Active and normal galaxies

Supermassive black holes and their host galaxies

E. M. Corsini, 
E. Dalla Bontà
, L. Morelli
, A. Pizzella

Recent years have seen dramatic progress in the study of the nuclear properties of galaxies. It resulted that masses of supermassive black holes are tightly related to large-scale properties of their host spheroids. This suggests that the formation and evolution of galaxies and supermassive black holes are closely entwined. During the PhD program dynamical measurements of the masses of supermassive black holes will be performed with state-of the-art observations and models. The project will be developed within an international collaboration involving the Hertfordshire University in UK, Max-Planck-Institut fuer extraterrestrische Physik in Germany, Space Telescope Science Institute in Baltimore in USA, and Herzberg Institute in Canada

On the connection between galaxy's shape and stellar population
M. D’Onofrio, C. Chiosi

Galaxies are known to obey a number of scaling relations between their structural, dynamical and photometrical parameters. The origin of such correlations is poorly understood, but several observations suggest that a fine-tuning exists between the structure and dynamics of galaxies and their stellar population content. A way to find the correct answer to this problem is that of simulating galaxy formation and evolution using even  better models of the physical processes occurring both in the baryonic and dark matter components.
Thanks to the sophisticated N-body Tree-SPH models available today it is possible to address many of such astrophysical questions.
We propose to introduce a PhD student to the modern world of galaxy simulations with the aim of explaining the origin of such unexplained observed phenomenon.

Dwarf galaxies


E. V. Held

Dwarf galaxies are important for our understanding of the processes that govern galaxy evolution and to test the predictions of hierarchical models of structure formation. Fortunately dwarfs are so well represented in our Local Group of galaxies that we can directly investigate their histories through their stellar populations. The LOcal Group Omegacam Survey (LOGOS) is a Guaranteed Time long term project aimed at a uniform, high image quality, very wide field multicolor photometry of all dwarf galaxies in the Local Group visible from the southern hemisphere. The aim of the survey, using the new Omegacam CCD array at the VLT Survey Telescope, is to study in detail their star formation histories up to a few million years ago, reaching the outer most regions of the systems. 
The PhD student will become part of a large international collaboration and share these scientific goals in the Thesis. Data obtained in 2012 for the first two dwarf galaxies will provide the basis for a prompt start of the work. The PhD student will develop the reduction and analysis tools for wide-field Omegacam observations and the discussion of the scientific results. To this aim, very good programming and logical skills and a solid background in stellar astronomy are a prerequisite. Time permitting, the Thesis may also extend its scope to include massive globular clusters with complex stellar populations, which possibly are the nuclei of disrupted dwarf galaxies. The acquired expertise in the analysis of wide-field imaging data will be a much valued asset in today's observational astronomy and find vast application in the post-doctorate research career of the PhD student.

The properties of gas in galactic nuclei
M. Mapelli


Recent sub-millimeter and radio observations (with ALMA, SMA and JVLA) of the gas in the central parsecs of the Milky Way show a variety of interesting gas features (e.g. inflows of dense molecular gas). A model is missing that fully describes the thermo-dynamical state of gas in the central parsec around a quiescent or active super-massive black hole. The student will perform hydro-dynamical simulations of molecular gas around super-massive black holes. The simulations will include an accurate treatment of non-equilibrium chemistry. The final goal is make predictions for future ALMA and SKA observations of nearby galactic nuclei.

 More details on our group and on these topics can be found at web.pd.astro.it/mapelli/group.html

Multifrequency properties of quasars


P. Marziani, P. Mazzei

The doctoral project is focused on the interpretation of the spectral energy distribution (SED) of quasars over a broad range of electromagnetic frequencies, from radio to hard-X. The novelty of the approach involves the separation of sources along the so-called Eigenvector 1 quasar sequence that organizes quasar properties on a physical basis. The main aims are (1) to provide an empirical analysis of the quasar SED systematic differences along the sequence, (2) to isolate the active nucleus contribution from star formation, and (3) to connect measured  parameters with physical properties of the active nucleus such as central black hole mass, spin, bolometric luminosity, and Eddington ratio. Aim (2) may be mainly focused on exvtreme quasars that have been identified as highly accreting, possibly at super-Eddington rates. 
The work will be based on a statistical and physical analysis of high-quality spectral datasets collected from surveys or dedicated observations. This includes VLT proprietary observations, HST and SDSS archival spectra, as well as FIR/submillimeter data. The methodology involving the Eigenvector 1 sequence has been successfully applied to a variety of quasar problems and has yielded tens of papers in major journals from several research groups. 
A prospective doctoral student will select a suitable sample following already-established criteria, will measure optical and UV emission lines and continuum interpreting lines and SEDs in the framework of state-of-the-art theoretical models. She/he will learn spectroscopy and photometric data analysis with a broad array of state-of-the-art instruments operating in different frequencies, and will familiarize her/himself with theoretical models of accretion and of star formation processes in the nuclei of galaxies. 
The graduate student will be part of a larger collaboration involving researchers in Italy, Mexico, and Spain, and is expected to achieve systematic, general results that are relevant for the formulation of joint AGN/host galaxy evolution scenarios as well as for the global understanding of the evolution of galaxies. The new results could lead to 2/3 major papers in three-year timeframe of the doctoral curriculum.

Insights on active galactic nuclei through multiple frequency analysis of exceptionally variable high energy sources 

S. Ciroi, M.Berton, G. La Mura, L. Foschini

This PhD project aims at the coordinated analysis of high energy emitting active galactic nuclei (AGNs) using a combination of optical and high energy detectors. The research program is mainly focused on the properties of the blazar class of AGNs, where a prominent relativistic jet is believed to emerge at close angles with our line of sight towards the source. Spectro-photometric studies of sources undergoing significant flaring activity in the high energy domain, along with optical and lower frequency observations, are required to clarify the nature of radiation emission in these objects, particularly for our understanding of the role of relativistic jets in the high energy sources, as well as in more general AGN contexts. The eligible candidate will be working within a group involved in a wide instrumental network, including the Fermi LAT mission, the MAGIC experiment and the Asiago observatory.

Long term monitoring of unobscured active galactic nuclei: unveiling the physics of the central engine 

S. Ciroi, M.Berton, G. La Mura, L. Foschini

Nuclear activity in galaxies is among the most effective radiation sources in almost every frequency range of the electro-magnetic spectrum.
 Although a comprehensive interpretation of the most general properties of AGNs has already been provided, many details of the processes which take place in an active nucleus still have to be clarified. Since the spatial scales of the regions actually involved in the non-stellar activity are far beyond the resolution of our current and foreseeable instrumentation, the only way to understand the nature of this phenomenon is to study in detail its temporal evolution and to account for the origin of the different spectral components, which make up the observed signal. The purpose of this PhD research project is to analyze in detail the spectra of AGNs collected in long term monitoring campaigns, where hints of a direct view of the central energy source are present. The PhD researcher will work on the interpretation of different spectral features, and of their evolution, by means of the most advanced models and he will be involved in the acquisition and reduction of new observations, as well. Direct experiences with observational facilities, such as the Asiago observatory, and with data produced by space observatories, like SWIFT, XMM and AGILE, will be part of the project.