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Papers by Derek Ward-Thompson

The Astrophysical Journal

We present BISTRO Survey 850 μm dust emission polarization observations of the L1495A-B10 region ... more We present BISTRO Survey 850 μm dust emission polarization observations of the L1495A-B10 region of the Taurus molecular cloud, taken at the James Clerk Maxwell Telescope (JCMT). We observe a roughly triangular network of dense filaments. We detect nine of the dense starless cores embedded within these filaments in polarization, finding that the plane-of-sky orientation of the core-scale magnetic field lies roughly perpendicular to the filaments in almost all cases. We also find that the large-scale magnetic field orientation measured by Planck is not correlated with any of the core or filament structures, except in the case of the lowest-density core. We propose a scenario for early prestellar evolution that is both an extension to, and consistent with, previous models, introducing an additional evolutionary transitional stage between field-dominated and matter-dominated evolution, observed here for the first time. In this scenario, the cloud collapses first to a sheet-like structu...

Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wave-lengths wit... more Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wave-lengths with the Herschel Space Observatory have provided us with unprecedented images of the initial and boundary conditions of the star formation process. The Herschel results emphasize the role of interstellar filaments in the star formation process and connect remarkably well with nearly a decade’s worth of numerical simulations and theory that have consistently shown that the ISM should be highly filamentary on all scales and star formation is intimately related to self-gravitating filaments. In this review, we trace how the apparent complexity of cloud structure and star formation is governed by relatively simple universal processes- from filamentary clumps to galactic scales. We emphasize two crucial and complementary aspects: (i) the key observational results obtained with Herschel over the past three years, along with relevant new results obtained from the ground on the kinematics of inter...

We present a comparison of Submillimetre Common User Bolometer Array-2 (SCUBA-2) 850-μm and Hersc... more We present a comparison of Submillimetre Common User Bolometer Array-2 (SCUBA-2) 850-μm and Herschel 70–500-μm observations of the L1495 filament in the Taurus Molecular Cloud with the goal of characterizing the SCUBA-2 Gould Belt Survey (GBS) data set. We identify and characterize starless cores in three data sets: SCUBA-2 850-μm, Herschel 250-μm, and Herschel 250-μm spatially filtered to mimic the SCUBA-2 data. SCUBA-2 detects only the highest-surface-brightness sources, principally detecting protostellar sources and starless cores embedded in filaments, while Herschel is sensitive to most of the cloud structure, including extended low-surface-brightness emission. Herschel detects considerably more sources than SCUBA-2 even after spatial filtering. We investigate which properties of a starless core detected by Herschel determine its detectability by SCUBA-2, and find that they are the core’s temperature and column density (for given dust properties). For similartemperature cores, ...

The Astrophysical Journal, 2020

We present Herschel SPIRE and PACS maps of the Cepheus Flare clouds L1157, L1172, L1228, L1241, a... more We present Herschel SPIRE and PACS maps of the Cepheus Flare clouds L1157, L1172, L1228, L1241, and L1251, observed by the Herschel Gould Belt Survey of nearby star-forming molecular clouds. Through modified blackbody fits to the SPIRE and PACS data, we determine typical cloud column densities of (0.5–1.0) × 1021 cm−2 and typical cloud temperatures of 14–15 K. Using the getsources identification algorithm, we extract 832 dense cores from the SPIRE and PACS data at 160–500 μm. From placement in a mass versus size diagram, we consider 303 to be candidate prestellar cores, and 178 of these to be “robust” prestellar cores. From an independent extraction of sources at 70 μm, we consider 25 of the 832 dense cores to be protostellar. The distribution of background column densities coincident with candidate prestellar cores peaks at (2–4) × 1021 cm−2. About half of the candidate prestellar cores in Cepheus may have formed as a result of the widespread fragmentation expected to occur within ...

Astronomy & Astrophysics, 2020

Context. Herschel observations of nearby clouds in the Gould Belt support a paradigm for low-mass... more Context. Herschel observations of nearby clouds in the Gould Belt support a paradigm for low-mass star formation, starting with the generation of molecular filaments, followed by filament fragmentation, and the concentration of mass into self-gravitating prestellar cores. In the case of the Ophiuchus molecular complex, a rich star formation activity has been documented for many years inside the clumps of L1688, the main and densest cloud of the complex, and in the more quiescent twin cloud L1689 thanks to extensive surveys at infrared and other wavelengths. Aims. With the unique far-infrared and submillimeter continuum imaging capabilities of the Herschel Space observatory, the closeby (d = 139 pc) Ophiuchus cloud was extensively mapped at five wavelengths from 70 to 500 μm with the aim of providing a complete census of dense cores in this region, including unbound starless cores, bound prestellar cores, and protostellar cores. Methods. Taking full advantage of the high dynamic rang...

The Astrophysical Journal, 2019

The Astrophysical Journal, 2018

The Astrophysical Journal, 2017

Monthly Notices of the Royal Astronomical Society, 2016

The Astrophysical Journal, 2016

Protostars and Planets VI, 2014

Polarized thermal emission from dust grains can be used to trace magnetic fields in molecular clo... more Polarized thermal emission from dust grains can be used to trace magnetic fields in molecular clouds and the ISM. The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and has produced degree scale polarization maps of multiple nearby molecular clouds with arcminute resolution. The success of BLASTPol has motivated a next-generation instrument, BLAST-TNG, with additional resolution and sensitivity to fully understand the role magnetic fields play in the early stages of the star formation process. BLAST-TNG will use an array of ~1500 linear polarization sensitive pixels populated with Microwave Kinetic Inductance Detectors (MKIDs) combined with a 2.5 m diameter carbon fiber primary mirror to make diffraction limited observations at 250, 350, and 500 microns. With 16 times the mapping speed of BLASTPol, sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to examine nearby molecular clouds and the diffuse galactic dust polarization spectrum in unprecedented detail. Additionally, the instrument will be in a unique position to link the all-sky, five arcminute resolution, dust polarization maps of Planck with the high resolution, but small area, polarization maps from ALMA allowing us to trace magnetic fields from protostellar cores out to the surrounding molecular clouds and ISM. BLAST-TNG is scheduled to fly from Antarctica in 2016 for 28 days and will be the first balloon-borne telescope to offer a quarter of the flight for "shared risk" observing by the community.