A5056586661- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Superconducting and THz Device Technology
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Spectroscopy and Laser Applications
- Vehicle emissions and performance
- Radio Astronomy Observations and Technology
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Solar and Space Plasma Dynamics
- Astrophysics and Cosmic Phenomena
- Advanced Combustion Engine Technologies
- Advanced Chemical Physics Studies
- Calibration and Measurement Techniques
- Atomic and Molecular Physics
- Space Exploration and Technology
- Spacecraft and Cryogenic Technologies
- Scientific Research and Discoveries
- SAS software applications and methods
University of Victoria
2016-2025
Herzberg Institute of Astrophysics
2016-2025
National Research Council Canada
2013-2024
UK Astronomy Technology Centre
2024
Royal Observatory
2024
University of British Columbia
2022
Cornell University
2018-2022
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
University of Hawaii at Hilo
2013-2018
view Abstract Citations (538) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoevaporation of Disks around Massive Stars and Application to Ultracompact H II Regions Hollenbach, David ; Johnstone, Doug Lizano, Susana Shu, Frank Young massive stars produce sufficient Lyman continuum photon luminosity Phii significantly affect the structure evolution accretion disks surrounding them. A nearly static, ionized, isothermal 104 K atmosphere...
We present a model for the photoevaporation of circumstellar disks or dense clumps gas by an external source ultraviolet radiation. Our includes thermal and dynamic effects 6-13.6 eV far-ultraviolet (FUV) photons Lyman continuum EUV incident upon idealized as spheres radius rd enclosed mass M*. For sufficiently large values rd/M*, radiation field evaporates surface dust. Analytical numerical approximations to resulting flows are presented; depends on rd, M*, flux FUV photons, column density...
Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify substructures 12 disks and measure properties to investigate how they form. This subsample selected from a high-resolution ($\sim0.12''$) 1.33 mm survey 32 Taurus star-forming region, which was designed cover wide range sub-mm brightness be unbiased previously known substructures. While axisymmetric rings gaps common within...
We present the SCUBA Legacy Catalogues, two comprehensive sets of continuum maps (and catalogues) using data at 850 microns and 450 various astronomical objects obtained with Submillimetre Common User Bolometer Array (SCUBA). The Fundamental Map Dataset contains only where superior atmospheric opacity calibration were available. Extended is comprised regardless quality calibration. Each 1.2 degree x locations existed in JCMT archive, imaged matrix inversion method. 1423 1357 microns. 1547...
We present the results of Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around 85 nearby young stars. The observations were obtained with Altair system at North telescope, angular differential imaging was used to suppress speckle noise central star. Typically, are sensitive separations beyond 0.5'' 5 σ contrast sensitivities in magnitude difference 1.6 μm 9.5 0.5'', 12.9 1'', 15.0 2'', 16.5 5''. These sufficient detect more massive than...
We present a global study of low mass, young stellar object (YSO) surface densities in nearby (< 500 pc) star forming regions based on comprehensive collection Spitzer Space Telescope surveys. show that the distribution YSO solar neighbourhood is smooth distribution, being adequately described by lognormal function from few to 10^3 YSOs per pc^2, with peak at 22 stars/pc^2 and dispersion 0.85. do not find evidence for multiple discrete modes star-formation (e.g. clustered distributed)....
We present the full catalog of Young Stellar Objects (YSOs) identified in 18 molecular clouds surveyed by Spitzer Space Telescope "cores to disks" (c2d) and "Gould Belt" (GB) Legacy surveys. Using standard techniques developed c2d project, we identify 3239 candidate YSOs clouds, 2966 which survive visual inspection form our final Gould Belt. compile extinction corrected SEDs for all calculate tabulate infrared spectral index, bolometric luminosity, temperature each object. find that 326...
`Water In Star-forming regions with Herschel' (WISH) is a key program on the Herschel Space Observatory designed to probe physical and chemical structure of young stellar objects using water related molecules follow abundance from collapsing clouds planet-forming disks. About 80 sources are targeted covering wide range luminosities evolutionary stages, cold pre-stellar cores warm protostellar envelopes outflows disks around stars. Both HIFI PACS instruments used observe variety lines H2O,...
Context. Water is a key tracer of dynamics and chemistry in low-mass star-forming regions, but spectrally resolved observations have so far been limited sensitivity angular resolution, only data from the brightest protostars published.
Abstract The Near Infrared Camera for the James Webb Space Telescope (JWST) is delivering imagery that astronomers have hoped ever since JWST was proposed back in 1990s. In Commissioning Period extended from right after launch to early 2022 July, NIRCam has been subjected a number of performance tests and operational checks. camera exceeding prelaunch expectations virtually all areas, with very few surprises discovered flight. also delivered needed by Wavefront Sensing Team use aligning...
Abstract We present a high-resolution (∼0.″12, ∼16 au, mean sensitivity of 50 μ Jy beam −1 at 225 GHz) snapshot survey 32 protoplanetary disks around young stars with spectral type earlier than M3 in the Taurus star-forming region using Atacama Large Millimeter Array. This sample includes most mid-infrared excess members that were not previously imaged high spatial resolution, excluding close binaries and objects extinction, thereby providing more representative look disk properties 1–2 Myr....
Abstract The hot Neptune desert is one of the most sparsely populated regions exoplanet parameter space, and atmosphere observations its few residents can provide insights into how such planets have managed to survive in an inhospitable environment. Here, we present transmission LTT 9779 b, only known retained a significant H/He-dominated atmosphere, taken with JWST NIRISS/SOSS. 0.6–2.85 μ m spectrum shows evidence for muted spectral features, rejecting perfectly flat line at >5 σ . We...
<ns4:p>The study of transient and variable events, including novae, active galactic nuclei, black hole binaries, has historically been a fruitful path for elucidating the evolutionary mechanisms our universe. The such events in millimeter submillimeter is, however, still its infancy. Submillimeter observations probe variety materials, as optically thick dust, which are hard to other wavelengths. sensitive number emission mechanisms, from aforementioned cold hot free-free emission,...
We present results from a survey of the central 700 arcmin2 region ρ Ophiuchi molecular cloud at 850 μm using Submillimeter Common-User Bolometer Array (SCUBA) on James Clerk Maxwell Telescope. Using clump-finding procedure developed by Williams et al., we identify 55 independent objects and compute size, flux, degree concentration. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that clumps have internal temperatures 10-30 K surface pressures P/k...
We present the first high dynamic range and sensitivity images of submillimeter wavelength continuum emission at 450 850 μm "integral-shaped filament" in northern portion Orion A cloud, which contains nearest site ongoing high-mass star formation. The trace morphology spectral index optically thin from interstellar dust, they constrain grain temperature emissivity. reveal a remarkable chain compact sources embedded narrow (<1' = 0.14 pc), column density filament that extends over 50' (7 pc)...
We examine the ability of photoevaporative disk winds to explain low-velocity components observed in forbidden line spectra low-mass T Tauri stars. Using analytic model Shu and coworkers Hollenbach as a basis, we characteristics outflows with hydrodynamic simulations. General results from simulations agree well predictions, although some small differences are present. Most importantly, flow material surface develops at smaller radii than approximations, velocity is only one-third sound...
We present an overview of data available for the Ophiuchus and Perseus molecular clouds from Phase I COMPLETE Survey Star-Forming Regions. This survey provides a range complementary to Spitzer Legacy Program "From Molecular Cores Planet Forming Disks." includes following: extinction maps derived Two Micron All Sky (2MASS) near-infrared using NICER algorithm; temperature IRAS 60 100 μm emission; H atomic gas; 12CO 13CO submillimeter continuum images emission dust in dense cores. Not...
We present an analysis of ~3.5 deg2 submillimeter continuum and extinction data the Perseus molecular cloud. identify 58 clumps in map, we 39 structures ("cores") 11 associations ("super cores") map. The cumulative mass distributions cores have steep slopes (α ~ 2 1.5-2, respectively), steeper than Salpeter initial function (IMF; α = 1.35), while distribution super has a shallow slope 1). Most are well fit by stable Bonnor-Ebert spheres with 10 K < T 19 5.5 <(Pext/k) 6.0. found only highest...
This paper describes a James Clerk Maxwell Telescope (JCMT) legacy survey that has been awarded roughly 500 hr of observing time to be carried out from 2007 2009. In this survey, we will map with SCUBA‐2 (Submillimetre Common‐User Bolometer Array 2) almost all the well‐known low‐mass and intermediate‐mass star‐forming regions within 0.5 kpc are accessible JCMT. Most these locations associated Gould Belt. From observations, produce flux‐limited snapshot star formation near Sun, providing...
In this paper, we present the first observations of Ophiuchus molecular cloud performed as part James Clerk Maxwell Telescope (JCMT) Gould Belt Survey (GBS) with SCUBA-2 instrument.We demonstrate methods for combining these data previous HARP CO, Herschel, and IRAM N 2 H + in order to accurately quantify properties sources Ophiuchus.We produce a catalogue all found by SCUBA-2.We separate into protostars starless cores.We list cores perform full virial analysis, including external...
We present initial results from the Herschel GT key program: observations of EXtra-Ordinary Sources (HEXOS) and outline promise potential spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well continuous coverage across gaps imposed by atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. show spectrum Orion KL between 480 560 GHz 1.06 1.115 THz. From these data, we confirm that separately measures dust...
We determine the magnetic field strength in OMC 1 region of Orion A filament via a new implementation Chandrasekhar-Fermi method using observations performed as part James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with POL-2 instrument. combine BISTRO data archival SCUBA-2 and HARP to find plane-of-sky $B_{\rm pos}=6.6\pm4.7$ mG, where $\delta B_{\rm pos}=4.7$ mG represents predominantly systematic uncertainty. develop for measuring angular...
We present ALMA 850 $\mu$m continuum observations of the Orion Nebula Cluster that provide highest angular resolution ($\sim 0\rlap{.}''1 \approx 40$ AU) and deepest sensitivity 0.1$ mJy) region to date. mosaicked a field containing $\sim 225$ optical or near-IR-identified young stars, 60$ which are also optically-identified "proplyds". detect emission at towards 80$% proplyd sample, 50$% larger sample previously-identified cluster members. Detected objects have fluxes 0.5$-80 mJy. remove...
ALMA has observed a plethora of ring-like structures in planet forming discs at distances 10-100 au from their host star. Although several mechanisms have been invoked to explain the origin such rings, common explanation is that they trace new-born planets. Under planetary hypothesis, natural question how reconcile apparently high frequency gap-carving planets with paucity Jupiter mass around main sequence stars those separations. Here, we provide an analysis population emerging observations...