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Published February 2020 | Published
Journal Article Open

Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53

Abstract

The observed properties of the Lyman-α (Ly α) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Ly α spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at z = 6.532 with moderate Ly α equivalent width (EW₀ ≈ 38 Å). These data are combined with deep resolved [CII]_(158μm) spectroscopy obtained with ALMA and UV imaging from HST and we also detect UV continuum with MUSE. Ly α emission is clearly detected with S/N ≈ 40 and FWHM of 374 km s⁻¹. Ly α and [C II] are similarly extended beyond the UV, with effective radius r_(eff) = 2.1 ± 0.2 kpc for a single exponential model or r_(eff,Lyα,halo) = 3.45^(+1.08)_(−0.87) kpc when measured jointly with the UV continuum. The Ly α profile is broader and redshifted with respect to the [C II] line (by 213 km s⁻¹), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components with plausibly different H I column densities. We place VR7 in the context of other galaxies at similar and lower redshift. The Ly α halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local (∼10 kpc) neutral gas conditions that determine the observed Ly α properties in VR7 resemble the conditions in post-reionization galaxies.

Additional Information

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 December 12. Received 2019 December 12; in original form 2019 September 10. Published: 20 December 2019. We thank the referee for their suggestions and constructive comments that helped to improve the presentation of our results. Based on observations obtained with the Very Large Telescope, program 99.A-0462. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #14699. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.01451.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. MG acknowledges support from NASA grant NNX17AK58G. GP and SC gratefully acknowledge support from Swiss National Science Foundation grant PP00P2_163824. BD acknowledges financial support from the National Science Foundation, grant number 1716907. We have benefited greatly from the public available programming language PYTHON, including the NUMPY, MATPLOTLIB, SCIPY (Jones et al. 2001; Hunter 2007; van der Walt, Colbert & Varoquaux 2011) and ASTROPY (Astropy Collaboration 2013) packages, the astronomical imaging tools SEXTRACTOR, SWARP, and SCAMP (Bertin & Arnouts 1996; Bertin 2006, 2010) and the TOPCAT analysis tool (Taylor 2013).

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Created:
August 19, 2023
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October 19, 2023