High-resolution ALMA Study of the Proto-Brown-Dwarf Candidate L328-IRS

Abstract

This paper presents our observational attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, in order to investigate whether L328-IRS is in the substellar mass regime. Observations were made for the central region of L328-IRS with the dust continuum and CO isotopologue line emission at ALMA band 6, discovering the detailed outflow activities and a deconvolved disk structure of a size of $\sim$87 AU $\times$ 37 AU. We investigated the rotational velocities as a function of the disk radius, finding that its motions between 130 AU and 60 AU are partially fitted with a Keplerian orbit by a stellar object of $\sim 0.30{\mathrm{M}}_{\odot }$, while the motions within 60 AU do not follow any Keplerian orbit at all. This makes it difficult to lead a reliable estimation of the mass of L328-IRS. Nonetheless, our ALMA observations were useful enough to well constrain the inclination angle of the outflow cavity of L328-IRS as $\sim 66^{\circ }$, enabling us to better determine the mass accretion rate of $\sim 8.9\times 10^{-7}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$. From assumptions that the internal luminosity of L328-IRS is mostly due to this mass accretion process in the disk, or that L328-IRS has mostly accumulated the mass through this constant accretion rate during its outflow activity, its mass was estimated to be $\sim 0.012-0.023{\mathrm{M}}_{\odot }$, suggesting L328-IRS to be a substellar object. However, we leave our identification of L328-IRS as a proto-brown dwarf to be tentative because of various uncertainties especially regarding the mass accretion rate.

arXiv commentAccepted in ApJ, 24 pages, 12 figures

References in corpus (22)

• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• The Formation of Brown Dwarfs as Ejected Stellar Embryos
• Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation
• Stellar, Brown Dwarf, and Multiple Star Properties from Hydrodynamical Simulations of Star Cluster Formation
• The "Mysterious" Origin of Brown Dwarfs
• Episodic accretion at early stages of evolution of low mass stars and brown dwarfs: a solution for the observed luminosity spread in HR diagrams?
• The Formation and Early Evolution of Low-mass Stars and Brown Dwarfs
• Formation of a Keplerian disk in the infalling envelope around L1527 IRS: transformation from infalling motions to Kepler motions
• The Formation of Free-Floating Brown Dwarves and Planetary-Mass Objects by Photo-Erosion of Prestellar Cores
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Evolution of Protostellar Outflow around Low-mass Protostar
• Molecular Outflows Driven by Low-Mass Protostars. I. Correcting for Underestimates When Measuring Outflow Masses and Dynamical Properties
• A submillimetre survey of the kinematics of the Perseus molecular cloud - II. Molecular outflows
• The Spitzer c2d Survey of Nearby Dense Cores: I: First Direct Detection of the Embedded Source in IRAM 04191+1522
• A Hybrid Scenario for the Formation of Brown Dwarfs and Very Low Mass Stars
• The Episodic, Precessing Giant Molecular Outflow from IRAS 04239+2436 (HH 300)
• ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures
• IC348-SMM2E: a Class 0 proto-brown dwarf candidate forming as a scaled-down version of low-mass stars
• No Keplerian Disk >10 AU around the Protostar B335: Magnetic Braking or Young Age?
• The Spitzer c2d Survey of Nearby Dense Cores. V. Discovery of a VeLLO in the "Starless" Dense Core L328
• The Circumbinary Outflow: A Protostellar Outflow Driven by a Circumbinary Disk
• Distances to dense cores that contain Very Low Luminosity Objects

Cited by in corpus (7)

• Early Planet Formation in Embedded Disks (eDisk). IV. The Ringed and Warped Structure of the Disk around the Class I Protostar L1489 IRS
• TRAO Survey of the nearby filamentary molecular clouds, the universal nursery of stars (TRAO FUNS). II. Filaments and Dense cores in IC 5146
• Testing Disk Identification Methods Through Numerical Simulations of Protostellar Evolution
• Early Planet Formation in Embedded Disks (eDisk) V: Possible Annular Substructure in a Circumstellar Disk in the Ced110 IRS4 System
• A low-velocity bipolar outflow from a deeply embedded object in Taurus revealed by the Atacama Compact Array
• CO Outflow Survey of 68 Very Low Luminosity Objects: a Search for Proto-Brown Dwarf Candidates
• ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds