We present the Obelisk project, a cosmological radiation-hydrodynamics simulation following the assembly and reionization of a protocluster progenitor during the first two billions of years from the big bang, down to $z = 3.5$. The simulation resolves haloes down to the atomic cooling limit, and tracks the contribution of different sources of ionization: stars, active galactic nuclei, and collisions. The Obelisk project is designed specifically to study the coevolution of high redshift galaxies and quasars in an environment favouring black hole growth. In this paper, we establish the relative contribution of these two sources of radiation to reionization and their respective role in establishing and maintaining the high redshift ionizing background. Our volume is typical of an overdense region of the Universe and displays star formation rate and black hole accretion rate densities similar to high redshift protoclusters. We find that hydrogen reionization happens inside-out and is completed by $z \sim 6$ in our overdensity, and is predominantly driven by galaxies, while accreting black holes only play a role at $z \sim 4$.
We report fourteen and twenty-eight protocluster candidates at z=5.7 and 6.6 over 14 and 19 deg^2 areas, respectively, selected from 2,230 (259) Lya emitters (LAEs) photometrically (spectroscopically) identified with Subaru/Hyper Suprime-Cam (HSC) deep images (Keck, Subaru, and Magellan spectra and the literature data). Six out of the 42 protocluster candidates include 1-12 spectroscopically confirmed LAEs at redshifts up to z=6.574. By the comparisons with the cosmological Lya radiative transfer (RT) model reproducing LAEs with the reionization effects, we find that more than a half of these …
Present-day clusters are massive halos containing mostly quiescent galaxies, while distant protoclusters are extended structures containing numerous star-forming galaxies. We investigate the implications of this fundamental change in a cosmological context using a set of N-body simulations and semi-analytic models. We find that the fraction of the cosmic volume occupied by all (proto)clusters increases by nearly three orders of magnitude from z=0 to z=7. We show that (proto)cluster galaxies are an important, and even dominant population at high redshift, as their expected contribution to the c…
The study of galaxy protoclusters is beginning to fill in unknown details of the important phase of the assembly of clusters and cluster galaxies. This review describes the current status of this field and highlights promising recent findings related to galaxy formation in the densest regions of the early universe. We discuss the main search techniques and the characteristic properties of protoclusters in observations and simulations, and show that protoclusters will have present-day masses similar to galaxy clusters when fully collapsed. We discuss the physical properties of galaxies in proto…
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, …
Galaxy Protoclusters as Drivers of Cosmic Reionization: II. Te-Based Metallicities of Lyman-α Emitters
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Las Campanas Observatory, Carnegie Science（拉斯坎帕纳斯天文台，卡内基科学）；University of California Santa Barbara（加州大学圣塔芭芭拉分校）；Instituto de Astrofísica de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales（迭戈·波特莱斯大学工程与科学学院天体物理研究所）；Texas A&M University（德克萨斯农工大学）；George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University（德克萨斯农工大学乔治·P和辛西娅·伍兹基础物理与天文学研究所）；Caltech/IPAC（加州理工学院/IPAC）；Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Space Telescope Science Institute（太空望远镜科学研究所）
The large-scale overdensities of galaxies at z~2-7 known as protoclusters are believed to be the sites of cluster formation, and deep, wide survey projects such as the Large Synoptic Survey Telescope (LSST) and the Wide Field Infrared Survey Telescope (WFIRST) will deliver significant numbers of these interesting structures. Spectroscopic confirmation and interpretation of these targets, however, is still challenging, and will require wide-field multi-plexed spectroscopy on >20 m-class telescopes in the optical and near-infrared. In the coming decade, detailed studies of protoclusters will ena…
The THESAN project: environmental drivers of Local Group reionization
University of Southern California（南加州大学）；Carnegie Observatories（卡内基观测站）；The University of Texas at Dallas（德克萨斯大学达拉斯分校）；York University（约克大学）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学 Kavli 宇宙物理数学研究所（WPI）、UTIAS）；Tsinghua University（清华大学）；Massachusetts Institute of Technology（麻省理工学院）
Reionization and the ISM/Stellar Origins with JWST and ALMA (RIOJA): The core of the highest redshift galaxy overdensity at $z = 7.88$ confirmed by NIRSpec/JWST
We present results from a new cosmological hydrodynamics simulation campaign of protocluster (PC) regions, FOREVER22: FORmation and EVolution of galaxies in Extremely-overdense Regions motivated by SSA22. The simulations cover a wide range of cosmological scales using three different zoom set-ups in a parent volume of $(714.2~\rm cMpc)^{3}$: PCR (Proto-Cluster Region; $V= (28.6~{\rm cMpc})^{3} $, SPH particle mass, $m_{\rm{SPH}} = 4.1 \times 10^{6}~\rm M_{\odot}$ and final redshift, $z_{\rm end}=2.0$), BCG (Brightest proto-Cluster Galaxy; $V \sim (10~{\rm cMpc})^{3} $, $m_{\rm SPH} = 5.0\times…
Deep X-ray View of a Distant Protocluster Anchored by a Quasar at $z=6.63$: No Evidence for Enhanced X-ray AGN Activity
Peking University（北京大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Nanjing University（南京大学）；University of Michigan（密歇根大学）
The most luminous galaxies at high-redshift are generally considered to be hosted in massive dark-matter halos of comparable number density, hence residing at the center of overdensities/protoclusters. We assess the validity of this assumption by investigating the clustering around the brightest galaxies populating the cosmic web at redshift $z\sim8-9$ through a combination of semi-analytic modeling and Monte Carlo simulations of mock Hubble Space Telescope WFC3 observations. The innovative aspect of our approach is the inclusion of a log-normal scatter parameter $Σ$ in the galaxy luminosity v…
ASPIRE: The Environments and Dark Matter Halos of Luminous Quasars in the Epoch of Reionization
University of Michigan（密歇根大学）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；Space Telescope Science Institute（太空望远镜科学研究所）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Newcastle University（纽卡斯尔大学）；INAF–Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所空间科学与天体物理观测站）；Department of Astronomy, University of Geneva（日内瓦大学天文学系）
The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: A Molecular Gas Line Search
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Millennium Nucleus for Galaxies (MINGAL)（银河系千年核团（MINGAL））；Las Campanas Observatory, Carnegie Institution of Washington（卡内基华盛顿机构拉斯坎帕纳斯天文台）；Universidad Diego Portales（迭戈·波特莱斯大学）；University of Washington（华盛顿大学）；University of California, Santa Barbara（加州大学圣巴巴拉分校）；Cosmic Dawn Center (DAWN)（宇宙黎明中心（DAWN））；Imperial College London（伦敦帝国理工学院）；International Centre for Radio Astronomy Research (ICRAR), University of Western Australia（西澳大利亚大学国际射电天文研究中心（ICRAR））；Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM（巴黎萨克雷大学、巴黎西岱大学、CEA、CNRS、AIM）；Space Telescope Science Institute（太空望远镜科学研究所）
本研究通过 ALMA 的 Ex-MORA 巡天开展 $0.5<z<5$ 范围的分子气体线搜寻，探测到 52 个星系，揭示了不同演化阶段星系的气体性质，证明广域线搜寻可有效获取大质量气体储库。
We present a spectroscopic survey of high-redshift, luminous galaxies over four square degrees on the sky, aiming to build a large and homogeneous sample of Ly$α$ emitters (LAEs) at $z\approx5.7$ and 6.5, and Lyman-break galaxies (LBGs) at $5.5<z<6.8$. The fields that we choose to observe are well-studied, such as SXDS and COSMOS. They have deep optical imaging data in a series of broad and narrow bands, allowing efficient selection of galaxy candidates. Spectroscopic observations are being carried out using the multi-object spectrograph M2FS on the Magellan Clay telescope. M2FS is efficient t…
