Skip to main content
Home
Department Of Physics text logo
  • Research
    • Our research
    • Our research groups
    • Our research in action
    • Research funding support
    • Summer internships for undergraduates
  • Study
    • Undergraduates
    • Postgraduates
  • Engage
    • For alumni
    • For business
    • For schools
    • For the public
Menu
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.

Dr Rebecca Bowler

Visitor

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Beecroft Institute for Particle Astrophysics and Cosmology
  • Galaxy formation and evolution
rebecca.bowler@physics.ox.ac.uk
  • About
  • Brief CV
  • Talks
  • ED&I
  • Links
  • Teaching
  • Publications

Angular correlation functions of bright Lyman-break galaxies at 3 ≲ z ≲ 5

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1651

Authors:

Isabelle Ye, Philip Bull, Rebecca AA Bowler, Rachel K Cochrane, Nathan J Adams, Matt J Jarvis

Abstract:

Abstract We investigate the clustering of Lyman-break galaxies at redshifts of 3 ≲ z ≲ 5 within the COSMOS field by measuring the angular two-point correlation function. Our robust sample of ~60,000 bright (mUV ≲ 27) Lyman-break galaxies was selected based on spectral energy distribution fitting across 14 photometric bands spanning optical and near-infrared wavelengths. We constrained both the 1- and 2-halo terms at separations up to 300 arcsec, finding an excess in the correlation function at scales corresponding to <20 kpc, consistent with enhancement due to clumps in the same galaxy or interactions on this scale. We then performed Bayesian model fits on the correlation functions to infer the Halo Occupation Distribution parameters, star formation duty cycle, and galaxy bias in three redshift bins. We examined several cases where different combinations of parameters were varied, showing that our data can constrain the slope of the satellite occupation function, which previous studies have fixed. For an MUV-limited sub-sample, we found galaxy bias values of $b_g=3.18^{+0.14}_{-0.14}$ at z ≃ 3, $b_g=3.58^{+0.27}_{-0.29}$ at z ≃ 4, $b_g=4.27^{+0.25}_{-0.26}$ at z ≃ 5. The duty cycle values are $0.62^{+0.25}_{-0.26}$, $0.40^{+0.34}_{-0.22}$, and $0.39^{+0.31}_{-0.20}$,respectively. These results suggest that, as the redshift increases, there is a slight decrease in the host halo masses and a shorter timescale for star formation in bright galaxies, at a fixed rest-frame UV luminosity threshold.
More details from the publisher

Evidence for inverse Compton scattering in high-redshift Lyman-break galaxies

Monthly Notices of the Royal Astronomical Society (2025) staf1505

Authors:

IH Whittam, MJ Jarvis, Eric J Murphy, NJ Adams, RAA Bowler, A Matthews, RG Varadaraj, CL Hale, I Heywood, K Knowles, L Marchetti, N Seymour, F Tabatabaei, AR Taylor, M Vaccari, A Verma

Abstract:

Radio continuum emission provides a unique opportunity to study star-formation unbiased by dust obscuration. However, if radio observations are to be used to accurately trace star-formation to high redshifts, it is crucial that the physical processes which affect the radio emission from star-forming galaxies are well understood. While inverse Compton (IC) losses from the cosmic microwave background (CMB) are negligible in the local universe, the rapid increase in the strength of the CMB energy density with redshift [∼(1 + z)4] means that this effect becomes increasingly important at z ≳ 3. Using a sample of ∼200, 000 high-redshift (3 < z < 5) Lyman-break galaxies selected in the rest-frame ultraviolet (UV), we have stacked radio observations from the MIGHTEE survey to estimate their 1.4-GHz flux densities. We find that for a given rest-frame UV magnitude, the 1.4-GHz flux density and luminosity decrease with redshift. We compare these results to the theoretical predicted effect of energy losses due to inverse Compton scattering off the CMB, and find that the observed decrease is consistent with this explanation. We discuss other possible causes for the observed decrease in radio flux density with redshift at a given UV magnitude, such as a top-heavy initial mass function at high redshift or an evolution of the dust properties, but suggest that inverse Compton scattering is the most compelling explanation.
More details from the publisher

The ALMA-CRISTAL survey: Resolved kinematic studies of main sequence star-forming galaxies at 4 < z < 6

Astronomy and Astrophysics 701 (2025)

Authors:

LL Lee, NM Förster Schreiber, R Herrera-Camus, D Liu, SH Price, R Genzel, LJ Tacconi, D Lutz, R Davies, T Naab, H Übler, M Aravena, RJ Assef, L Barcos-Muñoz, RAA Bowler, A Burkert, J Chen, RL Davies, I De Looze, T Diaz-Santos, J González-López, R Ikeda, I Mitsuhashi, A Posses, M Relaño Pastor, A Renzini, M Solimano, JS Spilker, A Sternberg, K Tadaki, K Telikova, S Veilleux, V Villanueva

Abstract:

We present a detailed kinematic study of a sample of 32 massive (9.5 ⩽ log(M */M⊙) ⩽ 10.9) main sequence star-forming galaxies (MS SFGs) at 4 < z < 6 from the ALMA-CRISTAL programme. The data consist of deep (up to 15 hr observing time per target), high-resolution (∼1 kpc) ALMA observations of [C II]158 μm line emission. This dataset allowed us to carry out the first systematic, kiloparsec-scale (kpc-scale) characterisation of the kinematics nature of typical massive SFGs at these epochs. We find that ∼50% of the sample are disk-like, with a number of galaxies located in systems of multiple components. Kinematic modelling reveals these main sequence disks exhibit high-velocity dispersions (σ 0), with a median disk velocity dispersion of ∼70 km s−1 and V rot/σ 0 ∼ 2, which is consistent with dominant gravity driving. The elevated disk dispersions are in line with the predicted evolution based on Toomre theory and the extrapolated trends from z ∼ 0–2.5 MS star-forming disks. The inferred dark matter (DM) mass fraction within the effective radius f DM(< R e) for the disk systems decreases with the central baryonic mass surface density. This is consistent with the trend reported by kinematic studies at z ≲ 3; roughly half the disks display f DM(< R e)≲ 30%. The CRISTAL sample of massive MS SFGs provides a reference of the kinematics of a representative population and extends the view onto typical galaxies beyond previous kpc-scale studies at z ≲ 3.
More details from the publisher

The ALMA REBELS survey: [OIII]88μm line scans of UV-bright z ≳ 7.6 galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1287

Authors:

IF van Leeuwen, RJ Bouwens, JA Hodge, PP van der Werf, HSB Algera, S Schouws, M Aravena, RAA Bowler, P Dayal, A Ferrara, R Fisher, Y Fudamoto, C Gulis, T Herard-Demanche, H Inami, I de Looze, A Pallottini, R Smit, L Sommovigo, M Stefanon

Abstract:

Abstract We present the [OIII]88μm spectral scan results from the ALMA Large Program REBELS (Reionization Era Bright Emission Line Survey). The generally high luminosity of [OIII]88μm and ALMA’s Band 7 efficiency motivated its use for line scans of REBELS targets at z > 8. Spectral scans of four sources covered 326.4-373.0 GHz (z = 8.10-9.39), reaching [OIII]88μm luminosities of ∼7.6 × 108 L⊙ (5σ) for a FWHM of 400 km s−1. No credible lines are detected for the four targets. For REBELS-04, the non-detection is unexpected given the ≥92% coverage of the redshift likelihood distribution and its estimated SFR of 40 M⊙ yr−1. Possible explanations for the faint [OIII]88μm emission (assuming a FWHM of 100 km s−1) include high ISM densities (>ncrit ≈ 510 cm−3) and low ionization parameters (log10 Uion ≲ −2.5). For REBELS-37, a subsequent detection of [CII]158μm (z = 7.643) confirmed it lay outside our scan range. For REBELS-11 and REBELS-13, it remains unclear if the non-detection is due to the depth of the line scan or redshift coverage. REBELS-04 and REBELS-37 show significant (≥3.8σ) dust continuum emission in Band 7. If the photometric redshift of REBELS-04 is accurate, i.e., $z_{\mathrm{phot}}=8.57^{+0.10}_{-0.09}$ or $z_{\mathrm{phot}}=8.43^{+0.10}_{-0.10}$ accounting for additional neutral hydrogen in the circumgalactic medium, REBELS-04 would constitute the most distant dust-detected galaxy identified with ALMA to date. Additional Band 6 dust observations of REBELS-37 constrain the shape of the far-IR SED, ruling out cold dust temperatures (≲ 28 K) at 3σ. Further insight into these galaxies will require spectroscopic redshifts and deeper multi-band dust observations.
More details from the publisher
More details

MIGHTEE: A first look at MIGHTEE quasars

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1187

Authors:

Sarah V White, Ivan Delvecchio, Nathan Adams, Ian Heywood, Imogen H Whittam, Catherine L Hale, Neo Namane, Rebecca AA Bowler, Jordan D Collier

Abstract:

Abstract In this work we study a robust, Ks-band complete, spectroscopically-confirmed sample of 104 unobscured (Type-1) quasars within the COSMOS and XMM-LSS fields of the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, at 0.60 < zspec < 3.41. The quasars are selected via gJKs colour-space and, with 1.3-GHz flux-densities reaching rms ≈ 3.0 μ Jy beam−1, we find a radio-loudness fraction of 5percnt. Thanks to the deep, multiwavelength datasets that are available over these fields, the properties of radio-loud and radio-quiet quasars can be studied in a statistically-robust way, with the emphasis of this work being on the active-galactic-nuclei (AGN)-related and star-formation-related contributions to the total radio emission. We employ multiple star-formation-rate estimates for the analysis so that our results can be compared more-easily with others in the literature, and find that the fraction of sources that have their radio emission dominated by the AGN crucially depends on the SFR estimate that is derived from the radio luminosity. When redshift dependence is not taken into account, a larger fraction of sources is classed as having their radio emission dominated by the AGN. When redshift dependence is considered, a larger fraction of our sample is tentatively classed as ‘starbursts’. We also find that the fraction of (possible) starbursts increases with redshift, and provide multiple suggestions for this trend.
More details from the publisher

Pagination

  • Current page 1
  • Page 2
  • Page 3
  • Page 4
  • Page 5
  • Page 6
  • Page 7
  • Page 8
  • Page 9
  • …
  • Next page Next
  • Last page Last

Footer Menu

  • Contact us
  • Giving to the Dept of Physics
  • Work with us
  • Media

User account menu

  • Log in

Follow us

FIND US

Clarendon Laboratory,

Parks Road,

Oxford,

OX1 3PU

CONTACT US

Tel: +44(0)1865272200

University of Oxfrod logo Department Of Physics text logo
IOP Juno Champion logo Athena Swan Silver Award logo

© University of Oxford - Department of Physics

Cookies | Privacy policy | Accessibility statement

Built by: Versantus

  • Home
  • Research
  • Study
  • Engage
  • Our people
  • News & Comment
  • Events
  • Our facilities & services
  • About us
  • Current students
  • Staff intranet