Poster Presentation

An ALMA Identification of L328-IRS as a Proto-Brown Dwarf?

Author(s):

Presenter: Chang Won Lee (KASI)

This poster presents our attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, and its mass accretion rate by using the data obtained with an ALMA facility in order to help to confirm whether the L328-IRS is in a regime of substellar object. Observations were made for L328-IRS region with the dust continuum and CO isotopologue line emission at ALMA band 6 and the ALMA data were analysed with a 3D illustration program to show that L328-IRS system consists of an outflow of about an inclination of ~25 degree backward of sky plane which has three conic structures and different opening angles, a rotating disk, and infalling envelope where there are little outflow activities. Our deconvolved disk structure of a size of ~87 AU ×37 AU is rotating in a way that its motions are partially fitted with a Keplerian motions between 130 AU and 60 AU by a stellar object of ~0.30 M⊙ while the rotational speed decreases toward the center of disk from ~60 AU radius at higher rate than expected from that of a solid rotation, making it difficult to present a reliable estimation of the mass of L328-IRS. This may be due to an influence by other kinematics near the L328-IRS such as outflows and infalling motions near the central region of the disk. However, our identification of the detailed parameters of the outflow enabled us to make a better determination of the mass accretion rate of ~1.8 × 10-7 M⊙ yr-1. This value gives the mass of L328-IRS of ~0.03 M⊙ from which the accretion luminosity is being equal to its internal luminosity, being very consistent with the mass of (~0.03 M⊙) accreted through this constant accretion rate during the Class 0 phase. Our observations confirm that the L328-IRS is forming through collapsing motions of the gaseous envelope with a small mass accretion rate. However, identification of L328-IRS as a proto-brown dwarf still remains to be confirmed in future.