James Petley's Outputs (10)

A decade of sub-arcsecond imaging with the International LOFAR Telescope (2025)
Journal Article
Morabito, L. K., Jackson, N., de Jong, J., Escott, E., Groeneveld, C., Mahatma, V., Petley, J., Sweijen, F., Timmerman, R., & van Weeren, R. J. (2025). A decade of sub-arcsecond imaging with the International LOFAR Telescope. Astrophysics and Space Science, 370(2), Article 19. https://doi.org/10.1007/s10509-025-04406-x

The International LOFAR Telescope (ILT) is a pan-European radio interferometer with baselines up to 2000 km. This provides sub-arcsecond resolution at frequencies of <200 MHz. Since starting science operations in 2012, the ILT has carried out observa...

Connection between steep radio spectral slopes and dust extinction in QSOs: evidence for outflow-driven shocks in dusty QSOs (2025)
Journal Article
Fawcett, V. A., Harrison, C. M., Alexander, D. M., Morabito, L. K., Kharb, P., Rosario, D. J., Baghel, J., Ghosh, S., Sasikumar, S., Petley, J., Sargent, C., & Calistro Rivera, G. (2025). Connection between steep radio spectral slopes and dust extinction in QSOs: evidence for outflow-driven shocks in dusty QSOs. Monthly Notices of the Royal Astronomical Society, 537(2), 2003-2023. https://doi.org/10.1093/mnras/staf105

Recent studies have found a striking positive correlation between the amount of dust obscuration and enhanced radio emission in quasi-stellar objects (QSOs). However, what causes this connection remains unclear. In this paper we analyse uGMRT Band-3... Read More about Connection between steep radio spectral slopes and dust extinction in QSOs: evidence for outflow-driven shocks in dusty QSOs.

A novel Bayesian approach for decomposing the radio emission of quasars – II. Link between quasar radio emission and black hole mass (2025)
Journal Article
Yue, B. H., Duncan, K. J., Best, P. N., Arnaudova, M. I., Morabito, L. K., Petley, J. W., Röttgering, H. J. A., Shenoy, S., & Smith, D. J. B. (2025). A novel Bayesian approach for decomposing the radio emission of quasars – II. Link between quasar radio emission and black hole mass. Monthly Notices of the Royal Astronomical Society, 537(2), 858-875. https://doi.org/10.1093/mnras/staf077

Whether the mass of supermassive black hole ( M BH ) is directly linked to the quasar radio luminosity remains a long-debated issue, and understanding the role of M BH in the evolution of quasars is pivotal to unveiling the mechanism of active galact... Read More about A novel Bayesian approach for decomposing the radio emission of quasars – II. Link between quasar radio emission and black hole mass.

Ubiquitous radio emission in quasars: Predominant AGN origin and a connection to jets, dust, and winds (2024)
Journal Article
Calistro Rivera, G., Alexander, D. M., Harrison, C. M., Fawcett, V. A., Best, P. N., Williams, W. L., Hardcastle, M. J., Rosario, D. J., Smith, D. J. B., Arnaudova, M. I., Escott, E., Gürkan, G., Kondapally, R., Miley, G., Morabito, L. K., Petley, J., Prandoni, I., Röttgering, H. J. A., & Yue, B.-H. (2024). Ubiquitous radio emission in quasars: Predominant AGN origin and a connection to jets, dust, and winds. Astronomy & Astrophysics, 691, Article A191. https://doi.org/10.1051/0004-6361/202348982

We present a comprehensive study of the physical origin of radio emission in optical quasars at redshifts z < 2.5. We focus particularly on the associations between compact radio emission, dust reddening, and outflows identified in our earlier work....

Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images (2024)
Journal Article
de Jong, J. M. G. H. J., van Weeren, R. J., Sweijen, F., Oonk, J. B. R., Shimwell, T. W., Offringa, A. R., Morabito, L. K., Röttgering, H. J. A., Kondapally, R., Escott, E. L., Best, P. N., Bondi, M., Ye, H., & Petley, J. W. (2024). Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images. Astronomy & Astrophysics, 689, Article A80. https://doi.org/10.1051/0004-6361/202450595

We present the deepest wide-field 115–166 MHz image at sub-arcsecond resolution spanning an area of 2.5◦ × 2.5◦ centred at the ELAIS-N1 deep field. To achieve this, we improved the direction-independent (DI) and direction-dependent (DD) calibrations... Read More about Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images.

A novel Bayesian approach for decomposing the radio emission of quasars: I. Modelling the radio excess in red quasars (2024)
Journal Article
Yue, B. -., Best, P. N., Duncan, K. J., Calistro-Rivera, G., Morabito, L. K., Petley, J. W., …Smith, D. J. B. (2024). A novel Bayesian approach for decomposing the radio emission of quasars: I. Modelling the radio excess in red quasars. Monthly Notices of the Royal Astronomical Society, 529(4), 3939-3957. https://doi.org/10.1093/mnras/stae725

Studies show that both radio jets from the active galactic nuclei (AGNs) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain unclear. Here... Read More about A novel Bayesian approach for decomposing the radio emission of quasars: I. Modelling the radio excess in red quasars.

How does the radio enhancement of broad absorption line quasars relate to colour and accretion rate? (2024)
Journal Article
Petley, J. W., Morabito, L. K., Rankine, A. L., Richards, G. T., Thomas, N. L., Alexander, D. M., …Kolwa, S. (2024). How does the radio enhancement of broad absorption line quasars relate to colour and accretion rate?. Monthly Notices of the Royal Astronomical Society, 529(3), 1995-2007. https://doi.org/10.1093/mnras/stae626

The origin of radio emission in different populations of radio-quiet quasars is relatively unknown, but recent work has uncovered various drivers of increased radio-detection fraction. In this work, we pull together three known factors: optical colou... Read More about How does the radio enhancement of broad absorption line quasars relate to colour and accretion rate?.

The LOFAR Two-Metre Sky Survey: VI. Optical identifications for the second data release (2023)
Journal Article
Hardcastle, M. J., Horton, M. A., Williams, W. L., Duncan, K. J., Alegre, L., Barkus, B., …Torres, M. (2023). The LOFAR Two-Metre Sky Survey: VI. Optical identifications for the second data release. Astronomy & Astrophysics, 678, Article A151. https://doi.org/10.1051/0004-6361/202347333

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 optical identifications of... Read More about The LOFAR Two-Metre Sky Survey: VI. Optical identifications for the second data release.

A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems (2022)
Journal Article
Andonie, C., Alexander, D. M., Rosario, D., Laloux, B., Georgakakis, A., Morabito, L. K., Villforth, C., Avirett-Mackenzie, M., Rivera, G. C., Del Moro, A., Fotopoulou, S., Harrison, C., Lapi, A., Petley, J., Petter, G., & Shankar, F. (2022). A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems. Monthly Notices of the Royal Astronomical Society, 517(2), 2577-2598. https://doi.org/10.1093/mnras/stac2800

To understand the active galactic nuclei (AGNs) phenomenon and their impact on the evolution of galaxies, a complete AGN census is required; however, finding heavily obscured AGNs is observationally challenging. Here we use the deep and extensive mul... Read More about A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems.

Connecting radio emission to AGN wind properties with Broad Absorption Line Quasars (2022)
Journal Article
Petley, J., Morabito, L., Alexander, D., Rankine, A., Fawcett, V., Rosario, D., Matthews, J., Shimwell, T., & Drabent, A. (2022). Connecting radio emission to AGN wind properties with Broad Absorption Line Quasars. Monthly Notices of the Royal Astronomical Society, 515(4), 5159-5174. https://doi.org/10.1093/mnras/stac2067

Broad Absorption Line Quasars (BALQSOs) show strong signatures of powerful outflows, with the potential to alter the cosmic history of their host galaxies. These signatures are only seen in ∼10% of optically selected quasars, although the fraction si... Read More about Connecting radio emission to AGN wind properties with Broad Absorption Line Quasars.