Neutron-capture elements in dwarf galaxies III: A homogenized analysis\n of 13 dwarf spheroidal and ultra-faint galaxies

Abstract

We present a large homogeneous set of stellar parameters and abundances\nacross a broad range of metallicities, involving $13$ classical dwarf\nspheroidal (dSph) and ultra-faint dSph (UFD) galaxies. In total this study\nincludes $380$ stars in Fornax, Sagittarius, Sculptor, Sextans, Carina, Ursa\nMinor, Draco, Reticulum II, Bootes I, Ursa Major II, Leo I, Segue I, and\nTriangulum II. This sample represents the largest, homogeneous, high-resolution\nstudy of dSph galaxies to date. With our homogeneously derived catalog, we are\nable to search for similar and deviating trends across different galaxies. We\ninvestigate the mass dependence of the individual systems on the production of\n$\\alpha$-elements, but also try to shed light on the long-standing puzzle of\nthe dominant production site of r-process elements. We use data from the Keck\nobservatory archive and the ESO reduced archive to reanalyze stars from these\n$13$ dSph galaxies. We automatize the step of obtaining stellar parameters, but\nrun a full spectrum synthesis to derive all abundances except for iron. The\nhomogenized set of abundances yielded the unique possibility to derive a\nrelation between the onset of type Ia supernovae and the stellar mass of the\ngalaxy. Furthermore, we derived a formula to estimate the evolution of\n$\\alpha$-elements. Placing all abundances consistently on the same scale is\ncrucial to answer questions about the chemical history of galaxies. By\nhomogeneously analysing Ba and Eu in the 13 systems, we have traced the onset\nof the s-process and found it to increase with metallicity as a function of the\ngalaxy's stellar mass. Moreover, the r-process material correlates with the\n$\\alpha$-elements indicating some co-production of these, which in turn would\npoint towards rare core-collapse supernovae rather than binary neutron star\nmergers as host for the r-process at low [Fe/H] in the investigated dSph\nsystems.\n