ALMA FIR View of Ultra-high-redshift Galaxy Candidates at z ∼ 11-17: Blue Monsters or Low-z Red Interlopers?
Ouchi, Masami; Papovich, Casey; Finkelstein, Steven L.; Buat, Véronique; Burgarella, Denis; Pérez-González, Pablo G.; Seillé, Lise-Marie; Arrabal Haro, Pablo; Bagley, Micaela B.; Casey, Caitlin M.; Chworowsky, Katherine; Cleri, Nikko J.; Costantin, Luca; Cooper, M. C.; Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro; Grogin, Norman A.; Hutchison, Taylor A.; Kartaltepe, Jeyhan S.; Kirkpatrick, Allison; Kocevski, Dale D.; Koekemoer, Anton M.; Larson, Rebecca L.; Lucas, Ray A.; Somerville, Rachel S.; Weiner, Benjamin J.; Wilkins, Stephen M.; Yung, L. Y. Aaron; Zavala, Jorge A.; Fujimoto, Seiji; Jiménez-Andrade, E. F.; Murphy, E. J.; Brammer, Gabriel; Daddi, Emanuele; Juneau, Stéphanie; Tacchella, Sandro; McKinney, Jed; Amorín, Ricardo O.; Simons, Raymond C.; Fudamoto, Yoshinobu; Valentino, Francesco; Le Bail, Aurélien; Franco, Maximilien; Cooper, Olivia R.; Ciesla, Laure; Yoon, Ilsang; Carilli, Chris L.; Rose, Caitlin; Magnelli, Benjamin; Kojima, Takashi; Akins, Hollis; Long, Arianna
United States, Denmark, France, United Kingdom, Japan, Germany, Spain, Malta, Chile, Mexico
Abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations of a remarkably bright galaxy candidate at ${z}_{\mathrm{phot}}={16.7}_{-0.3}^{+1.9}$ (M UV = -21.6), S5-z17-1, identified in James Webb Space Telescope (JWST) Early Release Observation data of Stephen's Quintet. We do not detect the dust continuum at 866 μm, ruling out the possibility that S5-z17-1 is a low-z dusty starburst with a star formation rate of ≳30 M ⊙ yr-1. We detect a 5.1σ line feature at 338.726 ± 0.007 GHz exactly coinciding with the JWST source position, with a 2% likelihood of the signal being spurious. The most likely line identification would be [O III]52 μm at z = 16.01 or [C II]158 μm at z = 4.61, whose line luminosities do not violate the nondetection of the dust continuum in both cases. Together with three other z ≳ 11-13 candidate galaxies recently observed with ALMA, we conduct a joint ALMA and JWST spectral energy distribution (SED) analysis and find that the high-z solution at z ~ 11-17 is favored in every candidate as a very blue (UV continuum slope of ≃-2.3) and luminous (M UV ≃ [ - 24:-21]) system. Still, we find in several candidates that reasonable SED fits (Δχ 2 ≲ 4) are reproduced by type II quasar and/or quiescent galaxy templates with strong emission lines at z ~ 3-5, where such populations predicted from their luminosity functions and EW([O III]+Hβ) distributions are abundant in survey volumes used for the identification of the z ~ 11-17 candidates. While these recent ALMA observation results have strengthened the likelihood of the high-z solutions, lower-z possibilities are not completely ruled out in several of the z ~ 11-17 candidates, indicating the need to consider the relative surface densities of the lower-z contaminants in the ultra-high-z galaxy search.