Author: Raffaella Schneider

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Available Thesis: Stellar archaeology as a tool to explore the nature of the first stars

Supervisor: Raffaella Schneider

Surveys of metal-poor stars in the halo and in the dwarf satellites of the Milky Way can provide interesting constraints on early chemical enrichment and low-metallicity star formation. A proper comparison between theoretical models and observation data must account for the complex interplay between radiative and chemical feedback effects that shape the evolution of the first stars and their transition to more evolved stellar populations. The aim of the proposed project is to investigate how first star formation and early chemical evolution is imprinted into the low-metallicity tail of the metallicity distribution function observed i the Galactic halo and in nearby dwarf spheroidal galaxies. To this aim we will use our semi-analytical models for early galaxy and black hole formation.

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Stellar Astrophysics course

https://www.phys.uniroma1.it/fisica/en/node/10210

This course is given by Raffaella Schneider and it is a compulsory course for the master degree in Astronomy and Astrophysics of the University of Rome “La Sapienza”.

It is usually held from late February to the mid of June.

The course aims to describe the structure and evolution of stars in the more general context of galaxy evolution. At the end of the course, students will gain a deep knowledge of the physical processes that regulate the structure and evolution of stars of different mass, from the pre-main sequence phase to the final evolutionary phases. In the second part of the course we will introduce fundamental elements of the physics of the interstellar medium to understand the star formation process and its consequences on the evolution of galaxies.

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The assembly of dusty galaxies at z > 4: statistical properties

The recent discovery of high redshift dusty galaxies implies a rapid dust enrichment of their interstellar medium (ISM). To interpret these observations, we run a cosmological simulation in a 30h−1 cMpc/size volume down to z ≈ 4. We use the hydrodynamical code dustyGadget, which accounts for the production of dust by stellar populations and its evolution in the ISM. We find that the cosmic dust density parameter is mainly driven by stellar dust at z > 10, so that mass- and metallicity-dependent yields are required to assess the dust content in the first galaxies. At z < 9 the growth of grains in the ISM of evolved systems (Log(M⋆/M⊙) > 8.5) significantly increases their dust mass, in agreement with observations in the redshift range 4 < z < 8. Our simulation shows that the variety of high redshift galaxies observed with ALMA can naturally be accounted for by modeling the grain-growth timescale as a function of the physical conditions in the gas cold phase. In addition, the trends of dust-to-metal (DTM) and dust-to-gas (D) ratios are compatible with the available data. A qualitative investigation of the inhomogeneous dust distribution in a
representative massive halo at z ≈ 4 shows that dust is found from the central galaxy up to the closest satellites along polluted filaments with Log(D) < −2.4, but sharply declines at distances d > 30 kpc along many lines of sight, where Log(D) < −4.0.