Spectroscopic Confirmation of CEERS NIRCam-selected Galaxies at z ≃ 8-10

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.
Bibliographical reference

The Astrophysical Journal

Advertised on:
7
2023
Number of authors
48
IAC number of authors
1
Citations
89
Refereed citations
48
Description
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.
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