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Unmasking the history of 3C 293 with LOFAR sub‐arcsecond imaging

Kukreti, Pranav and Morganti, Raffaella and Shimwell, Timothy W. and Morabito, Leah K. and Beswick, Robert J. and Brienza, Marisa and Hardcastle, Martin J. and Sweijen, Frits and Jackson, Neal and Miley, George K. and Moldon, Javier and Oosterloo, Tom and de Gasperin, Francesco (2021) 'Unmasking the history of 3C 293 with LOFAR sub‐arcsecond imaging.', 6th Workshop on Compact Steep Spectrum (CSS) and GHz-Peaked Spectrum (GPS) Radio Sources Toruń, Poland, 10-14 May 2021.


Active galactic nuclei show episodic activity, which can be evident in galaxies that exhibit restarted radio jets. These restarted jets can interact with their environment, leaving signatures in the radio spectral energy distribution. Tracing these signatures requires resolved spectral index measurements over a broad frequency range. We present such a study for the radio galaxy 3C 293. Using the International Low Frequency Array Telescope (ILT), we probe spatial scales as fine as ∼0.2″ at 144 MHz and to constrain the spectrum, we combine these data with Multi-Element Radio Linked Interferometer Network and Very Large Array archival data at frequencies up to 8.4 GHz. In the inner lobes (∼2 kpc), we detect the presence of a compact steep spectrum (CSS) source with a spectral turnover at ∼225 MHz, caused by free-free absorption from the rich surrounding medium. We find evidence of interaction of the lobes with the rich interstellar medium of the host galaxy. The outer lobes (extending up to ∼100 kpc) have a remarkably uniform spatial distribution of spectral index and only mild spectral curvature (of ∼0.2). Overall, it appears that 3C 293 has gone through multiple (two to three) epochs of activity. This study adds 3C 293 to the new sub-group of restarted galaxies with short interruption time periods (≲1 Myr). This is the first time a spatially resolved study has been performed that simultaneously studies a young CSS source as well as the older outer lobes at such low frequencies.

Item Type:Conference item (Paper)
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Available under License - Creative Commons Attribution 4.0.
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Publisher statement:© 2021 The Authors. Astronomische Nachrichten published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Date accepted:22 November 2021
Date deposited:24 January 2022
Date of first online publication:07 December 2021
Date first made open access:24 January 2022

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