Speaker
Description
Classical Cepheids (DCEPs) are crucial for calibrating the extragalactic distance ladder, ultimately enabling the determination of the Hubble constant through the period-luminosity (PL) and period-Wesenheit (PW) relations that they exhibit. The purpose of the C-MetaLL survey is to understand how the PL and PW relations depend on metallicity. The DCEPs are also very important tracers of the young populations placed along the Galactic disc. Our goal is to extend the range of measured metallicities towards the metal-poor regime to cover the parameter space better. To this end, we observed objects in a wide range of Galactocentric radii, allowing us to study in detail the abundance gradients present in the Galactic disc.
The sample presented is composed of a total of 292 pulsators, whose spectra were obtained with a variety of high-resolution spectrographs, analysed in a homogeneous way and published in the context of the C-MetaLL survey. For each target, we derived accurate atmospheric parameters, radial velocities, and abundances for up to 29 different species. The iron abundances range between 0.5 and −1 dex with a rather homogeneous distribution in metallicity. These data were used to study the abundance gradients of the Galactic disc in a range of Galactocentric radii (RGC) spanning the range of 5-20 kpc. For most of the elements, we have found a clear negative gradient, with a slope of −0.064 ± 0.003 dex kpc−1 for the [Fe/H] case.
Through a qualitative fit with the Galactic spiral arms, we show how our farthest targets ( RGC >10 kpc) trace both the Norma-Outer and the extension of the Outer-Scutum-Centaurus arms. The possible association of our targets with the two spiral arms could justify the sensible change of abundance trend for some of the elements analysed. These results show the great potential of high-resolution spectroscopy in constraining and characterizing the spiral structures, especially in regions still poorly explored.
