroscopy on large samples of very faint objects is a strong requirement for the Next Generation Space Telescope (NGST). We are presenting the IFMOS concept, a 1 to 5 microns integral field spectrograph developed under contract with ESA. Image slicers are feeding compact spectrograph modules with very few moving parts. The wide field survey mode has low spatial - low spectral resolution over a field similar to 46 x 40 arcsec(2) (0.19 arcsec per resolved element). The high spatial -high spectral resolution mode covers a field 3.8 x 2.6 arcsec(2) sampled at 0.05 arcsec, a pointed object mode at the diffraction limit of the telescope. A detailed opto-mechanical design has been produced, meeting the environmental requirements for the NGST payload.

Abstract:

The results from the IFMOS ESA 1-5 microns integral field multiobject spectrograph study are presented. A review of the science requirements indicates that integral field 2D spectroscopy is a powerful concept of great value for the NGST. We present the opto-mechanical design of the instrument, based on image slicers. A low resolution and a high resolution channels are working in parallel, with only one mechanical motion. The low resolution channel covers a field 40 x 46 arcsec(2) at R similar to 150, while the high resolution channel covers 2.6 x 3.8 arcsec at R = 3000. We show that the performances on single sources is equal or better than classical dispersive spectrographs, and yet very efficient on large galaxy surveys, and conclude that IFMOS is both scientifically attractive and technically feasible.

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.