Search Publications
Feige 86: Gaia confirms its Horizontal Branch nature
Bonifacio, P.; Monaco, L.
The halo star Feige 86 was considered in the 1960's and 1970's a solar metallicity chemically peculiar, He-weak B type star. Margherita Hack was the first to study its UV spectrum acquired with the IUE satellite. Later studies of this star by Hack and collaborators suggested that, in spite of the fact its iron abundance is slightly above solar, th…
Young Stellar Distance Indicators and the Extragalactic Distance Scale
Anderson, R.
The extragalactic distance scale is perhaps the most important application of stellar distance indicators. Among these, classical Cepheids are high-accuracy standard candles that support a $1.4\%$ measurement of Hubble's constant, $H_0$. The accuracy of Cepheid distances is thus directly relevant for understanding the implications of the Hubble te…
The Extragalactic Population of Accreting Neutron Stars and the Ultraluminous X-ray Sources Paradigm: from ULTraS to PULSULTraS
Salvaterra, R.; Tiengo, A.; de Luca, A. +11 more
The unambiguous identification of the nature of a neutron star in X-rays is achieved through the detection of coherent signals reflecting the spin period of the compact object. The search for coherent signals in the whole XMM-Newton source catalog was one of the main aims of the EU/FP7-funded project EXTraS (active in 2014-2016). The ULTraS and PU…
Supermassive Black Hole Winds in X-rays
Bianchi, S.; Cappi, M.; Ponti, G. +22 more
SUBWAYS (Supermassive Black HoleWinds in X-rays) is an international program designed to provide a unique observational framework to test the validity of physical models for Active Galactic Nuclei (AGN) outflows. Its ultimate goal is to understand the AGN impact onto their host galaxies.Within this framework, we have been awarded a Large Program o…
Deep and accurate near-infrared photometry of the Galactic globular cluster omega Cen .
Prada Moroni, P. G.; Degl'Innocenti, S.; Marchetti, E. +17 more
We present deep and accurate Near-Infrared (NIR) photometry of the Galactic Globular Cluster omega Cen . Data were collected using the Multi-Conjugate Adaptive Optics Demonstrator (MAD) mounted on the VLT (ESO). We combined the NIR photometry with optical space data collected with the Advanced Camera for Surveys (ACS) for the same region of the cl…
Optical SBFs of shell galaxies.
Cantiello, M.; Brocato, E.; Raimondo, G. +1 more
We measure F814W Surface Brightness Fluctuations (SBFs) for a sample of distant shell galaxies observed with the Advanced Camera for Survey (ACS) on board of HST. To evaluate the distance at galaxies, theoretical SBF magnitudes for the ACS@HST filters are computed for single-burst stellar populations covering a wide range of ages (1.5\div 14 Gyr) …
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…