A Lyman-α protocluster at redshift 6.9

Abstract

Protoclusters, the progenitors of the most massive structures in the Universe, have been identified at redshifts of up to 6.6. Besides exploring early structure formation, searching for protoclusters at even higher redshifts is particularly useful to probe the reionization. Here we report the discovery of the protocluster LAGER-z7OD1 at a redshift of 6.93, when the Universe was only 770 million years old and could be experiencing rapid evolution of the neutral hydrogen fraction in the intergalactic medium. The protocluster is identified by an overdensity of 6 times the average galaxy density, and with 21 narrowband selected Lyman-$\alpha$ galaxies, among which 16 have been spectroscopically confirmed. At redshifts similar to or above this record, smaller protogroups with fewer members have been reported. LAGER-z7OD1 shows an elongated shape and consists of two subprotoclusters, which would have merged into one massive cluster with a present-day mass of $3.7\times 10^{15}$ solar masses. The total volume of the ionized bubbles generated by its member galaxies is found to be comparable to the volume of the protocluster itself, indicating that we are witnessing the merging of the individual bubbles and that the intergalactic medium within the protocluster is almost fully ionized. LAGER-z7OD1 thus provides a unique natural laboratory to investigate the reionization process.

arXiv comment9 pages, 5 figures, and 1 table. Accepted by Nature Astronomy

References in corpus (53)

• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• Mass function of dark matter halos
• An analytic model for the spatial clustering of dark matter haloes
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Statistics of 207 Lya Emitters at a Redshift Near 7: Constraints on Reionization and Galaxy Formation Models
• First Data Release of the Hyper Suprime-Cam Subaru Strategic Program
• A Large Structure of Galaxies At Redshift z~3 and its Cosmological Implications
• The End of the Reionization Epoch Probed by Ly-alpha Emitters at z=6.5 in the Subaru Deep Field
• Cosmological Reionization by Stellar Sources
• Ancient Light from Young Cosmic Cities: Physical and Observational Signatures of Galaxy Proto-Clusters
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• Luminosity functions of Lyman-alpha emitters at z=6.5, and z=5.7: evidence against reionization at z=6
• Large Lyman-alpha opacity fluctuations and low CMB tau in models of late reionization with large islands of neutral hydrogen extending to z<5.5
• Studying Reionization with Ly-alpha Emitters
• The Discovery of Primeval Large-Scale Structures with Forming Clusters at Redshift 6
• Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program Strategy and Clustering Properties of ~2,000 Lya Emitters at z=6-7 over the 0.3-0.5 Gpc${}^2$ Survey Area
• An Atlas of z=5.7 and z=6.5 Ly alpha Emitters
• The Impact of The IGM on High-Redshift Lyman Alpha Emission Lines
• First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z ~ 7
• The Great Observatories Origins Deep Survey: Constraints on the Lyman Continuum Escape Fraction Distribution of Lyman--Break Galaxies at 3.4<z<4.5
• Lyman Alpha Galaxies: Primitive, Dusty or Evolved Galaxies?
• Quasar Strömgren Spheres Before Cosmological Reionization
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization III. the Ly$\alpha$ Equivalent-width Distribution and Ionized Structures at $z>7$
• An overdensity of galaxies at z=5.9 +/-0.2 in the Ultra Deep Field confirmed using the ACS grism
• No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations
• The Effects of Reionization on Lyman-alpha Galaxy Surveys
• MApping the Most Massive Overdensities (MAMMOTH) II -- Discovery of an Extremely Massive Overdensity BOSS1441 at $z=2.32$
• SILVERRUSH. VIII. Spectroscopic Identifications of Early Large Scale Structures with Protoclusters Over 200 Mpc at z~6-7: Strong Associations of Dusty Star-Forming Galaxies
• LCDM predictions for galaxy protoclusters I: the relation between galaxies, protoclusters and quasars at z~6
• The Lyman Continuum escape fraction of faint galaxies at z~3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC
• Spitzer Constraints on the Stellar Populations of Lyman-Alpha Emitting Galaxies at z = 3.1
• Onset of Cosmic Reionization: Evidence of An Ionized Bubble Merely 680 Myrs after the Big Bang
• The Volume Fraction of Ionized Intergalactic Gas at Redshift z=6.5
• SILVERRUSH. VII. Subaru/HSC Identifications of 42 Protocluster Candidates at z~6-7 with the Spectroscopic Redshifts up to z=6.574: Implications for Cosmic Reionization
• A physical model for the evolving UV luminosity function of high redshift galaxies and their contribution to the cosmic reionization
• The Ly$\alpha$ Luminosity Function and Cosmic Reionization at $z\sim$ 7.0: a Tale of Two LAGER Fields
• Properties of Dark Matter Halos as a Function of Local Environment Density
• A Giant Protocluster of Galaxies at Redshift 5.7
• CHORUS II. Subaru/HSC Determination of the Ly$\alpha$ Luminosity Function at $z=7.0$: Constraints on Cosmic Reionization Model Parameter
• Spectroscopic investigation of a reionized galaxy overdensity at z=7
• First Spectroscopic Confirmations of z ~ 7.0 Lya Emitting Galaxies in the LAGER Survey
• Observational Properties of Simulated Galaxies in Overdense and Average Regions at High Redshifts z= 6-12
• An Overdensity of Lyman-alpha Emitters at Redshift z=5.7 near the Hubble Ultra Deep Field
• Lyman Continuum Escape Fraction in Ly$\alpha$ Emitters at $z\simeq 3.1$
• Modelling of Lyman-alpha Emitting Galaxies and Ionized Bubbles at the Era of Reionization
• The Ultraluminous Lyman Alpha Luminosity Function at z=6.6
• A Magellan M2FS Spectroscopic Survey of Galaxies at 5.5<z<6.8: Program Overview and a Sample of the Brightest Lyman-alpha Emitters
• The Magellan M2FS Spectroscopic Survey of High-Redshift Galaxies: A Sample of 260 Ly$\alpha$ Emitters at Redshift $z\approx 5.7$
• Radiative feedback and cosmic molecular gas: the role of different radiative sources
• MOS spectroscopy of protocluster candidate galaxies at z=6.5
• GTC Observations of an Overdense Region of LAEs at z=6.5
• Design for the First Narrowband Filter for the Dark Energy Camera: Optimizing the LAGER Survey for z ~ 7 Galaxies
• An ionised bubble powered by a proto-cluster at z = 6.5

Cited by in corpus (39)

• EIGER I. a large sample of [OIII]-emitting galaxies at $5.3<z<6.9$ and direct evidence for local reionization by galaxies
• Early results from GLASS-JWST. XIV: A spectroscopically confirmed protocluster 650 million years after the Big Bang
• Finding Peas in the Early Universe with JWST
• LAGER Ly$\alpha$ Luminosity Function at $z\sim 7$, Implications for Reionization
• JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3
• Strong Ly$\alpha$ Emission in an Overdense Region at $z=6.8$: A Very Large ($R\sim 3$ physical Mpc) Ionized Bubble in COSMOS?
• COSMOS2020: Discovery of a protocluster of massive quiescent galaxies at $z=2.77$
• The ALMA REBELS Survey: Efficient Ly$\alpha$ Transmission of UV-Bright z$\simeq$7 Galaxies from Large Velocity Offsets and Broad Line Widths
• The Prevalence of Galaxy Overdensities Around UV-Luminous Lyman $\alpha$ Emitters in the Epoch of Reionization
• JADES: Primaeval Lyman-$\alpha$ emitting galaxies reveal early sites of reionisation out to redshift $z\sim 9$
• Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems
• Dark-ages Reionization and Galaxy Formation Simulation XX. The Ly$\alpha$ IGM transmission properties and environment of bright galaxies during the Epoch of Reionization
• Radio and Far-IR Emission Associated with a Massive Star-forming Galaxy Candidate at z$\simeq$6.8: A Radio-Loud AGN in the Reionization Era?
• Predicted future fate of COSMOS galaxy protoclusters over 11 Gyr with constrained simulations
• An Hα Impression of Lyα Galaxies at $z\simeq 6$ with Deep JWST/NIRCam Imaging
• Evaluating Lya Emission as a Tracer of the Largest Cosmic Structure at z~2.47
• Implications of the Environments of Radio-detected AGN in a Complex Protostructure at z$\sim$3.3
• Detection of companion galaxies around hot dust-obscured hyper-luminous galaxy W0410-0913
• Astraeus VIII: A new framework for Lyman-$\alpha$ emitters applied to different reionisation scenarios
• Groups and protocluster candidates in the CLAUDS and HSC-SSP joint deep surveys
• NOEMA formIng Cluster survEy (NICE): Characterizing eight massive galaxy groups at $1.5<z<4$ in the COSMOS field
• Conditions for direct black hole seed collapse near a radio-loud quasar 1 Gyr after the Big Bang
• CHORUS IV: Mapping the Spatially Inhomogeneous Cosmic Reionization with Subaru HSC
• Lyman-alpha Emitters in Ionized Bubbles: Constraining the Environment and Ionized Fraction
• The XXL survey. XLIX. Linking the members star formation histories to the cluster mass assembly in the z=1.98 galaxy cluster XLSSC 122
• Lyman Alpha line properties at $z\simeq 3.78$ and their environmental dependence: a case study around a massive proto-cluster
• Galaxy populations in protoclusters at cosmic noon
• Toward Axion Signal Extraction in Semiconductor Spin Qubits Via Spectral Engineering
• Probing Patchy Reionization with the Void Probability Function of Lyman-$\alpha$ Emitters
• LATIS: A Sample of IGM-selected Protoclusters and Protogroups at $z\sim 2.5$
• Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation
• Reionization in Protocluster Environments at $z>7$ with JWST/NIRSpec
• Constraints on the Epoch of Reionization with Roman Space Telescope and the Void Probability Function of Lyman-Alpha Emitters
• Selecting Clusters and Protoclusters via Stellar Mass Density: II. Application to HSC-SSP Observations
• A resolved Lyman-Alpha profile with doubly peaked emission at z~7
• A Single Line-Emitter Identified in an Unbiased Search with JWST/NIRSpec: Multi-Object Coronagraphy for Slitless Spectroscopy
• The Nature of High-Redshift Massive Quiescent Galaxies -- Searching for RUBIES-UDS-QG-z7 in FLARES
• Finding High-Redshift Galaxies with JWST
• A joint measurement of galaxy luminosity functions and large-scale field densities during the Epoch of Reionization