The multi-wavelength properties of nearby low-luminosity Active Galactic Nuclei (LLAGN) with the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies survey (LeMMINGs)

Abstract

The radio and multi-wavelength properties of active galactic nuclei (AGN) have been well documented in the literature, contributing to the unified picture of AGN as a super-massive black hole surrounded by various sub-structures. The study of low-luminosityAGN(LLAGN) is less well documented or understood, due largely to their intrinsic faintness. In this thesis, I study the radio emission of a statistically-complete sample of 280 nearby LLAGN using the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies survey (LeMMINGs), to detect the presence of kpc-scale radio jets. I compare the radio emission to the multi-wavelength properties of the host galaxy and LLAGN to understand the physical accretion mechanism in different types of LLAGN system. First, I present two in-depth multi-wavelength case studies of nearby LLAGN, observed with the LeMMINGs ‘deep’ survey: NGC4151 and NGC6217, studying long-term variability and the nuclear structures in these sources. I then present the LeMMINGs ‘shallow’ survey radio data for a statistically-complete sample of 280 nearby LLAGN based off the Palomar survey. I compare these observations with other available data in the literature, including X-ray observations from the Chandra X-ray Observatory to assess the multi-wavelength correlations of different types of LLAGN. Furthermore, I denote a type of star-forming galaxy, namely the ‘jetted H II galaxies’, that show similar multi-wavelength properties to that of other LLAGN, indicating that they may be hiding a LLAGN. Finally, the Fundamental Plane of Black Hole Activity (FPBHA) is correlation between the X-ray luminosity, radio luminosity and mass for black holes, spanning over eight orders of mass from Black hole X-ray binaries (BHXRBs) upto super-massive black holes in AGN. I construct the FPBHA for the LeMMINGs ‘shallow’ sample objects, including a sub-sample of BHXRBs, to investigate the correlation coefficients of the plane and test its validity with LLAGN sources. The results are consistent with previous formulations of the FPBHA but suggest that choice of LLAGN sub-sample is important for regressing the FPBHA parameters.

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ORCID for David Richard Alexander Williams: orcid.org/0000-0001-7361-0246

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