Browsing University of Hertfordshire by Author "Duncan, K. J."

Now showing items 1-20 of 29

    • Accretion mode versus radio morphology in the LOFAR Deep Fields 

      Mingo, B.; Croston, J. H.; Best, P. N.; Duncan, K. J.; Hardcastle, M. J.; Kondapally, R.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Williams, W. L.; Baldi, R. D.; Bonato, M.; Bondi, M.; Dabhade, P.; Gürkan, G.; Ineson, J.; Magliocchetti, M.; Miley, G.; Pierce, J. C. S.; Röttgering, H. J. A. (2022-02-16)
      Radio-loud active galaxies have two accretion modes [radiatively inefficient (RI) and radiatively efficient (RE)], with distinct optical and infrared signatures, and two jet dynamical behaviours, which in arcsec- to ...

    • Alignment in the orientation of LOFAR radio sources 

      Osinga, E.; Miley, G. K.; Weeren, R. J. van; Shimwell, T. W.; Duncan, K. J.; Hardcastle, M. J.; Mechev, A. P.; Röttgering, H. J. A.; Tasse, C.; Williams, W. L. (2020-08-25)
      Various studies have laid claim to finding an alignment of the polarization vectors or radio jets of active galactic nuclei (AGN) over large distances, but these results have proven controversial and so far, there is no ...

    • Cosmic evolution of low-excitation radio galaxies in the LOFAR Two-meter Sky Survey Deep Fields 

      Kondapally, R.; Best, P. N.; Cochrane, R. K.; Sabater, J.; Duncan, K. J.; Hardcastle, M. J.; Haskell, P.; Mingo, B.; Röttgering, H. J. A.; Smith, D. J. B.; Williams, W. L.; Bonato, M.; Rivera, G. Calistro; Gao, F.; Hale, C. L.; Małek, K.; Miley, G. K.; Prandoni, I.; Wang, L. (2022-04-26)
      Feedback from low-excitation radio galaxies (LERGs) plays a key role in the lifecycle of massive galaxies in the local Universe; their evolution, and the impact of these active galactic nuclei on early galaxy evolution, ...

    • Discovery of 24 radio-bright quasars at $4.9 \leq z \leq6.6$ using low-frequency radio observations 

      Gloudemans, A. J.; Duncan, K. J.; Saxena, A.; Harikane, Y.; Hill, G. J.; Zeimann, G. R.; Rottgering, H. J. A.; Yang, D.; Best, P. N.; Banados, E.; Drabent, A.; Hardcastle, M. J.; Hennawi, J. F.; Lansbury, G.; Magliocchetti, M.; Miley, G. K.; Nanni, R.; Shimwell, T. W.; Smith, D. J. B.; Venemans, B.P.; Wagenveld, J. D. (2022-12-31)
      High redshift quasars ($z>5$) that also shine brightly at radio wavelengths are unique signposts of supermassive black hole activity in the early universe. However, bright radio sources at $z\ge5$ are extremely rare and ...

    • The environments of radio-loud AGN from the LOFAR Two-Metre Sky Survey (LoTSS) 

      Croston, J. H.; Hardcastle, M. J.; Mingo, B.; Best, P. N.; Sabater, J.; Shimwell, T. W.; Williams, W. L.; Duncan, K. J.; Röttgering, H. J. A.; Brienza, M.; Gürkan, G.; Ineson, J.; Morabito, L. M.; Miley, G. K.; O'Sullivan, S. P.; Prandoni, I. (2018-10-10)
      An understanding of the relationship between radio-loud active galaxies and their large-scale environments is essential for realistic modelling of radio-galaxy evolution and environmental impact, for understanding AGN ...

    • Extragalactic Peaked-Spectrum Radio Sources at Low-Frequencies are Young Radio Galaxies 

      Slob, M. M.; Callingham, J. R.; Röttgering, H. J. A.; Williams, W. L.; Duncan, K. J.; Gasperin, F. de; Hardcastle, M. J.; Miley, G. K. (2022-12-20)
      We present a sample of 373 peaked-spectrum (PS) sources with spectral peaks around 150 MHz, selected using a subset of the two LOw Frequency ARray (LOFAR) all-sky surveys, the LOFAR Two Meter Sky Survey and the LOFAR LBA ...

    • Giant radio galaxies in the LOFAR Two-metre Sky Survey-I 

      Dabhade, P.; Rottgering, H. J. A.; Bagchi, J.; Shimwell, T. W.; Hardcastle, M. J.; Sankhyayan, S.; Morganti, R.; Jamrozy, M.; Shulevski, A.; Duncan, K. J. (2020-03-01)
      Giant radio galaxies (GRGs) are a subclass of radio galaxies which have grown to megaparsec scales. GRGs are much rarer than normal sized radio galaxies ( less than 0.7 Mpc) and the reason for their gigantic sizes is still ...

    • The life cycle of radio galaxies in the LOFAR Lockman Hole field 

      Jurlin, N.; Morganti, R.; Brienza, M.; Mandal, S.; Maddox, N.; Duncan, K. J.; Shabala, S. S.; Hardcastle, M. J.; Prandoni, I.; Röttgering, H. J. A.; Mahatma, V.; Best, P. N.; Mingo, B.; Sabater, J.; Shimwell, T. W.; Tasse, C. (2020-06-08)
      Radio galaxies are known to go through cycles of activity, where phases of apparent quiescence can be followed by repeated activity of the central supermassive black hole. A better understanding of this cycle is crucial ...

    • LOFAR Properties of SILVERRUSH Lya emitter candidates in the ELAIS-N1 Field 

      Gloudemans, A. J.; Duncan, K. J.; Kondapally, R.; Sabater, J.; Cochrane, R. K.; Röttgering, H. J. A.; Best, P. N.; Bonato, M.; Bondi, M.; Malek, K.; McCheyne, I.; Smith, D. J. B.; Prandoni, I.; Wang, L. (2021-04-07)
      Lyman alpha emitters (LAEs) in the Epoch of Reionization (EoR) offer valuable probes of early galaxy evolution and the process of reionization; however, the exact evolution of their abundance and the nature of their emission ...

    • The LOFAR Two Metre Sky Survey: Deep Fields Data Release 1. III. Host-galaxy identifications and value added catalogues 

      Kondapally, R.; Best, P. N.; Hardcastle, M. J.; Nisbet, D.; Bonato, M.; Sabater, J.; Duncan, K. J.; McCheyne, I.; Cochrane, R. K.; Bowler, R. A. A.; Williams, W. L.; Shimwell, T. W.; Tasse, C.; Croston, J. H.; Goyal, A.; Jamrozy, M.; Jarvis, M. J.; Mahatma, V. H.; R\öttgering, H. J. A.; Smith, D. J. B.; Wo\łowska, A.; Bondi, M.; Brienza, M.; Brown, M. J. I.; Br\üggen, M.; Chambers, K.; Garrett, M. A.; G\ürkan, G.; Huber, M.; Kunert-Bajraszewska, M.; Magnier, E.; Mingo, B.; Mostert, R.; Nikiel-Wroczy\\ński, B.; OŚullivan, S. P.; Paladino, R.; Ploeckinger, T.; Prandoni, I.; Rosenthal, M. J.; Schwarz, D. J.; Shulevski, A.; Wagenveld, J. D.; Wang, L. (2021-04-07)
      We present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the LOFAR Two Metre Sky Survey (LoTSS): the LoTSS Deep Fields. ...

    • The LOFAR Two-metre Sky Survey (LoTSS) III. First Data Release: optical/IR identifications and value-added catalogue 

      Williams, W. L.; Hardcastle, M. J.; Best, P. N.; Sabater, J.; Croston, J. H.; Duncan, K. J.; Shimwell, T. W.; Röttgering, H. J. A.; Nisbet, D.; Gürkan, G.; Alegre, L.; Cochrane, R. K.; Goyal, A.; Hale, C. L.; Jackson, N.; Jamrozy, M.; Kondapally, R.; Kunert-Bajraszewska, M.; Mahatma, V. H.; Mingo, B.; Morabito, L. K.; Prandoni, I.; Roskowinski, C.; Shulevski, A.; Smith, D. J. B.; Tasse, C.; Urquhart, S.; Webster, B.; White, G. J.; Beswick, R. J.; Callingham, J. R.; Chyży, K. T.; Gasperin, F. de; Harwood, J. J.; Hoeft, M.; Iacobelli, M.; McKean, J. P.; Mechev, A. P.; Miley, G. K.; Schwarz, D. J.; Weeren, R. J. van (2018-11-09)
      The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing sensitive, high-resolution 120-168 MHz survey of the Northern sky with diverse and ambitious science goals. Many of the scientific objectives of LoTSS rely upon, or are ...

    • The LOFAR Two-Metre Sky Survey : VI. Optical identifications for the second data release 

      Hardcastle, M. J.; Horton, M. A.; Williams, W. L.; Duncan, K. J.; Alegre, L.; Barkus, B.; Croston, J. H.; Dickinson, H.; Osinga, E.; Röttgering, H. J. A.; Sabater, J.; Shimwell, T. W.; Smith, D. J. B.; Best, P. N.; Botteon, A.; Brüggen, M.; Drabent, A.; Gasperin, F. de; Gürkan, G.; Hajduk, M.; Hale, C. L.; Hoeft, M.; Jamrozy, M.; Kunert-Bajraszewska, M.; Kondapally, R.; Magliocchetti, M.; Mahatma, V. H.; Mostert, R. I. J.; O'Sullivan, S. P.; Pajdosz-Śmierciak, U.; Petley, J.; Pierce, J. C. S.; Prandoni, I.; Schwarz, D. J.; Shulewski, A.; Siewert, T. M.; Stott, J. P.; Tang, H.; Vaccari, M.; Zheng, X.; Bailey, T.; Desbled, S.; Goyal, A.; Gonano, V.; Hanset, M.; Kurtz, W.; Lim, S. M.; Mielle, L.; Molloy, C. S.; Roth, R.; Terentev, I. A.; Torres, M. (2023-10-01)
      The second data release of the LOFAR Two-Metre Sky Survey (LoTSS) covers 27% of the northern sky, with a total area of ∼5700 deg1. The high angular resolution of LOFAR with Dutch baselines (6 arcsec) allows us to carry out ...

    • The LOFAR Two-metre Sky Survey Deep Fields Data Release 1 V. Survey description, source classifications and host galaxy properties 

      Best, P. N.; Kondapally, R.; Williams, W. L.; Cochrane, R. K.; Duncan, K. J.; Hale, C. L.; Haskell, P.; Malek, K.; McCheyne, I.; Smith, D. J. B.; Wang, L.; Botteon, A.; Bonato, M.; Bondi, M.; Rivera, G. Calistro; Gao, F.; Gurkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Mingo, B.; Miraghaei, H.; Morabito, L. K.; Nisbet, D.; Prandoni, I.; Rottgering, H. J. A.; Sabater, J.; Shimwell, T.; Tasse, C.; Weeren, R. van (2023-04-29)
      Source classifications, stellar masses and star formation rates are presented for 80,000 radio sources from the first data release of the Low Frequency Array Two-metre Sky Survey (LoTSS) Deep Fields, which represents the ...

    • The LOFAR Two-metre Sky Survey Deep fields: : The star formation rate - radio luminosity relation at low frequencies 

      Smith, D. J. B.; Haskell, P.; Gürkan, G.; Best, P. N.; Hardcastle, M. J.; Kondapally, R.; Williams, W.; Duncan, K. J.; Cochrane, R. K.; McCheyne, I.; Röttgering, H. J. A.; Sabater, J.; Shimwell, T. W.; Tasse, C.; Bonato, M.; Bondi, M.; Jarvis, M. J.; Leslie, S. K.; Prandoni, I.; Wang, L. (2021-04-07)
      In this paper, we investigate the relationship between 150 MHz luminosity and the star-formation rate - the SFR-L150 MHz relation - using 150 MHz measurements for a near-infrared selected sample of 118 517 z < 1 galaxies. ...

    • The LOFAR Two-metre Sky Survey Deep Fields: Data release 1. IV. Photometric redshifts and stellar masses 

      Duncan, K. J.; Kondapally, R.; Brown, M. J. I.; Best, P. N.; Röttgering, H. J. A.; Bondi, M.; Bowler, R. A. A.; Cochrane, R. K.; Gürkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Kunert-Bajraszewska, M.; Leslie, S. K.; Małek, K.; Morabito, L. K.; O'Sullivan, S. P.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Smith, D. J. B.; Wang, L.; Wołowska, A. (2021-04-07)
      The Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) is a sensitive, high-resolution 120-168 MHz survey split across multiple tiers over the northern sky. The first LoTSS Deep Fields data release consists of deep ...

    • The LOFAR Two-metre Sky Survey: the radio view of the cosmic star formation history 

      Cochrane, R. K.; Kondapally, R.; Best, P. N.; Sabater, J.; Duncan, K. J.; Smith, D. J. B.; Hardcastle, M. J.; Röttgering, H. J. A.; Prandoni, I.; Haskell, P.; Gürkan, G.; Miley, G. K. (2023-05-26)
      We present a detailed study of the cosmic star formation history over $90$ per cent of cosmic time ($0\lesssim z\lesssim4$), using deep, radio continuum observations that probe star formation activity independent of dust. ...

    • The LOFAR window on star-forming galaxies and AGN - curved radio SEDs and IR-radio correlation at 0 < z < 2.5 

      Rivera, G. Calistro; Williams, W. L.; Hardcastle, M. J.; Duncan, K. J.; Röttgering, H.~J.~A.; Best, Philip N.; Brüggen, Marcus; Chyzy, K.T.; Conselice, C. J.; De Gasperin, Francesco; Engels, D.; Gürkan, G.; Intema, Huib T.; Jarvis, M. J.; Mahony, E. K.; Miley, G.K.; Morabito, L. K.; Prandoni, I.; Sabater, J.; Smith, D. J. B.; Tasse, C.; van der Werf, P.; White, Glenn J. (2017-08-11)
      We present a study of the low-frequency radio properties of star forming (SF) galaxies and active galactic nuclei (AGN) up to redshift $z=2.5$. The new spectral window probed by the Low Frequency Array (LOFAR) allows us ...

    • LOFAR-Boötes : Properties of high- and low-excitation radio galaxies at 0.5 < z < 2.0 

      Williams, W. L.; Rivera, G. Calistro; Best, Philip N.; Hardcastle, M. J.; Röttgering, H.~J.~A.; Duncan, K. J.; De Gasperin, Francesco; Jarvis, M. J.; Miley, G.K.; Mahony, E. K.; Morabito, L. K.; Nisbet, D. M.; Prandoni, I.; Smith, D. J. B.; Tasse, C.; White, Glenn J. (2018-04-11)
      This paper presents a study of the redshift evolution of radio-loud active galactic nuclei (AGN) as a function of the properties of their galaxy hosts in the Boötes field. To achieve this we match low-frequency radio sources ...

    • A LOFAR-IRAS cross-match study : the far-infrared radio correlation and the 150-MHz luminosity as a star-formation rate 

      Wang, L.; Gao, F.; Duncan, K. J.; Williams, W. L.; Rowan-Robinson, M.; Sabater, J.; Shimwell, T. W.; Bonato, M.; Calistro-Rivera, G.; Chyzy, K. T.; Farrah, D.; Gurkan Uygun, Gulay; Hardcastle, M. J.; McCheyne, I.; Prandoni, I.; Read, S. C.; Rottgering, H. J. A.; Smith, D. J. B. (2019-11-01)
      Aims. We aim to study the far-infrared radio correlation (FIRC) at 150 MHz in the local Universe (at a median redshift z~0:05) and improve the use of the rest-frame 150-MHz luminosity, L150, as a star-formation rate (SFR) ...

    • The LoTSS view of radio AGN in the local Universe. The most massive galaxies are always switched on 

      Sabater, J.; Best, P.N.; Hardcastle, M. J.; Shimwell, T. W.; Tasse, C.; Williams, W. L.; Brüggen, M.; Cochrane, R. K.; Croston, J. H.; Gasperin, F. de; Duncan, K. J.; Gürkan, G.; Mechev, A. P.; Morabito, Leah K.; Prandoni, I.; Röttgering, H. J. A.; Smith, D. J. B.; Harwood, J. J.; Mingo, B.; Mooney, S.; Saxena, A. (2018-11-15)
      This paper presents a study of the local radio source population, by cross-comparing the data from the first data release (DR1) of the LOFAR Two-Metre Sky Survey (LoTSS) with the Sloan Digital Sky Survey (SDSS) DR7 main ...