Reionization Era Bright Emission Line Survey: Selection and Characterization of Luminous Interstellar Medium Reservoirs in the z > 6.5 Universe

Abstract

The Reionization Era Bright Emission Line Survey (REBELS) is a cycle-7 ALMA Large Program (LP) that is identifying and performing a first characterization of many of the most luminous star-forming galaxies known in the z > 6.5 universe. REBELS is providing this probe by systematically scanning 40 of the brightest UV-selected galaxies identified over a 7 deg2 area for bright [C ii]158 μm and [O iii]88 μm lines and dust-continuum emission. Selection of the 40 REBELS targets was done by combining our own and other photometric selections, each of which is subject to extensive vetting using three completely independent sets of photometry and template-fitting codes. Building on the observational strategy deployed in two pilot programs, we are increasing the number of massive interstellar medium (ISM) reservoirs known at z > 6.5 by ∼4–5× to >30. In this manuscript, we motivate the observational strategy deployed in the REBELS program and present initial results. Based on the first-year observations, 18 highly significant ≥ 7σ [C ii]158 μm lines have already been discovered, the bulk of which (13/18) also show ≥3.3σ dust-continuum emission. These newly discovered lines more than triple the number of bright ISM-cooling lines known in the z > 6.5 universe, such that the number of ALMA-derived redshifts at z > 6.5 rival Lyα discoveries. An analysis of the completeness of our search results versus star formation rate (SFR) suggests an ∼79% efficiency in scanning for [C ii]158 μm when the SFRUV+IR is >28 M ⊙ yr−1. These new LP results further demonstrate ALMA’s efficiency as a “redshift machine,” particularly in the Epoch of Reionization.

Early Results from GLASS-JWST. XVI. Discovering a Bluer z ∼ 4–7 Universe through UV Slopes

“…Spectroscopic observations of high-z sources with Ly-α provide additional galaxy constraints on gas and dust geometries (e.g., Oesch et al 2015;Matthee et al 2018;Jung et al 2019), albeit with limitations (Leonova et al 2022;. Atacama Large Millimeter/submillimeter Array (ALMA) has been successful in detecting large numbers of sources at z > 6 in dust emission with high efficiency (e.g., Hashimoto et al 2018;Bouwens et al 2022c), but galaxy selections for ALMA follow-up are strongly biased toward UV bright sources (e.g., Bouwens et al 2022c). Thus, even with recent advancements, the formation timescales of galaxies in the early universe and their UV luminosity, mass, and dust evolution are not well constrained (Dayal et al 2022;Finkelstein et al 2022;Tacchella et al 2022).…”

Early Results from GLASS-JWST. I: Confirmation of Lensed z ≥ 7 Lyman-break Galaxies behind the Abell 2744 Cluster with NIRISS

“…Confirmations via Lyα (which is strongly affected by the surrounding intergalactic medium; Treu et al 2013;Mason et al 2019) and other rest-frame UV lines in the near-infrared (NIR) with, e.g., Keck and the Very Large Telescope (VLT), have seen limited success and been found predominantly in the most luminous sources (e.g., Vanzella et al 2011;Finkelstein et al 2015;Oesch et al 2015;Zitrin et al 2015;Roberts-Borsani et al 2016;Laporte et al 2017a;Stark et al 2017;Mainali et al 2018;Hoag et al 2019;Mason et al 2019;Endsley et al 2021;Laporte et al 2021;Roberts-Borsani et al 2022b). Atacama Large Millimeter/submillimeter Array (ALMA) has provided an alternate avenue for spectroscopic confirmation and characterization in the far-infrared (FIR), with an increasing number of [O III] 88 μm, [C II] 158 μm, and/or dust continuum detections (e.g., Laporte et al 2017b;Hashimoto et al 2018;Tamura et al 2019;Bouwens et al 2022a). However, in both cases high redshift observations are strongly affected by the intervening atmosphere of Earth, highlighting the need for space-based observations.…”

“…However, as one enters the reionization era, Lyα becomes a biased tracer of exceptional systems and environments due to its attenuation by a neutral intergalactic medium (IGM). FIR lines, in contrast, have only been observed in the most luminous, dusty, and starforming systems (e.g., Laporte et al 2017b;Bouwens et al 2022a). As such, a large and key population of LBGs that generally do not show Lyα emission (Giavalisco 2002;Shapley 2011) currently lack spectroscopic confirmations, potentially skewing our understanding of galaxy properties and our interpretation of the reionization process and its main drivers.…”

JWST Reveals a Possible z ∼ 11 Galaxy Merger in Triply Lensed MACS0647–JD

“…It then jointly tracks the buildup of dark matter halos and their baryonic components (gas, stellar, metal, and dust mass) between z ∼ 40-4.5 including the impact of both internal (supernova) and external (reionziation) feedback; here, we consider a case that ignores reionization feedback since reionization affects 20% of the volume of the universe at z ∼ 10.5 (Dayal et al 2020). The key strength of this model lies in its minimal free parameters (the star formation efficiency and fraction of supernova energy coupling to gas) and the fact that is it baselined against all available high-z data sets including the evolving UV luminosity function, the stellar mass function, and the most recent dust estimates at z ∼ 7 from the Reionization Era Bright Emission Line Survey ALMA large program (Bouwens et al 2022).…”