Kinematics of Type II Cepheids of the Galactic Halo

Autor:	Wallerstein, George, Farrell, Elizabeth M.
Rok vydání:	2018
Předmět:	Astrophysics - Solar and Stellar Astrophysics Astrophysics - Astrophysics of Galaxies
Druh dokumentu:	Working Paper
DOI:	10.3847/1538-3881/aaee6d
Popis:	In a step toward understanding the origin of the Galactic Halo, we have reexamined Type II Cepheids (T2C) in the field with new input from the second data release (DR2) of Gaia. For 45 T2C with periods from 1 to 20 days, parallaxes, proper motions, and [Fe/H] values are available for 25 stars. Only 5 show [Fe/H] < -1.5, while the remaining stars show thick disk kinematics and [Fe/H] > -0.90. We have compared the T2C stars of the field with their cousins in the globular clusters of the Halo and found that the globular clusters with T2C stars show metallicities and kinematics of a pure Halo population. The globulars may have formed during the overall collapse of the Galaxy while the individual thick disk T2C stars may have been captured from small systems that self-enriched prior to capture. The relationship of these two populations to the micro-galaxies currently recognized as surrounding the Galaxy is unclear. Comment: 7 pages, 3 figures, 4 tables
Databáze:	arXiv
Externí odkaz:	http://arxiv.org/abs/1811.02003 Zobrazit plný text záznamu View this record from Arxiv