Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies
Artikel i vetenskaplig tidskrift, 2020

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 15″ 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.

Techniques: interferometric

Radio continuum: general

Författare

F. De Gasperin

Universität Hamburg

J. Vink

Universiteit Van Amsterdam

Netherlands Institute for Space Research (SRON)

J. McKean

Netherlands Institute for Radio Astronomy (ASTRON)

Rijksuniversiteit Groningen

A. Asgekar

Shell Technology Centre

Netherlands Institute for Radio Astronomy (ASTRON)

I.M. Avruch

Netherlands Institute for Radio Astronomy (ASTRON)

M. J. Bentum

Netherlands Institute for Radio Astronomy (ASTRON)

Technische Universiteit Eindhoven

R. Blaauw

Netherlands Institute for Radio Astronomy (ASTRON)

A. Bonafede

Universität Hamburg

Istituto di Radioastronomia

Universita di Bologna

J.W. Broderick

Curtin University

M. Brueggen

Universität Hamburg

F. Breitling

Astrophysikalisches Institut Potsdam

W. N. Brouw

Netherlands Institute for Radio Astronomy (ASTRON)

Rijksuniversiteit Groningen

H. R. Butcher

Australian National University

B. Ciardi

Max-Planck-Gesellschaft

V. Cuciti

Universität Hamburg

M. De Vos

Netherlands Institute for Radio Astronomy (ASTRON)

S. Duscha

Netherlands Institute for Radio Astronomy (ASTRON)

J. Eisloffel

Thüringer Landessternwarte Tautenburg

D. Engels

Universität Hamburg

R. A. Fallows

Netherlands Institute for Radio Astronomy (ASTRON)

T. M.O. Franzen

Netherlands Institute for Radio Astronomy (ASTRON)

M. A. Garrett

Universiteit Leiden

University of Manchester

A.W. Gunst

Netherlands Institute for Radio Astronomy (ASTRON)

J.R. Hörandel

FOM-Institute of Subatomic Physics - NIKHEF

Radboud Universiteit

Vrije Universiteit Brüssel (VUB)

G. Heald

CSIRO Astronomy and Space Science

M. Hoeft

Thüringer Landessternwarte Tautenburg

M. Iacobelli

Netherlands Institute for Radio Astronomy (ASTRON)

L.V.E. Koopmans

Rijksuniversiteit Groningen

A. Krankowski

Uniwersytet Warminsko-Mazurski w Olsztynie

P. Maat

Netherlands Institute for Radio Astronomy (ASTRON)

G. Mann

Astrophysikalisches Institut Potsdam

M. Mevius

Netherlands Institute for Radio Astronomy (ASTRON)

G. Miley

Universiteit Leiden

R. Morganti

Netherlands Institute for Radio Astronomy (ASTRON)

Rijksuniversiteit Groningen

A. Nelles

Friedrich-Alexander-Universität Erlangen Nurnberg (FAU)

Deutsches Elektronen-Synchrotron (DESY)

M. J. Norden

Netherlands Institute for Radio Astronomy (ASTRON)

A. R. Offringa

Netherlands Institute for Radio Astronomy (ASTRON)

Rijksuniversiteit Groningen

E. Orrú

Netherlands Institute for Radio Astronomy (ASTRON)

H. Paas

Rijksuniversiteit Groningen

V. N. Pandey

Rijksuniversiteit Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

M. Pandey-Pommier

USN - Station de Radioastronomie de Nancay

CRAL Le Centre de Recherche Astronomique de Lyon

R. Pekal

Poznanskie Centrum Superkomputerowo Sieciowe

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

W. Reich

Max-Planck-Gesellschaft

A. Rowlinson

Universiteit Van Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

H. Rottgering

Universiteit Leiden

D. J. Schwarz

Universität Bielefeld

A. Shulevski

Universiteit Van Amsterdam

O. Smirnov

Rhodes University

Observatory

C. Sobey

CSIRO Astronomy and Space Science

M. Soida

Uniwersytet Jagiellonski w Krakowie

M. Steinmetz

Astrophysikalisches Institut Potsdam

M. Tagger

Universite d'Orleans

M. C. Toribio

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Arnold van Ardenne

Netherlands Institute for Radio Astronomy (ASTRON)

A. J. van der Horst

George Washington University

M. P. van Haarlem

Netherlands Institute for Radio Astronomy (ASTRON)

R. van Weeren

Universiteit Leiden

C. Vocks

Astrophysikalisches Institut Potsdam

O. Wucknitz

Max-Planck-Gesellschaft

P.M. Zarka

Université PSL

P. Zucca

Netherlands Institute for Radio Astronomy (ASTRON)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 635 A150

Ämneskategorier

Astronomi, astrofysik och kosmologi

Geofysik

Signalbehandling

DOI

10.1051/0004-6361/201936844

Mer information

Senast uppdaterat

2020-05-15