ThePlanckclusters in the LOFAR sky
Astronomy and Astrophysics, vol. 672, pp. A41
Abstract
Context.Extended radio sources in the sky require a dense sampling of short baselines to be properly imaged by interferometers. This problem arises in many areas of radio astronomy, such as in the study of galaxy clusters, which may host megaparsec-scale diffuse synchrotron sources in the form of radio halos. In clusters where no radio halos are detected, owing to intrinsic absence of emission or extrinsic (instrumental and/or observational) effects, it is possible to determine upper limits. Aims.We consider a sample ofPlanckgalaxy clusters from the Second Data Release of the LOFAR Two Meter Sky Survey (LoTSS-DR2) where no radio halos are detected. We aim to use this sample to test the capabilities of LOFAR to recover diffuse extended emission and derive upper limits. Methods.Through the injection technique, we simulated radio halos with various surface brightness profiles. We then predicted the corresponding visibilities and imaged them along with the real visibilities. This method allows us to test the fraction of flux density losses owing to inadequateuvcoverage and obtain thresholds at which the mock emission becomes undetectable by visual inspection. Results.The denseuvcoverage of LOFAR at short spacings allows us to recover ≳ 90% of the flux density of targets with sizes up to ~15′. We find a relation that provides upper limits based on the image noise and extent (in terms of number of beams) of the mock halo. This relation can be safely adopted to obtain upper limits without injecting when artefacts introduced by the subtraction of the discrete sources are negligible in the central region of the cluster. Otherwise, the injection process and visual inspection of the images are necessary to determine more reliable limits. Through these methods, we obtain upper limits for 75 clusters to be exploited in ongoing statistical studies.
Authors 15
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Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Istituto di Radioastronomia di Bologna · National Institute for Astrophysics
Affiliation as printed
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Leiden University · Istituto di Radioastronomia di Bologna · Leiden Observatory · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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Universität Hamburg · Istituto di Radioastronomia di Bologna · National Institute for Astrophysics
Affiliation as printed
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Istituto di Radioastronomia di Bologna · National Institute for Astrophysics
Affiliation as printed
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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Leiden University · Leiden Observatory · Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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Trieste Astronomical Observatory · National Institute for Astrophysics
Affiliation as printed
Istituto Nazionale di Astrofisica (INAF) – Astronomical Observatory of Trieste, Trieste, Italy
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Trieste Astronomical Observatory · National Institute for Astrophysics
Affiliation as printed
Istituto Nazionale di Astrofisica (INAF) – Astronomical Observatory of Trieste, Trieste, Italy
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Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
Istituto Nazionale di Astrofisica (INAF) – Istituto di Radioastronomia (IRA), via Gobetti 101, 40129 Bologna, Italy
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Affiliation as printed
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
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Affiliation as printed
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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Centre National de la Recherche Scientifique · Rhodes University · Université Paris Sciences et Lettres · Observatoire de Paris · Galaxies, Etoiles, Physique et Instrumentation
Affiliation as printed
Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
GEPI & USN, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
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