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Series II: Outlines, Titles and Abstracts of presentations

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Techniques to measure asymmetry and other non-parametric parameters sensitive to mergers and tidal interactions

1.1 Galactic scale measurements

The subsection begins with the subcomponents of galaxy, such as bulges, bars & stellar disk, which will be introduced by Zezhong and Huiling. These structures are consist of stellar objects, which makes the star formation history become important for understanding structure evolution, and this part of measurement will be introduced by Shun. Then Yun and Dewang will also introduce the measurements of other 2 important subcomponent of galaxy: gas and dark matter halo.

Zezhong Liang

Title: Measurement of Properties of Galactic Bars and Implications

Bars are considered to be long-lived asymmetric components that are prevail in local galaxies, and thus can play a significant role in redistributing angular momentum and matter through galactic disk. Quantifying bar properties, i.e. measuring bar length (size) and strength, is beneficial to understanding evolution of barred systems, yet in practice standard definition and method are still lacking. Indeed, various methods have been proposed to quantify bar properties preferentially from near infra-red imaging. In this talk, I will review methods to estimate bar properties, including isophotal analysis, Fourier analysis, multi-component or orthogonal decomposition, and gravititional potential (torque) field, and relavent tests or justifications of these method through simulations or mock images. Some observational results on correlation between bar properties and galaxy properties, e.g. with galaxy stellar masses, morphology and gas fraction, will also be briefly reviewed as an example of application.

Yun Zheng

Title: Measuring the Hi thick disk

The vertical structure of HI gas discs is an important tracer of the galactic potential and dynamical effects in spiral galaxies. Observationally,the vertical structure of an HI disk is quantified by the scale height to first order,which reflects properties consistent with the hydrostatic equilibrium model. I will talk about the measurement of the Hi thick disk through the method of sophisticated kinematical modellings focus on edge-on galaxies, which maybe helpful for the future IFU data analysis of CSST.

Dewang Xu

Title: Measuring the properties of the stellar halo

Stellar haloes are diffuse and often highly substructured envelope of stars surrounding the galaxy disks. Stellar halos are the inevitable outcome of the galaxy's merger. Hence, stellar haloes are the important laboratory for unraveling the past assembly histories of their central galaxies. Star counts can provide information like ages, metallicities, mass, and kinematics for our galaxy and very nearby spiral galaxies. However, robustly exploring the extragalactic stellar haloes is challenging due to the low surface brightness. Approximately 30 mag/arcsec^2 is needed to give reliable observations of the stellar haloes. So studies of stellar haloes around extragalactic galaxies have typically relied on either stacking or deep, "pencil-beam" studies. Some recent notable exceptions exist (Huang et al. 2018 using HSC survey and Rich et al. 2019 using 0.7m telescope to study 119 galaxy haloes). Furthermore, telephoto array telescopes, such as Dragonfly and Huntsman, are incredibly proper to explore the stellar haloes. This talk will discuss these methods and mainly focus on using HSC to explore the stellar halo by stacking method or just for individual galaxies. Moreover, I will review the comparison between observations and simulations. At last, I will talk about the dependence (or not) of stellar haloes on galaxy total stellar mass and central concentration.

Shun Wang

Title: Probe the star formation history by SED fitting

Spectral energy distribution (SED) fitting has been a widely used technique for deriving galaxy properties. By comparing and matching the observed SED to a set of model/tempelate SEDs or combinations of them, one can obtain a wealth of knowledge about the galaxy. Specifically, SED fitting can be used to derive the star formation history (SFH) of galaxies, which is critical for astronomers to understand galaxy evolution in different environments. I'll start from introducing the well-known work of Salim et al. (2007) which is based on broad band photometry from SDSS and GALEX data. And then focus on the more up-to-date work of Salim et al. (2016) with more details and improvements, e.g. templates, fitting method, systemmatics and comparison to individual tracers of star formation rate (Ha and mid-IR) and previous work. More recently, Zhou et al. (2021) developed an SED fitting method that focuses on the characteristic features in SED. I'll introduce their method, discuss its privileges and the obtained insights of galaxy evolution. In addition, I'd like to also introduce other SED fitting methods used in literatures and present a brief comparison among them.

Huiling Chen

Title: The thick disks of extra-galaxies: decomposition method and significance

The thick disk is a faint and extended stellar component of a galaxy. It was first found by the deep surface photometry of external early-type galaxies and later elaborate measurements in our own Galaxy. And several work proposed that the thick disk was quite common in S0 galaxies. However, accurate decomposition of thick disk is very difficult since it only has significant difference of distribution vertically. Most studies about the thick disks choose edge-on galaxies as their sample. One of the methods uses multi-color imaging which shows a clear difference on vertical color gradients to support the existence and help analysis the thick disk. Besides, model fitting can also be used to decompose the components of galaxies and directly measure the structure of the thick disk. Scientifically, if the parameters of the thick disks can be determined, it will not only provide us with more information about the stellar distribution in galaxies which is important for us to understand the formation and evolution of galaxies, but also allow us to determine other components of galaxy such as the bulge more accurately.

1.2 Mergers and interacting pairs

Following the logic flow, Xuchen will start will the asymmetry measurement of single galaxy, which will reflect the information of its merger history. Then, Yang will discuss the measurement of parameters which are sensitive to galaxy mergers and interactions, including stellar mass distribution and dust mass distribution. For complementary, Niankun will give the introduction for HI distribution. Then in summary, Pei will give a general overview for the effects of environment on galaxy evolution, which will lead the connection to Part 3.

Pei Zuo

Title: The diagnostics of environmental effects on galaxy evolution based on multiwavelength observations

The influence of environment affects galaxy evolution in various way. The properties of galaxies, such as, morphology, gas content, star formation, and color are significantly different in the residence of field, groups, or clusters. The gravitational interactions with other galaxies or the cluster potential and hydrodynamical effects as ram pressures stripping are the main effects of environment. The diagnostics based on multiwavelength observations, which include optical imaging, HI interferometric data, CO emissions, Hα or UV, X-ray, and radio continuum halo can be used for investigating environmental effects in galaxy groups, galaxy clusters, and different types of galaxies. These diagnostic tools can help us understand how the different components in the environment affect the evolution of galaxies in details, such as, asymmetry of stellar disk, ram pressure of gas, perturbed and extraplanar star formation distribution, and X-ray tail, etc. I will interview the observational tools of diagnosing the effects of environment and present the latest progress of multiwavelength analysis of galaxy evolution caused by environment.

Xuchen Lin

Title: Asymmetry - measurement and scientific significance

Galaxy's morphology is one of the most accessible tracers of its physical structure. The organization of light that reaches us at a certain wavelength can tell us the galaxy's current composition and its possible history. Asymmetry is the most intuitive morphology of a galaxy, which might indicate the galaxies history of perturbation. Decades ago, there has been attempt to measure it reliably. In this talk, I'll introduce the motivation of asymmetry measurements and its refinements during the past years. Then, its function in the research of environmental effects will be discussed.

Niankun Yu

Title: H I Content and Distribution in Nearby Early-type Galaxies

Early-type galaxies (ETGs) are typically red and dispersion-dominated with little or no gas. The neutral atomic hydrogen (H I) detection rate for ETGs is less than 10% in dense cluster environments, while ~40%-60% in the field. The H I distribution varies from regular disk to unsettled morphology, such as tidal or accretion tails, and H I clouds in the circular-galactic medium. However, large H I reservoirs are detected in some ETGs, such as NGC 612, IC 4200, and some ETGs detected by HIPASS. The abundant H I in ETGs show large, regular disks or ring like structures. Around 60% H I deficient ETGs with low stellar velocity dispersion show gas replenishment in the central region, which is likely to be detected in radio continuum and star formation activity.

Yang Li

Title: Measurement and application of structure parameters sensitive to galaxy dynamical perturbation

Different from traditional wide field surveys, deep surveys provide opportunities to measure more low surface brightness substructures around galaxies. Visual inspection of galaxy morphology and asymmetry are inefficient and non-quantitative. Many non-parametric measurements of galaxy-galaxy interaction or mergers are in the place to trace not only types of the dynamic process, but also stage or strength of it. In this talk we will discuss about a few kinds of techniques to measure the galaxy asymmetry, including Gini- M20, Multimode, Intensity and Deviation (MID), lopsidedness, tidal parameter, et al., and their dynamical origins. In addition, we will briefly introduce application of Machine Learning in identification of galaxy pairs.

1.3 Galaxy clusters

Begin with Kaixiang, the structure decomposition and classification of cluster members will be first discussed. In addition, Chao will also talk about the measurements of intra-cluster light. Then the other important properties of galaxy clusters is the dynamics, which will be introduced by Dong about the phase-space diagram. This lead to the question of how important the dark matter halo affect the dynamics and gas accretion, which will be introduced by Dingyi.

Kaixiang Wang

Title: Diffuse stellar envelopes and the formation of ultra-compact dwarf galaxies

Ultra-compact dwarf galaxies (UCDs) appear to be an intermediate population of stellar systems that bridge the gap between globular clusters (GCs) and dwarf elliptical galaxies in the size-luminosity plane. Since the discovery of UCDs over two decades ago, there has been controversy over their nature: are they truly nucleated dwarf galaxies that have been tidal stripped, or are they the most massive GCs? Recent observational evidence supports a tidal stripping origin for at least some UCDs. UCDs can therefore be used to trace the assembly history of massive galaxies. However, identifying the origin of individual UCDs is quite expensive for these barely resolved objects. And the contribution of each formation channel is not well constrained yet. In this talk, I will briefly review the previous work on both observations and simulations to investigating the origin of UCDs, and will also focus on the morphology and structure decomposition technique of some UCDs that are embedded in diffuse stellar envelopes. At last, I will discuss the ability of space telescopes (e.g. CSST and JWST) on identifying a complete sample of stripped nuclei and searching for black holes in these compact stellar systems (CSSs).

Chao Ma

Title: Measuring intra-cluster light in the galaxy cluster.

Intra-cluster light (ICL) is an important component of galaxy cluster or group. It is the diffuse, low-surface brightness starlight occupying the intergalactic space, comprised of stars which are not belong to any particular cluster galaxy. The stars constituting ICL are commonly believed to originate from the ongoing tidal interaction between galaxy members. The physical scales of the ICL is several hundreds of kpc. As luminous tracer of global gravitational potential of its host cluster, characterizing ICL can not only decode the information of cluster assembly history, but also aid our understanding of galaxy evolution. However, the studies of ICL have been limited due to low surface brightness and the entanglement with extended envelopes of bright cluster galaxies, and different studies have resulted in inconsistent results. In my talk, I will firstly introduce a plethora of ICL formation mechanisms that have been proposed in the literature. Then the main part will review the previous technical methods in quantifying and modeling ICL distribution. In the last, as a byproduct of my HFF cluster analysis, I will present our new way to derive the real distribution of ICL.

Dong Yang

Title: The Phase-Space Diagram for studying orbital history

Many physical processes take place at galaxy cluster and work together in galaxy quenching and morphology transformation. However, they work at varying cluster-centric radius with different timescales, which means they are sensitive to the path taken through the cluster, or, the orbital history of satellites. The orbital history can be parameterized in a number of ways, like time since infall, the closest distance to the center or the number of orbits completed since infall. In this talk, I will introduce the phase space diagram (the diagram of cluster-centric radius and velocity offset) for constraining the orbital history. I will show the reason why it can be used for studying the orbital history and then give some examples for nearby clusters.

Dingyi Zhao

Title: How to measure mass of dark matter halo

The measurement of dark matter halo's mass will help us to understand the formation and evolution of galaxies, provide a basis for interpreting the large scale structure observation, constrain the cosmology parameters and distinguish various dark matter models to probe the nature of dark matter. In principle, we can use the kinematics of some tracers, e.g., globular clusters, member galaxies, to model the distribution of the dark matter density distribution, then get the mass of dark matter halo. But this method has large limitation and its scatter will be large when the number of the tracers is small. Fortunately, Some other studies, such as the correlation function, reveal that the mass of dark matter halo is related with other parameters. This enable people estimate the mass of dark matter halo indirectly. The presentation will review some methods used to measure the mass of dark matter halo, for example, using the kinematics of satellite galaxy, using weak gravitational lensing, abundance matching method and so on.

2. Quasar/AGN variability

Outline

As an important observational property, the variability of quasars/AGNs provides basic characterization of the objects, and powerful tools to understand the physics of the central engine and the relation between the nucleus and the host galaxy.

Discussions on this topic begin with an overall introduction to the variability of AGNs, and expand to several directions. Reverberation Mapping (RM) of broad emission lines with both spectroscopic and photometric observations is capable of estimating the size of broad line region (BLR) and the virial mass of the supermassive black hole. Similarly, RM of the continuum can probe the fine geometry of the accretion disk, which goes beyond the spatial resolution of current facilities. With large time-domain surveys and space telescopes to be in place, future RM campaigns will yield exciting results on the distant universe. In addition to the X-ray-to-IR variability, the radio variability is important as it indicates the AGN activity in quasars. The physical connection between the X-ray and radio flux variations is interesting in understanding the AGN unification model. The last talk will be a review on the very recent progress in changing-look (CL) AGNs. As a relatively new sub-type of AGNs, the CL-AGNs provide a unique way to study the relationship between the AGNs and their host galaxies. Although CSST is a time-domain facility itself, the combination of CSST data and other surveys will greatly benefit the variability studies of quasars/AGNs.

Yuming Fu

Title: Introduction to the Variability of AGNs

Abstract: AGNs show luminosity variations on time scales from hours to years. Studies on AGN variability have been essential in understanding the physics of the central regions of AGNs, and in selecting quasar candidates for large sky surveys. To quantify the AGN variability and analyze the light curves, some statistical tools are developed, including the structure function and the Damped Random Walk (DRW) model. The correlations and delays between variations in different continuum or line components provide crucial information on the size and location of different components of the central region, giving birth to the Reverberation Mapping (RM) technique for measuring black hole masses. The spectral variability can even reveal AGN at transient phases, such as changing-look AGNs and tidal disruption events. In this talk I will introduce the basic characteristics of the variability of AGNs, and methods for interpreting observational results. I will also discuss the feasibility of variability studies by combining multi-epoch data from CSST and other space and ground-based telescopes.

Qinchun Ma

Title: Spectroscopic and Photometric Reverberation Mapping of Broad Emission Lines of AGNs

Abstract: According to the standard model of AGNs, the continuum light from the central accretion disk travels across the broad line region (BLR), generating broad emission lines through the photoionization process. The Reverberation Mapping (RM) technique exploits the time lag between light curves of optical continuum and broad emission lines to deduce the size and structure of BLR and to estimate the virial mass of the central supermassive black hole. Spectroscopic RM (SRM) programs have obtained hundreds of time lags between the broad emission lines and the continua, and established empirical relationship between the BLR size and the AGN continuum luminosity (R-L relation). Most of the previous SRM campaigns concentrate on the H$\beta$ emissions of low-redshift AGNs, while recent campaigns have been paying more attention to other broad emission lines such as H$\alpha$, MgII and CIV for higher redshift AGNs. Different broad emission lines can help us better understand the structure of BLR. Photometric RM (PRM) employs a broad-band filter to monitor the continuum variation and other suitable bands to trace the broad emission lines. Due to the high efficiency of time-domain surveys, PRM can monitor much more AGNs than SRM can do. Photometric surveys such as ZTF and the future LSST provide abundant data for PRM. However, because of the continuum contribution to the broad emission line band, PRM needs very good cadence, high photometric accuracy and careful analyses of data. We expect the CSST can improve the accuracy of light curves for PRM with better flux calibration to ground-based surveys.

Ruancun Li

Title: Mapping Physical Properties of Accretion Disk from Continuum Reverberation

Abstract: With the rare exceptions of recent interferometric observations of AGNs including 3C 273 and NGC 3783, the centi-parsec scales of AGNs in the UV/optical are too small to be directly resolved. Consequently, the most powerful tool available to probe the central regions of active galactic nuclei is reverberation mapping (RM), which substitutes time resolution for spatial resolution. Observationally, longer-wavelength continuum variations follow shorter-wavelength continuum variations from the UV through the NIR, predicting a temperature gradient that was largely consistent with the expectation from a standard Shakura–Sunyaev thin accretion disk, and a lamppost picture of the variable source. The fine geometry of this lamppost was also extensively studied by X-ray RM. Theoretically, however, the physical origins of this intrinsic variability are still unclear. Analytical calculations have shown the thermal instability in the inner disk region can cause small-scale phase transition, but the amplitude and timescale can not match observation very well. Recently, 3D global radiation magnetohydrodynamic (RMHD) simulations have also shown that the opacity bump-driven turbulence could account for such variability. With the help from CSST, future continuum RM studies can potentially help us grasp the dominate physics in the inner region of the accretion disk.

Yuanqi Liu

Title: Radio Variability as the Indication of AGN Activity in Quasars

Abstract: The variability of quasars over the entire electromagnetic spectra became known soon after the discoveries of such objects. Radio observations of optically selected samples of quasars showed that $\sim 10%$ of the objects are powerful radio sources. For radio-loud quasars, we can identify the changing jets through their radio variability. For instance, VLBI observations have revealed the own movements of some components in the jet of 3C 273. In radio-quiet AGNs, the absence of luminous jets allows us to probe radio emission from a wide range of possible mechanisms, including star formation, AGN-driven wind, free-free emission from photoionized gas, low-power jets and the innermost accretion disk coronal activity. Intrinsic variability (excluding the propagation induced effects) can be a strong indicator of AGN activity in radio-quiet quasars. In this talk, I will introduce the features and indications of radio variability in both radio-loud and radio-quiet quasars. Meanwhile, I will also mention the connection between X-ray and radio flux variations when being physically related (from a corona). With the high precision of localization given by CSST, long-term radio observations will provide more convincing results of AGN activity, especially in radio-quiet quasars.

Junjie Jin

Title: The Changing-look AGNs and Their Variability

Abstract: The “Changing-look” active galactic nuclei (CL-AGNs) are a newly-discovered class of AGNs that show the appearance (or disappearance) of broad emission lines within a short time scale (a few years to decades) and are often associated with dramatic changes in their continua emissions. Discoveries of CL-AGNs indicate a more complex picture of the AGN unification model. While the physical origin of CL-AGNs is still not fully understood, a few mechanisms are plausible explanations, including: 1) Variable obscuration, 2) Variable accretion rate and 3) Tidal disruption events (TDEs). The variability of CL-AGNs has been found in photometric bands from X-ray to mid-IR, and in the optical emission lines (e.g. Ha, Hb and MgII) and continua from spectroscopy, which provides powerful tools for finding CL-AGNs. The characteristics of variability are key to distinguishing between different mechanisms of CL-AGNs. CL-AGNs are also ideal samples to study AGNs and their host galaxies in a unique way. For example, the “turn-off” CL-AGNs provide us an unprecedented chance to directly investigate the host galaxy properties with minimal contamination from the luminous central engine. RM on CL-AGNs also helps us understand whether BLR changes after the type transition. In this talk, I will briefly review the discoveries of CL-AGNs and their possible physical mechanisms. I will also give some examples to show how to use the CL-AGNs as ideal cases to study the properties of AGNs and their host galaxies.

3. BPT diagram and other diagnostics to separate AGN from star forming activity

Outline

Since its first identification by observation in 1970s, black hole, especially its active phase known as Active Galactic Nucleus (AGN), has attracted increasing attention by worldwide astronomers. Despite myriads of studies, there are still lots of mysteries about AGN waiting for solved, such as AGN cycle, AGN feedback, and coevolution of AGN and host galaxies. This topic does not try to answer all these fancy mysteries but focuses on a more fundamental problem – how to construct a reliable and complete sample of AGNs for further analysis. To this end, we will first give an introduction of the multi-band diagrams for AGN selection in terms of their mechanisms and caveats (Lulu Zhang). Then, this topic will focus on the most widely used diagram for AGN identification – the BPT diagram, beginning with its mechanism and evolutionary history (Yuchen Liu), followed by the influence factors on its performance, specifically on the key BPT features that may change at high redshift (Weiyang Liu).

Lulu Zhang

Title: Introduction of Multi-band Diagrams for AGN Selection

Abstract: Supermassive black hole (SMBH) resides in most, if not all, massive galaxies, and ∼ 40% of these black holes manifest as AGNs. However, identifying AGNs is still a challenging work as any of the indicators for black hole activity (i.e., black hole accretion and subsequent physical processes) has its limitation. In general, multi-wavelength spectral energy distribution (SED) is required for complete and reliable census of AGNs. Without full spectral coverage of the electromagnetic radiation by AGNs, a lot of physical or empirical methods are developed to identify AGNs. Among them, the BPT diagrams are of the most widely used ones that will be introduced by following talks. As the supplement to BPT diagrams when even the optical spectrum is not fully available, this topic review gives an introduction about other useful diagrams for AGN identification (i.e., TBT Diagram; DEW Diagram; Color-Excitation Diagram; Mass-Excitation Diagram; P1 Color Classification; Mid-IR Color-Color Diagrams), especially about their physical mechanisms and applicable conditions.

Yuchen Liu

Title: Brief Introduction for Mechanism of BPT Diagram and their Application

Abstract: The extragalactic objects can be affected by many kinds of excitation mechanisms, which can operate different emission line features. So the intensity ratio becomes an important diagnostic for classfying the spectra of extra-galactic objects, which helps understand the relative fraction of star formation, AGN, and shocks in these galaxies. A common method to determine the excitation mechanism of galaxies is known as the BPT diagram, which initially use [OIII]λ5007/Hβ,[NII]λ6583/Hα and [O I]λ6300/Hα for distinguishing among normal HII regions, planetary nebulae, and objects with harder ionizing excitations (AGNs) and setting up a comprehensive classification system. The BPT diagram was firstly come up with in 1980s, and evolved a lot thereafter. For example, other lines like [S II](λ6716+λ6731)/Hα are involved and found sensitive to the hardness of ionizing radiation field. And many useful line ratios in the infrared are also included. In this talk, first, I will briefly introduce how BPT diagram was made, and explain its important role on the classifications of extragalactic objects. Also, I will talk about some different line ratios for different samples and their advantages.

Weiyang Liu

Title: BPT Diagram at High Redshift

Abstract: AGN and star-forming galaxies form two sequences on the BPT diagram. The position of sequence can be affected by the metallicity of the ionized gas, the ISM pressure, the hardness of the ionizing radiation field, and the ionization parameter. The evolution of galaxy properties will therefore change the position of galaxies on the BPT diagram as a function of redshift. For example, star forming galaxies at high redshift show an offset toward larger [N II]/Hα and [O III]/Hβ ratios on the BPT diagram compared with local galaxies, which may be caused by a higher ionization parameter, an elevated N/O at fixed O/H and/or a harder ionizing radiation field. In this report, I will first introduce how the key BPT features may change at high redshift based on photoionization model. Then I will show some observational results. Finally, I will explain different possible causes of this offset.

4. Slitless spectroscopy

Outline

Applied to plenty of research fields, from stars to cosmology, slitless spectroscopy has been a powerful tool to select different type of objects and study their properties. This series of talk aims to be a source of inspiration for CSST slitless spectroscopy science by reviewing the core science of HST slitless spectroscopy. We will firstly give a brief introduction to the entire history of slitless spectroscopy, including HST and CSST up-to-date instruments, pipelines and surveys (given by Jin Wu). Then, we divided the galaxy & QSO science goals of HST slitless spectroscopy surveys into two parts matching the following two talks. The first part mainly focusing on the emission (absorptions) lines, including their detection method, characteristics and application (given by Zhiwei Pan). The second part will present the other direction such as continuum detection & application, environment effects and so on (given by Yuxuan Pang). Yuxuan will also lead a brief discussion of CSST slitless spectroscopy task at last.

Jin Wu

Title: The history of slitless spectrum observations: instruments, techniques, telescopes and surveys

Abstract: Spectroscopy is a fundamental technique for people to study physical properties of astronomical objects. The earliest recorded spectroscopic observations were those for the Sun using prisms by human eyes. The objective prisms system were also used to build the earliest star catalogues. With the increasing of observation depth and photometric accuracy, the overlapping contaminations of nearby objects became non-negligible. People had to select dispersion directions to avoid contaminations for specific objects, and the contaminated objects were never used due to the limited data processing techniques. In recent years, with the development of computing power and data processing methods, we are able to make global models for slitless spectroscopic observation fields and recover some contaminated spectra These techniques will dramatically improve the utilization ratio of general purposed slitless spectroscopic surveys, like the HST and CSST survey. In this talk, I will firstly go through the history timeline and give a brief introduction to the development of slitless spectroscopic observations. I will present the relevant instruments, telescopes, and techniques to show you the basic concepts of slitless spectroscopic observations. Then I will introduce the data processing methods and softwares of slitless spectroscopy. Finally, I will talk about the CSST slitless spectroscopy and the recent progress of its data reduction pipeline.

Zhiwei Pan

Title: The slitless spectroscopy science with emission (absorptions) lines

Abstract: The HST slitless spectroscopy mode opens a new studying era of galaxy evolution. Among the several HST insturments, the latest ACS and WFC3 with corresponding grisms have become very helpful tools to help obtain slitless spctra with enough quaility for science, so in this talk I only invovle the survey (e.g., GRAPES, PEARS, 3D-HST, CLEAR, and so on) using ACS and WFC3. Since the emission line is the most available, reliable, and useful information that we can derive from the slitless spctra, I will focus on the science with emission lines. In the first part, I will introduce the most basic and direct science, sample selection and confirmation. In the meantime, redshift of these sample could be measured from the emission (absorption) lines or some break features. A sample with spectroscopic redshift can be used for further study (e.g.,cosmology, clustering, luminosity function, and so on). Secondly, some extended scinece with emission lines will be covered. For example, poeple could estimate the EW and line rations in order to explore gas metallicity, star formation rate (SFR), and other properties.

Yuxuan Pang

Title: The slitless spectroscopy science with other information

Abstract: Following the topic 2, the last talk will briefly focus on the HST slitless spectroscopy survey, GLASS, FIGS, and CLEAR, which mainly cover following science goals. First, using more deeper slitless spectra in several different directions, we could get the continuum of fainter objects with the help of forward modeling method. Second, using the modeling results, one can briefly derive the star formation history (SFH) of those galaxies, which helps us learn the galaxy formation in the cosmic noon. Third, Combining the continuum and more precise absorption line results together also helps us to estimate the metallicity in stellar phase, which could tell us the metallicity enrichment process and metallicity gradient in galaxies. What’s more, several case studies in GLASS survey that focus on the environment effects on emission lines or SFR will be discussed. At last, a brief discussion of CSST slitless spectroscopy survey will be given.

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