A dusty starburst masquerading as an ultra-high redshift galaxy in JWST CEERS observations

3 Aug 2022  ·  Jorge A. Zavala, Veronique Buat, Caitlin M. Casey, Denis Burgarella, Steven L. Finkelstein, Micaela B. Bagley, Laure Ciesla, Emanuele Daddi, Mark Dickinson, Henry C. Ferguson, Maximilien Franco, E. F. Jim'enez-Andrade, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Aurélien Le Bail, E. J. Murphy, Casey Papovich, Sandro Tacchella, Stephen M. Wilkins, Adriano Fontana, Mauro Giavalisco, Andrea Grazian, Norman A. Grogin, Lisa J. Kewley, Dale D. Kocevski, Allison Kirkpatrick, Jennifer M. Lotz, Laura Pentericci, Pablo G. Perez-Gonzalez, Nor Pirzkal, Swara Ravindranath, Rachel S. Somerville, Jonathan R. Trump, Guang Yang, L. Y. Aaron Yung, Omar Almaini, Ricardo O. Amorin, Marianna Annunziatella, Pablo Arrabal Haro, Bren E. Backhaus, Guillermo Barro, Peter Behroozi, Eric F. Bell, Rachana Bhatawdekar, Laura Bisigello, Fernando Buitrago, Antonello Calabro, Marco Castellano, Oscar A. Chavez 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 Dave, Alexander de la Vega, Avishai Dekel, David Elbaz, Vicente Estrada-Carpenter, Vital Fernández, Keely D. Finkelstein, Jonathan Freundlich, Seiji Fujimoto, Ángela García-Argumánez, Jonathan P. Gardner, Eric Gawiser, Carlos Gómez-Guijarro, 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, Ray A. Lucas, Benjamin Magnelli, 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 Jr., Paola Santini, Lise-Marie Seillé, 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 ·

Lyman Break Galaxy (LBG) candidates at $z\gtrsim12$ are rapidly being identified in JWST/NIRCam imaging. 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 like F150W and F200W while being well-detected in redder filters (e.g., F277W, F356W, F444W). However, dust-enshrouded star-forming galaxies at lower redshifts ($z\lesssim7$) may also mimic the near-infrared colors of $z>12$ LBGs, representing potential contaminants in LBG candidate samples. Here, we report a galaxy, CEERS_DSFG_1, that drops out in the F115W, F150W, and F200W filters, for which a photometric redshift fit to the JWST data alone predicts a redshift of $z_{\rm phot}\sim18$. However, we show it is a dusty star-forming galaxy (DSFG) at $z\approx5$ based on deep millimeter interferometric observations conducted with NOEMA. We also present a $2.6\sigma$ SCUBA-2 detection at 850$\,\mu\rm m$ around the position of a recently reported $z\approx16.7$ LBG candidate in the same field, CEERS-93316. While we cannot conclusively show this detection is astrophysical or associated with this object, we illustrate that if it is associated, the available photometry are consistent with a $z\sim5$ DSFG with strong nebular emission lines despite its blue NIR colors. Hence, we conclude that robust (sub)millimeter detections in NIRCam dropout galaxies likely imply $z\sim4-6$ redshift solutions, where the observed near-infrared 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.

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Astrophysics of Galaxies