Type-II Cepheids are the old (>10 Gyr), low-mass counterparts to Classical Cepheids. As such, they can be found in the thick disk, the halo, the bulge, and globular clusters. Anomalous Cepheids are variable stars that are more massive than T2Cs and RR Lyrae stars. These stars provide accurate distances and chemical abundances for many alpha-, iron-peak, and neutron-capture elements. By creating a sedulous catalog of Anomalous and Type-II Cepheids and determining accurate distances and chemical abundances of these stars, we plan to search for possible imprints of thick disk formation and merger events. The thick disk plays a key role in understanding the history of the Milky Way - for instance, the possible inside-out evolution or the possible formation of a pseudo-bulge from thick disk populations. This is all the more true after the recent slew of discoveries of massive mergers Milky Way has had in its lifetime (for e.g. Gaia-Enceladus-Sausage, Sequoia, etc.); many of which may have quenched star formation in the disk and led to the formation of the metal-rich halo. With hundreds of Type-II Cepheids straddling the thick disk, they are an ideal tool to probe the early times of the Milky Way.

Supervisor:    Eva Grebel   (ARI)