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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

This content will become publicly available on March 4, 2026

Title: A Quasar-anchored Protocluster at z = 6.6 in the ASPIRE Survey. I. Properties of [O iii ] Emitters in a 10 Mpc Overdensity Structure
Abstract A SPectroscopic survey of bIased halos in the Reionization Era is a quasar legacy survey primarily using JWST to target a sample of 25z > 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 atz= 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 arcmin2with NIRCam imaging/wide-field slitless spectroscopy of the same field to investigate the spatial extent of the putative protocluster. The F356W grism data target [Oiii]+Hβat 5.3 < z < 7 and reveal a population of 124 line emitters down to a flux limit of 1.2 × 10−18erg s−1cm−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 cMpc3volume of 12.5 ± 2.6, anchored by the quasar. Comparing to the [Oiii] luminosity function from the Emission line galaxies and Intergalactic Gas in the Epoch of Reionization project, we find a dearth of faint [Oiii] 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 [Oiii] 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.  more » « less
Award ID(s):
2513040 2308258
PAR ID:
10609789
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; « less
Publisher / Repository:
ApJ
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
981
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
113
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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