Periodic Reporting for period 2 - ELEMENTS (Role of extreme events in Galaxy evolution)
Okres sprawozdawczy: 2022-12-01 do 2024-05-31
The periodic table, which orders all chemical elements according to their basic atomic properties, was proposed by Dimitri Mendeleev more than 150 years ago. This table laid foundations of modern science and technology and allowed a vast landscape of discovery, among the most exciting ones being the prediction and characterization of natural elements unknown at that time, but also species created later on in particle accelerators. However, up to present, the cosmic origin of the majority of elements in this table is not known, representing one of the main unsolved problems in physics. In which astrophysical events, when, and how were heavy elements formed?
This ERC project represents the first systematic investigation of nucleosynthesis of heavy elements using new astronomical data and modern techniques. Our main objectives are to trace and characterize the history of production of different chemical elements in the Galaxy. This will be done by applying novel theoretical methods to allow precise measurements of element abundances in stellar spectra, including transition metals, alkaline earth, and lanthanides. Combining our new data with state-of-the-art Galactic chemical evolution models will make it possible to place strong quantitative constraints on the origins of heavy elements beyond iron.
Why do we need to know where and how do chemical elements form? This is because once we have the answer to this question, we can create the “astronomical time machine”. In other words, we will be able to predict – on the basis of their measured (observed) chemical composition – the formation time, present-day structure, and fate of different objects in the Universe, such as stars, galaxies, and planets.
This ERC project represents the first systematic investigation of nucleosynthesis of heavy elements using new astronomical data and modern techniques. Our main objectives are to trace and characterize the history of production of different chemical elements in the Galaxy. This will be done by applying novel theoretical methods to allow precise measurements of element abundances in stellar spectra, including transition metals, alkaline earth, and lanthanides. Combining our new data with state-of-the-art Galactic chemical evolution models will make it possible to place strong quantitative constraints on the origins of heavy elements beyond iron.
Why do we need to know where and how do chemical elements form? This is because once we have the answer to this question, we can create the “astronomical time machine”. In other words, we will be able to predict – on the basis of their measured (observed) chemical composition – the formation time, present-day structure, and fate of different objects in the Universe, such as stars, galaxies, and planets.
In the first period of the project, we have primarily focused on the theoretical foundations and methods to enable accurate and precise astrophysical diagnostics, that is the analysis of stellar spectra using state-of-the art methods. This work has included the development of atomic models for key heavy elements of astronomical interest, including Ba, Y, Sr, and Eu. These non-LTE (non-local thermodynamic equilibrium NLTE) models were subject to a series of tests on the spatially resolved intensity spectra of the Sun to ensure the high quality of the diagnostics, as required by the ERC project. In parallel, we have pursued a dedicated line of theoretical research to ensure the availability of 3-dimensional stellar model atmospheres, which in combination with the afore-mentioned atomic models, are essential inputs for detailed radiative transfer models, which are used to interpret stellar spectroscopic observations. Finally, the framework that is necessary for the holistic NLTE analysis of stellar spectra with 1D and 3D models has been set up and thoroughly tested with respect to its ability to provide stellar chemical abundances of the relevant trans-Fe group elements via the model-based analysis of the astronomical data. Finally, we have carried out several comprehensive studies using Galactic chemical evolution models and archival astronomical data (ESO observatory telescopes) to showcase the potential of the comparative diagnostics and ability to discriminate between different astrophysical production sites, including canonical channels (asymptotic giant branch stars, explosions of single massive stars), but also magnetars, neutron star mergers, and massive binaries. All of this work was published in a series of peer-reviewed articles and was presented at multiple astronomical workshops and conferences, in order to facilitate the knowledge transfer and maximize the impact of the work.
In the coming two years, we expect the first science data from the 4MOST facility, especially the spectra obtained within the high-resolution survey of the Galactic disc and bulge (4MIDABLE-HR), which the PI of this ERC grant co-leads together with Thomas Bensby. The atomic models, radiation transfer methods, and numerical techniques that we have developed successfully thanks to the ERC grant will be readily applied to the 4MOST datasets, enabling detailed quantitative exploitation of the multi-million stellar spectra. The expected results include comprehensive maps of chemical abundances and kinematics homogeneously probing the thin and thick disc components, but also the bar and the bulge, across the spatial volumes accessible by 4MOST. These chemo-dynamical maps will be tested against predictions of GCE models and will allow us to verify the multimodality of the nuclear production sites, to confine the parameter space of stellar sources capable of hosting slow- and rapid-neutron capture processes, and to constrain the role of extreme events in the evolution of the Galaxy.