Table of Links
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Dara & Instruments
3.1. CHIME and GMIMS surveys and 3.2. CHIME/GMIMS Low Band North
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Features of the Tadpole
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The Origin of the Tadpole
5.1. Neutral Hydrogen Structure
5.2. Ionized Hydrogen Structure
APPENDIX
A. RESOLVED AND UNRESOLVED FARADAY COMPONENTS IN FARADAY SYNTHESIS
4.5. Artifacts
The CHIME maps are sensitive to structures on a wide range of angular scales. Some artifacts are described in detail in CHIME Collaboration (2022). One is evident in the single diagonal stripe in the top left corner of Figures 2 and 3, which is a line at the right ascension of Tau A. Curved striations, seen in the Stokes Q and U images (Figure 2) and the Faraday synthesis images (Figure 3), correspond to fixed zenith angles (or, equivalently, declinations). Point sources appear as a single point with bright copies at the same declination on either side of the source due to grating lobes, resulting in an apparent triple source. The sources themselves appear in Stokes Q in equatorial coordinates due to leakage, with symmetric sidelobes, while in Stokes U only the asymmetric sidelobes, with opposite signs, appear. In the Galactic coordinates shown in this paper, leakage sources appear in both Q and U, along with their sidelobes.
Grating lobes also appear for larger-scale structures, having a slight effect on the appearance of the images of the tadpole region. In the CHIME 410 MHz pI map in Figure 5, a copy of the head of the tadpole can be seen as an outline that stands out in polarized intensity, centered on ℓ ≈ 138.5◦ , b ≈ 8.5◦ . The location and the separation between this and the center of the head agrees with the position of the grating lobes in relation to the main lobes of the point sources. This ‘ghost’ copy of the tadpole also appears in the 410 MHz polarization angle image in Figure 5, is generally more apparent at the lower frequencies, and is quite evident in the Faraday depth slices shown in Figure 6.
There is also declination-dependent striping, which appears as curved stripes in Galactic coordinates in Figure 2 and other images, although it is much less pronounced in angle images and Faraday synthesis products. This arises from cross talk between adjacent feeds (CHIME Collaboration 2022, Figure 18). We could remove the striping using image processing techniques, but this cosmetic improvement to the images is unnecessary for our science. Ultimately, the inclusion of the DRAO 15 m survey (Ordog et al in prep) will allow us to exclude baselines ≲ 5 m from the final CHIME-GMIMS data product; we expect this to considerably reduce this striping.
Authors:
(1) Nasser Mohammed, Department of Computer Science, Math, Physics, & Statistics, University of British Columbia, Okanagan Campus, Kelowna, BC V1V 1V7, Canada and Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(2) Anna Ordog, Department of Computer Science, Math, Physics, & Statistics, University of British Columbia, Okanagan Campus, Kelowna, BC V1V 1V7, Canada and Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(3) Rebecca A. Booth, Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada;
(4) Andrea Bracco, INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy and Laboratoire de Physique de l’Ecole Normale Superieure, ENS, Universit´e PSL, CNRS, Sorbonne Universite, Universite de Paris, F-75005 Paris, France;
(5) Jo-Anne C. Brown, Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada;
(6) Ettore Carretti, INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy;
(7) John M. Dickey, School of Natural Sciences, University of Tasmania, Hobart, Tas 7000 Australia;
(8) Simon Foreman, Department of Physics, Arizona State University, Tempe, AZ 85287, USA;
(9) Mark Halpern, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada;
(10) Marijke Haverkorn, Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands;
(11) Alex S. Hill, Department of Computer Science, Math, Physics, & Statistics, University of British Columbia, Okanagan Campus, Kelowna, BC V1V 1V7, Canada and Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(12) Gary Hinshaw, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada;
(13) Joseph W. Kania, Department of Physics and Astronomy, West Virginia University, P.O. Box 6315, Morgantown, WV 26506, USA and Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USA;
(14) Roland Kothes, Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(15) T.L. Landecker, Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(16) Joshua MacEachern, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada;
(17) Kiyoshi W. Masui, MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA and Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA;
(18) Aimee Menard, Department of Computer Science, Math, Physics, & Statistics, University of British Columbia, Okanagan Campus, Kelowna, BC V1V 1V7, Canada and Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(19) Ryan R. Ransom, Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada and Department of Physics and Astronomy, Okanagan College, Kelowna, BC V1Y 4X8, Canada;
(20) Wolfgang Reich, Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany;(21) Patricia Reich, 16
(22) J. Richard Shaw, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada
(23) Seth R. Siegel, Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, ON N25 2YL, Canada, Department of Physics, McGill University, 3600 rue University, Montreal, QC H3A 2T8, Canada, and Trottier Space Institute, McGill University, 3550 rue University, Montreal, QC H3A 2A7, Canada;
(24) Mehrnoosh Tahani, Banting and KIPAC Fellowships: Kavli Institute for Particle Astrophysics & Cosmology (KIPAC), Stanford University, Stanford, CA 94305, USA;
(25) Alec J. M. Thomson, ATNF, CSIRO Space & Astronomy, Bentley, WA, Australia;
(26) Tristan Pinsonneault-Marotte, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada;
(27) Haochen Wang, MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA and Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA;
(28) Jennifer L. West, Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada, PO Box 248, Penticton, BC V2A 6J9, Canada;
(29) Maik Wolleben, Skaha Remote Sensing Ltd., 3165 Juniper Drive, Naramata, BC V0H 1N0, Canada.
This paper is