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Special Seminar



"Kinematics of High-velocity Gaia White Dwarfs in the Local Galactic Halo"
Bokyoung Kim (Georgia State University)

The Galactic halo, which suffuses our Galaxy in a spheroid heap, is where the oldest stars dwell. Understanding the kinematics of the halo stars provides critical insight into the early formation and evolutionary history of the Milky Way. Large data surveys, like the Sloan Digital Sky Survey (SDSS), have significantly improved our view of the Galactic halo in the last decade, mostly from the study of its more luminous members, like red giants and massive main sequence (FG) stars. However, studying the majority population of the halo, which is mainly composed of old low-mass stars, has remained a challenge because of these stars’ faintness. Thanks to the Gaia first and second data releases in 2016 and 2018, we are now entering a new era of precision stellar astronomy with positions, magnitudes, motions, and distances measured for over 2 billion stars, including unprecedented numbers of low-mass stars. In an attempt to find large numbers of low-mass stars from the Galactic halo population, we have selected a subset of ~3.5 million Gaia stars with precise distances and large proper motions, all located within 500 pc. Through a careful analysis, we have succeeded in identifying 485,393 low-mass members (mostly K and M dwarfs) of the local halo population, and we now propose to analyse their motions in fine detail. As Gaia DR2 only contains radial velocity information for bright stars, we put forth a number of alternative, but simple methods that will allow us to study the kinematic of these faint objects. In this talk, we will present one of the applications of these methods with preliminary results: high-velocity white dwarfs in the local Galactic halo.

Date September 25, 2019
Start/End Time 11:00 AM - 12:00 PM
Location B34, W130
Event Type Seminars/Colloquia
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