In this paper we characterize the congruence associated to the direct sum of all irreducible representations of a finite semigroup over an arbitrary field, generalizing results of Rhodes for the field of complex numbers. Applications are given to obtain many new results, as well as easier proofs of several results in the literature, involving

We report on the detection of two Hα-emitting extremely compact objects from deep images of the A634 and A539 clusters of galaxies at z~0.03. Follow-up long-slit spectroscopy of these two unresolved sources revealed that they are members of their respective clusters, showing H II-type spectra. The luminosity and the extreme equivalent width of Hα +

Multi-object spectroscopic observations of A697 were carried out at the TNG telescope in December 2003 during the program of proposal AOT8/CAT-G6. (1 data file).

By detecting ionised-gas emission in 75% of the cases, the SAURON integral-field spectroscopic survey has further demonstrated that early-type galaxies often display nebular emission. Furthermore, the SAURON data have shown that such emission comes with an intriguing variety of morphologies, kinematic behaviours and line ratios. Perhaps most

We present deep, high angular-resolution HST NICMOS imaging in the Hubble Deep Field South (HDF-S), focusing on a subset of 14 distant red galaxies (DRGs) at z~2.5 that have been preselected to have J-K>2.3. We find a clear trend between the rest-frame optical sizes of these sources and their luminosity-weighted stellar ages as inferred from their

We report the discovery of a new X-ray source detected in a 5ks observation starting on 2007-02-14.08 UT as part of our ongoing Chandra/HST M31 transient program. The source was detected at coordinates RA(J2000) 00:44:12.4, Dec(J2000) 41:25:48.2, at the edge of the ACIS-S field of view, which results in larger than usual position errors of 2.2" and