Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies

被引：24

作者：

de Gasperin, F. ^{[1
]}

Vink, J. ^{[2
,3
,4
]}

McKean, J. P. ^{[5
,6
]}

Asgekar, A. ^{[6
,28
]}

Avruch, I ^{[6
]}

Bentum, M. J. ^{[6
,7
]}

Blaauw, R. ^{[6
]}

Bonafede, A. ^{[1
,14
,15
]}

Broderick, J. W. ^{[38
]}

Brueggen, M. ^{[1
]}

Breitling, F. ^{[25
]}

Brouw, W. N. ^{[5
,6
]}

Butcher, H. R. ^{[27
]}

Ciardi, B. ^{[29
]}

Cuciti, V ^{[1
]}

de Vos, M. ^{[6
]}

Duscha, S. ^{[6
]}

Eisloeffel, J. ^{[11
]}

Engels, D. ^{[1
]}

Fallows, R. A. ^{[6
]}

Franzen, T. M. O. ^{[6
]}

Garrett, M. A. ^{[8
,19
]}

Gunst, A. W. ^{[6
]}

Hoerandel, J. ^{[33
,34
,35
]}

Heald, G. ^{[26
]}

Hoeft, M. ^{[11
]}

Iacobelli, M. ^{[6
]}

Koopmans, L. V. E. ^{[5
]}

Krankowski, A. ^{[24
]}

Maat, P. ^{[6
]}

Mann, G. ^{[25
]}

Mevius, M. ^{[6
]}

Miley, G. ^{[8
]}

Morganti, R. ^{[5
,6
]}

Nelles, A. ^{[22
,23
]}

Norden, M. J. ^{[6
]}

Offringa, A. R. ^{[5
,6
]}

Orru, E. ^{[6
]}

Paas, H. ^{[5
]}

Pandey, V. N. ^{[5
,6
]}

Pandey-Pommier, M. ^{[31
,32
]}

Pekal, R. ^{[37
]}

Pizzo, R. ^{[6
]}

Reich, W. ^{[36
]}

Rowlinson, A. ^{[2
,6
]}

Rottgering, H. J. A. ^{[8
]}

Schwarz, D. J. ^{[30
]}

Shulevski, A. ^{[2
]}

Smirnov, O. ^{[9
,10
]}

Sobey, C. ^{[26
]}

机构：

[1] Univ Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany

[2] Univ Amsterdam, Anton Pannekoek Inst Astron, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands

[3] Univ Amsterdam, GRAPPA, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands

[4] SRON Netherlands Inst Space Res, SRON, Utrecht, Netherlands

[5] Univ Groningen, Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands

[6] ASTRON Netherlands Inst Radio Astron, Oude Hoogeveensedijk 4, NL-7991 PD Dwingeloo, Netherlands

[7] Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands

[8] Leiden Univ, Leiden Observ, Niels Bohrweg 2, NL-2333 CA Leiden, Netherlands

[9] Rhodes Univ, Dept Phys & Elect, ZA-6139 Grahamstown, South Africa

[10] South African Radio Astron Observ, ZA-7925 Cape Town, South Africa

[11] Thuringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany

[12] Jagiellonian Univ, Astron Observ, Ul Orla 171, PL-30244 Krakow, Poland

[13] Univ Orleans, CNRS, LPC2E, Orleans, France

[14] Univ Bologna, Dipartimento Fis & Astron, Via P Gobetti 93-2, I-40129 Bologna, Italy

[15] INAF, Ist Radioastron, Bologna Via Gobetti 101, I-40129 Bologna, Italy

[16] SU UP UO, PSL, CNRS, LESIA,Observ Paris, F-92195 Meudon, France

[17] SU UP UO, PSL, CNRS, USN,Observ Paris, F-92195 Meudon, France

[18] Chalmers Univ Technol, Dept Space Earth & Environm, Onsala Space Observ, S-43992 Onsala, Sweden

[19] Univ Manchester, Jodrell Bank Ctr Astrophys, Dept Phys & Astron, Alan Turing Bldg,Oxford Rd, Manchester M13 9PL, Lancs, England

[20] George Washington Univ, Dept Phys, 725 21st St NW, Washington, DC 20052 USA

[21] George Washington Univ, APSIS, Washington, DC 20052 USA

[22] Friedrich Alexander Univ Erlangen Nurnberg, ECAP, D-91058 Erlangen, Germany

[23] DESY, Platanenallee 6, D-15738 Zeuthen, Germany

[24] Univ Warmia & Mazury, Space Radiodiagnost Res Ctr, Prawochenskiego 9, PL-10720 Olsztyn, Poland

[25] Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany

[26] CSIRO Astron & Space Sci, POB 1130, Bentley, WA 6102, Australia

[27] Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia

[28] Shell Technol Ctr, Bangalore 562149, Karnataka, India

[29] Max Planck Inst Astrophys, Karl Schwarzschild Str 1, D-85748 Garching, Germany

[30] Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany

[31] Nancay Observ Paris, Stn Radioastron, USN, Route Souesmes, F-18330 Nancay, France

[32] Univ Lyon1, Univ Lyon, Ens Lyon, CNRS,Ctr Rech Astrophys Lyon,UMR5574, 9 Av Charles Andre, F-69230 St Genis Laval, France

[33] Radboud Univ Nijmegen, IMAPP, Dept Astrophys, POB 9010, NL-6500 GL Nijmegen, Netherlands

[34] Nikhef, Sci Pk 105, NL-1098 XG Amsterdam, Netherlands

[35] Vrije Univ Brussel, Phys Dept, Pleinlaan 2, B-1050 Brussels, Belgium

[36] Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany

[37] PAS, IBCH, PSNC, Poznan, Poland

[38] Curtin Univ, Int Ctr Radio Astron Res, GPO Box U1987, Perth, WA 6845, Australia

来源：

ASTRONOMY & ASTROPHYSICS | 2020年 / 635卷

基金：

欧洲研究理事会;

关键词：

radio continuum; general; techniques; interferometric; SUPERNOVA REMNANT; CRAB-NEBULA; CALIBRATION; ABSORPTION; FILAMENTS; SPECTRUM; GALAXY;

D O I：

10.1051/0004-6361/201936844

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (<100 MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21 cm line from the epoch of reionisation. Aims. We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 1500 with a high dynamic range and good image fidelity. Methods. We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30 MHz and 77 MHz using the Low Band Antenna system. We reduced the datasets and obtained an image for each A-team source. Results. The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30 MHz and 77 MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further.

引用

页数：7

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