Chemical Analysis of the Brightest Star of the Cetus II Ultra-Faint Dwarf Galaxy Candidate
/ Authors
K. Webber, T. T. Hansen, J. Marshall, J. Simon, A. Pace, B. Mutlu-Pakdİl, A. Drlica-Wagner, C. E. Mart'inez-V'azquez, M. Aguena, S. Allam
and 35 more authors
O. Alves, E. Bertin, D. Brooks, A. Rosell, J. Carretero, L. Costa, J. Vicente, P. Doel, I. Ferrero, D. Friedel, J. Frieman, J. Garc'ia-Bellido, G. Giannini, D. Gruen, R. Gruendl, S. Hinton, D. Hollowood, K. Honscheid, K. Kuehn, J. Mena-Fern'andez, F. Menanteau, R. Miquel, R. Ogando, M. Pereira, A. Pieres, A. P. Malag'on, E. Sanchez, B. Santiago, J. A. Smith, M. Smith, E. Suchyta, G. Tarlé, C. To, N. Weaverdyck, B. Yanny
/ Abstract
We present a detailed chemical abundance analysis of the brightest star in the ultra-faint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, abundances or upper limits of 18 elements from Carbon to Europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the alpha-elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova (SN) originating from a star with a mass of ~11.2 solar masses. In addition, the star has a Potassium abundance of [K/Fe] = 0.81 which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature which is also present in a number of UFD galaxies. A comparison including globular clusters (GC) and stellar stream stars suggests that high K is a specific characteristic for some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies.