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Scientific Report 2007-2009
Astronomy & Astrophysics
tic dynamics and of general relativity (A1, A2, A3 and A4). In particular, we advanced an
original interpretation of galactic nuclei activity (Active Galactic Nuclei, AGN) as fed by decayed
massive globular clusters in the central galactic regions. We also study the chemical evolution
of spheroidal and largely-populated star systems (like globular clusters and elliptical galaxies), in
order to produce models of sufficient accuracy to be compared to photometric and spectrometric
observational data. Solar activity phenomena are also studied in terms of periodicities in the
solar energetic proton fluxes (A5). Researchers are involved in studying our Galaxy by observing
dust emission in the infrared and microwave bands using data from balloon-borne experiments
(BOOMERanG) and from the Herschel satellite (A6).
Extragalactic Astrophysics
Clusters of galaxies are the largest gravitationally
bound objects in the Universe. They form at
the intersection of filaments and sheets of galaxies,
as evident from large redshift surveys of galaxies
and from numerical simulations. A large fraction
of the mass of each cluster is in the form of a hot
(millions of K), ionized tenuous gas, filling the potential
well of the cluster, and producing X-rays.
Most of the mass is in the form of dark matter,
as evident from dynamical consideration and from
lensing measurements on background sources. Researchers
in our department estimate the redshift
of distant clusters photometrically, using measurements
of the spectral energy density from the ultra-
of the most massive clusters known, is also a gen-
Figure 3: The cluster of galaxies Abell 1689, one
violet to the near infrared. In this way they identify eral relativity laboratory. Light from distant, background
galaxies is deflected by the mass (visible and
very distant clusters and can follow-up with X-ray
observations, allowing studies of the evolution of dark) present in the cluster, and produces characteristic
arcs around the center of the cluster. credits:
galaxy populations in the clusters. We also study
NASA/ESA HST
the gravitational lensing produced by clusters and
in general by the distribution of dark matter (A7),
and study clusters through the Sunyaev-Zeldovich effect (see next paragraph).
Active Galactic Nuclei are galaxies where the nucleus produces more radiation than the rest
of the galaxy. This is due to a powerful supermassive black-hole located in the center of the
AGN, with its ultra-hot accretion disk, surrounded by an obscuring torus and producing huge
jets of relativistic particles. Depending on the orientation of the AGN with respect to the line
of sight, we have different manifestations of the AGN, named radio loud and radio quiet quasars,
blazars, broad line radio galaxies, narrow line radio galaxies, Seyfert galaxies. Researchers in our
department study AGN mainly with optical and X-rays observations (A8, A9, A10 and A11). They
use proprietary telescopes to contribute to a multi-wavelength network monitoring the variability
of AGNs, which is the key to select AGN and understand the violent processes happening in the
nucleus. They have contributed to large international missions for high-energy astrophysics, like
Beppo-SAX, and more recently Swift and Fermi, and use the conspicuous flux of data to develop
new and detailed models of these sources.
Cosmology
The Observational Cosmology Group (G31) was founded in our Department in 1981, by prof.
Francesco Melchiorri, one of the Pioneers of Cosmic Microwave Background (CMB) research.
The idea of studying the distant past of the Universe by measuring its photonic remnant (the
CMB) resulted in a series of very successful experiments carried out by the group, to measure
the spectrum of the CMB, its anisotropy, and its polarization. All these observables are sensitive
Sapienza Università di Roma 145 Dipartimento di Fisica