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Spectroscopic confirmation of CEERS NIRCam-selected galaxies at z ≃ 8–10

2026-06-04T09:35:46Z

Title: Spectroscopic confirmation of CEERS NIRCam-selected galaxies at z ≃ 8–10 Authors: Arrabal Haro, Pablo; Dickinson, Mark; Finkelstein, Steven L.; Fujimoto, Seiji; Fernández, Vital; Kartaltepe, Jeyhan S.; Jung, Intae; Cole, Justin W.; Burgarella, Denis; Chworowsky, Katherine; Hutchison, Taylor A.; Morales, Alexa M.; Papovich, Casey; Simons, Raymond C.; Amorín, Ricardo O.; Backhaus, Bren E.; Bagley, Micaela B.; Bisigello, Laura; Calabrò, Antonello; Castellano, Marco; Cleri, Nikko J.; Davé, Romeel; Dekel, Avishai; Ferguson, Henry C.; Fontana, Adriano; Gawiser, Eric; Giavalisco, Mauro; Harish, Santosh; Hathi, Nimish P.; Hirschmann, Michaela; Holwerda, Benne W.; Huertas-Company, Marc; Koekemoer, Anton M.; Larson, Rebecca L.; Lucas, Ray A.; Mobasher, Bahram; Pérez-González, Pablo G.; Pirzkal, Nor; Rose, Caitlin; Santini, Paola; Trump, Jonathan R.; de la Vega, Alexander; Wang, Xin; Weiner, Benjamin J.; Wilkins, Stephen M.; Yang, Guang; Yung, L. Y. Aaron; Zavala, Jorge A. Abstract: We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from Cosmic Evolution Early Release Science (CEERS) survey NIRCam imaging with photometric redshifts zphot > 8. We measure emission line redshifts of z = 7.65 and 8.64 for two galaxies. For two other sources without securely detected emission lines we measure and by fitting model spectral templates to the prism data, from which we detect continuum breaks consistent with Lyα opacity from a mostly neutral intergalactic medium. The presence of strong breaks and the absence of strong emission lines give high confidence that these two galaxies have redshifts z > 9.6, but the redshift values derived from the breaks alone have large uncertainties given the low spectral resolution and relatively low S/N of the CEERS NIRSpec prism data. The two z ∼ 10 sources observed are relatively luminous (MUV < −20), with blue continua (−2.3 ≲ β ≲ −1.9) and low dust attenuation ( ); and at least one of them has a high stellar mass for a galaxy at that redshift ( ). Considered together with spectroscopic observations of other CEERS NIRCam-selected high-z galaxy candidates in the literature, we find a high rate of redshift confirmation and low rate of confirmed interlopers (8%). Ten out of 35 z > 8 candidates with CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of emission lines in their spectra is consistent with redshifts z > 9.6. We find that z > 8 photometric redshifts are generally in agreement (within their uncertainties) with the spectroscopic values, but also that the photometric redshifts tend to be slightly overestimated (〈Δz〉 = 0.45 ± 0.11), suggesting that current templates do not fully describe the spectra of very-high-z sources. Overall, the spectroscopy solidifies photometric redshift evidence for a high spatial density of bright galaxies at z > 8 compared to theoretical model predictions, and further disfavors an accelerated decline in the integrated UV luminosity density at z > 8.

Dusty starbursts masquerading as ultra-high redshift galaxies in JWST CEERS observations

2026-06-02T12:44:39Z

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

CEERS key paper. IV. A triality in the nature of HST-dark galaxies

2026-05-28T14:04:55Z

Title: CEERS key paper. IV. A triality in the nature of HST-dark galaxies Authors: Pérez-González, Pablo G.; Barro, Guillermo; Annunziatella, Marianna; Costantin, Luca; García-Argumánez, Ángela; McGrath, Elizabeth J.; Mérida, Rosa M.; Zavala, Jorge A.; Haro, Pablo Arrabal; Bagley, Micaela B.; Backhaus, Bren E.; Behroozi, Peter; Bell, Eric F.; Bisigello, Laura; Buat, Véronique; Calabrò, Antonello; Casey, Caitlin M.; Cleri, Nikko J.; Coogan, Rosemary T.; Cooper, M. C.; Cooray, Asantha R.; Dekel, Avishai; Dickinson, Mark; Elbaz, David; Ferguson, Henry C.; Finkelstein, Steven L.; Fontana, Adriano; Franco, Maximilien; Gardner, Jonathan P.; Giavalisco, Mauro; Gómez-Guijarro, Carlos; Grazian, Andrea; Grogin, Norman A.; Guo, Yuchen; Huertas-Company, Marc; Jogee, Shardha; Kartaltepe, Jeyhan S.; Kewley, Lisa J.; Kirkpatrick, Allison; Kocevski, Dale D.; Koekemoer, Anton M.; Long, Arianna S.; Lotz, Jennifer M.; Lucas, Ray A.; Papovich, Casey; Pirzkal, Nor; Ravindranath, Swara; Somerville, Rachel S.; Tacchella, Sandro; Trump, Jonathan R.; Wang, Weichen; Wilkins, Stephen M.; Wuyts, Stijn; Yang, Guang; Yung, L. Y. Aaron Abstract: The new capabilities that JWST offers in the near- and mid-infrared (IR) are used to investigate in unprecedented detail the nature of optical/near-IR-faint, mid-IR-bright sources, with HST-dark galaxies among them. We gather JWST data from the CEERS survey in the Extended Groth Strip, jointly with HST data, and analyze spatially resolved optical-to-mid-IR spectral energy distributions to estimate photometric redshifts in two dimensions and stellar population properties on a pixel-by-pixel basis for red galaxies detected by NIRCam. We select 138 galaxies with F150W − F356W > 1.5 mag and F356W < 27.5 mag. The nature of these sources is threefold: (1) 71% are dusty star-forming galaxies (SFGs) at 2 < z < 6 with and a variety of specific SFRs (<1 to >100 Gyr−1); (2) 18% are quiescent/dormant (i.e., subject to reignition/rejuvenation) galaxies (QGs) at 3 < z < 5, with and poststarburst mass-weighted ages (0.5–1.0 Gyr); and (3) 11% are strong young starbursts with indications of high equivalent width emission lines (typically, [O iii]+Hβ) at 6 < z < 7 (XELG-z6) and . The sample is dominated by disk-like galaxies with remarkable compactness for XELG-z6 (effective radii smaller than 0.4 kpc). Large attenuations in SFGs, 2 < A(V) < 5 mag, are found within 1.5 times the effective radius, approximately 2 kpc, while QGs present A(V) ∼ 0.2 mag. Our SED-fitting technique reproduces the expected dust emission luminosities of IR-bright and submillimeter galaxies. This study implies high levels of star formation activity between z ∼ 20 and z ∼ 10, where virtually 100% of our galaxies had already formed 108M⊙, 60% had assembled 109M⊙, and 10% up to 1010M⊙ (in situ or ex situ).

CEERS key paper. III. the diversity of galaxy structure and morphology at z = 3–9 with JWST

2026-05-28T13:50:33Z

Title: CEERS key paper. III. the diversity of galaxy structure and morphology at z = 3–9 with JWST Authors: Kartaltepe, Jeyhan S.; Rose, Caitlin; Vanderhoof, Brittany N.; McGrath, Elizabeth J.; Costantin, Luca; Cox, Isabella G.; Yung, L. Y. Aaron; Kocevski, Dale D.; Wuyts, Stijn; Ferguson, Henry C.; Bagley, Micaela B.; Finkelstein, Steven L; Amorín, Ricardo O.; Andrews, Brett H.; Haro, Pablo Arrabal; Backhaus, Bren E.; Behroozi, Peter; Bisigello, Laura; Calabrò, Antonello; Casey, Caitlin M.; Coogan, Rosemary T.; Cooper, M. C.; Croton, Darren; de la Vega, Alexander; Dickinson, Mark; Fontana, Adriano; Franco, Maximilien; Grazian, Andrea; Grogin, Norman A.; Hathi, Nimish P.; Holwerda, Benne W.; Huertas-Company, Marc; Iyer, Kartheik G.; Jogee, Shardha; Jung, Intae; Kewley, Lisa J.; Kirkpatrick, Allison; Koekemoer, Anton M.; Liu, James; Lotz, Jennifer M.; Lucas, Ray A.; Newman, Jeffrey A.; Pacifici, Camilla; Pandya, Viraj; Papovich, Casey; Pentericci, Laura; Pérez-González, Pablo G.; Petersen, Jayse; Pirzkal, Nor; Rafelski, Marc; Ravindranath, Swara; Simons, Raymond C.; Snyder, Gregory F.; Somerville, Rachel S.; Stanway, Elizabeth R.; Straughn, Amber N.; Tacchella, Sandro; Trump, Jonathan R.; Vega-Ferrero, Jesús; Wilkins, Stephen M.; Yang, Guang; Zavala, Jorge A. Abstract: We present a comprehensive analysis of the evolution of the morphological and structural properties of a large sample of galaxies at z = 3–9 using early James Webb Space Telescope (JWST) CEERS NIRCam observations. Our sample consists of 850 galaxies at z > 3 detected in both Hubble Space Telescope (HST)/WFC3 and CEERS JWST/NIRCam images, enabling a comparison of HST and JWST morphologies. We conduct a set of visual classifications, with each galaxy in the sample classified three times. We also measure quantitative morphologies across all NIRCam filters. We find that galaxies at z > 3 have a wide diversity of morphologies. Galaxies with disks make up 60% of galaxies at z = 3, and this fraction drops to ∼30% at z = 6–9, while galaxies with spheroids make up ∼30%–40% across the redshift range, and pure spheroids with no evidence for disks or irregular features make up ∼20%. The fraction of galaxies with irregular features is roughly constant at all redshifts (∼40%–50%), while those that are purely irregular increases from ∼12% to ∼20% at z > 4.5. We note that these are apparent fractions, as many observational effects impact the visibility of morphological features at high redshift. On average, Spheroid-only galaxies have a higher Sérsic index, smaller size, and higher axis ratio than disk or irregular galaxies. Across all redshifts, smaller spheroid and disk galaxies tend to be rounder. Overall, these trends suggest that galaxies with established disks and spheroids exist across the full redshift range of this study, and further work with large samples at higher redshift is needed to quantify when these features first formed.