Speaker
Description
Within the MIGHTEE deep continuum images, we discovered one of the rarest subpopulations of radio galaxies (RGs) called triple-double radio galaxies (TDRGs). They are characterised by three pairs of radio lobes, each pair of lobes representing an episode of nuclear activity. TDRGs are key tools to understand the duty cycle of RGs. In this work, we report the seventh known TDRG, J022248−060934. It is hosted by a field galaxy at a spectroscopic redshift of 𝑧≈ 0.94 and it has a total projected linear size of 1.5 Mpc. In total intensity, J022248−060934 has a bright core and triple-double, edge-brightened-like peaks of radio emission. The polarimetry of the source reveals an inhomogeneous hosting environment. The spectral index and curvature maps show an inverted core and a steepening of the spectrum towards the outer lobes. Such spectral features indicate current nuclear activity at the core and much older outer lobes. We also perform a spectral age study of the source, which is the first of such analyses for TDRGs. We found a lower limit for the total age of ∼18 Myr. We also derive a short inactive period between the active phases and a rapid duty cycle of 90 per cent for the first cycle of activity. Our spectral ageing analysis thus shows that the triple-double structure in TDRGs is not the product of long quiescent periods, as suggested by previous works based on kinematic ages.
| Stream | Science or Engineering |
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