Context: High-redshift ultra luminous infrared galaxies contribute the bulk of the cosmic IR background and are the best candidates for very massive galaxies in formation at z>1.5. Aims: It is necessary to identify the energy source for their huge luminosities, starburst or AGN activity, in order to correctly interpret the role of ULIRGs in galaxy

The photospheric Mn I 539.4 nm line in the solar spectrum shows unusual variability with the solar cycle in that its depth decreases with increasing activity. citet{nv-2001A&A...369L..13D} claimed that this phenomenon is due to interlocking between the chromospheric Mg II h & k lines and an overlapping Mn I multiplet. In this contribution we test

We request 13.9 hours of IRS GTO time to observe two recently discovered very low-mass T dwarfs, the early-T HN PegB and the very late-T ULAS J0034. As inferred from models, the two T dwarfs have similar masses of around 20 MJupiter, and similar gravities, but very different effective temperatures of Teff ~1100 K and 650 K for HN PegB and ULAS

Aims:To conduct an intensive study of the rich, X-ray luminous galaxy cluster Abell 773 at z = 0.22 containing a diffuse radio halo to determine its dynamical status. Methods: Our analysis is based on new spectroscopic data obtained at the TNG telescope for 107 galaxies, 37 spectra recovered from the CFHT archive and new photometric data obtained

GREGOR is a new open solar telescope with an aperture of 1.5 m. It replaces the former 45-cm Gregory Coudé telescope on the Canary island Tenerife. The optical concept is that of a double Gregory system. The main and the elliptical mirrors are made from a silicon-carbide material with high thermal conductivity. This is important to keep the mirrors

We discuss the emission of gravitational radiation produced in encounters of dark matter galactic halos. To this aim we perform a number of numerical simulations of typical galaxy mergers, computing the associated gravitational radiation waveforms as well as the energy released in the processes. Our simulations yield dimensionless gravitational