James Webb Space Telescope Feed Post


Literature
Date: 10/16/2024

Arxiv: Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGNs at z \simeq 9-11 in the GLASS field Published: 10/14/2024 9:00:22 PM Updated: 10/14/2024 9:00:22 PM

Paper abstract: We present JWST/NIRSpec PRISM follow-up of candidate galaxies at z=9-11selected from deep JWST/NIRCam photometry in GLASS-JWST Early Release Sciencedata. We spectroscopically confirm six sources with secure redshifts at z =9.52-10.43, each showing multiple emission lines. An additional object islikely 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 firstJWST-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 oursample, including GHZ9, have EW(CIII])>20A and occupy a region compatible withAGN emission in the EW(CIII]) vs CIV/CIII] diagram. The spectroscopic sampleconfirms a high abundance of galaxies at z > 9. We measure a number density ofz=10 galaxies in the GLASS-JWST ERS field that is a factor of >3 higher thanother JWST-based estimates at demagnified rest-frame magnitudes of -21 < Muv <-19. We find that the positions of these galaxies in redshift and angular spaceare not consistent with all of them being part of a unique progenitor ofpresent-day galaxy clusters. The high density of objects in the GLASS regioncan be explained either by clustering on large scales or by a superposition ofdifferent forming structures of which we observe only the brightest members. Byconsidering all the spectroscopic z=10 sources in the Abell-2744 field, weidentify two potential galaxy proto-clusters centered around GHZ9 and JD1, withrelative separations between their members of 1-2 pMpc. The potential AGNnature of three of the sources in our sample lends support to a scenario inwhich the high abundance of bright sources determined by JWST surveys at cosmicdawn may be affected by AGN contribution to their UV luminosity.