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The variability of brightest cluster galaxies at high radio frequencies

Rose, Tom and Edge, Alastair and Kiehlmann, Sebastian and Baek, Junhyun and Chung, Aeree and Jung, Tae-Hyun and Kim, Jae-Woo and Readhead, Anthony C. S. and Sedgewick, Aidan (2022) The variability of brightest cluster galaxies at high radio frequencies. Monthly Notices of the Royal Astronomical Society, 509 (2). pp. 2869-2884. ISSN 0035-8711. doi:10.1093/mnras/stab3217.

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Variability of a galaxy’s core radio source can be a significant consequence of AGN accretion. However, this variability has not been well studied, particularly at high radio frequencies. As such, we report on a campaign monitoring the high radio frequency variability of 20 nearby, cool-core brightest cluster galaxies. From our representative sample, we show that most vary significantly on timescales of approximately one year and longer. Our highest cadence observations are at 15 GHz and are from the Owens Valley Radio Observatory (OVRO). They have a median time interval of 7 days and mostly span between 8 and 13 years. We apply a range of variability detection techniques to the sources’ lightcurves to analyse changes on week to decade long timescales. Most notably, at least half of the sources show 20 per cent peak to trough variability on 3 year timescales, while at least a third vary by 60 per cent on 6 year timescales. Significant variability, which is important to studies of the Sunyaev-Zel’dovich Effect in the radio/sub-mm, is therefore a common feature of these sources. We also show how the variability relates to spectral properties at frequencies of up to 353 GHz using data from the Korean VLBI network (KVN), the NIKA2 instrument of the IRAM 30m telescope, and the SCUBA-2 instrument of the James Clerk Maxwell Telescope.

Item Type:Article
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URLURL TypeDescription Paper
Rose, Tom0000-0002-8310-2218
Readhead, Anthony C. S.0000-0001-9152-961X
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 No v ember 2. Received 2021 November 1; in original form 2021 July 26. Published: 10 November 2021. We thank the anonymous reviewer for their time and comments, which have helped to improve the paper. This research has made use of data from the OVRO 40-m monitoring program that was supported in part by the National Aeronautics and Space Administration (NASA) grants NNX08AW31G, NNX11A043G, and NNX14AQ89G, and National Science Foundation (NSF) grants AST-0808050 and AST-1109911, and private funding from Caltech and the Max Planck Institute for Radio Astronomy (MPIfR). We are grateful to the staff of the KVN (Korean VLBI Network) who helped to operate the array and to correlate the data. The KVN and a high-performance computing cluster are facilities operated by the KASI (Korea Astronomy and Space Science Institute). The KVN observations and correlations are supported through the high-speed network connections among the KVN sites provided by the KREONET (Korea Research Environment Open NETwork), which is managed and operated by the KISTI (Korea Institute of Science and Technology Information). The following people contributed to the acquisition and analysis of the KVN data: Jae-Woo Kim and Tae-Hyun Jung. Their affiliations are given on the title page of this paper. We would like to thank the Institut de Radioastronomie Millimétrique (IRAM) staff for their support during the numerous campaigns. The NIKA2 dilution cryostat has been designed and built at the Institut Néel. We are grateful to the staff of the James Clerk Maxwell Telescope, which is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; Center for Astronomical Mega-Science (as well as the National Key R&D Program of China with No. 2017YFA0402700). Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities and organizations in the United Kingdom and Canada. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.00629.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. For the majority of the time over which this research was carried out, TR was supported by the Science and Technology Facilities Council (STFC) through grant ST/R504725/1. TR also thanks the Waterloo Centre for Astrophysics and generous funding to Brian McNamara from the Canadian Space Agency and the National Science and Engineering Research Council of Canada. ACE acknowledges support from STFC grant ST/P00541/1. JWK acknowledges support from the National Research Foundation of Korea (NRF), grant no. NRF-2019R1C1C1002796, funded by the Korean government (MSIT). SK acknowledges support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme under grant agreement no. 771282. AC and JB acknowledge support from the National Research Foundation of Korea (NRF), grant no. 2018R1D1A1B07048314. This research made use of ASTROPY (The Astropy Collaboration 2013, 2018), MATPLOTLIB (Hunter 2007), NUMPY (van der Walt, Colbert & Varoquaux 2011; Harris et al. 2020), PYTHON (Van Rossum & Drake 2009), and SCIPY (Jones, Oliphant & Peterson 2011; Virtanen et al. 2020). We thank their developers for maintaining them and making them freely available. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University in Finland. Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department
Funding AgencyGrant Number
Max Planck Institute for Radio Astronomy (MPIfR)UNSPECIFIED
National Key Research and Development Program of China2017YFA0402700
Canada Foundation for InnovationUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/R504725/1
Waterloo Centre for AstrophysicsUNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Science and Technology Facilities Council (STFC)ST/P00541/1
National Research Foundation of KoreaNRF-2019R1C1C1002796
European Research Council (ERC)771282
National Research Foundation of Korea2018R1D1A1B07048314
Subject Keywords:galaxies: clusters: general – radio continuum: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20220118-801849000
Persistent URL:
Official Citation:Tom Rose, Alastair Edge, Sebastian Kiehlmann, Junhyun Baek, Aeree Chung, Tae-Hyun Jung, Jae-Woo Kim, Anthony C S Readhead, Aidan Sedgewick, The variability of brightest cluster galaxies at high radio frequencies, Monthly Notices of the Royal Astronomical Society, Volume 509, Issue 2, January 2022, Pages 2869–2884,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112945
Deposited By: Tony Diaz
Deposited On:18 Jan 2022 22:53
Last Modified:18 Jan 2022 22:53

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