Droplets II: Internal Velocity Structures and Potential Rotational Motions in Pressure-dominated Coherent Structures

Abstract

We present an analysis of the internal velocity structures of the newly identified sub-0.1 pc coherent structures, droplets, in L1688 and B18. By fitting 2D linear velocity fields to the observed maps of velocity centroids, we determine the magnitudes of linear velocity gradients and examine the potential rotational motions that could lead to the observed velocity gradients. The results show that the droplets follow the same power-law relation between the velocity gradient and size found for larger-scale dense cores. Assuming that rotational motion giving rise to the observed velocity gradient in each core is a solid-body rotation of a rotating body with a uniform density, we derive the "net rotational motions" of the droplets. We find a ratio between rotational and gravitational energies, $\beta$, of $\sim 0.046$ for the droplets, and when including both droplets and larger-scale dense cores, we find $\beta \sim 0.039$. We then examine the alignment between the velocity gradient and the major axis of each droplet, using methods adapted from the histogram of relative orientations (HRO) introduced by Soler et al. (2013). We find no definitive correlation between the directions of velocity gradients and the elongations of the cores. Lastly, we discuss physical processes other than rotation that may give rise to the observed velocity field.

arXiv commentaccepted to ApJ in Oct, 2019; in press

References in corpus (38)

• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Theory of Star Formation
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• Planck 2013 results. XI. All-sky model of thermal dust emission
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Structural Analysis of Molecular Clouds: Dendrograms
• Filamentary structure of star-forming complexes
• Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds
• Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region
• How to Calculate Molecular Column Density
• Collapse of Magnetized Singular Isothermal Toroids: II. Rotation and Magnetic Braking
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• An Imprint of Molecular Cloud Magnetization in the Morphology of the Dust Polarized Emission
• Outflows and Jets from Collapsing Magnetized Cloud Cores
• An Ammonia Spectral Atlas of Dense Cores in Perseus
• Giant Molecular Clouds in M33 -- II. High Resolution Observations
• Direct observation of a sharp transition to coherence in Dense Cores
• A Large Catalog of Accurate Distances to Molecular Clouds from PS1 Photometry
• Nonideal MHD Effects and Magnetic Braking Catastrophe in Protostellar Disk Formation
• The Gould's Belt Distances Survey (GOBELINS) I. Trigonometric parallax distances and depth of the Ophiuchus complex
• Chains of dense cores in the Taurus L1495/B213 complex
• The Green Bank Ammonia Survey (GAS): First Results of NH3 mapping the Gould Belt
• Formation and evolution of interstellar filaments; Hints from velocity dispersion measurements
• The Formation of Self-Gravitating Cores in Turbulent Magnetized Clouds
• Turbulent Molecular Cloud Cores: Rotational Properties
• The JCMT Gould Belt Survey: First results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population
• Magnetic fields during the early stages of massive star formation - I. Accretion and disk evolution
• The Initial Conditions of Clustered Star Formation I: NH3 Observations of Dense Cores in Ophiuchus
• Disc formation in turbulent massive cores: Circumventing the magnetic braking catastrophe
• Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to Protostars
• The Green Bank Ammonia Survey: Dense Cores Under Pressure in Orion A
• The Angular Momentum of Magnetized Molecular Cloud Cores: A 2D-3D Comparison
• Droplets I: Pressure-Dominated Sub-0.1 pc Coherent Structures in L1688 and B18
• Dense gas kinematics and a narrow filament in the Orion A OMC1 region using NH3
• The specific angular momentum radial profile in dense cores: improved initial conditions for disk formation
• Mass Assembly of Stellar Systems and their Evolution with the SMA - 1.3 mm Subcompact Data Release
• Geometry, Kinematics, and Magnetization of Simulated Prestellar Cores
• Investigating the Complex Velocity Structures within Dense Molecular Cloud Cores with GBT-Argus

Cited by in corpus (13)

• The Physics of Star Cluster Formation and Evolution
• Does the magnetic field suppress fragmentation in massive dense cores?
• Turbulence, Coherence and Collapse: Three Phases for Core Evolution
• Physical and chemical structure of the Serpens filament -- fast formation and gravity-driven accretion
• The spin, expansion and contraction of open star clusters
• Physics of Non-Universal Larson's Relation
• Evolution of the angular momentum during gravitational fragmentation of molecular clouds
• Alignment of dense molecular core morphology and velocity gradients with ambient magnetic fields
• Evolution and Kinematics of Protostellar Envelopes in the Perseus Molecular Cloud
• A Survey of Deuterated Ammonia in the Cepheus Star-Forming Region L1251
• ALMA Datacubes and Continuum Maps of the Irradiated Western Wall in Carina
• Does the HCN/CO ratio trace the star-forming fraction of gas? II. Variations in CO and HCN Emissivity
• Can Protostellar Outflows Set Stellar Masses?