Dusty Starbursts Masquerading as Ultra-high Redshift Galaxies in JWST CEERS Observations

Jorge A. Zavala , Véronique Buat (1) , Caitlin M. Casey , Steven L. Finkelstein , Denis Burgarella (1) , Micaela B. Bagley , Laure Ciesla (1) , Emanuele Daddi (2) , Mark Dickinson , Henry C. Ferguson , Maximilien Franco , E. F. Jiménez-Andrade , Jeyhan S. Kartaltepe , Anton M. Koekemoer , Aurélien Le Bail (2) , E. J. Murphy , Casey Papovich , Sandro Tacchella , Stephen M. Wilkins , Itziar Aretxaga , Peter Behroozi , Jaclyn B. Champagne , Adriano Fontana , Mauro Giavalisco , Andrea Grazian , Norman A. Grogin , Lisa J. Kewley , Dale D. Kocevski , Allison Kirkpatrick , Jennifer M. Lotz , Laura Pentericci , Pablo G. Pérez-González , Nor Pirzkal , Swara Ravindranath , Rachel S. Somerville , Jonathan R. Trump , Guang Yang , L. Y. Aaron Yung , Omar Almaini , Ricardo O. Amorín , Marianna Annunziatella , Pablo Arrabal Haro , Bren E. Backhaus , Guillermo Barro , Eric F. Bell , Rachana Bhatawdekar , Laura Bisigello , Fernando Buitrago , Antonello Calabrò , Marco Castellano , Óscar A. Chávez Ortiz , Katherine Chworowsky , Nikko J. Cleri , Seth H. Cohen , Justin W. Cole , Kevin C. Cooke , M. C. Cooper , Asantha R. Cooray , Luca Costantin , Isabella G. Cox , Darren Croton , Romeel Davé , Alexander de La Vega , Avishai Dekel , David Elbaz (2) , Vicente Estrada-Carpenter , Vital Fernández , Keely D. Finkelstein , Jonathan Freundlich (3) , Seiji Fujimoto , Ángela García-Argumánez , Jonathan P. Gardner , Eric Gawiser , Carlos Gómez-Guijarro (2) , Yuchen Guo , Timothy S. Hamilton , Nimish P. Hathi , Benne W. Holwerda , Michaela Hirschmann , Marc Huertas-Company , Taylor A. Hutchison , Kartheik G. Iyer , Anne E. Jaskot , Saurabh W. Jha , Shardha Jogee , Stéphanie Juneau , Intae Jung , Susan A. Kassin , Peter Kurczynski , Rebecca L. Larson , Gene C. K. Leung , Arianna S. Long , Ray A. Lucas , Benjamin Magnelli (2) , Kameswara Bharadwaj Mantha , Jasleen Matharu , Elizabeth J. Mcgrath , Daniel H. Mcintosh , Aubrey Medrano , Emiliano Merlin , Bahram Mobasher , Alexa M. Morales , Jeffrey A. Newman , David C. Nicholls , Viraj Pandya , Marc Rafelski , Kaila Ronayne , Caitlin Rose , Russell E. Ryan , Paola Santini , Lise-Marie Seillé (1) , Ekta A. Shah , Lu Shen , Raymond C. Simons , Gregory F. Snyder , Elizabeth R. Stanway , Amber N. Straughn , Harry I. Teplitz , Brittany N. Vanderhoof , Jesús Vega-Ferrero , Weichen Wang , Benjamin J. Weiner , Christopher N. A. Willmer , Stijn Wuyts

1 LAM - Laboratoire d'Astrophysique de Marseille
2 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
3 ObAS - Observatoire astronomique de Strasbourg

Lyman-break galaxy (LBG) candidates at z ≳ 10 are rapidly being identified in James Webb Space Telescope (JWST)/NIRCam observations. Due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame UV photons, these sources are expected to drop out in the bluer filters while being well detected in redder filters. However, here we show that dust-enshrouded star-forming galaxies at lower redshifts (z ≲ 7) may also mimic the near-infrared (near-IR) colors of z > 10 LBGs, representing potential contaminants in LBG candidate samples. First, we analyze CEERS-DSFG-1, a NIRCam dropout undetected in the F115W and F150W filters but detected at longer wavelengths. Combining the JWST data with (sub)millimeter constraints, including deep NOEMA interferometric observations, we show that this source is a dusty star-forming galaxy (DSFG) at z ≈ 5.1. We also present a tentative 2.6σ SCUBA-2 detection at 850 μm around a recently identified z ≈ 16 LBG candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z ~ 5 dusty galaxy with strong nebular emission lines despite its blue near-IR colors. Further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. Our analysis shows that robust (sub)millimeter detections of NIRCam dropout galaxies likely imply z ~ 4-6 redshift solutions, where the observed near-IR break would be the result of a strong rest-frame optical Balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame UV Lyman break. This provides evidence that DSFGs may contaminate searches for ultra-high redshift LBG candidates from JWST observations.

Keywords: Lyman-break galaxies; Galaxy photometry; Submillimeter astronomy; Millimeter astronomy; Luminous infrared galaxies; Starburst galaxies; James Webb Space Telescope; Near infrared astronomy; Dust continuum emission; Emission line galaxies; 734; 573; 979; 611; 1647; 1061; 946; 1570; 2291; 1093; 412; 459; Astrophysics - Astrophysics of Galaxies; High-redshift galaxies; Galaxies

Domains: Sciences of the Universe [physics]

Jorge A. Zavala, Véronique Buat, Caitlin M. Casey, Steven L. Finkelstein, Denis Burgarella, et al.. Dusty Starbursts Masquerading as Ultra-high Redshift Galaxies in JWST CEERS Observations. The Astrophysical journal letters, 2023, 943, ⟨10.3847/2041-8213/acacfe⟩. ⟨insu-04030807⟩