Estimation of photometric metalicities for stars observed in the S-PLUS survey

• Grant number: 25/03403-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: May 01, 2025
• End date: February 28, 2027
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Felipe de Almeida Fernandes
• Grantee: Murilo Antonio Menegati
• Host Institution: Instituto Nacional de Pesquisas Espaciais (INPE). Ministério da Ciência, Tecnologia e Inovação (Brasil). São José dos Campos , SP, Brazil
• Associated research grant: 24/00822-5 - Narrow-band photometry applications for galactic archaeology, AP.JP

Abstract

This project aims to explore the sensitivity of the narrow bands of S-PLUS to determine metallicities, [alpha/Fe], and [C/Fe] for millions of stars without the need for spectroscopic observations. This approach has the advantage of providing data for a significantly larger number of stars-typically orders of magnitude higher than what spectroscopy can achieve. Additionally, it covers a much broader spatial area, limited only by the coverage of photometric surveys.Different machine learning techniques have already been used for this purpose in S-PLUS. The use of artificial neural networks has resulted in two publications (Whitten et al., 2021; Quispe-Huaynasi et al., 2023). We have also explored the use of Random Forest techniques and the fitting of synthetic isochrones, both of which have shown promising results that we expect to publish in the near future. As part of this project, we plan to use the latest spectroscopic data from the literature (LAMOST, SDSS, and RAVE) as a training set to continue improving the determination of photometric metallicities from narrow-band photometry. Various machine learning techniques (ANN and Random Forest) and synthetic isochrone fitting will be applied, as our experience shows that using an ensemble of results from different methods is more accurate than individual methods alone.The main originality of this study lies in the use of a much wider area, covered in the most recent data releases of S-PLUS and not yet explored in previous publications. DR5 will cover more than 4,000 square degrees in the Southern Hemisphere, and we expect that 9,000 square degrees will be available by the end of the research. We will also make use of the SHORTs survey (which covers the same region but with shorter exposures to avoid saturating brighter stars) and the X-PLUS all-sky catalog (which is part of this project and is generated from Gaia spectroscopy) to acquire data on bright stars, which are better suited for spectroscopic follow-up.