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Abstract:

We discuss how measurements of the absorption of gamma -rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in galaxy formation. We use semi-analytic models (SAMs) of galaxy formation, set within the hierarchical structure formation scenario, to obtain predictions of the EEL from 0.1 to 1000 mum. SAMs incorporate simplified physical treatments of the key processes of galaxy formation - including gravitational collapse and merging of dark matter halos, gas cooling and dissipation, star formation, supernova feedback and metal production - and have been shown to reproduce key observations at low and high redshift. Here we also introduce improved modelling of the spectral energy distributions in the mid-to-far-IR arising from emission by dust grains. Assuming a flat ACDM cosmology with Omega (m) = 0.3 and Hubble parameter h = 0.65, we investigate the consequences of variations in input assumptions such as the stellar initial mass function (IMF) and the efficiency of converting cold gas into stars. We conclude that observational studies of the absorption of gamma -rays with energies from similar to 10 Gev to similar to 10 TeV will help to determine the EEL, and also help to explain its origin by constraining some of the most uncertain features of galaxy formation theory, including the IMF, the history of star formation, and the reprocessing of light by dust.

Abstract:

We present results from integral field spectroscopy of the narrow line region of NGC 1068, carried out with the MPE 3D near infrared imaging spectrometer. A map and velocity field of the [Fe II] fine structure line at 1.64mum is presented. The kinematics of the [Fe II] emission, which arises in partially ionized zones, shows red shifted emission in the north eastern cone of the NLR, and blue shifted emission in the south west, reversed relative to high ionization species such as [Si VI] or [0 111]. We propose a model geometry of the narrow line region which is consistent with existing data and explains the observed [Fe II] kinematics.

Abstract:

The SINFONI integral field spectrometer for the VLT will provide near-infrared spatially resolved spectra at spatial resolutions close to the diffraction limit of the telescope (0." 05 at 2 pm). 1024 spectra can be simultaneously obtained, covering a 32x32 pixel field of view with similar to 100% filling factor. The spectral resolution is R similar to 4500, corresponding to a kinematic resolution of 67 km s(-1). SINFONI is ideally suited to study stellar kinematics in the nuclear regions of normal spiral galaxies, using the near-infrared H and K band CO stellar absorption features. Integral field data from SINFONI will provide high-resolution two-dimensional maps of nuclear velocity dispersion and rotation, which in turn will constrain the anisotropy parameter and yield robust estimates of the central dark mass.

Abstract:

The large populations of young star clusters observed in interacting galaxies like NGC4038 4039 ("The Antennae") are widely believed to be the progenitors of part of the globular cluster systems seen in local elliptical galaxies. For a comprehensive study of the young clusters in the Antennae we have obtained near infrared broad and narrow band images (SOFI on the NTT). integral field spectroscopy (MPE-3D at the AAT) and medium and high resolution spectroscopy (ISAAC VLT-UT1 and UVES VLT-UT2). We find that all of the bright star clusters are young (< 20 Myr), with the interaction region hosting the youngest clusters (similar to 5 Myr). The nuclear starbursts are older (similar to 65 Myr), but also show snore recent star formation activity. Age variations on small spatial scales are seen throughout the merger. Cluster masses range from 10(5) to a few x 10(6) M-circle dot. A comparison between dynamically determined masses and those estimated from photometry in combination with starburst models suggests variations in the IMF from cluster to cluster.