Nancy Grace Roman space telescope will conduct a High Latitude Spectroscopic Survey (HLSS) over 2000 square degrees at high redshift. I will introduce the flowdown of the Roman science objectives of galaxy and cosmology based on numerical simulations. With this reference model, we forecast the performance of the survey, including the galaxy type, number density, clustering property and...
We develop a new statistic, the projected three-dimensional correlation function, for the clustering analysis of the imaging galaxy survey data. This method can retain some of the radial information that is lost in conventional tomographic angular correlation analysis. As it is not strongly correlated with the angular correlation results, it can also provide important crosscheck. We have...
Dark Energy Spectroscopic Instrument (DESI) is the first on-going Stage IV spectroscopic redshift survey, covering a wide sky area and redshift range. As one of the key goals, DESI will measure the Baryon Acoustic Oscillations (BAO) from different tracers, including BGS, LRG, ELG and QSO at different redshifts. The density field reconstruction is significantly important to reduce the...
Time-ordered data (TOD) from ground-based CMB experiments is usually filtered before map-making to reduce the contamination from ground and atmospheric emissions. However, when the observation region contains strong point sources, the filtering process will cause a considerable leakage around the point sources, which should be eliminated to provide a clean CMB polarization map for scientific...
I will talk about different boundaries of a dark matter halo focusing on our recently proposed depletion boundary. I will explain its physics and measurements, and illustrate how this new boundary could help us to gain new insights into halo evolution and to provide much improved description of the cosmic structure.
Recent observations revealed that the dark matter mass contained in two ultra diffuse galaxies in the vicinity of an elliptical galaxy, NGC 1052, is several hundred times lower than the predictions by the theoretical models of galaxy formation and evolution. The dynamics of the galaxies is described by only the gravity of stars. As such dark matter deficient galaxies can be a challenge for the...
We propose a novel mechanism for constraining warm dark matter (WDM) models via the so-called “memory of reionization” effect, which is that gas in the intergalactic medium (IGM) after cosmic reionization can be affected significantly by inhomogeneous reionization of hydrogen. The suppression of small-scale structure due to WDM affects the evolution of post-reionization IGM, while thermal...
观测以及Lambda冷暗物质模型框架下的标准星系演化模型都表明星系的恒星质量与其暗物质晕质量之间密切相关：红移0处，在Lstar星系（即质量约为5x10^11太阳质量）的暗物质晕中，恒星-暗物质晕质量比达到最高（~1%-5%）。然而，最近对星系团中超弥散星系UDG的研究表明近邻宇宙中可能存在一类维里质量与Lstar星系相当，但恒星-暗物质质量比极低的星系族群，这类特殊星系又被称为未发育完全的Lstar星系（FLG）。我们通过HI动力学的方法，首次寻找到了一批高置信度的FLG星系候选体，其有着极低的恒星质量（10^7-10^9太阳质量）、巨大的暗物质晕（>5x10^11太阳质量）、以及极低的恒星-暗物质质量比（<0.1%）。FLG星系的发现否定了修正牛顿动力学（MOND）理论。此外我们还发现50%的FLG候选者位于由星系团或星系群引力主导的区域，其热气体可能在早期宇宙中受到潮汐或冲压的...
We carried out a program to identify extremely overdense structures at z~2-3 and investigate connections between galaxy and structure formation. The two very massive structures at z=2.24 are mapped with Ha emission-line galaxies, SMGs and LAEs, and exhibit astonishing features unseen before. In this talk we introduce these finding about different galaxy populations in connections with the...
Characterizing the structural properties of galaxies in high-redshift protoclusters is key to our understanding of the environmental effects on galaxy evolution in the early stages of galaxy and structure formation. We assess the structural properties of H$\alpha$ emission-line candidates (HAEs) in the densest regions of massive protoclusters at z=2-3, using HST $H$-band imaging data. Our...
The Photometric objects Around Cosmic webs (PAC) approach developed in \cite{2022ApJ...925...31X} has the advantage of making full use of the spectroscopic and deeper photometric surveys. With the merits of PAC, we can accurately measure quasars-galaxy cross-correlations at small scale down to $0.1\,h^{-1}{\rm{Mpc}}$ and at different stellar mass bins. We calculate the excess surface density...
I will present a review on how to use targets provided by galaxies, galaxy groups and reconstructed density field to study the cosmic web, galaxy formation and evolution.
We develop a deep learning technique to reconstruct the dark matter density field from the redshift-space distribution of dark matter halos. We implement a UNet-architecture neural network and successfully trained it using the COLA fast simulation, which is an approximation of the N-body simulation with $512^3$ particles in a box size of $500 \mpch$. We evaluate the resulting UNet model not...
Obtaining well-calibrated probability density functions (PDFs) of photometric redshift (photo-z) for galaxies without using spectroscopy remains a challenge for many science goals. Deep learning tools have proven to be powerful for this task and gained growing popularity. These include, in particular, state-of-the-art deep neural networks that are typically fed with multi-band galaxy images or...
The gas components play very important role in the baryon cycles and evolution processes in galaxy formation. In this talk, we present our recent work on simulating the observations of HI gas in ISM and hot ionized gas in CGM and ICM.
For the cold gas, we generate the mock observation of the 21cm interferometer signals by radio arrays for HI gas in galaxies. We developed a software OmniUV,...
Gas is the essential component in a galaxy that dominates its evolution. It also provides insight into the large-scale structure and the evolution of the Universe. In this talk, I will introduce an overview of treatments of gas and star formation in our updated semi-analytic model. Our model includes a self-consistent partition of HI and H$_2$ in the cold gas disk, as well as environmental...
Accurately modeling the cold gas content in the universe is challenging for current theoretical models. We propose a new empirical model NeutralUniverseMachine to describe the evolution of HI and H2 gas along with the dark matter halos based on the UniverseMachine catalog. It is able to accurately fit the observed HI and H2 mass functions, molecular-to-atomic ratio, HI-halo mass relation,...
We present a new H I mass estimator that relates log10(MHI/M*) to a linear combination of four galaxy properties: stellar surface mass density, color index u − r, stellar mass, and concentration index, with the scatter of individual galaxies around the mean H I mass modeled with a Gaussian distribution function. We calibrate the estimator using the xGASS sample, including both H I detection...
