Title: Little Red Dots in the Early Universe: AGN, Galaxy, or Both?
Abstract: The launch of JWST has revolutionized the picture of the early universe in many aspects. Among its discoveries, the identification of a class of compact, extremely red objects has been particularly intriguing. These objects are characterized by point-like morphology and red colors from observed-frame ~ 2-5 μm, earning them the moniker “Little Red Dots” (LRDs). LRDs exhibit a unique “v” shape SED that is red in the rest-frame optical and blue in the UV, which are hard to be simultaneously described by galaxy-only or AGN-only models. They are found to be ubiquitous from redshifts z ~4 up to z ~9. There are lots of controversies about the nature of the LRDs. It is widely accepted that AGNs at least contribute part of the SED of LRDs, which is supported by the generally observed broad Balmer lines and compact sizes. However, there is evidence that contradicts the AGN scenario, such as the X-ray weakness, prominent Balmer break, and the flat mid-IR SED observed in some LRDs. Many AGN-galaxy hybrid models are invoked to explain the SED of LRDs. In this talk, I will give an observational overview of the LRDs. Then, I will introduce our recent systematic investigation of LRD variability and discuss the prospects of CSST in this field.
talk-2
Title: The Never-ending Story Between Black Hole and Their Host Stellar Component:
Scaling Relations Starting From Cosmic Dawn
Abstract: In the local universe, tight correlations have been found between the mass of the supermassive
black holes and their host galaxy properties, such as central velocity dispersion and the stellar
mass. Linking physics from the vicinity of black holes to galactic scale or even large scale
structures, these scaling relations has become the local benchmark for calibrating various fueling
and feedback models. In recent years, efforts have been made to push the measurement of these
scaling relations to earlier universe in order to directly trace the coevolution track of black holes
and galaxies. However, due to the various sample selection and measuring techniques adopted
so far, results at intermediate redshift (cosmic noon) are still ambiguous, while results at higher
redshift (cosmic dawn) are chaotic. In this talk, I will start by introducing scaling relations in the
local universe, the current coevolution scenario, and the measurement techniques for obtaining
these results. Then, I will move on to higher redshift, gradually unveiling the complicated
situations as well as discussing the latest JWST results
and their implications for black hole seeding and AGN physics. Finally, I will talk about my own efforts in
measuring host galaxy stellar mass for a peculiar type of AGN newly discovered at z>4.
talk-3
Title: The Black Hole Mass and Dynamical Mass Scaling Relation of Galaxies at Low and High Redshift
Abstract: The tight correlation between supermassive black holes (BHs) and their host galaxies bulge mass in the local Universe suggests that BHs and their host galaxies likely co-evolve. Many studies have attempted to extend this relationship to the more distant Universe by measuring BH mass and the properties of host galaxies in active galactic nuclei (AGN) host galaxies. Due to the AGN's overshining, it is challenging to directly measure the stellar mass, so these studies tend to estimate the dynamical mass (Mdyn) of the host galaxies through gas observations. However, the Mdyn-BH relation in high-redshift AGNs shows significant differences from that in low-redshift AGNs. In this talk, I will review the methods and main results regarding the measurement of galaxy rotation curves and dynamics at both low and high redshifts. I will discuss the key findings and issues in current studies of the Mdyn-BH relation at high redshift. Finally, I will conclude with a discussion on how to properly estimate Mdyn and the potential for future research in this area.
talk-4
Title: Extremely Dense Gas around Little Red Dots and High-redshift AGNs
Abstract: The James Webb Space Telescope (JWST) observations have revolutionized extragalactic research, particularly with the discovery of low-luminosity active galactic nuclei (AGNs) at high redshifts, powered by accreting black holes (BHs) with masses of 10^6-8 Msun. One remarkable distinction of these JWST-identified AGNs, compared to their low-redshift counterparts, is that at least ~20% of them present H \alpha and/or H \beta absorption, which must be associated with extremely dense gas along the line of sight. In this talk, I'll review these observation results and give physical insights into the thermal and dynamical properties of inflow/outflow gas in these highz AGN. I will also briefly mention a relationship between these absorption features and other characteristics of JWST-identified AGNs, such as X-ray weakness.
talk-5
Title: Bolometric Luminosity Estimation from Multi-band Data in SDSS Quasars
Abstract: Bolometric luminosity is the integrated emission of the spectral energy distribution (SED), defined as the total energy radiated per second by an object across all wavelengths in all directions. The bolometric luminosity of the quasar serves two crucial purposes: representing the mass accretion rate of the supermassive black hole (SMBH) and, when combined with black hole mass, determining the Eddington ratio. Thus, bolometric luminosity is vital for understanding SMBH accretion history. However, measuring it poses significant challenges. A common approach relies on just one monochromatic luminosity. I'll introduce bolometric methods from the past decade and their limitations. Finally, I'll present our latest findings on improving bolometric measurement accuracy basing larger quasar samples with multi-band data. Our method is based on an unsupervised neural network Self-Organizing Map (SOM) and can significantly reduce systematic errors in bolometric luminosity calculations. This approach applies to quasar populations across a wide range of luminosities and redshifts even with limited data. Additionally, I will discuss how CSST, a next-generation optical space telescope, can enhance the bolometric luminosity of quasars.
talk-6
Title: Revisiting the AGN contribution to cosmic reionization in JWST era
Abstract: The Epoch of Reionization (EoR) is one of the major cosmic phase transitions, when the Lyman continuum (LyC) photons turned the Universe from neutral to highly ionized. The major sources of LyC photons at the EoR have been long debated. High-redshift galaxies and quasars (also referring to active galactic nuclei, hereafter AGNs) are thought to be two plausible candidates, with unclear individual contributions. Owing to the intergalactic medium absorption, the contribution of high-redshift galaxies is unconstrained. The average escape fraction of LyC photons from galaxies is small and uncertain at high redshift. Instead, quasars are known to have higher escape fraction, close to unity. Previous studies of bright quasars indicate that their low number density at high redshift results in a negligible role in reionization. Recently, JWST observations reveal numerous faint AGNs, in excess of a hundred times compared to previously expected. In this talk, I will review previous studies on the high-redshift quasar luminosity function and AGN contribution to reionization, as well as the recent discoveries of faint AGNs by JWST. I will also introduce our recent work, which strongly re-constrains the faint end of the AGN UV luminosity function and the role of AGNs in cosmic reionization.
talk-7
Title: Summary talk on Topic 1
Abstract: The James Webb Space Telescope (JWST) has opened a new window into the early universe, providing unparalleled insights into the population of high-redshift, low-luminosity active galactic nuclei (AGNs), including a new class of objects known as Little Red Dots (LRDs). These objects have significant implications for a range of topics, from the formation mechanisms of supermassive black holes (BHs) and BH-galaxy coevolution to cosmic reionization and beyond. However, measuring the basic properties (e.g., bolometric luminosity, black hole mass, and host mass) of high-redshift AGNs remains a challenging task. Through the six talks within Topic 1: AGN Population and BH-Host Scaling Relations, we delved deeply into these subjects, highlighting key advancements and ongoing issues. In this talk, I will summarize the main points of these talks and discuss the unresolved challenges. Finally, I will discuss how forthcoming surveys with instruments like the China Space Station Telescope (CSST) can help to address these issues.
Topic-2
talk-8
Title: Galaxy evolution in dense environments: the gaseous view
Abstract: The environment where galaxies reside largely determines their evolution. In denser environments, galaxies generally have redder colour and more quiescent star-formation activity. As the major ingredient of star formation and a sensitive tracer of both feedback and environmental processes, the gas in galaxy can provide valuable information on the galaxy evolution. In this talk, I will review recent surveys that trace the galaxy evolution in dense environments by observing gaseous component in different phases, such as VESTIGE, GASP, and the MeerKAT Fornax Survey. High-quality and abundant data provide interesting individual cases. Most importantly, statistical studies on the galaxies in a single structure with a rather simple source selection become possible. It has been confirmed that ram-pressure stripping has dominating roles in high-density clusters; in less- massive groups, however, the details of the quenching processes are still unclear due to the entanglement between different possible mechanisms, such as tidal stripping (harassment), thermal evaporation, and starvation. Several studies have managed to model the gas- stripping process and estimate the relevant time scales in individual clusters or groups, but a larger sample is required for concrete conclusions.
talk-9
Title: How Is Cold Gas and Star Formation Affected by Disc Galaxy Stellar Structures?
Abstract: In the local Universe, the existing galactic stellar structures (bulge, bar, spiral arms) may play a role in affecting the disc cold gas distribution and properties, thus the star formation (SF) activity therein. Various physical mechanisms have been proposed to be at play, which include shear, streaming motion, gas compression and shocks associated with the disc non-axisymmetric structures, to name a few. As a result, mixed results regarding connection between cold gas and SF, and stellar structures properties and dynamics, have emerged from recent observations. Combining physically motivated characterisation of (non-)axisymmetric structures and observations of cold gas and SF provides us opportunities to study the interweaved, intricate mechanisms in behind. In this talk, I would like to give a brief review of how recent observations contribute to unravel the connection between stellar structures, disc cold gas distribution, SF, and the corresponding efficiency. Then, I will talk about our work in characterising the stellar structures through torque forces, and how this method might be extended to investigate the intricate physical mechanisms at play in behind.
talk-10
Title: ISM mass and spatial distribution over galaxy’s Hubble sequence
Abstract: Galaxies are intricate ecosystems where the cold interstellar medium forms stars, regulated by energy feedback from stars and the central black hole and replenished by accretion from the intergalactic medium. How does the interstellar medium connect to their galaxy’s morphology, stellar mass, star formation, and other global properties? How do these dependencies fit in the galaxy evolution framework throughout cosmic time? The nearby Universe offers an invaluable laboratory for investigating these key questions. In this talk, I will review recent observational advancements in various projects like the xCOLD GASS, DustPedia, EDGE-CALIFA, etc. These projects measure both the integrated quantities and spatial distributions of cold gas and dust in hundreds of local galaxies across the Hubble Sequence. They study the correlations of the interstellar medium with the stellar mass, star formation rate, and the environment. I will end the talk by discussing ideas of using spectral energy distribution analysis to reveal the amount and distribution of the interstellar medium and consider its potential applications for studying galaxies in the high-redshift Universe.
talk-11
Title: The Early Evolution of Galaxy Structure Across Cosmic Time: Demography and Case-Specific Context
Abstract: Understanding the formation and evolution of galaxies has remained a fundamental challenge since the early 20th century. Though morphological observables extracted from 2D images are static, the evolutionary pattern can be discerned through statistical studies of galaxies at different stages of their life. Meanwhile, large-scale surveys enable us to identify specific cases that might challenge the classic paradigm or help refine our current grasp of galaxy structural evolution. In this talk, I’ll discuss topics that concern galaxy morphological evolution in the JWST era, including (1) The statistical strategy to trace the morphological evolution across cosmic time; (2) New perspectives of substructure formation (bulge, disc, bar, etc) from recent high-z studies; (3) How the simulation counterparts (or not) at different cosmic epoch help us understand the processes that govern the assembly of galaxies into the Hubble sequence. By embracing the tremendously large imaging datasets with CSST and other future projects, we’ll be ready to reveal the internal and external processes that govern the structural assembly of galaxies across cosmic time.
talk-12
Title: Summary talk on Topic 2
Abstract: not available.
talk-13
Title: Spatially resolved SED fitting of nearby galaxies
Abstract: Multi-wavelength imaging data, ranging from the far-UV to the far-infrared, can provide powerful constraints on the stellar populations and dust properties of galaxies, and mitigate the infamous age-dust-metallicity degeneracy. In recent years, advances in stellar population synthesis codes and computational techniques have enabled the spatially resolved modeling of the full broadband spectral energy distribution (SED) of nearby galaxies on the kiloparsec scale. As the first talk on "Spectra and SED modeling", I'll briefly introduce the basic concepts of SED fitting and the related codes and models. I will then focus on the state-of-the-art methods for spatially resolved SED fitting, emphasizing their differences from the global fitting approach in terms of techniques and assumptions adopted. I will also discuss the applications of the method, in particular how the combination of SED data with gas observations can reveal the processes of star formation and dust evolution in galaxies.
talk-14
Title: Decoding Galaxy SEDs: Advances and Challenges in Recovering Star Formation Histories
Abstract: The spectral energy distribution (SED) of galaxies encodes valuable information on a number of astrophysical processes in galaxy evolution. Currently, the standard method for modeling galaxy SEDs is stellar population synthesis, which constructs SED using many components, including the initial mass function, star formation history (SFH), and metal enrichment history, among others. By decoding galaxy SEDs through forward-modeling the synthesized SED and adjusting model parameters, many physical properties can be extracted. Among these properties, deriving an accurate SFH is one of the major challenges in SED fitting, given both its pivotal role in galaxy evolution and the inherent modeling complexities. Current SFH recovery methods generally adopt three distinct paradigms: parametric models employing analytic functional forms, nonparametric approaches utilizing broad step functions with high flexibility, and emerging methods that incorporate SFH libraries derived from semi-analytic models or hydrodynamic simulations. In this talk, I will introduce the prevailing SFH priors, analyzing their respective strengths and weaknesses.
talk-15
Title: Unveiling Galaxy Properties and Evolution with Slitless Spectroscopy: From HST and JWST to Future Missions
Abstract: Slitless spectroscopy is an effective tool for systematically studying galaxies. Unlike slit-based spectroscopy, which targets pre-selected sources, slitless spectroscopy provides a complete spectroscopic sample across a wide field of view. This talk reviews recent advancements using HST and JWST, demonstrating how slitless spectroscopy, combined with multiwavelegth photometric data and SED-modeling techniques, efficiently collects unbiased galaxy samples over a wide range of redshift, enabling systematic studies of their physical properties, evolution, and environments. It also provides spatially resolved data for low-redshift galaxies, such as metallicity gradients, star formation, excitation states, and dust extinction. Although powerful, slitless spectroscopy requires specialized analysis techniques compared to standard imaging or spectroscopy. Future space telescopes like CSST, Euclid, and Roman, equipped with slitless spectroscopy capabilities, will further advance our understanding in these fields.
talk-16
Title: Unveiling AGN Accretion Properties Through SED Fitting
Abstract: The spectral energy distribution (SED) of active galactic nuclei (AGNs) provides crucial insights into their physical properties and accretion processes. AGN SEDs span a broad wavelength range, from radio to X-ray, with different components originating from distinct physical regions: the synchrotron emission from jets in radio bands, the thermal emission from the accretion disk in the optical and ultraviolet (UV), the inverse Compton scattering in the X-ray from the hot corona, and the infrared (IR) emission from dust torus. Understanding the shape and variability of AGN SEDs is essential for constraining black hole accretion and emission mechanisms. In this talk, I will introduce the principles of AGN SED fitting, including commonly used fitting packages and the key physical parameters that can be derived, such as bolometric luminosity, accretion rate, and Eddington ratio. I will also discuss some scientific usage of SED fitting, particularly in changing-look AGNs (CLAGNs). Through this discussion, I aim to highlight how SED fitting serves as a powerful tool for understanding AGN physics and evolution.
talk-17
Title: AGN-Host galaxy SED decomposition
Abstract: The decomposition of the spectral energy distribution (SED) of active galactic nuclei (AGN) and their host galaxies offers critical insights into the physical processes governing both components. AGN SEDs span a wide range of wavelengths, encompassing synchrotron emission from jets, thermal emission from the accretion disk, and infrared radiation from the dust torus. In contrast, host galaxy SEDs are shaped by stellar population processes and interstellar dust, which complicates the interpretation of the AGN-host system as a whole. This talk will review the current methods used for AGN-host galaxy SED decomposition, focusing on both imaging and spectral techniques. I will highlight recent advancements in these methods, with particular emphasis on their ability to constrain the accretion and star formation histories of AGN and their host galaxies. Additionally, I will discuss key scientific questions, including the evolution of the AGN-host relationship, the contribution of star formation to AGN activity, and the role of dust in shaping AGN emission. Finally, I will outline future directions in AGN-host galaxy SED decomposition, focusing on the integration of multiwavelength datasets from upcoming surveys and space telescopes.
talk-19
Title: Summary talk on Topic 3
Abstract: not available.
talk-18
Title: New Insights into the Milky Way’s Dynamics and Archeology——Recent Results from Gaia
Abstract: Recent advances in Galactic surveys, especially Gaia, have transformed our understanding of the Milky Way’s internal structure and evolutionary history. This talk presents key observational signatures of disc and halo components, including their morphology, kinematics, and the imprints of ancient accretion events. Together, these results help reconstruct the Galaxy’s formation and offer a refined picture of its present-day dynamics.
talk-20
Title: The Co-evolution of Dwarf/Dark Galaxies and Dark Matter Haloes in ΛCDM Simulations
Abstract: Dwarf galaxies, as systems dominated by dark matter, are regarded as one of the most sensitive laboratories for testing dark matter and galaxy formation models. In this talk, I plan to take a few historical and current challenges with ΛCDM at the dwarf galaxy scale as a narrative thread (e.g., missing satellites, core-cusp problem etc.), discussing possible solutions suggested by cosmological simulations within the ΛCDM framework, and how these studies may enlighten us about the co-evolution between dwarfs (including dark galaxies) and dark matter haloes, as well as the nature of dark matter.