Related papers: The White Dwarf Cooling Sequence of the Globular C…

We present the analysis of the luminosity function of a large sample of galaxy clusters from the Northern Sky Optical Cluster Survey, using latest data from the Sloan Digital Sky Survey. Our global luminosity function (down to M_r<= -16)…

We have examined the radial distribution of white dwarfs over a single HST/ACS field in the nearby globular cluster NGC 6397. In relaxed populations, such as in a globular cluster, stellar velocity dispersion, and hence radial distribution,…

It has been known for a long time that stellar metallicity plays a significant role in the determination of the ages of the different Galactic stellar populations, when main sequence evolutionary tracks are employed. Here we analyze the…

Recent observations of globular clusters in intermediate-age (2-4 Gyr old) merger remnants have provided the hitherto `missing link' between between young merger remnants and normal elliptical galaxies. The luminosity functions (LFs) of the…

We present the results obtained from an objective search for stellar clusters, both in the currently active nuclear starburst region, and in the post-starburst disk of M82. Images obtained with the HST/ACS in F435W(B), F555W(V), and…

We present a new method to compute stellar ages in Globular Clusters (GC) that is ten times more precise than the traditional isochrone fitting procedure. The method relies on accurate stellar evolutionary tracks and on photometry for GCs…

We continue our study of rich Galactic clusters by presenting deep CCD observations of both NGC 2168 (M35) and NGC 2323 (M50). Both clusters are found to be rich (NGC 2168 contains at least 1000 stars brighter than V = 22 and NGC 2323…

We have cross-correlated the 2dF QSO Redshift Survey (2QZ) white dwarf catalog with the GALEX 2nd Data Release and the Sloan Digital Sky Survey (SDSS) data release 5 to obtain ultraviolet photometry (FUV, NUV) for approximately 700 objects…

We have imaged $\sim$ 1 deg$^{2}$ in the V-band in the direction of the Hercules Cluster (Abell 2151). The data are used to compute for the first time the luminosity function (LF) of galaxies in the cluster down to the dwarf regime…

We present a detailed study of two luminous super star clusters in the starburst galaxy M82. Spectra, covering 3250-8790 A at a resolution of 1.6 A, were obtained at the 4.2 m William Herschel Telescope (WHT) for cluster F and the highly…

New age determinations of the galactic disk globular clusters 47 Tuc, M71 and NGC6352 have been performed with our up-to-date alpha-enhanced stellar models. We find that all three clusters are about 9.2 Gyr old and therefore coeval with the…

We analyze in detail various possible sources of systematic errors on the distances of globular clusters derived by fitting a local template DA white dwarf sequence to the cluster counterpart (the so-called WD-fitting technique). We find…

We use recent low-mass star models, which reproduce accurately the observed sequences of various globular clusters, to convert the observed luminosity functions into bolometric luminosity functions and mass functions down to the bottom of…

The dynamical evolution of the globular cluster systems in galaxies is predicted, based on the standard dynamical theory normalized to the example of the Milky Way. The major processes varying with the galactocentric distance are the tidal…

The Advanced Camera for Surveys on board the Hubble Space Telescope has been used to obtain deep high-resolution images of the giant early-type galaxy NGC 1316 which is an obvious merger remnant. These observations supersede previous,…

We have determined the composite luminosity function (LF) for galaxies in 60 clusters from the 2dF Galaxy Redshift Survey. The LF spans the range $-22.5<M_{b_{\rm J}}<-15$, and is well-fitted by a Schechter function with ${M_{b_{\rm…

JWST observations of the strongly lensed galaxy The Sparkler have revealed a population of gravitationally bound globular cluster (GC) candidates. Different analyses have resulted in broadly similar ages but significantly different…

The white dwarf luminosity function has proven to be an excellent tool to study some properties of the galactic disk such as its age and the past history of the local star formation rate. The existence of an observational luminosity…

Motivated by recent measurements which suggest that roughly half the mass of the galactic halo may be in the form of white dwarfs, we study the implications of such a halo. We first use current limits on the infrared background light and…

J191213.72-441045.1 is a binary system composed of a white dwarf and an M-dwarf in a 4.03-hour orbit. It shows emission in radio, optical, and X-ray, all modulated at the white dwarf spin period of 5.3 min, as well as various orbital…