REBELS-25: discovery of a dynamically cold disc galaxy at z = 7.31

ABSTRACT We present high-resolution ($\sim 0.14$ arcsec = 710 pc) Atacama Large Millimetre/submillimetre Array [C ii] 158 $\mu$m and dust continuum follow-up observations of REBELS-25, a [C ii]-luminous ($L_{\mathrm{[CII]}}=(1.7\pm 0.2)\times 10^9\, \mathrm{L_{\odot }}$) galaxy at redshift $z=7.3065\pm 0.0001$. These high-resolution, high signal-to-noise observations allow us to study the sub-kpc morphology and kinematics of this massive ($M_* = 8^{+4}_{-2} \times 10^9 \mathrm{{\rm M}_{\odot }}$) star-forming (SFR$_{\mathrm{UV+IR}} = 199^{+101}_{-63} \mathrm{{\rm M}_{\odot }} \mathrm{yr}^{-1}$) galaxy in the Epoch of Reionization. By modelling the kinematics with $^{\mathrm{3D}}$BAROLO, we find it has a low-velocity dispersion ($\bar{\sigma } = 33^{+9}_{-7}$ km s$^{-1}$) and a high ratio of ordered-to-random motion ($V_{\mathrm{rot, ~max}}/\bar{\sigma } = 11 ^{+6}_{-5}$), indicating that REBELS-25 is a dynamically cold disc. Additionally, we find that the [C ii] distribution is well fit by a near-exponential disc model, with a Sérsic index, n, of $1.3 \pm 0.2$, and we see tentative evidence of more complex non-axisymmetric structures suggestive of a bar in the [C ii] and dust continuum emission. By comparing to other high spatial resolution cold gas kinematic studies, we find that dynamically cold discs seem to be more common in the high-redshift Universe than expected based on prevailing galaxy formation theories, which typically predict more turbulent and dispersion-dominated galaxies in the early Universe as an outcome of merger activity, gas accretion, and more intense feedback. This higher degree of rotational support seems instead to be consistent with recent cosmological simulations that have highlighted the contrast between cold and warm ionized gas tracers, particularly for massive galaxies. We therefore show that dynamically settled disc galaxies can form as early as 700 Myr after the big bang

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-10-07
DOI
https://doi.org/10.1093/mnras/stae2217
Citations
52
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
26.33

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article

REBELS-25: discovery of a dynamically cold disc galaxy at z = 7.31

Pratika Dayal, A. Pallottini, Ilse De Looze, A. P. S. Hygate et al.
52 citations
Monthly Notices of the Royal Astronomical Society
Astronomy and Astrophysical Research
26.33
article

REBELS-25: discovery of a dynamically cold disc galaxy at z = 7.31

Pratika Dayal, A. Pallottini, Ilse De Looze, A. P. S. Hygate, Jacqueline Hodge, Sander Schouws, Andrea Ferrara, Thomas Herard-Demanche, Matus Rybak, R. J. Bouwens, Mauro Stefanon, Hanae Inami, Ivana van Leeuwen, Lucie E. Rowland, Hiddo Algera, Siân Phillips, Pavel E. Mancera Piña, P. van der Werf, R. A. A. Bowler, Pascal A. Oesch, Elisabete da Cunha, Manuel Aravena, Renske Smit, Laura Sommovigo
article en
52 citations

Abstract

ABSTRACT We present high-resolution ($\sim 0.14$ arcsec = 710 pc) Atacama Large Millimetre/submillimetre Array [C ii] 158 $\mu$m and dust continuum follow-up observations of REBELS-25, a [C ii]-luminous ($L_{\mathrm{[CII]}}=(1.7\pm 0.2)\times 10^9\, \mathrm{L_{\odot }}$) galaxy at redshift $z=7.3065\pm 0.0001$. These high-resolution, high signal-to-noise observations allow us to study the sub-kpc morphology and kinematics of this massive ($M_* = 8^{+4}_{-2} \times 10^9 \mathrm{{\rm M}_{\odot }}$) star-forming (SFR$_{\mathrm{UV+IR}} = 199^{+101}_{-63} \mathrm{{\rm M}_{\odot }} \mathrm{yr}^{-1}$) galaxy in the Epoch of Reionization. By modelling the kinematics with $^{\mathrm{3D}}$BAROLO, we find it has a low-velocity dispersion ($\bar{\sigma } = 33^{+9}_{-7}$ km s$^{-1}$) and a high ratio of ordered-to-random motion ($V_{\mathrm{rot, ~max}}/\bar{\sigma } = 11 ^{+6}_{-5}$), indicating that REBELS-25 is a dynamically cold disc. Additionally, we find that the [C ii] distribution is well fit by a near-exponential disc model, with a Sérsic index, n, of $1.3 \pm 0.2$, and we see tentative evidence of more complex non-axisymmetric structures suggestive of a bar in the [C ii] and dust continuum emission. By comparing to other high spatial resolution cold gas kinematic studies, we find that dynamically cold discs seem to be more common in the high-redshift Universe than expected based on prevailing galaxy formation theories, which typically predict more turbulent and dispersion-dominated galaxies in the early Universe as an outcome of merger activity, gas accretion, and more intense feedback. This higher degree of rotational support seems instead to be consistent with recent cosmological simulations that have highlighted the contrast between cold and warm ionized gas tracers, particularly for massive galaxies. We therefore show that dynamically settled disc galaxies can form as early as 700 Myr after the big bang

Monthly Notices of the Royal Astronomical SocietyVol. 535(3)
Hiroshima University (JP), University of Geneva (CH), Leiden University (NL), Scuola Normale Superiore (IT), Universitat de València (ES), University of Groningen (NL), The University of Western Australia (AU), University of Manchester (GB), Ghent University (BE), DAWN Center for Independent Living (US), Instituto de Física de Cantabria (ES), Flatiron Health (United States) (US), ARC Centre of Excellence for All-sky Astrophysics (AU), National Astronomical Observatory of Japan (JP), International Centre for Radio Astronomy Research (AU), Flatiron Institute (US), Space Research Organisation Netherlands (NL), Liverpool John Moores University (GB), Universidad Diego Portales (CL), Delft University of Technology (NL)
European Commission, Rijksuniversiteit Groningen, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Agencia Nacional de Investigación y Desarrollo, Horizon 2020 Framework Programme, Science and Technology Facilities Council, Fondo Nacional de Desarrollo Científico y Tecnológico, H2020 European Research Council
Openalex Percentile: Top 0%
Astronomy and Astrophysical Research
26.33
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