S. Van Loo
A5016065712- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Atmospheric Ozone and Climate
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Atomic and Molecular Physics
- Molecular Spectroscopy and Structure
- Astronomical Observations and Instrumentation
- Ionosphere and magnetosphere dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Black Holes and Theoretical Physics
- High-pressure geophysics and materials
- MRI in cancer diagnosis
- Advanced Chemical Physics Studies
- Magnetic confinement fusion research
- Dust and Plasma Wave Phenomena
- Fluid Dynamics Simulations and Interactions
- Advanced MRI Techniques and Applications
- Advanced Neuroimaging Techniques and Applications
University of Leeds
2015-2024
Ghent University
2022-2024
University of Sheffield
2022
Center for Astrophysics Harvard & Smithsonian
2012-2015
Harvard University
2012-2014
University of Florida
2010-2013
University of Twente
2012
Delft University of Technology
2012
Royal Observatory of Belgium
2002-2006
Vrije Universiteit Brussel
1999-2001
We present the first results from B-fields In STar-forming Region Observations (BISTRO) survey, using Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on James Clerk Maxwell Telescope (JCMT) in Hawaii. discuss survey's aims and objectives. describe rationale behind questions which survey will aim to answer. The most important of these is role magnetic fields star formation process scale individual filaments cores dense regions. data...
We present high-sensitivity 2'x4' maps of the J=2-1 rotational lines SiO, CO, 13CO and C18O, observed toward filamentary Infrared Dark Cloud (IRDC) G035.39-00.33. Single-pointing spectra SiO J=3-2 several regions in filament, are also reported. The images reveal that is widespread along IRDC (size >2 pc), showing two different components: one bright compact arising from three condensations (N, E S), other weak extended filament. While first component shows broad (linewidths ~4-7 kms-1) both...
We investigate giant molecular cloud (GMCs) collisions and their ability to induce gravitational instability thus star formation. This mechanism may be a major driver of formation activity in galactic disks. carry out series three dimensional, magnetohydrodynamics (MHD), adaptive mesh refinement (AMR) simulations study how trigger dense filaments clumps. Heating cooling functions are implemented based on photo-dissociation region (PDR) models that span the atomic transition can return...
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...
Abstract We present 850 μ m imaging polarimetry data of the ρ Oph-A core taken with Submillimeter Common-User Bolometer Array-2 (SCUBA-2) and its polarimeter (POL-2) as part our ongoing survey project, <?CDATA ${\boldsymbol{B}}$?> -fields In STar forming RegiOns (BISTRO). The polarization vectors are used to identify orientation magnetic field projected on plane sky at a resolution 0.01 pc. 10 subregions distinct fractions angles in 0.2 pc core; some them can be coherent structure Oph...
We report 850~$\mu$m dust polarization observations of a low-mass ($\sim$12 $M_{\odot}$) starless core in the $\rho$ Ophiuchus cloud, C, made with POL-2 instrument on James Clerk Maxwell Telescope (JCMT) as part JCMT B-fields In STar-forming Region Observations (BISTRO) survey. detect an ordered magnetic field projected plane sky core. The across $\sim$0.1~pc shows predominant northeast-southwest orientation centering between $\sim$40$^\circ$ to $\sim$100$^\circ$, indicating that is well...
We utilize magnetohydrodynamic (MHD) simulations to develop a numerical model for GMC-GMC collisions between nearly magnetically critical clouds. The goal is determine if, and under what circumstances, cloud can cause pre-existing subcritical clumps become supercritical undergo gravitational collapse. first implement new photodissociation region (PDR) based heating cooling functions that span the atomic molecular transition, creating multiphase ISM allowing modeling of non-equilibrium...
We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. further develop our three dimensional magnetized, turbulent, colliding GMC simulations by implementing formation sub-grid models. Two such models are explored: (1) "Density-Regulated," i.e., fixed efficiency per free-fall time above a set density threshold; (2) "Magnetically-Regulated," in regions that magnetically supercritical. Variations of parameters associated with these also explored....
We examine the role of gravitational instability in an isothermal, self-gravitating layer threaded by magnetic fields on formation filaments and dense cores. Using a numerical simulation, we follow non-linear evolution perturbed equilibrium layer. The linear such is described analytic work Nagai et al. find that cores form simultaneously. Depending initial field, resulting either spiderweb-like network (for weak fields) or parallel aligned perpendicular to field lines strong fields)....
We report on the results of four XMM–Newton observations separated by about ten days from each other Cyg OB2 #8A [O6If + O5.5III(f)]. This massive colliding wind binary is a very bright X-ray emitter — one first emitting O-stars discovered Einstein satellite as well confirmed non-thermal radio whose binarity was quite recently. The spectrum between 0.5 and 10.0 keV essentially thermal, best fitted with three-component model temperatures 3, 9 20 MK. luminosity corrected for interstellar...
We have used the adaptive mesh refinement hydrodynamic code, mg, to perform idealized 3D magnetohydrodynamical simulations of formation clumpy and filamentary structure in a thermally unstable medium without turbulence. A stationary spherical diffuse atomic cloud with uniform density pressure equilibrium low surroundings was seeded random variations allowed evolve. range magnetic field strengths threading been explored, from β = 0.1 1.0 zero case (β ∞), where is ratio thermal pressure. Once...
We report the results of a multi-wavelength investigation O4 V star 9 Sgr (= HD 164794). Our data include observations in X-ray domain with XMM-Newton, radio VLA as well optical spectroscopy. is one few presumably single OB stars that display non-thermal emission. This phenomenon attributed to synchrotron emission by relativistic electrons accelerated strong hydrodynamic shocks stellar wind. Given enormous supply photospheric UV photons wind Sgr, inverse Compton scattering these priori...
Aims.Our aim is to understand the formation of a magnetically dominated molecular cloud out an atomic cloud.
We present hydrodynamic simulations of self-gravitating dense gas in a galactic disk, exploring scales ranging from 1 kpc down to $\sim 0.1$~pc. Our primary goal is understand how filaments form Giant Molecular Clouds (GMCs). These structures, often observed as Infrared Dark (IRDCs) the Galactic plane, are thought be precursors massive stars and star clusters, so their formation may rate limiting step controlling global rates systems described by Kennicutt-Schmidt relation. study follows on...
We present the POL-2 850 $\mu$m linear polarization map of Barnard 1 clump in Perseus molecular cloud complex from B-fields In STar-forming Region Observations (BISTRO) survey at James Clerk Maxwell Telescope. find a trend decreasing fraction as function total intensity, which we link to depolarization effects towards higher density regions cloud. then use data infer plane-of-sky orientation large-scale magnetic field 1. This runs North-South across most cloud, with exception B1-c where it...
We present a model for the non-thermal radio emission from presumably single O stars, in terms of synchrotron relativistic electrons accelerated wind-embedded shocks. These shocks are associated with an unstable, chaotic wind. The main improvement respect to earlier models is inclusion radial dependence shock velocity jump and compression ratio, based on one-dimensional time-dependent hydrodynamical simulations. decrease ratio as function radius produces rapidly decreasing emissivity. This...
The star Cyg OB2 No. 9 is a well-known non-thermal radio emitter. Recent theoretical work suggests that all such O-stars should be in binary or multiple system. However, there no spectroscopic evidence of component. Re-analysis observations from the VLA this system over 25 years has revealed emission varies with period 2.35±0.02 yr. This interpreted as strong suggestion system, arising wind-collision region. We derived some preliminary orbital parameters for putative and revised mass-loss...
HD 167971 is a triple system consisting of 3.3-day eclipsing binary (O5-8 V + O5-8 V) and an O8 supergiant. It also well known non-thermal radio emitter. We observed the emission with Very Large Array (VLA) Australia Telescope Compact (ATCA). By combining these data VLA archive observations we constructed lightcurve covering 20-yr time-range. searched for, but failed to find, spectroscopic period in data. This could be due absence intrinsic synchrotron radiation colliding-wind region between...
To understand the formation of a magnetically dominated molecular cloud from an atomic cloud, we study interaction weak, radiative shock with magnetized cloud. The thermally stable warm is initially in static equilibrium surrounding hot ionized gas. A propagating through medium then interacts We follow dynamical evolution shocked time-dependent ideal magnetohydrodynamic code. By performing simulations 3D, investigate effect different magnetic field orientations including parallel,...
We present the first results for sputtering of grain mantles and cores obtained with self-consistent multifluid hydromagnetic models C-type shocks propagating through dusty media. The threshold shock speed mantle is about 10 km/s independent density. are completely vapourised in speeds 20-25 km/s. At such core commences gas-phase SiO forms. Core destruction not total any because grains destroyed near minimum at which J-type appear. Due to density-dependence critical this transition, higher...
We present hydrodynamic simulations of the evolution self-gravitating dense gas on scales 1 kiloparsec down to < parsec in a galactic disk, designed study clump formation from giant molecular clouds (GMCs). These structures are expected be precursors star clusters and this process may rate limiting step controling rates systems as described by Kennicutt-Schmidt relation. follow thermal ~5K using extinction-dependent heating cooling functions. do not yet include magnetic fields or localized...
We report the results of a multiwavelength study non-thermal radio emitter HD 168112 (O5.5III(f+)). The detailed analysis two quasi-simultaneous XMM-Newton and VLA observations reveals strong variability this star both in X-ray ranges. separated by five months reveal decrease flux ~30%. emission on other hand increases factor 5–7 between obtained roughly simultaneously with pointings. data hard that is most likely produced thermal plasma at kT ~ 2–3 keV while confirm status waveband....