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Series I: Titles and Abstracts of presentations

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Morphology and Structure (Subtopic of topic a: Morphology, Structure and Kinematic)

Hua Gao

Title: Overview of Bulge-to-disk Decomposition Techniques

Abstract: I will review the available techniques for photometric bulge-to-disk decomposition, including non-parametric vs. parametric methods, 1D vs. 2D fitting, and single-band vs. multiwavelength image fitting. In addition, I will briefly mention the developments of IFU decomposition techniques.

Dewang Xu

Title: The surface brightness profile breaks of disk galaxies

Abstract: According to different outskirt surface brightness profiles, disk galaxies are separated into three major classes: Type I disks, with surface brightness profiles well described by a single exponential function; Type II disks (down-bending), best described by a broken exponential function with a steeper decline in the disk outskirts; and Type III disks (up-bending), best described by a broken exponential function with a shallower decline in the outskirts. Statistics show that Type II profiles are more common in late-type galaxies, while Type III profiles are more common in early types. Some observers (e.g., Pohleen and Trujillo 2006, Watkins et al. 2019) divide Type II and Type III into more subgroups according to the possible origins. Why nature prefers exponential disks is uncertain, although many studies have attacked this problem from various perspectives. Generally, type II disks are attributed to dynamical star formation threshold and radial migration. Meanwhile, many explanations have been proposed for Type III disks, including radial migration, thick disk, stellar halos, mergers, and so on. In this talk, I will introduce the definition of these three broken disks and how to decide the break radius. I will briefly introduce the role of the environment and the redshift evolution. Lastly, I will talk about the diverse origins of disk breaks, mainly focusing on radial migration.

Niankun Yu

Title: The HI distribution in the Milky Way

Abstract: The Milky Way has a warped disk, which is obvious for both stellar and H I observation. The Milky Way is surrounded by the High Velocity Clouds, which has been confirmed by all-sky observations and whose sky coverage fraction is ~15%. Thousands of H I shells are identified, which mainly located within the Galactic disk. The H I shells associated with supernova remnants are observed, and the position-velocity diagram can show both positive and negative outflows. The H I radial distribution follows the exponential function, but at large radius the exponential function underestimate the H I surface density. The H I scale length increase with the galaxy radius, which is called the H I flaring. In conclusion, the galactic disk is warped, extended, flaring, filled by shells, and surrounded by high velocity clouds.

Yun Zheng

Title: HI disk warps

Abstract: HI warps are ubiquitous in disk galaxies and in many cases the warp is asymmetric or even one-sided. Sancisi (1976) showed that the HI warps in four out of five observed edge-on samples, while García-Ruiz et al. (2002) observed 20 out of the 26 of edge-on galaxies are warped. Briggs (1990) studied a sample of 12 warped galaxies and concluded that HI warp develops between R25 and the Holmberg radius, which emphasizes warps usually occur where the stellar disks fade. Van der Kruit (2007) studied the warped HI layer and truncated stellar disk in edge-on galaxies and suggested that the inner flat disk and the outer warped disk are distinct components, which have different formation histories and probably involving different epochs. They found a discontinuous and abrupt warped disk arising at the truncation of the stellar disk. The warps reveal some information about the halo that dominates its dynamics and the later stages of galaxy formation. In spite of decades of history, warps are still a puzzle. The mainstream interpretation of warps is the accretion of material with an angular momentum vector misaligned with that of the main disk (Jiang & Binney 1999), because the alignment of angular momentum in a warp model is hard to build only by internal disk-halo interaction, which imply the involvement with surrounding environments.

Pei Zuo

Title: The HI Asymmetry of Galaxies

Abstract: The stellar and gas distribution of discs in galaxies show features which vary from symmetric to asymmetric. The primary driver for galaxy morphology and kinematics is the gravitational potential from both baryonic and non-baryonic matter. Comparing with the asymmetry of stellar distribution, the asymmetry in HI is larger than that in stars quantitatively. Not only the lopsided and paired/merger galaxies exhibit asymmetric character in HI gas distribution or global spectral profile, but some isolated, massive galaxies show asymmetrical morphologies, which are expected to be affected by the external environment. Meanwhile, the internal mechanisms, like non-circular motions, are proposed to cause the asymmetries. In this presentation, I will review the HI asymmetry of morphologies for various type of galaxies and discuss the related kinematics and dynamical state.

Dong Yang

Title: Nonparametric measurements of galaxy's morphology and its relation with galaxy merger

Abstract: Galaxy’s morphology is one of the most accessible tracer of its real physical structure. It indicates the organization of light as projected into our line of sight and observed at a particular wavelength, from which we can learn the star formation history and galaxy assembly history. However there exists one basic and major obstacle, which is how to quantify one galaxy’s morphology with a few simple, but reliable measurements. In this talk, I will introduce some basic nonparametric measures of galaxy’s morphology. In addition I will take galaxy’s merger as an example to show the usage of these measurements.

Dongyao Zhao

Title: Role of Major Mergers in triggering luminous AGNs

Abstract: One of the most crucial but yet unknown factors on clarifying the role of nuclear activity in the coevolution of black holes and their hosts is how luminous AGNs are triggered. In numerical simulations, gas-rich major mergers are suggested as a promising mechanism to trigger luminous AGNs. The morphological signatures of major mergers, such as close pairs, double nuclei, disturbed morphologies, tidal tails, and shells and bridges are expected to be visible up to ~0.5-1.5 Gyr after the merger. Given that the AGN lifetime is thought to be ~100 Myr, the features of morphological disturbance should be observable in their host galaxies if luminous AGNs are triggered by gas-rich major mergers. A number of observational studies have examined the morphologies of the host galaxies of luminous AGNs to test the major-merger scenario. In this talk, I'll overview studies on the role of major mergers in triggering luminous AGNs using different AGN samples at different redshifts. I'll also overview the implications of these studies.

Qinchun Ma

Title: Researching the structure of accretion disk and BLR of AGN with Reverberation mapping.

Abstract: The reverberation mapping (RM) uses the time lag between continuum and broad emission line of AGN to extract a characteristic size of the broad line region (BLR). During these years, hundreds of AGNs have been measured the sizes of BLR by RM, but most of them only have H$\beta$ time lags. In recent years, some campaigns monitored several targets for a long time in a large wavelength coverage, so by studying and comparing the lags of different emission lines such as H$\beta$, C IV and Ly$\alpha$ for one AGN, they can research the structure of BLR. Furthermore, combining X-ray and UV/optical photometric monitoring, it can get the time lag between different wavelength in continuum, they can study the structure of accretion disk and exam the disk models. This talk will use some typical targets to introduce some results of structure of BLR and accretion disk for AGN gotten by RM.

  1. Space Telescope and Optical Reverberation Mapping Project. XII. Broad-Line Region Modeling of NGC 5548. [https://arxiv.org/abs/2010.00594]
  2. The Sloan Digital Sky Survey Reverberation Mapping Project: the XMM-Newton X-ray source catalog and multi-band counterparts. [https://arxiv.org/abs/2009.02193]
  3. Space Telescope and Optical Reverberation Mapping Project. XIII. An Atlas of UV and X-ray Spectroscopic Signatures of the Disk Wind in NGC 5548. [https://arxiv.org/abs/2011.09056]
  4. The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey. [https://arxiv.org/abs/1811.07956]
  5. Supermassive black holes with high accretion rates in active galactic nuclei. XI. Accretion disk reverberation mapping of Mrk 142. [https://arxiv.org/abs/2005.03685]
  6. Intensive disc-reverberation mapping of Fairall 9: 1st year of Swift & LCO monitoring. [https://arxiv.org/abs/2008.02134]

Kinematics and the relationship among these three properties (Subtopic of topic a: Morphology, Structure and Kinematic)

Min Du

Title: Formation and evolution of weakly-rotating, diffuse stellar structures in galaxies

Abstract: I will give an overview of the properties and current theories of weakly-rotating, diffuse stellar structures in galaxies, including both stellar halos and the envelopes of elliptical galaxies. I will introduce why the accretion of stellar components via minor/major mergers and tidal stripping is important. The clues provided by both observations and simulations will be shown. The disagreements and challenges from simulations will be discussed. Some new insights from the kinematic decomposition of TNG galaxies will also be presented.

Bitao Wang

Title: The formation of fast and slow rotators as seen by simulations and observations

Abstract: The kinematics of galaxies holds valuable information about their formation histories. As a first step, galaxies can be classified into fast and slow rotators according to the ratio of ordered to random motion. In this review, I would like to share with you mainly what I learned from simulations about how fast and slow rotators are formed. Because not all simulations produce sensible results, key observations of galaxy kinematics will be brought for comparison.

Juan

Title: The fall relation.

Abstract: In this talk I will review the relation between the specific stellar angular momentum and stellar mass in galaxies, the "Fall relation". With a normalization that depends on galaxy morphological type, increasing from early- to late-type galaxies, the Fall relation represents a key benchmark for models of galaxy evolution in a Lambda-CDM framework.

Qinyue Fei

Title: Molecular gas outflows in low redshift galaxies

Abstract: Molecular gas outflows are a common occurrence in galaxies. They can operate over the full extent of host galaxies, from the central region (few pc) to the whole galaxy (~kpc). These energetic galactic winds not only represent the feedbacks of star forming activity, the material carried by them are also used to form stars, which can contribute to the formation and evolution of galaxy. The feedback can (at least partially) explain the formation of so called 'red-and-dead' galaxies in present-day universe. What's more, the outflows can also be contributed by active galactic nuclei (AGN), and there are some suggestions that outflows/winds/jets may also regulate SMBH and growth and link it to the host galaxy. The identification and resolving of molecular outflows has now been possible for local galaxies, thanks to the application of synthesis imaging, high-sensitivity and high-angular resolution observations through interferometry array, e.g., ALMA. In this talk I will introduce some observations of molecular outflows in low redshift star forming galaxies traced by CO transitions. Some studies of scaling relations between outflows and properties of host galaxies and AGNs suggest that although starbursts are effective in powering massive molecular outflows, the presence of AGN may strongly enhance such outflows, and therefore have a profound feedback effect on the evolution of galaxies.

Hangyuan Li

Title : Gas inflows and outflows through the CGM

Abstract : The circumgalactic medium (CGM) of a galaxy is a vast gaseous halo located at the interface between the intergalactic medium (IGM) and the interstellar medium (ISM). It plays an important role in regulating gas flows in and out of galaxies, and provides the gas resvervoir for accretion onto the galaxy and the repository for the expelled gas. Recent studies show that galaxies accrete gas from the CGM through both hot and cold accretion, and the metal-rich outflows recycle through the CGM and mix with the accreting metal-poor IGM. In this talk I'll briefly introduce the gas inflows and outflows through the CGM. I'll also talk about some basic properties (mass, metallicites, etc.) and possible origins of the CGM, and how they can be explained by such gas flows. Finally I'll talk about the relationship between the CGM and the ISM.

Quasar Survey

Yongjung Kim

Title: A Brief History of Quasar Surveys

Abstract: Over the past half-century, since the first discovery of quasars, about a million quasars have been discovered so far through various observational surveys. These quasars allowed us to understand the growth of supermassive black holes along cosmic time and lay the foundation for observational cosmology together with the formation of galaxies and halos. In this talk, I will summarize the past remarkable quasar surveys, especially for the optical quasars that are related to the upcoming CSST survey. Furthermore, I will discuss what questions still remain and what problems CSST can solve with other future telescopes.

Yuxuan Pang

Title: Quasar Selection Methods

Abstract: Since 1980s, a large number of quasars have been discovered by various surveys. Appeared as point sources, quasars are selected with multi-band data because they have bright SEDs with large wavelength coverage. Quasars can be found with UV-optical data because of their typical power law continuum from the accretion disk, and they can be found with infrared data due to their power-law SEDs and the contribution from the hot dust. X-ray and radio data also provide efficient ways for finding quasars. In addition, quasars can be selected with their near-zero proper motions and long-term variability. From a different perspective, as more and more quasars are found by SDSS and other surveys, the quasar selection methods have changed from classic color cuts to more data-orientated methods including PDF, KNN and other ML algorithms. In this talk, I will briefly review these selection methods’ principle and applications. I will also discuss about the advantages and disadvantages of these selection methods as well as their potential for future surveys.

Zhiwei Pan

Title: The Quasar Luminosity Function

Abstract: The quasar luminosity function (QLF) describes the comoving number density of quasars as a function of luminosity and redshift, which is helpful for studying the evolution of quasars and their central super massive black holes. In this talk, I will firstly introduce the definition, the calculation, and the significance of QLF. Then I’d like to review the history and current status of QLF studying from low redshift to high redshift. Different shapes of QLF such as the double power-law and different evolution patterns such as pure density evolution (PDE) will be focused on in this section. Finally, from the perspective of theory, I will discuss how to interpret the form and evolution of QLF.

Jin Wu

Title: The Quasar Black hole mass Function

Abstract: The black hole mass function (BHMF) is the comoving number density of black holes as a function of black hole mass and redshift. It is one of the primary empirical tools available for mapping the growth of supermassive black holes and for constraining theoretical models of their evolution. In this talk, I will introduce the methods for estimating the black hole mass function and the black hole mass estimator used in each method. I will review the current results of BHMF measurements and discuss the trend of accretion activity among the SMBH population. At last, I will discuss the CSST slitless spectroscopy and how it can contribute to the measurements of BHM and BHMF.

Measure the mass of AGN host galaxies: methods and uncertainties

Junjie Jin

Title: Spectral fitting of the AGN host galaxies

Abstract: The spectral synthesis method is invaluable to study galaxies. They provide means to extract stellar masses, stellar ages, star formation histories, chemical enrichment, and dust content of galaxies from their spectra. In this talk I will give a brief introduction of spectral synthesis method and their application to active galactic nucleus (AGNs) host galaxies, as well as the problems in this application. At last, I will talk about some related works as examples to show the usage of this method.

Xiaotong Feng

Title: Measure the stellar mass of type-I AGN by 2D image decomposition

Abstract: For type-I AGNs, the stellar mass of host galaxy is difficult to measure using imaging. Because the host galaxy is faint and there is contamination from the bright nucleus. To get a robust measurement of stellar mass, we need two-dimensional (2D) image decomposition. This requires high spatial resolution imaging which is often achieved with the Hubble Space Telescope(HST). In this talk, I will introduce the method to decompose the AGN host galaxy. This includes some details such as the treatment of PSF, the principal structural components (e.g., bulge, bar, disk) and different mass-to-light ratio(M/L).

Jianan Li

Title: Dust and gas mass at z~6 revealed by (sub)millimeter observations

Abstract: During the past two decades, (sub)millimeter observations towards quasars at redshift 6 have uncovered the massive dust and gas contents in the host galaxies of the earliest SMBH-galaxy systems. In this talk, I will review the gas and dust mass estimates for z~6 quasars based on observations of the continuum, CO and fine structure lines e.g., [CII], [OI], and [CI]. Comparisons between the high-z quasars and local (U)LIRGs/starburst galaxies will also be discussed.

Yuanqi Liu

Title: Measure the dynamical mass of AGN host galaxies

Abstract: Dynamical mass estimate is essential in studying BH—host-galaxy scaling relations, which indicates the co-evolution of BH and host galaxy. Dynamical mass are clearly described as M_dyn = (RV^2)/G, which can be constrained with stellar and gas dynamical detections. In this talk, I would introduce the method to measure dynamical mass through gas observations. In local group, HI observations provide details for measure dynamical mass as HI is one of the best tracer of galaxy rotation. At redshift 6, the dynamical mass can be constrained through CII or CO observations resolved with ALMA. The uncertainty and future modification will also be discussed.

Qiong Li

Title: The Relationships Between the Different AGN Host Galaxies Mass and Other Parameters 

Abstract: Active galactic nuclei (AGNs) represent the growth phases of the supermassive black holes in the center of almost every galaxy. In this talk, we will introduce the connections between the different AGN host galaxies mass, and the relationship between galaxies mass and other important parameters, such as: star-formation rate and gas mass, the galaxies mass and luminosities, mass–metallicity relation etc. These empirical findings describe a picture in which the AGN host galaxies are built by a cooperation between merging, black-hole fueling, and feedback from AGNs.

Mingyang Zhuang

Title: Masses of AGN host galaxies estimated from SED fitting

Abstract:Tight relations found between masses of super massive black holes (SMBHs) and properties of their host galaxies, such as bulge masses and velocity dispersions, suggest that they may coevolve with each other. However, when SMBH is rapidly accreting (active galactic nucleus; AGN), the tremendous energy output from the accretion disk can dominate the observed spectral energy distributions of the entire galaxy, making it difficult to robustly measure the mass of its host galaxy. Fortunately, the intrinsic difference in energy powering mechanism at rest-frame optical and near-infrared wavelength between AGNs and stars makes it possible to separate contributions to the total observed SED from each component. I will briefly introduce the methodology and popular codes to perform SED fitting, decompose stellar emission and measure stellar mass.

Environmental effects on galaxies

Lulu Zhang

Title: The diverse evolutionary pathways of post-starburst galaxies and possible influence of environment

Abstract: Post-starburst galaxies (PSBs), also called “E+A” or “K+A” galaxies, are a kind of galaxies that have ended star formation within the last Gyr or so. Such galaxies are traditionally identified by their spectral features, which show very weak or no ionized emission lines (e.g., Ha, [O II]), indicating no O and B stars, but strong Balmer absorption lines and other metallic absorption lines (e.g., Ca, K), indicating the presence of A stars and older K stars. The elliptical morphology and other galaxy properties (i.e., Sersic index distribution, kinematics and the elemental abundances) suggest that PSBs are likely progenitors of earlytype galaxies. Furthermore, PSBs are proposed to be undergoing a transformation stage of galaxies that link so called “blue cloud” and “red sequence”, and hence they are crucial to the understanding of galaxy bimodality. However, how such transformation happens is still on debate, with environmental effect like ram pressure stripping, mergers as possible candidate mechanisms. This Topic Review will give an introduction about the physical properties of PSBs, especially the environmental effect on its formation.

Weiwei Xu

Title: How does the dense environment stop the star formation of galaxies?

Abstract: The striking variation in the stellar populations of galaxies in different environments clearly indicates the importance of such environmental influences on star formation. Galaxy clusters are dominated by passive galaxy populations, and are continuously growing through the accretion of galaxies and groups from the field, which are actively star-forming. This starforming activity must be quenched during the assimilation of the galaxies into the cluster. This transformation is a key process in creating the environmental dependence of galaxy properties. Firstly, I will introduce and compare the properties of galaxies located in different environment, including in cluster, in filament and in the field. Then, I will discuss the possible physical mechanism responsible for the characteristics difference, such as ram pressure, galaxy-galaxy collisions, and suffocation.

Chao Ma

Title: Cluster environmental effects on the galaxy morphology transformation

Abstract: Massive galaxy clusters are excellent laboratories to probe environmental effects on the galaxy physical and structural properties. It is well known that the cluster galaxies properties are starkly different from those in the field. In nearby clusters, galaxy populations are dominated by early-type galaxies (ETGs), while star-forming late-type galaxies (LTGs) fraction are highly suppressed, i.e., the so-called morphology-density relation. With the help of deep HST observation, clusters at intermedia-redshift contain much higher fraction of blue spirals than nearby clusters, but the S0 fraction is proportionally decreased (Butcher-Oemler effect). In order to reach the excess S0 populations seen in present-day clusters, the spiral- S0 transformations should continuously happen with redshift, under the influence of clusterspecific environmental processes. In this review, I will introduce the famous morphology-density relation and spiral-S0 transformation that exclusively occur in rich clusters. Then I will summarize the possible physical mechanisms leading to these two phenomena, as well as the supporting observational evidences.

Zezhong Liang

Title: Structures in Disk Galaxies affected by Environmental Effects

Abstract : It still remains a subject of debate whether Environmental effects play a significant row in affecting the structures of galaxies. A number of mechanisms, e.g. tidal interactions, minor mergers, and hydrodynamical interactions such as ram-pressure stripping, are considered to be able to affect the outermost of galactic disks, which is relatively weakly bounded, leading to change of break properties, unwinding of spiral arms, etc. Recent studies are providing observational evidence for influence of environmental effects on galactic structures, albeit incongruent conclusions. In this talk I'll focus on the role of environmental on affecting galactic structures in disk galaxies. I'll briefly introduce some of the theoretical and simulation results and some recent observational evidence.

Yang Li

Title: The evolutionary path and properties of red spiral galaxies

Abstract: The population of galaxies which have red color and late-type morphology are rare in local universe. The existence of massive red spiral galaxies challenges the scenario that galaxy quenching must be in company with the morphological transformation. Many efforts have been invested in understanding the origin of red spirals by studying their stellar populations, structures, kinematics and environments et al. It is generally established that red spiral galaxies are distinct from blue spiral galaxies in many aspects. Compared to blue spirals, red spirals have more concentrated light distribution and an enhanced fraction of bars, and they are found preferentially in environment of intermediate density and dominated by LINER-like emission. One of the possible scenarios which explains the red-spiral galaxies is that red-spiral galaxies are accreted on to massive haloes as blue spirals, after which their outer halo gas reservoirs are stripped by environmental effects without transforming their morphology, and quench the star formation. Transition of morphology of red spiral galaxies may be caused by mergers or their spontaneous dynamical evolution. A possible population of red early type spirals is also suggested to be the link between red spirals and red ellipticals. I will talk about several works and their conclusions on red spiral galaxy evolution, including their studies about structural components, SFHs, morphological types and environmental effects of the red spirals.

Siwei Zou

Title: Metallicity-environment dependencies between central massive galaxy and satellite galaxies

Abstract: The empirical correlation between galaxy metallicity and its mass has been found in the observations from the local universe to the cosmic noon (z ~2), which is known as the mass-metallicity relation (MZR). Environmental effects affect the MZR more significantly for low mass galaxies than high mass galaxies (M > 10^10 M ☉). In a dense region, the central massive galaxy does not show a significant correlation with the environment, however, the satellite galaxies exhibit a significant metallicity dependence on the environment. Zoom-in hydrodynamical simulation also shows that the metal budgets in the circumgalactic medium of a central massive galaxy mainly come from the intergalactic medium and galactic winds rather than satellites. I will review the observations and simulations at 0< z < 2 to study the MZR between satellite galaxies and central massive galaxies, and how does this relation correlates with the gas fraction in the satellite galaxies and the stages of a galaxy merger.

Shun Wang

Title: metallicity in interacting galaxies

Abstract: Galaxy interactions are major actors in the theater of galaxy evolution and the impact of interactions on the chemical evolution and gas kinematics have become a subject of intense scrutiny. We review several studies that explain the flattened metallicity gradients and diluted central metallicity by radial inflow of low-metallicity gas in both observations and simulations. More recent studies have shown that the mass ratio and environment may also play an in-negligible role in the interplay between tidal interaction and metal dilution and star formation enhancement. These studies also consistently suggest that the effects of interaction are strongly dependent on the distance between the interacting galaxies and/or the merger stage. The observed deviation of tidal interacting galaxies off the fundamental metallicity relation (FMR) suggests that the evolution of interacting galaxies is not encoded in the FMR.

Yuchen Liu

Title: HI deficient galaxies

Abstract: The ISM of a spiral galaxy which mostly made of atomic hydrogen is likely to be larger than the optical disk at its radii. As the outer gas of spiral galaxies can be influenced by the external environment interactions, the HI emission can be a sensitive indicator of these effects. Observations have shown that the spiral galaxies in galaxy clusters have less average HI than galaxies in the field. In this talk, I will present the properties of HI deficient galaxies and the possible cause of these galaxies according to some observations and simulations. At last, I will briefly talk about the specific interactions which are important in these environments.

Bumhyun Lee

Title: Environmental effects on the cold gas content of dwarf galaxies

Abstract: The shallow gravitational potential of dwarf galaxies makes them more sensitive to environmental effects in a galaxy cluster, compared to massive galaxies in a galaxy cluster. Therefore, it is expected that the environmental processes can rapidly transform blue dwarfs into dwarf ellipticals by dramatically removing their ISM and quenching their star formation within a very short time scale. In this talk, I will introduce recent studies of the environmental effects on the cold gas content of dwarf galaxies.

Feedback of baryons and black holes

RuancunLi

Title: Connection between star formation and black hole accretion focusing on Type-I AGNs

Abstract: The discovery in the past decade of tight correlations between the black hole mass and host spheroid properties implies that the supermassive black hole plays a critical role in galaxy formation. A recent study of nearby Type 1 AGNs found that, after removing the dependence of star formation rate (SFR) on molecular gas mass, star formation efficiency is strongly correlated with black hole accretion rate (Mdot), which can be interpreted as evidence of positive AGN feedback. However, some recent galactic scale hydrodynamical numerical simulations found that the time-integrated total effect of AGN feedback on star formation is negative. From the theoretical point of view, the discrepancy can originate from the different ``feedback mode” between simulations and real Type 1 AGNs. Additionally, the diversity of morphology of gas in galactic nuclei also complicates the attempts to make a correlation between SFR and Mdot. The cosmic ray-dominated jet and strong magnetic field around the black hole horizon are suggested also that have negative feedback on galaxy star formation.

Xiaoling Yu

Title: The major mechanism to drive turbulence in star-forming galaxies

Abstract: High gas velocity dispersion seems to be a common feature of galaxies at high redshift. The supersonic velocity dispersion implies a highly turbulent interstellar medium (ISM) of distant galaxies. Theoretical and observational studies also suggest that gas of distant galaxies has larger random motions compared to that in low redshift galaxies. These highly turbulent motions may play a crucial role in star formation. Both external and internal mechanisms have been suggested to explain these highly turbulent motions. In this talk, I will briefly introduce the role of star formation feedback in the turbulent motions of star-forming galaxies. Combined with the existing theoretical models, I will also introduce some progress about the origin of turbulence in star-forming galaxies.

Siwei Zou

Title: Cold and molecular gas in the AGN-driven outflows of high-z massive galaxies

Abstract: AGN feedback in the form of outflow is essential in the transition between massive star-forming galaxies into quiescent galaxies. Direct observations of outflows from AGN of chemical abundances near AGN will provide a stringent constraint on this transition phase. Not only Ionized gas but also massive molecular outflows at the scale of their host galaxies are detected in the multi-band spectra. Furthermore, AGN-driven winds redistribute the matter and heavy elements from galaxies to the circumgalactic medium (CGM). I will briefly review the AGN molecular outflow observations and their effects on the metallicity distribution in the CGM from simulations.

Yuanhang Ning

Title: Luminous Lyα emitters with AGN activities at moderate-high redshift

Abstract: Wide-field ground-based surveys have utilized Lyα emission to construct large samples of star-forming galaxies, so-called Lyα emitters (LAEs), which largely increase the number of sources at high redshifts (z > ~2). Due to the relatively high abundance, fainter LAEs have been mostly targeted by spectroscopic follow-up. However, little is known about the general properties of bright LAEs. LAEs at moderate high redshift (z ~ 2 — 3) have been found to have a significant AGN contribution. Recent studies also show that luminous LAEs at this redshift are a diverse population with a transition in the nature of LAEs, from star formation dominated to AGN dominated. These LAEs are potentially good samples to study how stellar feedback and AGN feedback affect galaxy evolution. I will simply review recent work about LAEs at moderate-high redshift, especially those luminous ones AGN activities.

Photometric Redshifts

Weiyang Liu

Title: Overview of Photometric Redshift

Abstract: Precise measurement of redshift is essential in extragalactic astronomy. Photometric redshifts (photo-z), though with lower precision, can provide redshift estimations for all sources detected in photometric images relatively cheaply. Photo-z utilizes key spectral features like the Balmer break, the Lyman break, and strong emission or absorption lines to estimate galaxy redshifts from magnitudes/colors. In this talk I will introduce two main classes of photo-z methods, i.e., template-fitting method and empirical method. The template-fitting method fits a spectral template using synthetic photometry, while the empirical method starts from a training set with known redshifts and uses a machine learning algorithm (e.g., Neural Network, Random Forest) to perform the estimation. Both methods have their own advantages and disadvantages. Photo-z performances are often assessed by three indices: bias, outliers fraction and precision. Over large fields of several deg^2, a precision about 0.05 is routinely reached at i < 26. Photo-z accuracy essentially depends on the image properties (e.g. depth, wavelength coverage), and in recent years it has become an integral part of galaxy surveys like DES and LSST.

Weiwei Xu and Yuxuan Pang

Title: Photometric Redshift Estimation of Galaxie

Abstract: Photometric redshift (photo-z) for galaxies is the main part of photo-z. Our review mainly divides into three parts, the classical SED fitting method, machine learning (ML) method and the discussion for future. In the first part, we will review the basic idea and pick up some important SED components which help to improve the photo z performance, and then several well-known template-fitting codes and their own specificity will be introduced. As for the second part, a few previous results using different ML methods (Random Forest, Neural Network, Support Vector Machines, k-nearest neighborhood, etc.) as well as the comparison between SED fitting and ML methods will be shown. Some extra information such as prior redshift and spatial information will also improve the results of photo-z. Finally, a few topics will be discussed including color-z function, hybrid method, and future photo-z for near-infrared era.

Zhiwei Pan

Title: Photometric Redshift Estimation of AGN

Abstract: Photometric redshift (photo-z) has been a useful tool in the study of AGN. In this talk, I will firstly give a little review of the photo-z methods of galaxies introduced by Topic 1and 2. In the second part, I will focus on the methods unique to AGN, e.g., using additional data such as apparent size, variability, and so on as prior information. Besides, different state-of-the-art methods (the classical SED fitting v.s. lots of ML methods v.s. hybrid methods) and corresponding photo-z performances for different types of AGN (Quasar, blazar, and so on) will be showed and compared in detail. Finally, I will we discuss some science that can be done with a sample of AGN with photometric redshifts.

Yuming Fu

Title: Photometric Redshift Estimation for CSST and Future Surveys

Abstract: In this talk I will briefly introduce the progress of the CSST photometric redshift (photo-z) pipeline, and discuss about possible improvements on current photo-z tools and projects. The CSST photometric redshift project has been testing SED template fitting, machine learning, and hybrid methods on mock CSST data to investigate observational effects on photo-z measurements, and to construct the optimal photo-z pipeline. While different photo-z methods yield similar and promising results, it is possible to further improve photo-z measurements with CSST data in synergy with upcoming surveys including Euclid and LSST. I will also introduce the deep imbalanced regression algorithm which may enhance the performance of photometric redshift estimation under imbalanced redshift distributions (which always exist). A novel paradigm called lifelong machine learning will be discussed to illustrate future photometric redshift platforms that learn from growing amount of data continuously.

Period: 1th March-30 August 2021

**LOC members: ** Changhao Chen (USTC), Yuming Fu (PKU, KIAA), Yuanqi Liu (PKU, KIAA), Zhiwei Pan (PKU, KIAA), Dong Yang (PKU, KIAA), Dingyi Zhao (PKU, KIAA), Mingyang Zhuang (PKU, KIAA) and Luwenjia Zhou (NJU).

**SOC members: **Lulu Fan (USTC), Luis C. Ho (PKU, KIAA), Song Huang (THU), Linhua Jiang (PKU, KIAA), Yingjie Peng (PKU, KIAA), Yong Shi (NJU), Ran Wang (PKU, KIAA), Jing Wang (PKU, KIAA) and Xuebing Wu (PKU, KIAA).

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