A5065951948- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Molecular Spectroscopy and Structure
- Spectroscopy and Laser Applications
- Atomic and Molecular Physics
- Computational Fluid Dynamics and Aerodynamics
- Advanced Chemical Physics Studies
- Advanced Combustion Engine Technologies
- Fluid Dynamics and Turbulent Flows
- Gamma-ray bursts and supernovae
- Ionosphere and magnetosphere dynamics
- Fluid Dynamics Simulations and Interactions
- Superconducting Materials and Applications
- Fusion materials and technologies
- Magnetic confinement fusion research
- Quantum Chromodynamics and Particle Interactions
- Geophysics and Gravity Measurements
- Combustion and flame dynamics
- Nuclear reactor physics and engineering
- Astronomy and Astrophysical Research
- Nuclear physics research studies
Shanghai Astronomical Observatory
2023-2024
University of California, Berkeley
2010-2022
University of California, Santa Barbara
2011
This paper describes ZEUS-MP, a multiphysics, massively parallel, message-passing implementation of the ZEUS code. ZEUS-MP differs significantly from thoroughly documented ZEUS-2D code, completely undocumented (in peer-reviewed literature) ZEUS-3D and marginally "version 1" first distributed publicly in 1999. offers an MHD algorithm that is better suited for multidimensional flows than module by virtue modifications to method characteristics scheme suggested Hawley & Stone. shown compare...
The Padoan and Nordlund model of the stellar initial mass function (IMF) is derived from low order statistics supersonic turbulence, neglecting gravity (e.g. gravitational fragmentation, accretion merging). In this work predictions that are tested using largest numerical experiments hydrodynamic (HD) magneto-hydrodynamic (MHD) turbulence to date (~1000^3 computational zones) three different codes (Enzo, Zeus Stagger Code). predicts a power law distribution for large masses, related energy...
Many astrophysical applications involve magnetized turbulent flows with shock waves. Ab initio star formation simulations require a robust representation of supersonic turbulence in molecular clouds on wide range scales imposing stringent demands the quality numerical algorithms. We employ super-Alfvénic decay as benchmark test problem to assess and compare performance nine popular MHD methods actively used model formation. The set codes includes: ENZO, FLASH, KT-MHD, LL-MHD, PLUTO, PPML,...
ABSTRACT We investigate the presence of hub-filament systems in a large sample 146 active proto-clusters, using H13CO+ J = 1-0 molecular line data obtained from ATOMS survey. find that filaments are ubiquitous and very common dense core scales (∼0.1 pc) to clump/cloud (∼1–10 pc). The proportion proto-clusters containing decreases with increasing dust temperature (Td) luminosity-to-mass ratios (L/M) clumps, indicating stellar feedback H ii regions gradually destroys as evolve. Clear velocity...
Abstract Magnetic fields of molecular clouds in the central zone (CMZ) have been relatively under-observed at sub-parsec resolution. Here, we report JCMT/POL2 observations polarized dust emission CMZ, which reveal magnetic field structures dense gas ∼0.5 pc The 11 our sample include two western part CMZ (Sgr C and a farside cloud candidate), four around Galactic longitude 0 (the 50 km s −1 cloud, CO 0.02−0.02, Stone , Sticks Straw among Three Little Pigs), five along Dust Ridge...
The most accurate measurements of magnetic fields in star-forming gas are based on the Zeeman observations analyzed by Crutcher et al. (2010). We show that their finding 3D field scales approximately as density$^{0.65}$ can also be obtained from analysis observed line-of-sight fields. present two large-scale AMR MHD simulations several thousand $M_\odot$ turbulent, isothermal, self-gravitating gas, one with a strong initial (Alfven Mach number $M_{A,0}= 1$) and weak ($M_{A,0}=10$). construct...
The "ATOMS," standing for {\it ALMA Three-millimeter Observations of Massive Star-forming regions}, survey has observed 146 active star forming regions with Band 3, aiming to systematically investigate the spatial distribution various dense gas tracers in a large sample Galactic massive clumps, study roles stellar feedback formation, and characterize filamentary structures inside clumps. In this work, observations, data analysis, example science "ATOMS" are presented, using case G9.62+0.19...
Abstract The Atacama Large Millimeter/submillimeter Array (ALMA) Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE) aims to investigate the process mass assembly its connection high-mass star formation theories protoclusters a dynamic view. We observed 11 massive ( M clump ≳ 10 3 ⊙ ), luminous L bol 4 blue-profile (infall signature) clumps by ALMA resolution ∼2200–5500 au (median value 3500 au) at 350 GHz (870 μ m). identified 248 dense cores,...
The low dust temperatures (<14 K) of Planck Galactic cold clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase star formation. "TOP-SCOPE" is a joint survey program targeting ∼2000 PGCCs in J = 1–0 transitions CO isotopologues ∼1000 850 μm continuum emission. objective surveys (SMT 10 m, KVN 21 NRO 45 m) statistically study occurring during formation evolution molecular clouds, across wide range environments. observations, data analysis, example science...
Star formation in a filamentary infrared dark cloud (IRDC) is simulated over the dynamic range of 4.2 pc to 28 au for period 3.5 × 105 yr, including magnetic fields and both radiative outflow feedback from protostars. At end simulation, star efficiency 4.3 per cent rate free-fall time εff ≃ 0.04, within observed values. The total stellar mass increases as ∼t2, whereas number protostars ∼t1.5. We find that density profile around most ∼ρ ∝ r−1.5. protostellar function approaches Chabrier...
Abstract We present the B -fields mapped in IRDC G34.43+0.24 using 850 μ m polarized dust emission observed with POL-2 instrument at James Clerk Maxwell telescope. examine magnetic field geometries and strengths northern, central, southern regions of filament. The overall geometry is ordered aligned closely perpendicular to filament’s main axis, particularly containing central clumps MM1 MM2, whereas MM3 north has orientations its major axis. are uniform large (POL-2 14″ SHARP 10″) small...
While magnetic fields are important in contemporary star formation, their role primordial formation is unknown. Magnetic of order 10^-16 G produced by the Biermann battery due to curved shocks and turbulence associated with infall gas into dark matter minihalos that sites first stars. These rapidly amplified a small-scale dynamo until they saturate at or near equipartition central region gas. Analytic results given for outcome dynamo, including effect compression collapsing The mass-to-flux...
We have identified 453 compact dense cores in 3 mm continuum emission maps the ATOMS (ALMA Three-millimeter Observations of Massive Star-forming regions) survey, and compiled three catalogues high-mass star forming cores. One catalogue, referred to as H/UC-HII includes 89 that enshroud hyper/ultra (H/UC) HII regions characterized by associated H40alpha emission. A second pure s-cHMC, 32 candidate Hot Molecular Cores (HMCs) showing rich spectra (N>20lines) complex organic molecules (COMs) but...
Optical and infrared polarization mapping recent Planck observations of the filamentary cloud L1495 in Taurus show that large-scale magnetic field is approximately perpendicular to long axis cloud. We use HAWC+ polarimeter on SOFIA probe complex B211 part Our results reveal a dispersion angles $36^\circ$, about five times measured larger scale by Planck. Applying Davis-Chandrasekhar-Fermi (DCF) method with velocity information obtained from IRAM 30m C$^{18}$O(1-0) observations, we find two...
Beginning with cosmological initial conditions at z=100, we simulate the effects of magnetic fields on formation Population III stars and compare our results predictions Paper I. We use Gadget-2 to follow evolution system while field is weak. introduce a new method for treating kinematic by tracking deformation tensor. The growth rate in this stage simulation lower than expected diffuse astrophysical plasmas, which have very low resistivity (high Prandtl number); attribute large numerical...
Abstract The internal structure of the prestellar core G208.68-19.02-N2 (G208-N2) in Orion Molecular Cloud 3 (OMC-3) region has been studied with Atacama Large Millimeter/submillimeter Array. dust continuum emission revealed a filamentary length ∼5000 au and an average H 2 volume density ∼6 × 10 7 cm −3 . At tip this structure, there is compact object, which we call nucleus , radius ∼150–200 mass ∼0.1 M ⊙ central ∼2 9 radial profile r −1.87±0.11 scaling ∼3.7 times higher than that singular...
Abstract Only a handful of massive starless core candidates have been discovered so far, but none them fully confirmed. Within the MM1 clump in filamentary infrared dark cloud G34.43+0.24 that was covered by Atacama Large Millimeter/submillimeter Array (ALMA) ATOMS survey at Band 3 (∼2″, 6000 au) and ALMA-QUARKS 6 (∼0.″3, 900 au), two prestellar MM1-C E1 with masses 71 20 M ⊙ radii 2100–4400 au were discovered. The cores show no obvious sign star formation activities. In particular, is very...
Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based ideal magnetohydrodynamics (MHD). However, MCs weakly ionized, so that timescale required for field to diffuse through neutral component plasma by ambipolar diffusion (AD) can be comparable dynamical timescale. We have performed a series 2563 and 5123 simulations supersonic but sub-Alfvénic systems with AD using heavy-ion approximation developed Li coworkers. Our calculations assumption...
Stellar feedback from high-mass stars (e.g., H{\sc ii} regions) can strongly influence the surrounding interstellar medium and regulate star formation. Our new ALMA observations reveal sequential formation taking place within one sub-virial filamentary clump (the G9.62 clump) in G9.62+0.19 complex. The 12 dense cores (MM 1-12) detected by are at very different evolutionary stages, starless core phase to UC region phase. Three (MM6, MM7/G, MM8/F) associated with outflows. mass-velocity...
Magnetic field is one of the key agents that play a crucial role in shaping molecular clouds and regulating star formation, yet complete information on magnetic not well constrained due to limitations observations. We study massive infrared dark cloud G035.39-00.33 from dust continuum polarization observations at 850 $\micron$ with SCUBA-2/POL-2 JCMT. The tends be perpendicular densest part main filament (F$_{M}$), whereas it has less defined relative orientation rest structure, where...
We perform ideal MHD high resolution AMR simulations with driven turbulence and self-gravity find that long filamentary molecular clouds are formed at the converging locations of large-scale flows filaments bounded by gravity. The magnetic field helps shape reinforce structures. main cloud has a length ~4.4 pc. Instead monolithic cylindrical structure, is shown to be collection fiber/web-like sub-structures similar such as L1495. Unless line-of-sight close mean direction, striations in...
Despite the rich observational results on interstellar magnetic fields in star-forming regions, it is still unclear how dynamically significant are at varying physical scales, because direct measurement of field strength observationally difficult. The Davis-Chandrasekhar-Fermi (DCF) method has been most commonly used to estimate from polarization data. It based assumption that gas turbulent motion driving source distortion via linear Alfv\'en waves. In this work, using MHD simulations...
Ambipolar diffusion (AD) is important in redistributing magnetic flux and damping Alfvén waves molecular clouds. The importance of AD on a length scale ℓ governed by the Reynolds number, RAD = ℓ/ℓAD, where ℓAD characteristic for AD. logarithmic mean number sample 15 clumps with measured fields 17, comparable to theoretically expected value. We identify several regimes turbulent medium, depending ratio flow time collision times between ions neutrals; observed Crutcher 1999 are all standard...
Performing a stable, long duration simulation of driven MHD turbulence with high thermal Mach number and strong initial magnetic field is challenge to high-order Godunov ideal schemes because the difficulty in guaranteeing positivity density pressure. We have implemented robust combination reconstruction schemes, Riemann solvers, limiters, Constrained Transport EMF averaging that can meet this challenge, using strategy, we developed new Adaptive Mesh Refinement (AMR) module ORION2 code....
ABSTRACT We present new 3-mm continuum and molecular lines observations from the ATOMS survey towards massive protostellar clump, MM1, located in filamentary infrared dark cloud (IRDC), G034.43+00.24 (G34). The observed are tracers of either dense gas (e.g. HCO+/H13CO+ J= 1–0) or outflows CS 2–1). most complete picture to date seven cores MM1 is revealed by dust emission. These found be gravitationally bound, with virial parameter, αvir &lt; 2. At least four identified a total outflowing...