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A Quasar-anchored Protocluster at z = 6.6 in the ASPIRE Survey. I. Properties of [O iii] Emitters in a 10 Mpc Overdensity Structure

Lookup NU author(s): Dr Tiago CostaORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2025. The Author(s). Published by the American Astronomical Society.A SPectroscopic survey of bIased halos in the Reionization Era is a quasar legacy survey primarily using JWST to target a sample of 25 z > 6 quasars with NIRCam slitless spectroscopy and imaging. The first study in this series found evidence of a strong overdensity of galaxies around J0305−3150, a luminous quasar at z = 6.61, within a single NIRCam pointing obtained in JWST Cycle 1. Here we present the first results of a JWST Cycle 2 mosaic that covers 35 arcmin2 with NIRCam imaging/wide-field slitless spectroscopy of the same field to investigate the spatial extent of the putative protocluster. The F356W grism data target [O iii]+Hβ at 5.3 < z < 7 and reveal a population of 124 line emitters down to a flux limit of 1.2 × 10−18 erg s−1 cm−2. Fifty-three of these galaxies lie at 6.5 < z < 6.8 spanning 10 cMpc on the sky, corresponding to an overdensity within a 2500 cMpc3 volume of 12.5 ± 2.6, anchored by the quasar. Comparing to the [O iii] luminosity function from the Emission line galaxies and Intergalactic Gas in the Epoch of Reionization project, we find a dearth of faint [O iii] emitters at log(L/erg s−1) < 42.3, which we suggest is consistent with either bursty star formation causing galaxies to scatter around the grism detection limit or modest suppression from quasar feedback. While we find a strong filamentary overdensity of [O iii] emitters consistent with a protocluster, we suggest that we could be insensitive to a population of older, more massive Lyman break galaxies with weak nebular emission on scales >​​​​​​10 cMpc.

Publication metadata

Author(s): Champagne JB, Wang F, Zhang H, Yang J, Fan X, Hennawi JF, Sun F, Banados E, Bosman SEI, Costa T, Eilers A-C, Endsley R, Jin X, Jun HD, Li M, Lin X, Liu W, Loiacono F, Lupi A, Mazzucchelli C, Pudoka M, Protusova K, Rojas-Ruiz S, Tee WL, Trebitsch M, Venemans BP, Zhuang M-Y, Zou S

Publication type: Article

Publication status: Published

Journal: Astrophysical Journal

Year: 2025

Volume: 981

Issue: 2

Print publication date: 10/03/2025

Online publication date: 04/03/2025

Acceptance date: 31/01/2025

Date deposited: 08/04/2025

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: Institute of Physics

URL: https://doi.org/10.3847/1538-4357/adb1bd

DOI: 10.3847/1538-4357/adb1bd

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