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Endsley, R, Stark, DP, Bouwens, RJ, Schouws, S, Smit, R, Stefanon, M, Inami, H, Bowler, RAA, Oesch, P, Gonzalez, V, Aravena, M, Da Cunha, E, Dayal, P, Ferrara, A, Graziani, L, Nanayakkara, T, Pallottini, A, Schneider, R, Sommovigo, L, Topping, M , Van Der Werf, P and Hutter, A (2022) The REBELS ALMA Survey: efficient Ly α transmission of UV-bright z ≃ 7 galaxies from large velocity offsets and broad line widths. Monthly Notices of the Royal Astronomical Society, 517 (4). pp. 5642-5659. ISSN 0035-8711
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The REBELS ALMA Survey efficient Ly α transmission of UV-bright z ≃ 7 galaxies from large velocity offsets and broad line widths.pdf - Published Version Download (2MB) | Preview |
Abstract
Recent work has shown that UV-luminous reionization-era galaxies often exhibit strong Lyman-alpha emission despite being situated at redshifts where the IGM is thought to be substantially neutral. It has been argued that this enhanced Ly α transmission reflects the presence of massive galaxies in overdense regions which power large ionized bubbles. An alternative explanation is that massive galaxies shift more of their Ly α profile to large velocities (relative to the systemic redshift) where the IGM damping wing absorption is reduced. Such a mass-dependent trend is seen at lower redshifts, but whether one exists at z ∼7 remains unclear owing to the small number of existing systemic redshift measurements in the reionization era. This is now changing with the emergence of [C ii]-based redshifts from ALMA. Here, we report MMT/Binospec Ly α spectroscopy of eight UV-bright (MUV ∼-22) galaxies at z ≃ 7 selected from the ALMA REBELS survey. We detect Ly α in four of eight galaxies and use the [C ii] systemic redshifts to investigate the Ly α velocity profiles. The Ly α lines are significantly redshifted from systemic (average velocity offset = 223 km s-1) and broad (FWHM ≈ 300-650 km s-1), with two sources showing emission extending to ≈750 km s-1. We find that the broadest Ly α profiles are associated with the largest [C ii] line widths, suggesting a potential link between the Ly α FWHM and the dynamical mass. Since Ly α photons at high velocities transmit efficiently through the z = 7 IGM, our data suggest that velocity profiles play a significant role in boosting the Ly α visibility of the most UV-luminous reionization-era galaxies.
| Item Type: | Article |
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| Additional Information: | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
| Uncontrolled Keywords: | 0201 Astronomical and Space Sciences; Astronomy & Astrophysics |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | Oxford University Press (OUP) |
| SWORD Depositor: | A Symplectic |
| Date Deposited: | 09 Jan 2023 12:44 |
| Last Modified: | 09 Jan 2023 12:45 |
| DOI or ID number: | 10.1093/mnras/stac3064 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/18565 |
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