Angela Bongiorno

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Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest(More)
To understand the evolution of galaxies, we need to know as accurately as possible how many galaxies were present in the Universe at different epochs. Galaxies in the young Universe have hitherto mainly been identified using their expected optical colours, but this leaves open the possibility that a significant population remains undetected because their(More)
We present a new measurement of the space density of high redshift (z ≃ 3.0-4.5), X–ray selected QSOs obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a statistically large (40 objects), X–ray selected (F0.5−2keV > 10 −15 erg cm s), homogeneous sample of z > 3 QSOs for which spectroscopic (22) or(More)
Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet(More)
We constrain the ratio of black hole (BH) mass to total stellar mass of type-1 AGN in the COSMOS survey at 1 < z < 2. For 10 AGN at mean redshift z ∼ 1.4 with both HST/ACS and HST/NICMOS imaging data we are able to compute total stellar mass M∗,total, based on restframe UV-to-optical host galaxy colors which constrain mass-to-light ratios. All objects have(More)
Aims. The identities of the main processes triggering and quenching star-formation in galaxies remain unclear. A key stage in evolution, however, appears to be represented by post-starburst galaxies. To investigate the prevalence of these galaxies and their impact on galaxy evolution in general, we initiated a multiwavelength study of galaxies with k + a(More)
We identify 42 “candidate groups” lying between 1.8 < z < 3.0 from a sample of 3502 galaxies with spectroscopic redshifts in the zCOSMOS-deep redshift survey within this same redshift interval. These systems contain three to five spectroscopic galaxies that lie within 500 kpc in projected distance (in physical space) and within 700 km/s in velocity. Based(More)
Observational constraints on the average radial distribution profile of AGN in distant galaxy clusters can provide important clues on the triggering mechanisms of AGN activity in dense environments and are essential for a completeness evaluation of cluster selection techniques in the X-ray and mmwavebands. The aim of this work is a statistical study with(More)