Spectroscopic Confirmation of CEERS NIRCam-selected Galaxies at z ≃ 8-10
Papovich, Casey; Cole, Justin W.; Yang, Guang; Finkelstein, Steven L.; Burgarella, Denis; Pérez-González, Pablo G.; Santini, Paola; Arrabal Haro, Pablo; Bagley, Micaela B.; Bisigello, Laura; Calabrò, Antonello; Castellano, Marco; Chworowsky, Katherine; Cleri, Nikko J.; Dickinson, Mark; Ferguson, Henry C.; Fontana, Adriano; Giavalisco, Mauro; Hathi, Nimish P.; Holwerda, Benne W.; Hutchison, Taylor A.; Kartaltepe, Jeyhan S.; Koekemoer, Anton M.; Larson, Rebecca L.; Lucas, Ray A.; Pirzkal, Nor; Trump, Jonathan R.; Weiner, Benjamin J.; Wilkins, Stephen M.; Yung, L. Y. Aaron; Zavala, Jorge A.; Fujimoto, Seiji; Mobasher, Bahram; Jung, Intae; Davé, Romeel; Hirschmann, Michaela; Morales, Alexa M.; de la Vega, Alexander; Wang, Xin; Amorín, Ricardo O.; Gawiser, Eric; Dekel, Avishai; Simons, Raymond C.; Huertas-Company, Marc; Backhaus, Bren E.; Harish, Santosh; Rose, Caitlin; Fernández, Vital
United States, Chile, France, Italy, United Kingdom, South Africa, Israel, Switzerland, Spain, China, Malta, Netherlands, Japan
Abstract
We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from Cosmic Evolution Early Release Science (CEERS) survey NIRCam imaging with photometric redshifts z phot > 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 $z={9.77}_{-0.29}^{+0.37}$ and ${10.01}_{-0.19}^{+0.14}$ 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 (M UV < -20), with blue continua (-2.3 ≲ β ≲ -1.9) and low dust attenuation ( ${A}_{V}\simeq {0.15}_{-0.1}^{+0.3}$ ); and at least one of them has a high stellar mass for a galaxy at that redshift ( $\mathrm{log}({M}_{\star }/{M}_{\odot })\simeq {9.3}_{-0.3}^{+0.2}$ ). 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.