LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy

Leah K. Morabito, Adam T. Deller, Huub Röttgering, George Miley, Eskil Varenius, Timothy W. Shimwell, Javier Moldón, Neal Jackson, Raffaella Morganti, Reinout J. van Weeren, J. B R Oonk

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    The correlation between radio spectral index and redshift has been exploited to discover highredshift radio galaxies, but its underlying cause is unclear. It is crucial to characterize the particle acceleration and loss mechanisms in high-redshift radio galaxies to understand why their radio spectral indices are steeper than their local counterparts. Low-frequency information on scales of ∼1 arcsec are necessary to determine the internal spectral index variation. In this paper we present the first spatially resolved studies at frequencies below 100MHz of the z = 2.4 radio galaxy 4C 43.15 which was selected based on its ultrasteep spectral index (α <-1; Sν ∼ να) between 365MHz and 1.4 GHz. Using the International Low Frequency Array Low Band Antenna we achieve subarcsecond imaging resolution at 55MHz with very long baseline interferometry techniques. Our study reveals low-frequency radio emission extended along the jet axis, which connects the two lobes. The integrated spectral index for frequencies

    Original languageEnglish
    Article numberstw1501
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number3
    Early online date29 Jun 2016
    Publication statusPublished - 21 Sep 2016


    • galaxies: active
    • Galaxies: individual: 4C 43.15
    • Galaxies: jets
    • Radio continuum: galaxies


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