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ALMA as a Redshift Machine: Using [C ii] to Efficiently Confirm Galaxies in the Epoch of Reionization

Schouws, S, Bouwens, R, Smit, R, Hodge, J, Stefanon, M, Witstok, J, Hilhorst, J, Labbé, I, Algera, H, Boogaard, L, Maseda, M, Oesch, P, Röttgering, H and van der Werf, P (2023) ALMA as a Redshift Machine: Using [C ii] to Efficiently Confirm Galaxies in the Epoch of Reionization. Astrophysical Journal, 954 (1). ISSN 0004-637X

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The [C ii]158μm line has long been proposed as a promising line to spectroscopically confirm galaxies in the epoch of reionization. In this paper, we present the results of new ALMA observations spectral scanning for [C ii] in six particularly luminous Lyman-break galaxies at z ∼ 7. The six sources were drawn from a sample of bright z ∼ 7 galaxies identified using the wide-area optical, near-IR, and Spitzer/IRAC data over the COSMOS/UltraVISTA field and were targeted on the basis of tight constraints on their redshifts from their IRAC [3.6]-[4.5] colors. We detect significant (>9σ) [C ii] lines in three of our six targets (50%) cospatial with the rest-UV emission from the ground/space-based near-IR imaging. The luminosities of the [C ii] lines lie in the range 5.6-8.8 × 108 L ⊙, consistent with the local [C ii]-SFR relation. Meanwhile, their [C ii]/L IR ∼ 1-3 × 10−3 ratios are slightly elevated compared to local (U)LIRGS. This could be due to lower dust-to-gas or dust-to-metal ratios. We also find that our sources display a large kinematic diversity, with one source showing signs of rotation, one source a likely major merger, and one dispersion-dominated source that might contain a bright star-forming clump. Our results highlight the effectiveness of spectral scans with ALMA in spectroscopically confirming luminous galaxies in the epoch of reionization, something that is being be applied on a significantly larger sample in the ongoing REBELS large program.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
SWORD Depositor: A Symplectic
Date Deposited: 12 Dec 2023 13:13
Last Modified: 12 Dec 2023 13:15
DOI or ID number: 10.3847/1538-4357/ace10c
URI: https://researchonline.ljmu.ac.uk/id/eprint/22085
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