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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Andrew Bunker

Professor of Astrophysics

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Galaxy formation and evolution
Andy.Bunker@physics.ox.ac.uk
Telephone: 01865 (2)83126
Denys Wilkinson Building, room 702
  • About
  • Publications

Growing a nuclear star cluster from star formation and cluster mergers: The JWST NIRSpec view of NGC 4654⋆

Astronomy & Astrophysics EDP Sciences 687 (2024) a83

Authors:

Katja Fahrion, Torsten Böker, Michele Perna, Tracy L Beck, Roberto Maiolino, Santiago Arribas, Andrew J Bunker, Stephane Charlot, Matteo Ceci, Giovanni Cresci, Guido De Marchi, Nora Lützgendorf, Lorenzo Ulivi
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JADES

Astronomy & Astrophysics EDP Sciences 687 (2024) a67

Authors:

Roberto Maiolino, Hannah Übler, Michele Perna, Jan Scholtz, Francesco D’Eugenio, Callum Witten, Nicolas Laporte, Joris Witstok, Stefano Carniani, Sandro Tacchella, William M Baker, Santiago Arribas, Kimihiko Nakajima, Daniel J Eisenstein, Andrew J Bunker, Stéphane Charlot, Giovanni Cresci, Mirko Curti, Emma Curtis-Lake, Anna de Graaff, Eiichi Egami, Zhiyuan Ji, Benjamin D Johnson, Nimisha Kumari, Tobias J Looser, Michael Maseda, Erica Nelson, Brant Robertson, Bruno Rodríguez Del Pino, Lester Sandles, Charlotte Simmonds, Renske Smit, Fengwu Sun, Giacomo Venturi, Christina C Williams, Christopher NA Willmer
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Nebular dominated galaxies: insights into the stellar initial mass function at high redshift

Monthly Notices of the Royal Astronomical Society Oxford University Press (2024)

Authors:

Alex Cameron, Harley Katz, Callum Witten, Aayush Saxena, Nicolas Laporte, Andrew Bunker

Abstract:

We identify a low-metallicity (12 + log(O/H) = 7.59) Ly𝛼-emitting galaxy at 𝑧 = 5.943 with evidence of a strong Balmer jump, arising from nebular continuum. While Balmer jumps are sometimes observed in low-redshift star-forming galaxies, this galaxy also exhibits a steep turnover in the UV continuum. Such turnovers are typically attributed to absorption by a damped Ly𝛼 system (DLA); however, the shape of the turnover and the high observed Ly𝛼 escape fraction ( 𝑓esc,Ly𝛼 ∼ 27%) is also consistent with strong nebular two-photon continuum emission. Modelling the UV turnover with a DLA requires extreme column densities (𝑁HI > 1023 cm−2 ), and simultaneously explaining the high 𝑓esc,Ly𝛼 requires a fine-tuned geometry. In contrast, modelling the spectrum as primarily nebular provides a good fit to both the continuum and emission lines, motivating scenarios in which (a) we are observing only nebular emission or (b) the ionizing source is powering extreme nebular emission that outshines the stellar emission. The nebular-only scenario could arise if the ionising source has ‘turned off’ more recently than the recombination timescale (∼1,000 yr), hence we may be catching the object at a very specific time. Alternatively, hot stars with 𝑇eff ≳ 105 K (e.g. Wolf-Rayet or low-metallicity massive stars) produce enough ionizing photons such that the two-photon emission becomes visible. While several stellar SEDs from the literature fit the observed spectrum well, the hot-star scenario requires that the number of ≳ 50 M⊙ stars relative to ∼ 5 − 50 M⊙ stars is significantly higher than predicted by typical stellar initial mass functions (IMFs). The identification of more galaxies with similar spectra may provide evidence for a top-heavy IMF at high redshift.
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JADES: Physical properties of Ly$\alpha$ and non-Ly$\alpha$ emitters at z ~ 4.8-9.6

(2024)

Authors:

Nimisha Kumari, Renske Smit, Joris Witstok, Marco Sirianni, Roberto Maiolino, Andrew J Bunker, Rachana Bhatawdekar, Kristan Boyett, Alex J Cameron, Stefano Carniani, Stephane Charlot, Mirko Curti, Emma Curtis-Lake, Francesco D'Eugenio, Daniel J Eisenstein, Kevin Hainline, Zhiyuan Ji, Gareth C Jones, Brant Robertson, Aayush Saxena, Jan Scholtz, Charlotte Simmonds, Christina C Williams, Christopher NA Willmer
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GA-NIFS: JWST/NIRSpec IFS view of the z~3.5 galaxy GS5001 and its close environment at the core of a large-scale overdensity

(2024)

Authors:

Isabella Lamperti, Santiago Arribas, Michele Perna, Bruno Rodríguez Del Pino, Chiara Circosta, Pablo G Pérez-González, Andrew J Bunker, Stefano Carniani, Stéphane Charlot, Francesco D'Eugenio, Roberto Maiolino, Hannah Übler, Chris J Willott, Elena Bertola, Torsten Böker, Giovanni Cresci, Mirko Curti, Gareth C Jones, Nimisha Kumari, Eleonora Parlanti, Jan Scholtz, Giacomo Venturi
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