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Dr Rebecca Bowler

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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
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  • Publications

The discovery of rest-frame UV colour gradients and a diversity of dust morphologies in bright z ≃ 7 Lyman-break galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press 510:4 (2021) 5088-5101

Authors:

Raa Bowler, F Cullen, Rj McLure, Js Dunlop, A Avison

Abstract:

We present deep ALMA dust continuum observations for a sample of luminous (MUV < −22) star-forming galaxies at z ≃ 7. We detect five of the six sources in the far-infrared (FIR), providing key constraints on the obscured star-formation rate (SFR) and the infrared-excess-β (IRX–β) relation without the need for stacking. Despite the galaxies showing blue rest-frame UV slopes (β ≃ −2) we find that 35–75 percent of the total SFR is obscured. We find the IRX–β relation derived for these z ≃ 7 sources is consistent with that found for local star-burst galaxies. Using our relatively high-resolution (FWHM ≃ 0.7 arcsec) observations we identify a diversity of dust morphologies in the sample. We find both compact emission that appears offset relative to the unobscured components and extended dust emission that is co-spatial with the rest-frame UV light. In the majority of the sources we detect strong rest-frame UV colour gradients (with up to Δβ ≃ 0.7–1.4) as probed by the multi-band UltraVISTA ground-based data. The observed redder colours are spatially correlated with the location of the FIR detection. Our results show that even in bright Lyman-break galaxies at z ≃ 7 the peak of the star-formation is typically hosted by the fainter, redder, regions in the rest-frame UV, which have an obscured fraction of fobs ≥ 0.8. As well as demonstrating the importance of dust obscured star-formation within the Epoch of Reionization, these observations provide an exciting taster of the rich spatially resolved datasets that will be obtained from JWST and high-resolution ALMA follow-up at these redshifts.
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A deep radio view of the evolution of the cosmic star formation rate density from a stellar-mass-selected sample in VLA-COSMOS

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 509:3 (2021) 4291-4307

Authors:

Eliab D Malefahlo, Matt J Jarvis, Mario G Santos, Sarah V White, Nathan J Adams, Rebecca AA Bowler
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MIGHTEE-H I: the baryonic Tully-Fisher relation over the last billion years

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 508:1 (2021) 1195-1205

Authors:

Anastasia A Ponomareva, Wanga Mulaudzi, Natasha Maddox, Bradley S Frank, Matt J Jarvis, Enrico M Di Teodoro, Marcin Glowacki, Renee C Kraan-Korteweg, Tom A Oosterloo, Elizabeth AK Adams, Hengxing Pan, Isabella Prandoni, Sambatriniaina HA Rajohnson, Francesco Sinigaglia, Nathan J Adams, Ian Heywood, Rebecca AA Bowler, Peter W Hatfield, Jordan D Collier, Srikrishna Sekhar
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Normal, dust-obscured galaxies in the epoch of reionization.

Nature 597:7877 (2021) 489-492

Authors:

Y Fudamoto, PA Oesch, S Schouws, M Stefanon, R Smit, RJ Bouwens, RAA Bowler, R Endsley, V Gonzalez, H Inami, I Labbe, D Stark, M Aravena, L Barrufet, E da Cunha, P Dayal, A Ferrara, L Graziani, J Hodge, A Hutter, Y Li, I De Looze, T Nanayakkara, A Pallottini, D Riechers, R Schneider, G Ucci, P van der Werf, C White

Abstract:

Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6 (refs. 1-3), during the so-called epoch of reionization. While a few of these UV-identified galaxies revealed substantial dust reservoirs4-7, very heavily dust-obscured sources at these early times have remained elusive. They are limited to a rare population of extreme starburst galaxies8-12 and companions of rare quasars13,14. These studies conclude that the contribution of dust-obscured galaxies to the cosmic star formation rate density at z > 6 is sub-dominant. Recent ALMA and Spitzer observations have identified a more abundant, less extreme population of obscured galaxies at z = 3-6 (refs. 15,16). However, this population has not been confirmed in the reionization epoch so far. Here, we report the discovery of two dust-obscured star-forming galaxies at z = 6.6813 ± 0.0005 and z = 7.3521 ± 0.0005. These objects are not detected in existing rest-frame UV data and were discovered only through their far-infrared [C II] lines and dust continuum emission as companions to typical UV-luminous galaxies at the same redshift. The two galaxies exhibit lower infrared luminosities and star-formation rates than extreme starbursts, in line with typical star-forming galaxies at z ≈ 7. This population of heavily dust-obscured galaxies appears to contribute 10-25% to the z > 6 cosmic star formation rate density.
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MIGHTEE-HI: discovery of an H I-rich galaxy group at z = 0.044 with MeerKAT

Monthly Notices of the Royal Astronomical Society Oxford University Press 506:2 (2021) 2753-2765

Authors:

Shilpa Ranchod, Roger P Deane, Anastasia Ponomareva, Tariq Blecher, Bradley S Frank, Matthew Jarvis, Natasha Maddox, Wanga Mulaudzi, Marcin Glowacki, Kelley M Hess, Madalina Tudorache, Nathan J Adams, Rebecca Bowler, Jordan D Collier, Russ Taylor, Lourdes Verdes-Montenegro

Abstract:

We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H I in this z ∼ 0.044 group, with a 3σ column density sensitivity of NHI=1.6×1020cm−2⁠. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H I total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of log10(Mdyn/M⊙)=12.32⁠, and is unusually gas-rich, with an H I-to-stellar mass ratio of log10(f∗HI)=−0.2⁠, which is 0.7 dex greater than expected. The group’s high H I content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H I in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope.
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