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

Schouws, S ORCID: 0000-0001-9746-0924, Bouwens, R ORCID: 0000-0002-4989-2471, Smit, R ORCID: 0000-0001-8034-7802, Hodge, J ORCID: 0000-0001-6586-8845, Stefanon, M ORCID: 0000-0001-7768-5309, Witstok, J ORCID: 0000-0002-7595-121X, Hilhorst, J ORCID: 0000-0001-5919-2295, Labbé, I ORCID: 0000-0002-2057-5376, Algera, H ORCID: 0000-0002-4205-9567, Boogaard, L ORCID: 0000-0002-3952-8588, Maseda, M ORCID: 0000-0003-0695-4414, Oesch, P ORCID: 0000-0001-5851-6649, Röttgering, H ORCID: 0000-0001-8887-2257 and van der Werf, P ORCID: 0000-0001-5434-5942 (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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Abstract

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
Date of acceptance:	21 June 2023
Date of first compliant Open Access:	12 December 2023
Date Deposited:	12 Dec 2023 13:13
Last Modified:	04 Jul 2025 15:15
DOI or ID number:	10.3847/1538-4357/ace10c
URI:	https://researchonline.ljmu.ac.uk/id/eprint/22085

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