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Using the Sloan Digital Sky Survey (SDSS), we probe the halo mass distribution by studying the velocities of satellites orbiting isolated galaxies. In a subsample that covers 2500 deg2 on the sky, we detect about 3000 satellites with absolute blue magnitudes going down to MB=-14; most of the satellites have MB=-16 to -18, comparable to the

IAUC 6104 available at Central Bureau for Astronomical Telegrams. IAUC 6104 available at Central Bureau for Astronomical Telegrams.

We present a quantitative analysis of the star formation history (SFH) of 12 fields in the Small Magellanic Cloud (SMC) based on unprecedented deep [(B - R), R] color-magnitude diagrams (CMDs). Our fields reach down to the oldest main-sequence turnoff with a high photometric accuracy, which is vital for obtaining accurate SFHs, particularly at

We have pursued two different methods to analyze the old stellar population near the Galactic plane, using data from the 2MASS survey. The first method is based on the isolation of the red clump giant population in the color-magnitude diagrams and the inversion of its star counts to obtain directly the density distribution along the line of sight

The origin of the abundance discrepancy, i.e., the fact that abundances derived from recombination lines are larger than those from collisionally excited lines, is one of the key problems in the physics of photoionized nebulae. In this work, we analyze and discuss data for a sample of Galactic and extragalactic H II regions where this abundance