Studio e Lavoro > Tesi di laurea

1) A sample of 30 ETGs with compact low-power jets (named FR0s) using new Very Large Array data (VLA, in L and C band). These sources are generally interpreted as the most common phase of radio activity of an ETG, when the AGN is not able to launch Mpc-scale jets.

2) A sample of 16 ETGs selected using the LOFAR LoTSS survey at 150 MHz, which show evidence of recurrent jet activity and for which new L- and S-band VLA data are available.

Depending on the student’s interests and skills the focus of the thesis can vary, but the main goals of this projects are:

1) Learning how to deal with different radio dataset from LOFAR to VLA;

2) Obtaining radio spectral index maps to derive physical information on the jet activity and radiative ages;

3) Using multi-band data (already available for the datasets) to understand the link between the host, the active SMBH and the large/small-scale environment which all play a crucial role in shaping the jet duty cycles of ETGs. At the end of the project, the student will have a general comprehension of the accretion-ejection phenomenon in local ETGs.

A novel interpretation has been suggested that several of these radio sources reside in double systems in different phases of their merging evolution with rapidly precessing jets which are unable to escape the inner region of the host galaxy.

The implication for this scenario is a transverse motion of the hot-spots respect the center of activity, in contrast with the reported evidence of proper motions of the hot spots expanding outwards. Indeed, some transverse motions have been already detected, and many of the reported expansion speeds need to be revised.

The thesis will consist in data reduction and analysis of VLBI data taken in various epochs for selected GPS radio sources, to possibly find new evidence for transverse motions of the hot-spots, and bring support to the precessing jet scenario.

The student will analyze observations taken with the Hydrogen Epoch of Reionization Array, a custom-built radio interferometric arrays that observes the 21 cm line in the 6 < z < 30 range. The student will work on the data calibration and foreground separation with the ultimate goal of improving the current 21 cm power spectrum, providing a better constraint on the physical properties of the first stars and galaxies – e.g., the average mass of the dark matter halo where they formed, their X-ray properties, how their star formation process started and evolve with time.

The thesis will consist in the analysis of the available data from Large-aperture Experiment to Detect the Dark Age (LEDA), located in Owens Valley in California, and/or simulations of the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH), deployed in the Karoo radio reserve in South Africa. Both experiments aim to measure the sky-averaged 21 cm signal in the 12 < z < 30 range.

The analysis will include the development of techniques to disentangle the signal from the much stronger Galactic and extra-galactic foregrounds and the characterization of the impact of the systematic effects.

As IM observations trace the underlying matter distribution of the Universe on large scales, a 21 cm detection would place tight constraints on cosmological parameters.

The student will take an active part in the MeerKLASS IM survey of the MeerKAT radio telescope.  The MeerKLASS data cover a  300~deg^2 sky patch with the goal to observe IM up to z ~ 0.4 and new data will be available soon. Thesis activities will include (but not necessarily limited to) data analysis, foreground separation, and simulations of the expected cosmological signal.

The student will use 1-4 GHz observations of the CIZA J2242.8+5301, the famous cluster hosting the Sausage radio relic, performed with the Jansky Very Large Array (JVLA). The total intensity and polarized emission of cluster radio galaxies will be modeled using the QU-fitting and the RM-synthesis approach. Subsequently, the obtained information will be compared with semi-analytical and/or cosmological simulations of galaxy clusters in order to derive the magnetic field properties for this famous galaxy cluster. The student will develop important coding skills using different programming languages (python and IDL) and will have the opportunity to work and visit collaborators based in Hamburg (Germany).

The aim of the thesis work is to use very deep multi-frequency observations performed with LOFAR, uGMRT, and VLA to study the morphological and spectral properties of the head-tail radio galaxies in Abell 2255. The analysis will allow the student to determine how magnetic fields and relativistic electrons evolve from the active black hole up to large distances from the host galaxy. By comparing these results with spectral aging models, the student will constrain the role of re-acceleration processes triggered by the interaction between the non-thermal components in the jets and the surrounding ICM.

References: Pizzo & de Bruyn 2009, A&A, 507, 639; Botteon et al. 2020, ApJ, 897, 93; Botteon et al. 2022, Science Advances, 8, eabq7623

The thesis work is focused on the analysis of multi-frequency observations obtained with LOFAR and GMRT. Preliminary images show the presence of diffuse radio emission at the center of NGC7618, whose nature is ambiguous. An intriguing possibility is that it traces material ejected by an AGN which is being distributed by sloshing motions. By combining radio and X-ray data, the student will aim to shed light on the origin of this newly discovered source.

References: Kraft et al., 2006, 640, 762; Roediger et al., 2012, 754, 147; Machacek et al., 2023, 958, 93

This thesis project focuses on FBOT AT2018cow, which is thus far the nearest (60 Mpc) and best studied target with a rich multi-wavelength dataset. In particular, the student will work on a new deep X-ray observation taken about 6 yr after the transient discovery, with the goal to: (i) map the long-term evolution and spectrum in X-rays of this enigmatic source and (i) shed light on the possible connection of FBOTs with manifestations of super-Eddington accretion on BHs.