Galaxy formation and evolution

Abstract:

We present K, L and M diffraction-limited images of NGC 1068 obtained with NAOS+CONICA at VLT/YEPUN over a 3.5" field around the central engine. Hot dust (Tcol = 550-650 K) is found in three different regions : (a) in the true nucleus, seen as a slightly NS elongated, core of extremely hot dust, "resolved" in K and L with respective diameters of ~5 pc and 8.5 pc ; (b) along the NS direction, as a "spiral arm" and a southern tongue ; (c) as a set of parallel elongated nodules ("wave-like") bracketting the jet. Several structures observed on radio maps, mid-IR or HST UV-visible maps are seen, so that a precise registration can be done from UV to 6 cm. These results do support the current interpretion that source (a) corresponds to emission from dust near sublimation temperature delimiting the walls of the cavity in the central obscuring torus. Structure (b) is thought to be a mixture of hot dust and active star forming regions along a micro spiral structure that could trace the tidal mechanism bringing matter to the central engine. Structure c)which was not known, exhibits too high a temperature for "classical'' grains ; it is most probably the signature of transiently heated very small dust grains (VSG) : "nano-diamonds", which are resistant and can form in strong UV field or in shocks, are very attractive candidates. The "waves'' can be condensations triggered by jet induced shocks, as predicted by recent models. First estimates, based on a simple VSG model and on a detailed radiative transfer model, do agree with those interpretations, both qualitatively and quantitatively.

Abstract:

Area spectroscopy has significant advantages over both traditional imaging and long-slit spectroscopy: it is more efficient in observing time, and yields substantially more information. Through Integral Field Units, area spectroscopy is becoming an essential part of new facility instruments on the latest large telescopes. We have been undertaking a programme on the Gemini 8-m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near-infrared. Here we present some preliminary results from 3D spectroscopy of z ∼ 1 objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc.

Abstract:

This contribution advocates anew method for comparing theoretical predictions to observations. Properties of virtual galaxies are computed using the hybrid model for hierarchical galaxy formation GALICS (for Galaxies In Cosmological Simulations), which takes advantage of large cosmological N-body simulations to plug in simple semi-analytic recipes describing the fate of the baryons. From such a fake galaxy catalog, one can build light cones, and project them onto virtual CCD devices, taking into account the technical characteristics of the detector/telescope. As a result, realistic mock images can be produced, which can then be directly compared to real observations.

Abstract:

We have discovered extended Lyman-α emission around a z = 4.5 QSO in a deep long-slit spectrum with Keck/LRIS at moderate spectral resolution (R ≈ 1000). The line emission extends 5 arcsec beyond the continuum of the QSO and is spatially asymmetric. This extended line emission has a spectral extent of 1000km/s, much narrower in velocity spread than the broad Lyman-α from the QSO itself and slightly offset in redshift. No evidence of continuum is seen for the extended emission line region, suggesting that this recombination line is powered by reprocessed QSO Lyman continuum flux rather than by local star formation. This phenomenon is rare in QSOs which are not radio loud, and this is the first time it has been observed at z > 4. It seems likely that the QSO is illuminating the surrounding cold gas of the host galaxy, with the ionizing photons producing Lyman-α fluorescence. As suggested by Haiman and Rees (2001), this 'fuzz' around a distant quasar may place strong constraints on galaxy formation and the extended distribution of cold, neutral gas.