Hyunju Yoo
A5079747537- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Solar and Space Plasma Dynamics
- Molecular Spectroscopy and Structure
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Fluid Dynamics and Turbulent Flows
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Geomagnetism and Paleomagnetism Studies
- Nuclear physics research studies
- Adaptive optics and wavefront sensing
- Phase Equilibria and Thermodynamics
- Gas Dynamics and Kinetic Theory
- Computational Fluid Dynamics and Aerodynamics
- High-pressure geophysics and materials
- Spectroscopy and Laser Applications
- Transportation Planning and Optimization
- Vehicle emissions and performance
Chungnam National University
2012-2024
Korea Astronomy and Space Science Institute
2016-2023
Hoseo University
2021
Kyung Hee University
2017-2018
Yonsei University
2016
Abstract Most protostars have luminosities that are fainter than expected from steady accretion over the protostellar lifetime. The solution to this problem may lie in episodic mass accretion—prolonged periods of very low punctuated by short bursts rapid accretion. However, timescale and amplitude for variability at phase is almost entirely unconstrained. In A James Clerk Maxwell Telescope/SCUBA-2 Transient Survey Protostars Nearby Star-forming Regions, we monitoring monthly with SCUBA-2...
We present the results of dust emission polarization measurements Ophiuchus-B (Oph-B) carried out using Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera with its associated polarimeter (POL-2) on James Clerk Maxwell Telescope (JCMT) in Hawaii. This work is part B-fields In Star-forming Region Observations (BISTRO) survey initiated to understand role magnetic fields star formation for nearby star-forming molecular clouds. a first look at geometry and strength Oph-B. The field...
We observed 146 Galactic clumps in HCN (4-3) and CS (7-6) with the Atacama Submillimeter Telescope Experiment (ASTE) 10-m telescope. A tight linear relationship between star formation rate gas mass traced by dust continuum emission was found for both high redshift (z>1) forming galaxies (SFGs), indicating a constant depletion time of ~100 Myr molecular z SFGs. However, low do not follow this relation seem to have longer global time. The correlations total infrared luminosities (L_TIR) line...
Abstract We analyze results from the first 18 months of monthly submillimeter monitoring eight star-forming regions in JCMT Transient Survey. In our search for stochastic variability 1643 bright peaks, only previously identified source, EC 53, shows behavior well above expected measurement uncertainty. Another four sources—two disks and two protostars—show moderately enhanced standard deviations brightness, as variables. For protostars, this apparent is result single epochs that are much...
Abstract We present the four-year survey results of monthly submillimeter monitoring eight nearby (<500 pc) star-forming regions by JCMT Transient Survey. apply Lomb–Scargle Periodogram technique to search for and characterize variability on 295 peaks brighter than 0.14 Jy beam −1 , including 22 disk sources (Class II), 83 protostars 0/I), 190 starless sources. uncover 18 secular variables, all them protostars. No single-epoch burst or drop events no inherently stochastic are observed....
During the protostellar phase of stellar evolution, accretion onto star is expected to be variable, but this suspected variability has been difficult detect because protostars are deeply embedded. In paper, we describe a sub-mm luminosity burst Class I protostar EC 53 in Serpens Main, first variable found during our dedicated JCMT/SCUBA-2 monitoring program eight nearby star-forming regions. remained quiescent for 6 months survey, from February August 2016. The emission began brighten...
We present and analyze observations of polarized dust emission at 850 $\mu$m towards the central 1 pc $\times$ hub-filament structure Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on James Clerk Maxwell Telescope (JCMT) as part BISTRO (B-fields in Star-forming Region Observations) survey. orientations magnetic field follow spiral Mon R2, which well-described by an axisymmetric model. estimate turbulent component using angle difference between our best-fit model underlying...
Investigating variability at the earliest stages of low-mass star formation is fundamental in understanding how a protostar assembles mass. While many simulations protostellar disks predict non-steady accretion onto protostars, deeper investigation requires robust observational constraints on frequency and amplitude events characterised across observable SED. In this study, we develop methods to robustly analyse repeated observations an area sky for submillimetre order determine magnitude...
Analysis of all-sky Planck submillimetre observations and the IRAS 100um data has led to detection a population Galactic cold clumps. The clumps can be used study star formation dust properties in wide range environments. Our aim is measure spectral energy distribution (SED) variations as function spatial scale wavelength. We examine SEDs at large scales using IRAS, Planck, Herschel data. At smaller scales, we compare with JCMT/SCUBA-2 850um maps that are filtered SCUBA-2 pipeline. Clumps...
We present the results of simultaneous 450 $\mu$m and 850 polarization observations toward massive star forming region NGC 2071IR, a target BISTRO (B-fields in Star-Forming Region Observations) Survey, using POL-2 polarimeter SCUBA-2 camera mounted on James Clerk Maxwell Telescope. find pinched magnetic field morphology central dense core region, which could be due to rotating toroidal disk-like structure bipolar outflow originating from young stellar object, IRS 3. Using modified...
ABSTRACT The Chandrasekhar–Fermi (CF) method is a powerful technique for estimating the strength of mean magnetic field projected on plane sky. In this paper, we present improving CF in which take into account averaging effect arising from independent eddies along line sight (LOS). conventional method, fluctuating divided by <?CDATA $\sqrt{4\pi \bar{\rho }}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msqrt> <mml:mrow> <mml:mn>4</mml:mn>...
Turbulence is ubiquitous in astrophysical fluids such as the interstellar medium (ISM) and intracluster (ICM). In turbulence studies, it customary to assume that fluid driven on a single scale. However, fluids, there can be many different driving mechanisms act scales. If are multiple energy-injection scales, process of energy cascade dynamo will compared with case this work, we perform three-dimensional incompressible/compressible magnetohydrodynamic (MHD) simulations. We drive Fourier...
We present the results on physical properties of filaments and dense cores in IC 5146, as a part TRAO FUNS project. carried out On-The-Fly mapping observations using Taeduk Radio Astronomy Observatory (TRAO) 14m telescope covering about 1 square degree area 5146 various molecular lines. identified 14 (24 total, including sub-filaments) from C$^{18}$O (1-0) data cube 22 $\rm N_{2}H^{+}$ data. examined filaments' gravitational criticality, turbulence properties, accretion rate to cores,...
Abstract We present the results of 850 μ m polarization and C 18 O (3 − 2) line observations toward western hub-filament structure (W-HFS) dark Streamer in IC 5146 using James Clerk Maxwell Telescope SCUBA-2/POL-2 HARP instruments. aim to investigate how relative importance magnetic field, gravity, turbulence affects core formation HFS by comparing energy budget this region. identified four cores estimated field strengths ( B pos ) hub filament Davis–Chandrasekhar–Fermi method. The is ∼80...
We performed a molecular line survey of 82 high-mass protostellar objects in search for inflow signatures associated with star formation. Using the H13CO+ (1−0) as an optically thin tracer, we detected statistically significant excess blue asymmetric profiles HCO+ transition, but nonsignificant excesses (3−2) and H2CO (212–111) transitions. The negative HCN transition suggests that are affected by dynamics other than motion. thus seems to be suitable tracer motions star-forming regions,...
The V380 Ori NE bipolar outflow was imaged in the SiO and CO lines, dense cores L1641 were observed 2.0–0.89 mm continuum. highly collimated jet shows point-symmetric oscillation patterns both position velocity, which suggests that axis is precessing driving source may belong to a non-coplanar binary system. By considering velocity variabilities together, accurate parameters derived. protostellar system viewed nearly edge-on, has flow speed of ∼35 km s−1 precession period ∼1600 years. length...
Turbulence dynamo deals with amplification of a seed magnetic field in turbulent medium and has been studied mostly for uniform or spatially homogeneous fields. However, some astrophysical processes (e.g. jets from active galaxies, galactic winds, ram-pressure stripping galaxy clusters) can provide localized In this paper, we numerically study fields medium. Throughout the assume that driving scale turbulence is comparable to size system. Our findings are as follows. First, amplify very...
Ten protostellar outflows in the Orion molecular clouds were mapped $^{12}$CO/$^{13}$CO ${J=6\rightarrow5}$ and $^{12}$CO ${J=7\rightarrow6}$ lines. The maps of these mid-$J$ CO lines have an angular resolution about 10$''$ a typical field size 100$''$. Physical parameters derived, including mass transfer rates, kinetic luminosities, outflow forces. sample was expanded by re-analyzing archival data nearby low-luminosity protostars, to cover wide range bolometric luminosities. Outflow derived...
We present 850~$\mu$m linear polarization and C$^{18}$O~(3-2) $^{13}$CO~(3-2) molecular line observations toward the filaments (F13 F13S) in Cocoon Nebula (IC~5146) using JCMT POL-2 HARP instruments. F13 F13S are found to be thermally supercritical with identified dense cores along their crests. Our findings include that fraction decreases denser regions, indicating reduced dust grain alignment efficiency. The magnetic field vectors at core scales tend parallel filaments, but disturbed high...
Abstract We present the results of molecular line observations performed toward NGC 2068 and 2071 regions Orion B cloud as TRAO-FUNS project to study roles filamentary structure in formation dense cores stars clouds. Gaussian decomposition for C 18 O spectra with multiple velocity components application a friends-of-friends algorithm decomposed allowed us identify few tens velocity-coherent filaments. also identified 48 from N 2 H + using core finding tool, FellWalker. virial analysis these...
Abstract We present recent observation results of Sgr A* at millimeter obtained with VLBI arrays in Korea and Japan. 7 mm monitoring is part our AGN large project. The epochs during 2013-2014, including high resolution maps, flux density two-dimensional size measurements are presented. source shows no significant variation structure related to the G2 encounter 2014. According MHD simulations by kawashima et al. , magnetic field energy can be expected increase several years after encounter;...
Abstract In the early stages of star formation, a protostar is deeply embedded in an optically thick envelope such that it not directly observable. Variations protostellar accretion rate, however, will cause luminosity changes are reprocessed by surrounding and observable at submillimeter wavelengths. We searched for flux variability toward 12 Planck Galactic Cold Clumps detected James Clerk Maxwell Telescope (JCMT)-SCUBA-2 Continuum Observations Pre-protostellar Evolution (SCOPE) survey....