We report the detection of main-sequence and blue horizontal-branch stars of the Ursa Minor dwarf spheroidal galaxy beyond its tidal radius, indicating the existence of a possible tidal extension in this satellite of the Milky Way. This tidal extension could spread out well beyond the area covered in our survey (R>80'), as suggested by the presence

The distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The pattern is that of clusters paired equidistant across a central galaxy with the apparent magnitudes and redshifts of their constituent galaxies being closely matched. The clusters and the galaxies in them tend to be

A new photometric system suitable for deep, precise and quick metallicity mapping in galaxies is proposed. We find a linear correlation between our metallicity index and the Mg_2 index for stellar, globular-cluster, and early-type galaxy spectra, and model spectral energy distributions of the simple stellar populations.

We present the results of a kinematical study of the H II regions in the central area of the giant irregular galaxy NGC 4449. A new method is defined to determine the sizes of the regions. We obtained the integrated parameters of the H II regions: radius, luminosity, radial velocity and velocity dispersion. We define the size and luminosity vs

We present a high-resolution kinematical study of the ionized gas in the circumnuclear region of NGC 4314. Our spectra reveal the presence of a central structure (apparently a ring or torus) located at ~ 2 arcsec from the nucleus, which we identify as the shocked interface between the nuclear bar and the gas inside the HII region ring.

We investigate current problems in obtaining reliable ages for old stellar systems based on stellar population synthesis modeling of their integrated spectra. In particular, we address the large ages derived for the globular cluster 47 Tuc, which is at odds with its color-magnitude diagram (CMD) age. Using a new age indicator, Hγσ