Normal and active galaxies

Relativistic effects in galaxy surveys
D. Bertacca

Maps of the Universe based on galaxy redshifts are distorted by several relativistic effects. LIGER takes a (N-body or hydrodynamic) Newtonian simulation as an input and outputs the distribution of galaxies in comoving redshift space, e.g. see Borzyszkowski, Bertacca & Porciani (2017). This result is achieved making use of a coordinate transformation and simultaneously
accounting for lensing magnification. The calculation includes both local corrections (i.e. peculiar velocities and Sachs Wolfe effect) and terms that have been integrated along the line of sight (e.g. integrated Sachs Wolfe effect, lensing convergence, magnification and time delay).  
In general, in a wide-angle survey, peculiar-velocity effects are not accurately described by the Kaiser limit at very large scales. The aim of this project is to measure the impact of redshift-space distortions, both the local and non-local terms, on the monopole of the galaxy power spectrum that will be measured in a Euclid-like survey.

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.

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.

Tracing the infalling regions of nearby cluster of galaxies
A.Moretti, D. Bettoni, B. Vulcani, M. Gullieuszik, B. Poggianti

One of the major problems in modern astrophysics is the understanding of how galaxy properties relate with the environment in which they live.
Within the standard cosmological framework of mass assembly, the biggest gravitationally bound structures are galaxy clusters, that started forming, though, at higher redshift. Galaxy clusters as we see today are the results of many episodes of gas and stars infall tracing the dark matter filaments that constitute the cosmological web.
While many aspects of the galaxy life in dense environments is known to a high level of details for nearby clusters, less information is available on the galaxy properties in the infalling regions, i.e. the filaments.
Thanks to the future availability of the WEAVE-Cluster survey, we will be able to map the galaxy properties in the infalling regions of 16 clusters selected from the WINGS sample out to 5 virial radii from the cluster center.
The PhD student will help analysing this dataset, with the aim to understand what is the nature, extent and importance of the filamentary structure around clusters, as well as analyze the substructuring properties of galaxies in these regions.
This will shed light on the main physical mechanisms shaping galaxy properties in different environments.

Isolated early-type galaxies as the cleanest environment to study
merging related phenomena

R. Rampazzo, P. Mazzei, S. Ciroi

Isolated early-type galaxies (Es+S0s, iETGs hereafter) are the rare counterparts of a galaxy family typically inhabiting clusters. Their spatial isolation translates into a "time isolation", up to 3 Gyrs, providing the cleanest
environment, within which to test the ETG evolution without additional  external effects.
Recent studies sketched a picture where most of iETGs are just the opposite of the mythical sample of unperturbed galaxies. Deep imaging revealed, at faint surface brightness levels, a nearly ubiquitous presence of a manifold of fine structures like shells, stellar fans, tails, rings and ripples. Since their extreme isolation, interactions did not yet harassed them erasing/smoothing out the above signatures of their accretions/merging origin.
We propose to the student a multi-wavelength approach to the iETGs study,
corroborated by simulations for the interpretation of their properties.
Catalogues of iETGs have been developed in the Northern Hemisphere.
We start increasing the still small sample of galaxies with deep imaging both in large and narrow bands photometry, using both normal and high resolution imaging. During the thesis, we will expect to produce and clean up a volume limited catalogue of candidates iETGs in the southern hemisphere, via dedicated VST deep observations and follow up spectroscopic observations.
Collaboration with foreign research groups in the field will enrich the PhD student's experience.

Dorado and its member galaxies: anatomy of a group under stress
R. Rampazzo,  E. Iodice, S. Ciroi, F. di Mille, P. Mazzei

Dorado is a nearby (18 Mpc), clumpy, still un-virilized group dispersed over several square degrees in the Southern Hemisphere. The galaxy morphology reveals, at a glance, that most of the member galaxies show peculiar features, irrespective to their morphological family, supporting the view that the group evolution is anything but passive.
We have collected a large  multi-wavelength data set, from wide-field VST images covering the entire group, to narrow band Halpha (LCO) images and FUV (UVIT) observations of the group backbone galaxies, from which to start to investigate the galaxy and the entire group into its "stress" phase.
Using these data set the student will have the possibility to investigate the galaxy structure down to 29-30 mag arcsec^{-2} g-band unveling,among the other, the connection between optical - Halpha - FUV and available HI observations, and mapping galaxies size and masses from giants down to puzzling ultra dwarf galaxies (UDGs). During his PhD thesis, the student is expected to develop his own observing plans, integrating information coming from imaging e.g. with kinematical and/or
new (CO, HI 21cm) radio observations. Collaboration with foreign research groups in the field will enrich the PhD student's experience.

The role of the group environment in galaxy evolution 
B. Vulcani
The majority of typically sized galaxies in the local Universe reside in a common dark matter halo with other similar galaxies known as a galaxy group. However, this was not always the case. Nine billion years ago, when the universe was one third its current age, these galaxies were almost exclusively the only massive galaxy in their dark matter haloes. I propose a thesis to understand the effect galaxy groups have on the evolution of galaxy properties, using mainly observational methods.
The project will trace the evolution of the star formation rate, dust content, morphology and total stellar mass of group galaxies from z=1.5 to 0 and compare such evolution to that of galaxies in more and less massive environments, with the intent of understanding the preprocessing in groups. The core of program is based on data coming from the Gemini Observations of Galaxies in Rich Early Environments (GOGREEN, PI Balogh), an ongoing Large program aimed at collecting imaging and deep spectroscopic data of 21 galaxy systems at 1 < z < 1.5.  To trace the evolution with cosmic time, data from the Grism-Lensed Amplified Survey from Space (GLASS, PI Treu) will be exploited in the redshift range 0.5<z<1 and data from the Wide-Field Nearby Galaxy Cluster Survey (WINGS, PI Fasano) and its follow ups will be exploited as local benchmark.
Follow ups for group galaxies in the local universe at various wavelengths are also envisioned (optical with MUSE, HI with Meerkat, CO with ALMA) to characterise the role of the group environments also on the spatially resolved properties of the galaxies.
I am highly involved in all the aforementioned collaborations and the student will be immediately inserted in an international context, participating to the collaboration meeting and visiting collaborators across the world, most likely in Canada and US. 

The Effect of Filaments on the Gas in Galaxies
B. Vulcani

Filaments that connect groups and clusters of galaxies are very common and they may contain up to 40 per cent of the matter in the Universe. Nonetheless, characterising filaments has remained difficult because they are very wispy and diffuse. As a consequence, their impact on the galaxy properties is still controversial, but of extreme importance to shed light on the processes that regulate galaxy evolution.
I propose a thesis to examine how galaxies evolve in the filamentary structure around clusters and groups in the local Universe. The filaments have been identified in the nearby universe around the Virgo cluster using SDSS spectroscopy. Data to characterise the warm ionized, neutral, and molecular gas and dust properties in galaxies are in hand and obtained with a range of different instrumentation (e.g. WISE, INT, ALMA, NOEMA, Nancay Radio Observatory).
The main aims of the project are: 1) characterize the content of the interstellar medium (ISM): by comparing field, group, and Virgo cluster core samples, we will determine the environmental density at which the ISM content of galaxies is first modified; 2) create spatially-resolved maps of the gas and dust: by measuring the extent, morphology, and asymmetry of the stellar, star forming   and dust disks we will understand how large scale structures affect the internal ISM of galaxies; 3) compare our data to theoretical models: by comparing our observations to these models we will be able to determine what mechanisms are dominant in what environmental regime.
I am highly involved in this collaboration and the student will be immediately inserted in an international context, participating to the collaboration meeting and visiting collaborators across the world, most likely in France, Switzerland and US. 

A few StePS forward in unveiling the complexity of galaxy evolution
B. Vulcani, B. Poggianti, A. Moretti, M. Gullieuszik

One of the major goals of extragalactic astrophysics is to understand the physical processes that cause the formation and evolution of luminous structures. Recently, ground-breaking progress has been made in the low-redshift Universe in describing how the main galaxy properties vary with both galaxy mass and host halo mass. However, detailed observations of the evolutionary changes of galaxy properties as a function of look-back time are needed to establish which mechanisms dominate galaxy evolution, what drives the star formation history of galaxies and their mass assembly in the different environments. We propose a thesis to characterise in detail the stellar and gas content of galaxies at intermediate redshift in the different environments making use of the data of StePS, one of the eight surveys that will be carried out during the first five years of WEAVE operations. The main goals of the project are to understand 1) what physical mechanisms drive the star formation histories of galaxies and its quenching over two thirds of the life of the Universe? 2) what is the role of environment vs. intrinsic galaxy properties in this evolution? 3) how do galaxies assemble their mass during the last 7 Gyr?
The project will benefit from the high quality of StePS spectra that will allow to derive galaxy stellar ages, star-formation timescales, stellar and gas metallicities, and dust attenuation, and infer the past evolution of galaxies at different masses and redshift, relating their star formation histories to their intrinsic (e.g., stellar mass, galaxy morphology) and environmental properties. These spectra will also provide gas kinematics and stellar velocity dispersions, which will allow us to perform a dynamical classification of our galaxies and make a link between star formation history, mass assembly history and dynamics.
The student will be immediately inserted in a broad international context and will have the possibility to collaborate with other team members both in Italy and abroad.