New Insights into Metallicity Gradients in the Milky Way from Cepheid Stars
A recent study titled "Cepheid Metallicity in the Leavitt Law (C- MetaLL) survey: VI: Radial abundance gradients of 29 chemical species in the Milky Way Disk" by E. Trentin and co-authors presents significant findings regarding the metallicity of Classical Cepheids (DCEPs) and their implications for understanding the Milky Way's structure.
The research focuses on the relationship between the pulsation properties of DCEPs and their metallicity, which is crucial for calibrating the extragalactic distance ladder. The study aims to expand the sample of DCEPs with precise metallicity measurements obtained through high-resolution spectroscopy.
The authors analyzed 331 spectra from 180 individual DCEPs, deriving atmospheric parameters, radial velocities, and abundances for up to 29 different chemical species. The findings reveal that iron abundances range from 0.5 to -1 dex, indicating a relatively uniform distribution of metallicity across the sample.
One of the key results is the identification of a clear negative gradient in the abundance of most elements, with a slope of -0.071 ± 0.003 dex kpc⁻¹ for iron. This gradient was observed across a range of Galactocentric radii from 5 to 20 kpc. The study also suggests that the farthest targets in the sample trace the Galactic spiral arms, providing insights into the structure of the Milky Way.
The homogeneity of the sample is expected to enhance the understanding of how metallicity influences the DCEP period-luminosity (PL) relations, which are vital for measuring cosmic distances. This research contributes to the broader field of astrophysics by refining the methods used to determine distances in the universe, ultimately aiding in the determination of the Hubble constant.
The paper can be cited as: Trentin, E., Catanzaro, G., Ripepi, V., Alonso-Santiago, J., Molinaro, R., Storm, J., De Somma, G., Marconi, M., Bhardwaj, A., Gatto, M., Musella, I., & Testa, V. (2024). Cepheid Metallicity in the Leavitt Law (C- MetaLL) survey: VI: Radial abundance gradients of 29 chemical species in the Milky Way Disk. arXiv:2404.17299.