Jason Fiege - NRC Herzberg Institute of Astrophysics

Jason Fiege
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Jason Fiege
NRC Herzberg Institute of Astrophysics

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Astrophysics (10)
Astrophysics of Galaxies (6)
Cosmology and Nongalactic Astrophysics (3)
Solar and Stellar Astrophysics (2)
Instrumentation and Methods for Astrophysics (2)

Publications Authored By Jason Fiege

Authors: Derek Ward-Thompson, Kate Pattle, Pierre Bastien, Ray S. Furuya, Woojin Kwon, Shih-Ping Lai, Keping Qiu, David Berry, Minho Choi, Simon Coudé, James Di Francesco, Thiem Hoang, Erica Franzmann, Per Friberg, Sarah F. Graves, Jane S. Greaves, Martin Houde, Doug Johnstone, Jason M. Kirk, Patrick M. Koch, Jungmi Kwon, Chang Won Lee, Di Li, Brenda C. Matthews, Joseph C. Mottram, Harriet Parsons, Andy Pon, Ramprasad Rao, Mark Rawlings, Hiroko Shinnaga, Sarah Sadavoy, Sven van Loo, Yusuke Aso, Do-Young Byun, Eswariah Chakali, Huei-Ru Chen, Mike C. -Y. Chen, Wen Ping Chen, Tao-Chung Ching, Jungyeon Cho, Antonio Chrysostomou, Eun Jung Chung, Yasuo Doi, Emily Drabek-Maunder, Stewart P. S. Eyres, Jason Fiege, Rachel K. Friesen, Gary Fuller, Tim Gledhill, Matt J. Griffin, Qilao Gu, Tetsuo Hasegawa, Jennifer Hatchell, Saeko S. Hayashi, Wayne Holland, Tsuyoshi Inoue, Shu-ichiro Inutsuka, Kazunari Iwasaki, Il-Gyo Jeong, Ji-hyun Kang, Miju Kang, Sung-ju Kang, Koji S. Kawabata, Francisca Kemper, Gwanjeong Kim, Jongsoo Kim, Kee-Tae Kim, Kyoung Hee Kim, Mi-Ryang Kim, Shinyoung Kim, Kevin M. Lacaille, Jeong-Eun Lee, Sang-Sung Lee, Dalei Li, Hua-bai Li, Hong-Li Liu, Junhao Liu, Sheng-Yuan Liu, Tie Liu, A-Ran Lyo, Steve Mairs, Masafumi Matsumura, Gerald H. Moriarty-Schieven, Fumitaka Nakamura, Hiroyuki Nakanishi, Nagayoshi Ohashi, Takashi Onaka, Nicolas Peretto, Tae-Soo Pyo, Lei Qian, Brendan Retter, John Richer, Andrew Rigby, Jean-François Robitaille, Giorgio Savini, Anna M. M. Scaife, Archana Soam, Motohide Tamura, Ya-Wen Tang, Kohji Tomisaka, Hongchi Wang, Jia-Wei Wang, Anthony P. Whitworth, Hsi-Wei Yen, Hyunju Yoo, Jinghua Yuan, Chuan-Peng Zhang, Guoyin Zhang, Jianjun Zhou, Lei Zhu, Philippe André, C. Darren Dowell, Sam Falle, Yusuke Tsukamoto

We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope (JCMT) in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions which the survey will aim to answer. Read More

We present observations of the Cepheus Flare obtained as part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Legacy Survey (GBLS) with the SCUBA-2 instrument. We produce a catalogue of sources found by SCUBA-2, and separate these into starless cores and protostars. We determine masses and densities for each of our sources, using source temperatures determined by the Herschel Gould Belt Survey. Read More

Several approaches exist to model gravitational lens systems. In this study, we apply global optimization methods to find the optimal set of lens parameters using a genetic algorithm. We treat the full optimization procedure as a two-step process: an analytical description of the source plane intensity distribution is used to find an initial approximation to the optimal lens parameters. Read More

Astronomical instruments generally possess spatially variant point-spread functions, which determine the amount by which an image pixel is blurred as a function of position. Several techniques have been devised to handle this variability in the context of the standard image deconvolution problem. We have developed an iterative gravitational lens modeling code called Mirage that determines the parameters of pixelated source intensity distributions for a given lens model. Read More

Strong gravitational lensing of an extended object is described by a mapping from source to image coordinates that is nonlinear and cannot generally be inverted analytically. Determining the structure of the source intensity distribution also requires a description of the blurring effect due to a point spread function. This initial study uses an iterative gravitational lens modeling scheme based on the semilinear method to determine the linear parameters (source intensity profile) of a strongly lensed system. Read More

Affiliations: 1NRC Herzberg Institute of Astrophysics, 2NRC Herzberg Institute of Astrophysics, 3NRC Herzberg Institute of Astrophysics, 4NRC Herzberg Institute of Astrophysics
Category: Astrophysics

The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in extinction against the diffuse infrared emission of the Galactic plane and in emission at 850 microns. Read More

The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the diffuse 8micron Galactic background, and in emission from cold dust at 850micron. Read More

Affiliations: 1Queen's University, 2Canadian Insitute for Theoretical Astrophysics, 3Queen's University, 4Dublin Institute for Advanced Study
Category: Astrophysics

The formation and collapse of a protostar involves the simultaneous infall and outflow of material in the presence of magnetic fields, self-gravity, and rotation. We use self-similar techniques to self-consistently model the anisotropic collapse and outflow by a set of angle-separated self-similar equations. The outflow is quite strong in our model, with the velocity increasing in proportion to radius, and material formally escaping to infinity in the finite time required for the central singularity to develop. Read More

Affiliations: 1Canadian Institute for Theoretical Astrophysics, 2McMaster University
Category: Astrophysics

We model the sub-millimetre polarization patterns that are expected for filamentary clouds that are threaded by helical magnetic fields. We previously developed a three parameter model of such clouds (Fiege & Pudritz 2000a), which are described by a concentration parameter $C$, and two flux to mass ratios $\Gz$ and $\Gphi$ to specify the mass loading of the poloidal and toroidal field lines respectively. Our models provide a simple and purely geometric explanation for the well-known ``polarization hole'' effect, in which the sub-millimetre polarization percentage decreases toward the regions of peak intensity. Read More

Affiliations: 1McMaster University, 2McMaster University
Category: Astrophysics

We present a new model of molecular cloud cores that originate from filamentary clouds that are threaded by helical magnetic fields. Only modest toroidal fields are required to produce elongated cores, with intrinsic axis ratios in the range 0.1 <= q <= 0. Read More

Affiliations: 1McMaster University, 2McMaster University
Category: Astrophysics

We develop a theory for filamentary molecular clouds including the effects of ordered magnetic fields, and external pressure. We first derive a form of the virial equation appropriate for filamentary clouds. By comparing with observational results collected from the literature, we find that the fields are likely helical. Read More

Affiliations: 1McMaster University, 2McMaster University
Category: Astrophysics

We review the physics of star formation, and its links with the state of the ISM in galaxies. Current obervations indicate that the preferred mode of star formation is clustered. Given that OB associations provide the dominant energy input into the ISM, deep links exist between the ISM and star formation. Read More

In Paper I (Fiege & Pudritz, 1999), we constructed models of filamentary molecular clouds that are truncated by a realistic external pressure and contain a rather general helical magnetic field. We address the stability of our models to gravitational fragmentation and axisymmetric MHD-driven instabilities. By calculating the dominant modes of axisymmetric instability, we determine the dominant length scales and growth rates for fragmentation. Read More

Affiliations: 1Queen's Univ, 2Queen's Univ, 3McMaster Univ
Category: Astrophysics

We study a self-similar circulation model for protostellar bipolar outflows. The model is axisymmetric and stationary, and now includes Poynting flux. Compared to an earlier version of the model, this addition produces faster and more collimated outflows. Read More

We study the equilibrium of pressure truncated, filamentary molecular clouds that are threaded by rather general helical magnetic fields. We first derive a new virial equation appropriate for magnetized filamentary clouds, which includes the effects of non-thermal motions and the turbulent pressure of the surrounding ISM. When compared with the data, we find that many filamentary clouds have a mass per unit length that is significantly reduced by the effects of external pressure, and that toroidal fields play a significant role in squeezing such clouds. Read More