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Using data acquired as part of a unique Hubble Heritage imaging program of broadband colors of the interacting spiral system M51/NGC 5195, we have conducted a photometric study of the stellar associations across the entire disk of the…
Compact groups are associations of a few galaxies in which the environment plays an important role in galaxy evolution. The low group velocity dispersion favors tidal interactions and mergers, which may bring stars from galaxies to the…
New GALEX observations have detected significant FUV (1530 Angstroms) and NUV (2310 Angstroms) emission from stellar substructures within the tidal tails of four ongoing galaxy mergers. The UV-bright regions are optically faint and are…
Dwarf galaxies generally follow a mass-metallicity (MZ) relation, where more massive objects retain a larger fraction of heavy elements. Young tidal dwarf galaxies (TDGs), born in the tidal tails produced by interacting gas-rich galaxies,…
We present the results of numerical simulations which show the formation of blue compact dwarf (BCD) galaxies from merging between very gas-rich dwarfs with extended HI gas disks. We show that dwarf-dwarf merging can trigger central…
Blue Compact Dwarf and Dwarf Irregular galaxies are generally believed to be unevolved objects, due to their blue colors, compact appearance and large gas fractions. Many of these objects show an ongoing intense burst of star formation or…
We study star formation in a sample of 1204 galaxies in minor (| \Delta m_z | \geq 2) pairs and compact groups, drawn from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). We analyze an analogous sample of 2409 galaxies in major (|…
[Abridged] We present a first detailed analysis of resolved stellar populations in the dwarf galaxies NGC 185 and NGC 205 based on archival V- and I-band WFPC2 pointings. For NGC 185 we deduce that star formation was probably still active…
We present a UV, optical and near-infrared (near-IR) study of the star-forming complexes in the nearby peculiar galaxy NGC 3718, using UVIT, GALEX, Spitzer and DECaLS imaging data. The galaxy has a disturbed optical morphology due to the…
Stellar halos offer fossil evidence for hierarchical structure formation. Since halo assembly is predicted to be scale-free, stellar halos around low-mass galaxies constrain properties such as star formation in the accreted subhalos and the…
We present an analysis of the stellar populations of 102 visually-selected early-type galaxies (ETGs) with spectroscopic redshifts (0.3<z<1.5) from observations in the Early Release Science program with the Wide Field Camera 3 (WFC3) on…
Most galaxies follow well-defined scaling relations of metallicity and stellar mass; however, some outliers at the low mass end of the observed galaxy population exhibit unusually high metallicity for their mass. Understanding how these…
Hubble Space Telescope Wide Field Planetary Camera 2 images of Hickson Compact Group 79, Seyfert's Sextet, are presented. Both point sources and extended sources detected on the three WF chips were photometered in four filters: F336W,…
A fraction of brightest cluster galaxies (BCGs) shows bright emission in the UV and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of…
I present recent observations and analyses of star cluster formation in a wide variety of environments -- from young star clusters and super star clusters in normal actively star-forming spirals and irregulars to starbursting dwarfs and…
We present a study of the morphology of star formation and the associated nuclear activity in a sample of 8 closely interacting southern galaxies, which are in different stages of interaction, starting with nearly merged nuclei that have…
Using the Canada-France-Hawaii Telescope we have obtained deep high-resolution CCD images in V and I of a 28'x28' field in the outer disk of M 31 at ~ 116' from the center along the major axis to the south-west, and covering a range of…
Through a homogeneous analysis of spectroscopic literature data of red giant stars, we determine the radial metallicity profiles of 30 dwarf galaxies in the Local Group. We explore correlations between the calculated metallicity gradients…
We present new broad-band optical and near-infrared CCD imaging together with deep optical intermediate-resolution spectroscopy of Mkn 1087 and its surrounding objects. We analyze the morphology and colors of the stellar populations of the…
Resolution of nearby giant HII regions into their stellar and nebular constituents provides fundamental insights for interpreting more distant and powerful starburst activity. The following summarizes recent advances in our understanding of…