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arXiv · 2410.10967

Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGNs at z $\simeq$ 9-11 in the GLASS field

L. Napolitano·M. Castellano·L. Pentericci·P. Arrabal Haro·A. Fontana·T. Treu·P. Bergamini·A. Calabro·S. Mascia·T. Morishita·G. Roberts-Borsani·P. Santini·E. Vanzella·B. Vulcani·D. Zakharova·T. Bakx·M. Dickinson·C. Grillo·N. Leethochawalit·M. Llerena·E. Merlin·D. Paris·S. Rojas-Ruiz·P. Rosati·X. Wang·I. Yoon·J. Zavala
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Abstract

We present JWST/NIRSpec PRISM follow-up of candidate galaxies at z=9-11 selected from deep JWST/NIRCam photometry in GLASS-JWST Early Release Science data. We spectroscopically confirm six sources with secure redshifts at z = 9.52-10.43, each showing multiple emission lines. An additional object is likely at z = 10.66, based on its Lya-break and a single emission feature, while one source is a lower redshift interloper. The sample includes the first JWST-detected candidate at z=10, GHZ1/GLASS-z10, which we confirm at z = 9.875, and the X-ray detected AGN GHZ9 confirmed at z = 10.145. Three objects in our sample, including GHZ9, have EW(CIII])>20A and occupy a region compatible with AGN emission in the EW(CIII]) vs CIV/CIII] diagram. The spectroscopic sample confirms a high abundance of galaxies at z > 9. We measure a number density of z=10 galaxies in the GLASS-JWST ERS field that is a factor of >3 higher than other JWST-based estimates at demagnified rest-frame magnitudes of -21 < Muv < -19. We find that the positions of these galaxies in redshift and angular space are not consistent with all of them being part of a unique progenitor of present-day galaxy clusters. The high density of objects in the GLASS region can be explained either by clustering on large scales or by a superposition of different forming structures of which we observe only the brightest members. By considering all the spectroscopic z=10 sources in the Abell-2744 field, we identify two potential galaxy proto-clusters centered around GHZ9 and JD1, with relative separations between their members of 1-2 pMpc. The potential AGN nature of three of the sources in our sample lends support to a scenario in which the high abundance of bright sources determined by JWST surveys at cosmic dawn may be affected by AGN contribution to their UV luminosity.

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L. Napolitano, M. Castellano, L. Pentericci, P. Arrabal Haro, A. Fontana, T. Treu, P. Bergamini, A. Calabro, S. Mascia, T. Morishita, G. Roberts-Borsani, P. Santini, E. Vanzella, B. Vulcani, D. Zakharova, T. Bakx, M. Dickinson, C. Grillo, N. Leethochawalit, M. Llerena, E. Merlin, D. Paris, S. Rojas-Ruiz, P. Rosati, X. Wang, I. Yoon, J. Zavala. 2024-10-14. Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGNs at z $\simeq$ 9-11 in the GLASS field. https://doi.org/10.1051/0004-6361%2F202452090

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