Dottorati OATs
CICLO XXXIV |
Cicli PrecedentiTematiche di Ricerca |
Borsa 1
The impact of a variable Initial Mass Function on galaxy evolution
Supervisors: F. Fontanot, G. De Lucia
Abstract: This PhD project is aimed at a detailed characterization of the impact of a variable Initial Mass Function (IMF) on the chemical and physical properties of galaxies. Different lines of evidence have recently suggested a non-universality of the IMF, with the strongest deviations found for the most massive early type galaxies (e.g. La Barbera et al. 2013, Cappellari et al. 2012). Results from different studies are often inconsistent, and the subject remain heavily debated in the community. The increase of available resolved dynamical information and high resolution spectroscopy is also making the subject of a variable IMF a
popular one. It is therefore timely to assess the theoretical expectations of such a scenario.
The recently developed GAEA model (Hirschmann, De Lucia & Fontanot 2016) represents an ideal tool to carry out this investigation, thanks to the improved modeling of chemical enrichment (which explicitly includes the differential contribution of SNeII, SNeIa and AGB stars) and stellar feedback (which allows us to reproduce the differential assembly of galaxy populations over cosmic epochs). In Fontanot et al. (2017, 2018), we have included in GAEA some of the proposed models for IMF variation (Weidner et al. 2013, and Papadopoulos et al., 2011), and analysed the basic predictions of these specific theories.
PhD fellowship outline The student will focus on three different aspects of the modeling:
- Characterization of the properties of galaxy populations in the variable IMF theories.
Moving from the basic predictions in Fontanot et al. (2017, 2018), we expect the student to study the physical properties, environment and star formation histories associated with different galaxy populations, and connect them with the observed evidences for a non-universal IMF. This analysis will allow us to get insight on the mechanisms determining the chemical and physical properties of model galaxies (and their redshift evolution). In this phase, the student will accustom with the GAEA code and its outputs. - Expand the range of tested theories for IMF variation. The modules currently available in GAEA represent just some of the possible approaches to IMF variation which have been proposed in the literature. We expect the student to implement new prescriptions, calibrate them and analyse their predictions, both in comparison with observed data and with previous models. The new prescriptions will allow us to study common trends among the proposed theories as well as to highlight possible discrepancies. In this phase, the student will need to modify the available semi-analytic model.
- Quantitative comparison with observed samples. Many observational studies of IMF variations are based on detailed modelling of spectral indices sensitive to the dwarf to giant stars ratio (Conroy & van Dokkum 2012, La Barbera et al., 2013). By coupling our galaxy formation model with the latest generation population synthesis models, it will be possible to predict how the strength of these spectral features varies as a function of galaxy properties and as a function of e.g. the environment. This will allow a quantitative comparison with available data, as well as the possibility to formulate specific predictions for future observational programmes.
Borsa 2
Lo studente vincitore avrà facoltà di scegliere tra uno dei seguenti temi di ricerca
2.a - Rosetta data fusion
Supervisor: M. Fulle
Work Plan: Fallout processes point out the importance of feedback in models of 67P activity. All the physical processes at work on the nucleus surface are strongly linked. We list here the general topics, which will be necessarily faced at different levels of detail according to the specific task selected by the candidate.
1. Inter-instrumental analysis of the data on the 67P perihelion activity, done on available papers by comparing the obtained results to infer the nucleus parameter uncertainties and their bias:
1a. Gas emission (ROSINA, MIRO, VIRTIS data)
1b. Refractory emission (ROSINA, MIRO, VIRTIS, OSIRIS, GIADA, COSIMA data)
2. Models of perihelion activity:
2a. Models of the nucleus structure.
2b. Ejection of gas and of sub-millimeter dust.
2c. Ejection of gas and of “chunks” (90% of the nucleus mass is ejected in form of ice and dust aggregates of bulk density of about 0.5 g/cc and of average mass of about 1 kg, named “chunks”).
2d. Constraints on the nucleus properties derived from the perihelion activity (e.g. dust/ice ratio).
3. Fallout processes:
3a. Injection of chunks in metastable orbits (rockets effects, gravity field and gas flux in non-spherical symmetry).
3b. Frictions collapsing the bound orbits on the nucleus.
3c. Fallout mass, its distribution on the nucleus, data comparison (images by ROLIS, OSIRIS).
4. Evolution of the 67P nucleus:
4a. Perihelion erosion, mass transfer from south to north and/or big/small lobes.
4b. Long term evolution of the nucleus shape and mass.
4c. How activity is sustained (minimal ice content in the fallout consistent with continuing activity, both on short and long timescales).
4d. Constraints on the nucleus homogeneity versus depth (CONSERT and RSI data).
4e. Constraints on the models of nucleus accretion in a protoplanetary disc.
2.b - Atmospheric radiative transfer in climate models of habitable exoplanets
Supervisors: G. Vladilo, M. Fulle
In particular, the plan is to incorporate the effect of Collision Induced Absorption, fundamental at high pressure, and an updated set of molecular cross-sections. As a subsequent step of the work, the radiative transfer module could be implemented in the global climate model of intermediate complexity PlaSim (Fraedrich et al. 2005 ), which provides the possibility to study tidally-locked exoplanets in the proximity of M-type stars. Other potential applications of the radiative transfer module include the modelization of the outer layers of Jupiter, taking advantage of upcoming data of the Juno mission.