We review the properties of globular clusters which make them useful for studying the Galactic halo, Galactic chemical evolution, and the early stages of the formation of the Milky Way. We review the evidence that GCs have a chemical inventory similar to those of halo field stars. We discuss the abundance ratios for dSph galaxies and show that it is possible to have formed at least part the Gal...

We present measurements of radial velocities for the narrow-line region (NLR) gas in the Seyfert 2 galaxy Mrk 3 out to ∼1 kpc from the nucleus. The observations consist of two datasets, both using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space T elescope (HST): 1) An [O III] slitless spectrum with the G430M grating of the inner 3 ′′ around the nucleus, and 2) a long-s...

Interacting galaxies favour the formation of star clusters but are also suspected to affect their evolution through an intense and rapidly varying tidal field. Treating this complex behaviour remains out-of-reach of (semi-)analytical studies. By computing the tidal field from galactic models and including it into star-by-star N-body simulations of star clusters, we monitor the structure and mas...

A search for fossil groups in the Sloan Digital Sky Survey was performed using virtual observatory tools. A cross-match of the positions of all SDSS Luminous Red Galaxies (with r < 19 and measured spectroscopic redshifts) with sources in the ROSAT All-Sky Survey catalog resulted in a list of elliptical galaxies with extended X-ray emission (with a galaxy/ROSAT-source distance of less than 0.5 a...

We describe our efforts to study dwarf galaxies with active nuclei, whose black holes, with masses ≤ 106 M⊙, provide the best current observational constraints on the mass distribution of primordial seed black holes. Although these low-mass galaxies do not necessarily contain classical bulges, Barth, Greene, & Ho (2005) show that their stellar velocity dispersions and black hole masses obey the...

We present the first determination of the pairwise velocity dispersion of galaxies at different luminosity with the final release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS). Our result surprisingly shows that the random velocities of the faint galaxies are very high, around 700 km s −1 , reaching similar values as the brightest galaxies. At intermediate luminosities slightly bright...

The Chandra image of the central region of the Coma cluster reveals that both its dominant galaxies, NGC 4874 and NGC 4889, retain the central parts of their X-ray gas coronae. The interstellar gas with a temperature of 1– 2 keV is confined by the hot intergalactic medium of the Coma cluster into compact clouds (only 3 kpc in radius) containing 108 M⊙ of gas. The physical state of the gas in th...

We investigate the conjecture by Sikora, Stawarz & Lasota (2007) that the observed AGN–radioloudness bimodality can be explained by the morphology related bimodality of black-hole spin distribution in the centers of galaxies: central black holes in giant elliptical galaxies may have (on average) much larger spins than black holes in spiral/disc galaxies. We study how accretion from a warped dis...

The [O II] λ3727 line, a commonly used estimator of star formation rate in extragalactic surveys, should be an equally effective tracer of star formation in the host galaxies of quasars, whose narrow-line regions are expected to produce weak low-ionization emission. Quasar spectra generally show little or no [O II] emission beyond that expected from the active nucleus itself. The inferred star ...

We investigate the dependences of galaxy star-formation history and galaxy morphology on environment, using color and Hα equivalent width as starformation history indicators, using concentration and central surface brightness as morphological indicators, and using clustocentric distance as an environment indicator. Clustocentric distance has the virtue that it can be measured with very high pre...