2020-11-27 Abstract
Title: Dwindle Dwindle Little Stars --- Hunting for Substellar Objects Young and Old, Rich and Poor
Speaker: Prof. Wen-Ping Chen (NCU)
Date: November 27 at 14:30
Location: R521, General Building II
Abstract:
With insufficient masses to sustain core hydrogen fusion, substellar objects continue to cool and fade after birth. Those heavier than 13 jupiter masses, called brown dwarfs, manage to ignite deuterium or lithium in the cores, thereby maintaining hydrostatic equilibrium for a short period of time. Those less massive than this do not undertake any nuclear reaction whatsoever in their lives and evolve like planets. So far a few thousand brown dwarfs and planetary-mass objects are known, almost exclusively found in the solar neighborhood, i.e., they are already aged. Searching for the youngest substellar objects --- so as to enable investigation of their formation and early evolution --- by spectroscopy is hampered by their faintness and often confusion with foreground or background contaminations. We describe our efforts to identify substellar candidates in nearby star-forming regions of 1 to 3 Myr old, when brown dwarfs are being formed or in their infancy. Our sample of substellar populations in star clusters, with known ages and distances, provides stringent constraints to confront theoretical modeling of ultracool atmospheres, and of chromospheric activity. We also present how these least-massive members as the most vulnerable members in stellar dynamics get ejected, leading to eventual disintegration of star clusters. We propose how next-generation surveys would turn up possible metal-poor brown dwarfs to extend our knowledge of Galactic stellar and substellar populations.