In this talk, I will present our survey of enormous Lya nebulae at z=2. These enormous Lya nebulae reside in the density peak of large-scale structures. Using Keck Cosmic Web Imager, combined with the Subaru/HSC, ALMA and VLA, we studied the detailed properties and kinematics of the circumgalactic medium (CGM) through the emission. Combined with simulations, our observations are able to...
The correlation between HI in the IGM and galaxies now attracts great interest. We have found a positive LAE-IGM HI correlation based on a 5.4 deg^2 narrowband survey targeting IGM HI overdense regions (Liang+2021). Compared with simulations, this relation provides us with an instructive probe to unveil pristine HI gas assembly and galaxy formation. However, lines-of-sight around a 17σ quasar...
Missing baryon problem is a long standing issue. Hydrodynamical simulations predict that the majority of the missing baryons is contained in the filaments of the cosmic web in the form of a plasma, called the warm-hot intergalactic medium (WHIM). So far, the direct measurement of the WHIM in cosmic filaments has been a challenge due to the weak signal and the entangled shape of cosmic...
One key question encompassing galaxy formation and evolution and the growth of structures is how galaxies get their gas from the cosmic web. Our ongoing survey for distant group and clusters can be used to study these aspects, based on various observables. I will report current results based on KCWI observations of Lya halos in our groups and clusters over 2<z<3.3, as well as multiwavelength...
It is known from theory and observations that galaxy evolution can be influenced by environmental effects. Processes like ram pressure stripping in groups, clusters or the cosmic web as well as tidal stripping can affect the final properties of galaxies. However, until now no estimates exist on the relative importance of different processes for the final properties of field galaxies. Based on...
With the use of the EAGLE simulation, I will present the spatial and thermal distribution of the baryons within the filaments of the Cosmic Web. In particular, I will characterise the properties of the hottest (log T(K) > 5.5) Warm-Hot Intergalactic Medium (WHIM), which remains largely undetected and is a candidate to solve the cosmological missing baryons problem. Due to its high temperature,...
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The Prime Focus Spectrograph will be an incredibly powerful instrument for large-area surveys of galaxies over most of cosmic time. With its wide wavelength coverage and multiplexing capabilities, it will be a powerful redshift machine. I will briefly describe the Strategic Survey Plan, and then focus on the Galaxy Evolution survey. With our Main survey, we will define the anisotropic...
Recent Lyman-α forest tomography measurements of the intergalactic medium (IGM) have revealed a wealth of cosmic structures at high redshift (z ∼ 2.5), including detection of large voids and protoclusters. In this talk, I will discuss ongoing work on the Tomographic Absorption Reconstruction and Density Inference Scheme (TARDIS), a chrono-cosmographic analysis tool for understanding the...
Gas in the Cosmic Web, long associated with the IGM on large scales and CGM on small scales must fuel galaxy reservoirs and bear the imprint of galaxy feedback and structure formation. However, empirically connecting galaxies, their CGM, and the IGM within a Cosmic Web context has proven elusive. I will present our Cosmic Web reconstruction method Monte Carlo Physarum Machine (MCPM), inspired...
HI is an important component of the CGM/IGM gas. I will present two powerful samples from the KBSS Survey that focus on the Lya absorption and emission around z~2 star-forming galaxies. For absorption, we use the spectra of ~3000 galaxies to assemble ~200,000 foreground-background galaxy pairs. The ensemble is used to construct a 2D map of Lya absorption at 20-4000 kpc. The map suggests that...
The FRB can shed light on the ‘missing’ baryons problem, because the dispersion of the FRB signals encodes information about the ionized gas along the line-of-sight. The majority of this dispersion is expected to come from the diffuse IGM tracing the cosmic web. However, the cosmic variance significantly decreases the sensitivity of the FRB. We introduce a technique to estimate the density...
Fast radio burst (FRB) dispersion measures (DMs) from radio observations record the presence of ionized baryons that are otherwise invisible to effectively all other techniques. Therefore, with FRBs, we may resolve the matter distribution in the cosmic web offering unique constraints on our cosmological paradigm. The number of FRBs localized to their host galaxies has steadily increased to the...
In order to investigate the structure formation and evolution at the distant Universe, emission line galaxies (ELGs) are suitable targets for upcoming spectroscopic surveys (PFS, Euclid, DESI). In order to address clustering properties of ELGs, we utilise galaxy formation hydrodynamical simulations: IllustrisTNG. We have developed the method to simulate emission line intensity with stellar...
The intrinsic alignment of galaxy shapes and spins originate from large-scale tidal field, which is a main contamination of the cosmic shear analysis. However, galaxy intrinsic alignment also carries useful information about both large scale tidal field and galaxy evolution. I will introduce how to exploit galaxy intrinsic alignment as a probe in the context of incoming surveys.
I will review some recent work in measuring intrinsic alignments between large-scale structure (LSS) and galaxy angular momenta and shapes, using hydrodynamic cosmological simulations. I will then preview an upcoming forecast of the LSS-galaxy alignment signal which will be measured by the Subaru Prime Focus Spectrograph (PFS), with data from the IllustrisTNG simulation and LSS reconstruction...
To study the dynamical evolution and connectivity of the cosmic web, we describe our adhesion model of cosmic structure formation based on Voronoi and Delaunay tessellations. Subsequently, we describe how a phase-space analysis allows us to assess the growth of structural complexity in terms of the emergence of singularities and caustics. We indicate how the connections that emerge out of...
How rotation is generated in a cosmological context is one of the key unsolved problems of cosmology. In the standard model of structure formation there is no primordial rotation and rotation must be generated as structures form. The cosmic web in general, and filaments in particular, are intimately connected with galaxy formation and have a strong effect on galaxy spin, regulating how they...
The comic web consists of voids, walls, filaments, and clusters, formed from Gaussian fluctuations. Understanding under what conditions these different structures emerge is central to the study of the large-scale structure. Here, we present a general formalism for setting up Gaussian random initial conditions satisfying non-linear. These allow us to link the non-linear conditions on the...
There are increasing evidences that the cosmic web biases galaxy formation. In particular, the cosmic web contributes to the modulation of galaxy properties with their spatial location. However, modeling these effects is made complex by the multiscale and anisotropic nature of the cosmic web. In this talk, I will present recent progress made towards providing a comprehensive and...
A generic prediction in a cold dark matter universe is the presence of a network of filaments, at the intersection of which galaxies form and evolve. Now the advent of IFU instruments enables us to directly trace the gas filaments and uncover galaxy formation and evolution within the filaments. In this regard, one of the best target is the SSA22 proto-cluster at z=3.1. Our MUSE observations...
HectoMAP is a dense redshift survey that yields a detailed map of the large scale structures at z < 0.7. HectoMAP is also covered by the Hyper Suprime Cam (HSC) Subaru Strategic Program (SSP) photometric survey enabling a range of applications that combine a dense redshift survey with both strong and weak lensing maps. Based on HectoMAP, we identify 346 galaxy clusters. We use this cluster...
We use VLT/KMOS to investigate the role of the environment in the evolution of galaxies in the Spiderweb protocluster at z=2.16. Based on Hα and [NII], we measure SFRs and metallicities for 39 protocluster members as a function of local density and global environment properties. Galaxies embedded in this structure display SFRs compatible with the Main Sequence, and slightly enhanced...
In this work, we try to understand the environmental and mass effects of quenching. Recently-quenched galaxies (RQGs) can deliver information about the quenching scenario. A statistical sample of RQGs is necessary for studying mass and environment dependence of quenching. However, the rarity of RQGs hampers statistical spectroscopic analysis. As a pilot work, we conduct a statistical...
We study the properties of the six optically dark galaxies detected in the GOODS-ALMA survey. While none of them are listed in CANDELS catalog down to H = 28.16 AB, we were able to de-blend two of them from their bright neighbor and measure an H-band flux. We present the spectroscopic scan follow-up of five of the six sources with ALMA. We show that nearly 70% of them belong to the same...
We present a cosmological zoom-in simulation of two 5x10^12 halos and a Mpc-long cosmic filament connecting them at z∼2, to study the evolution of the IGM and the cosmic web around this system at unprecedented resolution. At 5>z>3, the halos lie in a cosmic sheet with multiple coplanar filaments which contain most of the halos. The collapse of the sheet at z∼5 generates a strong shock that...
Our goal is to recover the linear peculiar velocity and density field from observations of galaxy peculiar velocities, specifically the Cosmicflows3 catalog. Our efforts are focused on attempting to recover the posterior probability function of the peculiar velocity field according to the ΛCDM model. By assuming the priors of the Λ CDM model we use a Hamiltonian Monte Carlo technique to sample...
Why do thin galactic discs survive in the concordance model? This question has long been set aside as an obvious consequence of angular momentum conservation. The true answer is more subtle and enlightening for astronomy and theoretical physics. It must involve capturing gravity-driven processes operating on multiple scales, working to spontaneously set up a remarkably robust level of...
Like their lower redshift counterparts, high-redshift clusters host an excess of massive quiescent galaxies. In this talk will explore where these galaxies were quenched. I will present a study of protocluster galaxies that reside in the distant outskirts of 15 galaxy clusters at 0.8≤z≤1.5. I will show that the massive protocluster galaxies are already quenched to a similar level as the...
MOONS is the new Multi-Object Optical and Near-infrared Spectrograph under construction for the VLT. This remarkable instrument will allow large-scale spectroscopic campaigns needed to study the formation and evolution of stars and galaxies over the entire history of the Universe. I will present the current planning for Galactic and Extragalactic large survey foreseen for MOONS. On a...
I introduce our studies of the richest galaxy clusters in rich superclusters in the local Universe, in the Corona Borealis supercluster and in the A2142 supercluster, and galaxy transformations in them. The richest clusters in these superclusters are surrounded by the regions of influence with characteristic density contrast $\Delta\rho \approx 30$. The regions of influence passed...
I will describe a method to reconstruct the initial conditions responsible for the cosmic web observed in the low-z universe, and present results of hydrodynamic simulations using these initial conditions. These simulations can be used to understand how the gas components in the local cosmic web evolve with time to produce the gaseous structures we see today.
The evolution of galaxies is linked to the growth of large scale structure in ways that are still poorly understood. This is, in part, because deep, wide-field spectroscopy is essential for associating individual galaxies with specific environments. I will summarize results from the GOGREEN imaging and spectroscopic survey of 21 galaxy clusters at 1<z<1.5. While we do find evidence that...
The protocluster’s (PC’s) are the densest region in the early universe, and many of them have recently been discovered. In high-density regions, galaxy formation is faster and star formation is more active than in the low-density environment. Therefore, PC is important for understanding both the evolution of galaxies and the cosmic star formation history in the Universe. We study the PC’s star...
The “cosmic noon” era is recognized as pivotal, but it has been challenging to connect early galaxies’ properties to the large-scale structures in which they are growing. An exciting method to chart the z~2.5 universe is to map the intergalactic medium by measuring Lyman-alpha absorption in the spectra of many faint galaxies. These maps provide a unique means to detect and study protoclusters...
By analyzing the morphology, color, & distribution of cluster galaxies, we can study the evolution of protoclusters into clusters and determine how environment impacts the transformation of high-z star-forming galaxies into low-z red sequence galaxies. While many high-z red sequence galaxies are found in clusters/protoclusters out to z ~ 2, determining when the protocluster environment impacts...
In this presentation, I will first present the impact of large scale environment on the recent building-up of about 415 clusters of galaxies from the IllustrisTNG simulation. The mass of clusters mainly influences the geometry of the matter distribution: massive halos are significantly more elliptical and more connected to the cosmic web than low-mass ones. Beyond the mass-driven effect,...
Cosmic voids are vast underdense regions of space in the large scale structure, whose statistical properties we've only recently been able to fully utilize. In particular, the cross-correlation of voids with galaxies allows us to explore redshift-space distortions and use the Alcock-Paczynski effect to constrain the laws of gravity and the expansion history of the Universe. In my talk I will...
In our work (arXiv:2010.03742), we investigate the influence of voids on galaxy formation. In contrast to the dense environment of galaxy clusters, a galaxy should have difficulty forming in the underdense environment of a cosmic void. The gravitational pull of the void's surroundings should weaken the matter infall onto a dark matter halo located in the void. The effect should be the...
The inference of cosmological quantities needs accurate and large cosmological simulations.Yet, the computational time takes millions of CPU hours for a modest coverage in cosmological scales (~(100 Mpc/h)^3). This ML method could have a decisive impact on the results derived from QSO surveys, e.g., SDSS3/4 data, which has a resolution power of R=1500 and R=2000. But it could be critical for...
Recent progresses in Machine Learning have unlocked new possibilities to tackle scientific problems by means of neural networks, and already many applications have been developed both in astrophysics and cosmology. In this presentation, using a Generative Adversarial Network (GAN), an unsupervised learning model, we demonstrate the possibility to learn the distribution of dark matter of the...
Cosmological survey data in the 2020s will be characterized by multi-wavelength information from thousands of square degrees of overlapping sky. This opens up the exciting prospect of a new era of multi-wavelength cosmological analyses that use all datasets simultaneously. I will refer to this ambitious program as Cross-Survey Cross-Correlation Cosmology (CSC3). The power of CSC3 will come...
In this talk I will provide an overview of the strategy adopted for the full DESI Survey, as well as an update on its progress to date. Using a new 5000-fiber instrument at the 4m Mayall Telescope at Kitt Peak National Observatory, DESI should obtain spectra of more than 40 million targets over 14,000 square degrees during the course of a five year survey. Full survey operations began in May...
Clusters are matched to nodes in several versions of the cosmic web created by the Disperse web finder, and filaments between nodes are then assigned to their cluster counterparts. This picks out parts of the underlying cosmic web. Properties of the correspondence and those clusters and nodes which don't have counterparts are described, similarly, cluster pairs with and without web assigned...
In this talk, we will present the methodology of recovering filaments from galaxy samples in the Sloan Digital Sky Survey (SDSS-IV) through directional density ridges, which can be practically estimated via our proposed Directional Subspace Constrained Mean Shift (DirSCMS) algorithm. The algorithm takes into account the nonlinear geometry of a celestial sphere on which the galaxy samples lie...
Anisotropic subhalo accretion through cosmic filaments has an impact on halo structures. Using high-resolution cosmological simulations, we quantify the strength of filamentary subhalo accretion on host haloes and show that, for the first time, the shape and orientation of host haloes weakly correlate with the strength of filamentary subhalo accretion even if the host halo masses are the same....
We used hydrodynamical zoom-in simulations to describe the geometry, collapse and feeding of clusters via filaments and groups, and to determine the histories of observed cluster galaxies. We created an inventory of galaxies in filaments feeding clusters; a combination of group-, backsplash- and pure filament galaxies, to compare pre-processing signatures to. Almost all galaxy groups become...
The outskirts and infall regions of galaxy clusters act as the points of contact linking the large-scale structure of the Universe to the dense virialized cores of the clusters. In these regions, the underlying dark matter density field manifests itself as the cosmic web, making them crucial in understanding the mass assembly processes of the Universe. Our work involves forecasting the...
To study the cosmic web, surveys are designed to acquire a large quantity of spectral and multi-wavelength imaging data. To be fully understood and exploited, these data must be analyzed in combination with advanced cosmological simulations. Ideally the latter must be first calibrated at z=0 with extremely faithful numerical counterparts of the local, best known, cosmic web. I will introduce...
Nonlinear gravitational collapse shaped the cosmic web and created a plethora of different density environments. To realise the full potential of galaxy surveys, we need to dissect different densities that are lumped together in 2-point statistics. This is particularly important for LCDM extensions including massive neutrinos, dark energy and modified gravity. I will show how to extract...
Next-generation data sets promise 1% cosmology, but 1% predictions from simulations are expensive to build likelihood approximations and inference frameworks. Instead of intensive simulations, we can use approximate solvers, or surrogates, which introduce model error with respect to the simulations, which translates into biased and underestimated confidence bounds on cosmological parameters....
The distribution of matter in the universe depicts a complex spatial pattern commonly referred to as the Cosmic Web in which massive nodes are linked together by elongated filaments found at the intersection of thin mildly-dense walls, themselves surrounding large and empty voids. Classifying, in simulations, the particles belonging to the several environments depending on level of local...
Lyα forest provides a unique probe of studying IGM matter distribution at high-z & upto small scales. While its 2-point clustering statistics have been studied widely, higher-order statistics remain largely unexplored. In addition to probing non-gaussianity in the density fields, they can also complement 2-point statistics in constraining cosmological & astrophysical parameters. In this talk,...
