演講資訊

摘要：

Brown dwarfs fill the gap between low-mass stars and giant planets with a typical mass <0.08 M⊙ formed either like planets in a disk around a star or like stars by gravitational contraction of a cloud of gas and dust. Brown dwarfs are significantly brighter and warmer at very young ages, star-forming regions (or young clusters) are the best site for finding in large numbers. They are also vital tracers of the low mass end of the star formation and key analogues to exoplanets around stars. The complete census of a star-forming cloud, to masses well below the deuterium burning limit, will also constrain the very low-mass end of the initial mass function, a key test of theories for star and brown dwarf formation.

IC348 and B5 (LDN-1471) are relatively young clusters located at the eastern edge of the Perseus cloud complex at a distance of 300 pc and 350pc respectively. IC348 (~3 Myr old) comprises 478 cluster members and the most massive star is a B5 star. The southwest ridge of the cluster (~10 arcmin) is currently undergoing star-formation with many embedded objects, and outflows. Barnard 5 is also known to have ongoing star formation, with a group of protostars, fragmenting cloud filaments, and Herbig-Haro objects; however, its low-mass membership is much unexploited. Therefore a thorough study of young stars and brown dwarfs in young star-forming regions will help us understand the Initial Mass Functions, disk fraction etc, and provides a good amount of sample to study the formation of brown dwarfs and low-mass stars. We have developed a technique to robustly identify young low mass stars in the active star-forming region of IC 348 and Barnard 5 via the 1.45 μm H2O absorption band seen in the spectra of M-L-T-Y type objects by combining 1.45 μm imaging with J and H photometry to estimate spectral types independent of reddening. We select our candidates based on the reddening-insensitive index (Q) by combining J, H and W-band photometry. Via this technique, we have identified two new brown dwarfs in IC348 and two late-M dwarf candidate members of the largely unexplored B5 globule in the cloud complex. We also use complementary data from Gaia EDR3, WISE, 2MASS, and PanSTARRS to look for possible members in Barnard 5.