Substellar-Mass Condensations in Prestellar Cores

Abstract

We present combined Submillimeter-Array (SMA) + single-dish images of the (sub)millimeter dust continuum emission toward two prestellar cores SM1 and B2-N5 in the nearest star cluster forming region, $\rho$ Ophiuchus. Our combined images indicate that SM1 and B2-N5 consist of three and four condensations, respectively, with masses of $10^{-2}-10^{-1}{M}_{\odot }$ and sizes of a few hundred AU. The individual condensations have mean densities of $10^8-10^9$ cm${}^{-3}$ and the masses are comparable to or larger than the critical Bonner-Ebert mass, indicating that the self-gravity plays an important role in the dynamical evolution of the condensations. The coalescence timescale of these condensations is estimated to be about $10^4$ yr, which is comparable to the local gravitational collapse timescale, suggesting that merging of the condensations, instead of accretion, plays an essential role in the star formation process. These results challenge the standard theory of star formation, where a single, rather featureless prestellar core collapses to form at most a couple of condensations, each of which potentially evolves into a protostar that is surrounded by a rotating disk where planets are created.

7 pages, 3 figures, accepted by ApJL

References in corpus (7)

• Theory of Star Formation
• The COMPLETE Survey of Star-Forming Regions: Phase I Data
• Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?
• The AzTEC mm-Wavelength Camera
• Formation Scenario for Wide and Close Binary Systems
• A Significant Population of Candidate New Members of the Rho Ophiuchi Cluster
• An Observed Lack of Substructure in Starless Cores II: Super-Jeans Cores

Cited by in corpus (17)

• The Turbulent Origin of Outflow and Spin Misalignment in Multiple Star Systems
• A First Look at BISTRO Observations of The $\rho$ Oph-A core
• How do stars gain their mass? A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star Forming Regions
• An ALMA Search for Substructure, Fragmentation, and Hidden Protostars in Starless Cores in Chamaeleon I
• Revealing H2D+ depletion and compact structure in starless and protostellar cores with ALMA
• ALMA Observations of Starless Core Substructure in Ophiuchus
• FRagmentation and Evolution of dense cores Judged by ALMA (FREJA). I (Overview). Inner $\sim$1000 au structures of prestellar/protostellar cores in Taurus
• The Dynamical State of The Serpens South Filamentary Infrared Dark Cloud
• Mapping the core mass function onto the stellar IMF: multiplicity matters
• Discovery of CCS Velocity-Coherent Substructures in the Taurus Molecular Cloud 1
• ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Detection of extremely high density compact structure of prestellar cores and multiple substructures within
• Earliest Stages of Protocluster Formation: Substructure and Kinematics of Starless Cores in Orion
• Extremely Dense Cores associated with Chandra Sources in Ophiuchus A: Forming Brown Dwarfs Unveiled?
• A centrally concentrated sub-solar mass starless core in the Taurus L1495 filamentary complex
• Dynamics, CO depletion, and deuterium fractionation of the dense condensations within the fragmented prestellar core Orion B9-SMM 6
• The physical and chemical properties of the $\rho$ ophiuchi A dense core
• Occurrence of instability through the protostellar accretion disks by landing of low-mass condensations