Publications (30)
Beam Measurements of Full Stokes Parameters for the FAST L-band 19-beam Receiver
Xunzhou Chen, Tao-Chung Ching, Di Li +7
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has been fully operational since 11 January 2020. We present a comprehensive analysis of the beam structure for eac…
Gain and Polarization Properties of a Large Radio Telescope from Calculation and Measurement: The John A. Galt Telescope
Xuan Du, Thomas L. Landecker, Timothy Robishaw +3
Measurement of the brightness temperature of extended radio emission demands knowledge of the gain (or aperture efficiency) of the telescope and measurement of the polarized compon…
Holographic Beam Mapping of the CHIME Pathfinder Array
Philippe Berger, Laura B. Newburgh, Mandana Amiri +32
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder radio telescope is currently surveying the northern hemisphere between 400 and 800 MHz. By mapping the large s…
Measuring Magnetic Field Strengths in Galactic Star-forming Regions via the Zeeman Effect with the SKA
Tyler L. Bourke, Tao-Chung Ching, Laura Fissel +14
Magnetic fields thread the interstellar medium from the largest to the smallest scales and play an important role in molecular cloud evolution and star formation. Quantifying this…
Joint Analysis of HI Absorption Zeeman Measurements and the Morphology of Filamentary HI Emission
Marta Nowotka, Susan E. Clark, Blakesley Burkhart +4
We present a joint analysis of HI absorption Zeeman measurements and the morphology of filamentary HI emission to investigate the three-dimensional structure of the magnetic field…
Parsec-scale magnetic fields in Arp 220
James McBride, Timothy Robishaw, Carl Heiles +2
We present the first very-long-baseline interferometry (VLBI) detections of Zeeman splitting in another galaxy. We used Arecibo Observatory, the Green Bank Telescope, and the Very…
An 84 microGauss Magnetic Field in a Galaxy at Redshift z=0.692
Arthur M. Wolfe, Regina A. Jorgenson, Timothy Robishaw +2
The magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and…
Revisiting rotationally excited CH at radio wavelengths: A case study towards W51
Arshia M. Jacob, Meera Nandakumar, Nirupam Roy +7
Ever since they were first detected in the interstellar medium, the radio wavelength (3.3 GHz) hyperfine-structure splitting transitions in the rotational ground state of CH have b…
A New Catalog of Faraday Rotation Measures and Redshifts for Extragalactic Radio Sources
Alison M. Hammond, Timothy Robishaw, B. M. Gaensler
We present a catalog of Faraday rotation measures (RMs) and redshifts for 4003 extragalactic radio sources detected at 1.4 GHz, derived by identifying optical counterparts and spec…
Extragalactic Zeeman Detections in OH Megamasers
Timothy Robishaw, Eliot Quataert, Carl Heiles
We have measured the Zeeman splitting of OH megamaser emission at 1667 MHz from five (ultra)luminous infrared galaxies ([U]LIRGs) using the 305 m Arecibo telescope and the 100 m Gr…
Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect
Timothy Robishaw, James A. Green, Gabriele Surcis +12
The measurement of Zeeman splitting in spectral lines---both in emission and absorption---can provide direct estimates of the magnetic field strength and direction in atomic and mo…
Dark Matter in Dwarf Galaxies: The First Dark Galaxy?
Joshua D. Simon, Timothy Robishaw, Leo Blitz
We present new HI observations of the high-velocity cloud (HVC) that we resolved near the Local Group dwarf galaxy LGS 3. The cloud is rotating, with an implied mass that makes it…
Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients
Bryan M. Gaensler, Marijke Haverkorn, Blakesley Burkhart +7
The interstellar medium of the Milky Way is multi-phase, magnetized and turbulent. Turbulence in the interstellar medium produces a global cascade of random gas motions, spanning s…
GMIMS-DRAGONS: A Faraday Depth Survey of the Northern Sky Covering 350-1030 MHz
Anna Ordog, Rebecca A. Booth, T. L. Landecker +25
Polarized synchrotron emission at meter to centimeter wavelengths provides an effective tracer of the Galactic magnetic field. Calculating Faraday depth, the most useful parameter…
Gas Rich Dwarf Spheroidals
Leo Blitz, Timothy Robishaw
We present evidence that nearly half of the dwarf spheroidal galaxies (dSph and dSph/dIrr) in the Local Group are associated with large reservoirs of atomic gas, in some cases larg…
HI mapping of the Leo Triplet: Morphologies and kinematics of tails and bridges
Gang Wu, David MartÃnez-Delgado, Christian Henkel +9
A fully-sampled and hitherto highest resolution and sensitivity observation of neutral hydrogen (HI) in the Leo Triplet (NGC 3628, M 65/NGC 3623, and M 66/NGC 3627) reveals six HI…
Science with the Murchison Widefield Array
Judd D. Bowman, Iver Cairns, David L. Kaplan +58
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the Southern Hem…
The GALFA-HI Survey: Data Release 1
J. E. G. Peek, Carl Heiles, Kevin A. Douglas +10
We present the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, and its first full data release (DR1). GALFA-HI is a high resolution (~ 4'), large area (13000 deg^2), high…
Measuring magnetism in the Milky Way with the Square Kilometre Array
Marijke Haverkorn, Takuya Akahori, Ettore Carretti +17
Magnetic fields in the Milky Way are present on a wide variety of sizes and strengths, influencing many processes in the Galactic ecosystem such as star formation, gas dynamics, je…
Spectral Polarization of the Redshifted 21 cm Absorption Line Toward 3C 286
Arthur M. Wolfe, Regina A. Jorgenson, Timothy Robishaw +2
A re-analysis of the Stokes-parameter spectra obtained of the z=0.692 21 cm absorption line toward 3C 286 shows that our original claimed detection of Zeeman splitting by a line-of…
HI Imaging of LGS 3 and an Apparently Interacting High-Velocity Cloud
Timothy Robishaw, Joshua D. Simon, Leo Blitz
We present a 93' by 93' map of the area near the Local Group dwarf galaxy LGS 3, centered on an HI cloud 30' away from the galaxy. Previous authors associated this cloud with LGS 3…
Detection of a ~20 kpc coherent magnetic field in the outskirt of merging spirals: the Antennae galaxies
Aritra Basu, S. A. Mao, Amanda A. Kepley +3
We present a study of the magnetic field properties of NGC 4038/9 (the `Antennae' galaxies), the closest example of a late stage merger of two spiral galaxies. Wideband polarimetri…
Magnetic fields in forming stars with the ngVLA
Charles L. H. Hull, Carlos Carrasco-González, Peter K. G. Williams +4
The magnetic field plays an important role in every stage of the star-formation process from the collapse of the initial protostellar core to the star's arrival on the main sequenc…
Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect
Timothy Robishaw, Marta Nowotka, Tao-Chung Ching +7
Zeeman splitting in spectral lines -- both in emission and absorption -- provides direct estimates of magnetic field strength and direction in magnetized gas in our own Milky Way a…
Wideband RFI Monitor Requirements, Design, and Commissioning at DRAO
Nicholas Bruce, Charl Baard, Stephen Harrison +7
In this paper, we introduce the radio frequency interference monitor deployed at the Dominion Radio Astrophysical Observatory. It provides 2 GHz of instantaneous bandwidth, support…
Polarization Calibration of the FAST L-band 19-beam Receiver: I. On-axis Mueller Matrix Parameters
Tao-Chung Ching, Carl Heiles, Di Li +6
We present the polarization calibration of the 19-beam receiver at 1420 MHz within the full illumination of the Five-hundred-meter Aperture Spherical Telescope from October 2018 to…
The Magnetic Field of the Irregular Galaxy NGC 4214
Amanda Kepley, Ellen Zweibel, Eric Wilcots +2
We examine the magnetic field in NGC 4214, a nearby irregular galaxy, using multi-wavelength radio continuum polarization data from the Very Large Array. We find that the global ra…
Magnetic Fields in Irregular Galaxies
Amanda A. Kepley, Stefanie Muehle, Eric M. Wilcots +4
Magnetic fields are an important component of the interstellar medium, especially in low-mass galaxies like irregulars where the magnetic pressure may be significant. However, few…
The Measurement of Polarization in Radio Astronomy
Timothy Robishaw, Carl Heiles
Modern dual-polarization receivers allow a radio telescope to characterize the full polarization state of incoming insterstellar radio waves. Many astronomers incorrectly consider…
On Measuring Accurate 21-cm Line Profiles with the Robert C. Byrd Green Bank Telescope
Timothy Robishaw, Carl Heiles
We use observational data to show that 21 cm line profiles measured with the Green Bank Telescope (GBT) are subject to significant inaccuracy. These include ~10% errors in the cali…