Identifying active galactic nuclei via brightness temperature with sub-arcsecond international LOFAR telescope observations

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Identifying active galactic nuclei via brightness temperature with sub-arcsecond international LOFAR telescope observations

Morabito, Leah K. (author): Durham University

Sweijen, F. (author): Universiteit Leiden (UL),Leiden University (UL)

Radcliffe, J. F. (author): University of Manchester,Universiteit van Pretoria,University of Pretoria

Best, P. N. (author): Royal Observatory

Kondapally, Rohit (author): Royal Observatory

Bondi, Marco (author): Istituto nazionale di astrofisica (INAF)

Bonato, Matteo (author): Istituto nazionale di astrofisica (INAF)

Duncan, K. J. (author): Royal Observatory

Prandoni, Isabella (author): Istituto nazionale di astrofisica (INAF)

Shimwell, T. W. (author): Universiteit Leiden (UL),Leiden University (UL),Netherlands Institute for Radio Astronomy (ASTRON)

Williams, W. L. (author): Universiteit Leiden (UL),Leiden University (UL)

van Weeren, R. J. (author): Universiteit Leiden (UL),Leiden University (UL)

Conway, John, 1963 (author): Chalmers tekniska högskola,Chalmers University of Technology

Rivera, G. Calistro (author): European Southern Observatory Santiago

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(creator_code:org_t)

2022-07-29
2022
English.
In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 515:4, s. 5758-5774

Related links:: https://research.cha... (primary) (free); show more...; https://doi.org/10.1...; https://research.cha...; show less...

Journal article (peer-reviewed)

Abstract Subject headings

Identifying active galactic nuclei (AGNs) and isolating their contribution to a galaxy's energy budget is crucial for studying the co-evolution of AGNs and their host galaxies. Brightness temperature (T-b) measurements from high-resolution radio observations at GHz frequencies are widely used to identify AGNs. Here, we investigate using new sub-arcsecond imaging at 144 MHz with the International LOFAR Telescope to identify AGNs using T-b in the Lockman Hole field. We use ancillary data to validate the 940 AGN identifications, finding 83 percent of sources have AGN classifications from SED fitting and/or photometric identifications, yielding 160 new AGN identifications. Considering the multiwavelength classifications, brightness temperature criteria select over half of radio-excess sources, 32 percent of sources classified as radio-quiet AGNs, and 20 percent of sources classified as star-forming galaxies. Infrared colour-colour plots and comparison with what we would expect to detect based on peak brightness in 6 arcsec LOFAR maps imply that the star-forming galaxies and sources at low flux densities have a mixture of star-formation and AGN activity. We separate the radio emission from star-formation and AGN in unresolved, T-b-identified AGNs with no significant radio excess and find the AGN comprises 0.49 +/- 0.16 of the radio luminosity. Overall, the non-radio excess AGNs show evidence for having a variety of different radio emission mechanisms, which can provide different pathways for AGNs and galaxy co-evolution. This validation of AGN identification using brightness temperature at low frequencies opens the possibility for securely selecting AGN samples where ancillary data are inadequate.

Subject headings

NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
NATURVETENSKAP -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
NATURAL SCIENCES -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
NATURVETENSKAP -- Fysik -- Annan fysik (hsv//swe)
NATURAL SCIENCES -- Physical Sciences -- Other Physics Topics (hsv//eng)

Keyword

galaxies: active
radiation mechanisms: non-thermal
galaxies: jets
radio continuum: galaxies
acceleration of particles

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By the author/editor: Morabito, Leah K ...; Sweijen, F.; Radcliffe, J. F.; Best, P. N.; Kondapally, Rohi ...; Bondi, Marco; show more...; Bonato, Matteo; Duncan, K. J.; Prandoni, Isabel ...; Shimwell, T. W.; Williams, W. L.; van Weeren, R. J ...; Conway, John, 19 ...; Rivera, G. Calis ...; show less...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Atom and Molecul ...

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Other Physics To ...

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By the university: Chalmers University of Technology

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