I am leader of the SAGA (Stellar Abundances and Galactic Archaeology) team. We are exploring novel methodologies to extract complete, precise, and accurate chemical abundances from large samples of stellar spectra. A set of high-quality stellar abundances is the missing piece of the Galactic chemical enrichment puzzle that our team aims to provide.

Stellar astrophysics is going through an industrial revolution . The Gaia mission of ESA (European Space Agency) is delivering precision astrometry (position, parallaxes and proper motions) and photometry for more than 109 stars. To complement Gaia, with precise radial velocities and chemical abundances, several spectroscopic surveys have been designed (e.g., Gaia-ESO, RAVE, GALAH, APOGEE, LAMOST, 4MOST, WEAVE). Together, they will obtain spectra for > 107 stars. Our ambition is to bring about a corresponding revolution in the quality of the data products that are extracted from this impressive number of stellar spectra.

Near-UV stellar spectroscopy: uncovering the past and building the future

Project funded by an OPUS grant from NCN (2019-2022; extended to 2023)

Current project members: R. Smiljanic and André Rodrigo da Silva (PhD student); Former member: Riano Giribaldi (post-doc)

This project concentrates in exploring the near-ultraviolet (near-UV) region of the stellar spectra that is observable from the ground (mostly between ∼ 3000 and ∼ 4500 Å). This spectral region is of difficult analysis because of the large number of atomic and molecular lines that are present in the spectra of F-, G-, and K-type stars.

We are working on improving our capabilities of computing synthetic stellar spectra in the near-UV. This improved capability will then be used to investigate different astrophysical problems:

Moreover, we are involved in the CUBES consortium, an international consortium developing a new near-UV spectrograph to be installed at the Very Large Telescope(VLT). Our capabilities of simulating near-UV stellar spectra are useful for defining the desired characteristics of this new instrument.

This project is giving our group improved resources to use near-UV stellar spectra not only to uncover some of the secrets of the past of our Galaxy (the nucleosynthesis of light and heavy elements; the accretion processes in the early Galaxy; and the formation of globular clusters) but also to be part of future developments of instrumentation in the ESO community.

Playing CHESS with stars

Project funded by a Sonata Bis grant from NCN (2020-2025)

Project members: R. Smiljanic; Maria Luiza L. Dantas (post-doc); Sergen Ozdemir and John E. Martínez Fernández (PhD students)

This project is going to provide multi-elemental stellar chemical abundances of unprecedented quality for a sample of more than 10 000 F-, G-, or K-type stars observed with the UVES spectrograph (Ultraviolet and Visual Echelle Spectrograph). The project aims to reveal the sequence of events that describe the chemical evolution of the Galaxy from the early stages to the present.

To achieve our ambitious goal, we will develop a new and innovative system for the large scale analysis of stellar spectroscopic data. This new CHEmical Survey analysis System, CHESS, will enable the extraction of complete, precise, and accurate chemical abundances from large samples of stellar spectra.

An important innovation of this analysis system is the combination of the physical modeling of stellar spectra, done using radiative transfer codes, with data-driven and machine learning methods.

By playing (running) CHESS with (a large sample of) stars, a quality jump in the determination of stellar chemical abundances will be achieved and, as consequence, we will take the understanding of the Galactic chemical enrichment to whole new level.