Search Publications
Multiple stellar populations in Galactic GCs: observational evidence
Piotto, Giampaolo
An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations. These multiple populations manifest themselves in a split of some evolutionary sequences of the cluster color-magnitude diagrams. In this paper we wi…
On the radial distribution of white dwarfs in the Galactic globular cluster omega Cen
Prada Moroni, P. G.; Degl'Innocenti, S.; Marchetti, E. +14 more
We present deep and accurate photometry (F435W, F625W, F658N) of the Galactic Globular Cluster omega Cen collected with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We identified ≈ 6,500 white dwarf (WD) candidates and compared their radial distribution with that of Main Sequence (MS) stars. We found a mild evid…
Jet-driven outflows in Seyfert galaxies .
Wilson, A. S.; Rosario, D. J.; Nelson, C. H. +1 more
Growing evidence over the past decade has indicated that low-luminosity active galaxies are often associated with outflows from their nuclei. In particular, a small but important fraction of Seyfert galaxies have extended collimated radio emission on the scales of the narrow-line region (NLR). In most of these cases, the emission-line gas displays…
Fueling QSOs: the relevance of mergers
Canalizo, G.; Schweizer, F.; Lacy, M. +4 more
To study the relevance of mergers for the fueling of QSOs, we are currently conducting an HST imaging campaign of a sample of QSO host galaxies classified as ellipticals in the literature. Here, we present results from a study of the first five QSO host galaxies imaged with HST/ACS. For the majority of objects, strong signs of interactions such as…
RR Lyrae stars in M31 globular clusters: B514
Clementini, G.; Marconi, M.; Cacciari, C. +8 more
We present preliminary results of a variable star search in the metal-poor globular cluster B514 of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys observations. A large number of RR Lyrae stars have been identified for the first time in a globular cluster of M31. The averag…
The BSS and binary content of NGC 5024 (M53): a combined LBT/HST study.
Pasian, F.; Fontana, A.; Grazian, A. +27 more
We present deep, wide-field imaging of the Globular Cluster NGC 5024, obtained at the Large Binocular Telescope. Images in U, B and V were obtained with the Large Binocular Camera, allowing to resolve the stars down to U ∼25.5 in a field of view of 25' × 24' . The combination of short and deep exposures allowed the construction of color-magnitude …
Stellar populations in the Local Group starburst galaxy IC10
Giuffrida, G.; Pulone, L.; Sanna, N. +10 more
We present preliminary results of a photometric investigation on IC10 using F555W and F814W data collected with WFPC2@HST covering two different regions. We provide a new estimate of both distance and reddening by adopting the Tip of the Red Giant Branch (TRGB). We find that the RGB stars in the two regions are located at the same distance, but pr…
NGC 2419: an ``intergalactic wanderer'' or a simple Galactic globular cluster? .
Di Criscienzo, M.; Clementini, G.; Ripepi, V. +8 more
We have carried out a new photometric study of the remote Galactic globular cluster NGC 2419, using proprietary and archive B,V,I time-series CCD photometry of the cluster, that allowed us to discover a large number of new variable stars and to obtain a new colour magnitude diagram that reaches V∼ 26 mag over a field of 50x43 square arcmin centere…
Young stellar populations in the Magellanic Clouds .
Vallenari, A.
We discuss the young population of stars and clusters in the Magellanic Clouds. We present the discovery of pre-main sequence candidates in the nebula N 11 in the Large Magellanic Clouds. The comparison of the Colour-Magnitude diagram with pre-main sequence tracks and the presence of Spitzer objects YSO I and II suggest that the star formation has…
Study of the QSO HE0354-5500 with combined HST imaging and VLT spectroscopy . An example of a deconvolution-based method for probing the QSOs host galaxies characteristics
Magain, P.; Courbin, F.; Hutsemékers, D. +2 more
The host galaxy of the QSO HE0354-5500 (M_B=-24.7, z=0.2674) is studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The morphology and dynamics of the host are described. The gas ionization and velocity are mapped as a function of the distance to the central QSO. Reflection or scattering of the QSO H…