Colloquiums and Seminars

The early growth of black holes (BHs) in atomic cooling halos is likely influenced by feedback on the surrounding gas. While the effects of radiative feedback are well-documented, mechanical feedback, particularly from AGN jets, has been comparatively less explored. Building on our previous work that examined the growth of a 100-solar-mass black hole in a constant density environment regulated by AGN jets, we have expanded the black hole mass range from 1 to 10,000 solar masses and adopted a more realistic density profile for atomic cooling halos. We provide an analytic models for jet cocoon propagation and feedback regulation. We also identify several critical radii—namely, the terminal radius of jet cocoon propagation, the isotropization radius of the jet cocoon, and the core radius of the atomic cooling halo—that are crucial in determining black hole growth, given specific gas properties and jet feedback models. In a significant portion of the parameter space, our findings show that jet feedback substantially disrupts the halo-core gas density during the initial feedback episode, halting black hole growth beyond 10,000 solar masses. Conversely, conditions characterized by low jet velocities and high gas densities enable sustained black hole growth over extended periods. We have identified the parameter space that allows a stellar-mass black hole to grow into a supermassive black hole at high redshift by accreting gas from an atomic cooling halo.

Detailed studies of our Local Group benchmark our understanding of galaxy formation. Stellar metallicities are key tracers of the baryonic astrophysics shaping galactic properties, but they are challenging to measure in distant and faint galaxies that are pushing push our understanding of dwarf galaxy formation to new regimes in luminosity, star formation history, and environment. For my thesis, I present hundreds of new stellar metallicities in faint, Local Group dwarf galaxies, measured through a novel use of HST narrowband Ca H&K imaging. Our imaging includes: 1) 463 stars in 13 ultra-faint dwarf galaxies (UFDs) around the Milky Way, which effectively doubles the number of stellar metallicities in all known UFDs, b) 374 stellar metallicities in the quenched field dwarf galaxy Tucana (Mv = -8.8, D = 1 Mpc), a factor of ~7 increase over literature spectroscopy, and c) 286 stellar metallicities in two M31 dwarfs And XVI and And XXVIII. I will present highlights from the wide range of science cases enabled by our data, which include: 1) chemical evolution modeling to put novel constraints on the baryon cycle in UFDs, 2) new metallicity benchmarks for cosmological simulations of the faintest galaxies, 3) high-fidelity metallicity gradients that constrain stellar feedback and DM core formation models in dwarf galaxies. I conclude with a discussion on the immense scientific potential for narrowband Ca H&K imaging to transform stellar metallicity studies at the edge of the LG and beyond.

Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGN) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously observed in accreting black holes. In my talk I will present the results of several dedicated high spatial resolution (~60-100 milliarcsecond) 100 GHz ALMA campaigns focussed on nearby radio-quiet AGN. We find an extremely high detection rate (~95%), which shows that nuclear emission at mm-wavelengths is nearly ubiquitous in accreting SMBHs. Our high-resolution observations show a tight correlation between the nuclear (1-23 pc) 100GHz and the intrinsic X-ray emission. This shows the potential of ALMA continuum observations to detect heavily obscured AGN (up to an optical depth of one at 100GHz, i.e. ~1e27 cm^-2), and to identify binary SMBHs with separations <100 pc, which cannot be probed by current X-ray facilities.

The initial mass function (IMF) is crucial for our understanding of star and galaxy formation and evolution, while our knowledge of the IMF in the early universe remains limited. Recent advancements in numerical simulations have revealed that stellar masses in primordial environments are significantly larger, reaching several hundred solar masses, compared to observations in present-day environments. This suggests the existence of an IMF transition throughout cosmic evolution. Through three-dimensional hydrodynamics simulations, we have discovered that both metallicity and redshift play crucial roles in determining the IMF. Metallicity influences the cooling capability, while the redshift affects the temperature floors by altering the cosmic microwave background temperature. Our simulations have revealed that the IMF becomes top-heavy in environments with Z/Zsun < 0.01 or z > 10. These results may provide an explanation for recent observations by the James Webb Space Telescope (JWST), which have revealed an unexpected abundance of high-redshift luminous galaxies, showing an increase in UV luminosity at fixed stellar mass.

The formation of supermassive black holes (SMBHs) is one of the biggest challenges in astrophysics. The Direct Collapse (DC) model provides seed BHs with a mass of 10^5 Msun and explains the origin of high-redshift SMBHs. It has been assumed that these seed BHs can only form in primordial gas. However, this condition is very restrictive, resulting in a low number density of seed BHs. Consequently, the DC model cannot account for the entire population of SMBHs. In this seminar, we investigate whether massive seed BHs can form in a metal-enriched universe, which is more prevalent. By conducting hydrodynamical simulations across various metallicity enrichments, we found that stars with masses greater than 10^4 - 10^5 Msun can form when Z/Z_sun <= 10^-3. In finite metallicity cases, dust cooling promotes low-mass star formation. However, the gas preferentially feeds the massive stars, similar to the primordial case, resulting in the formation of supermassive stars. This model offers a larger number of seed BHs compared to the previous DC model, providing a universal explanation for the origin of SMBHs in terms of their abundance.

Cold molecular gas is a key component in galaxy evolution, as it forms stars, bears feedbacks, and feeds supermassive blackholes. Interferometric observaions of the Atacama Large Millimeter/submillimeter Array (ALMA) have remarkably advanced this field in the past decade. For spiral galaxies, a larger sample with higher physical resolution than before is systematically surveyed. I will discuss the molecular gas morphology and kinematics in three megamaser (Seyfert-II) galaxies at resolutions of around 100 pc. We found prevelant irregularities, potentially related to active galactic nucleus feedback and supermassive blackhole feeding. For early-type galaxies, it is now feasible to spatially resolve giant molecular clouds (GMCs). I will talk about GMCs at 15-pc resolution in the lenticular galaxy, NGC1387. Their dynamical states (Larson relations, virial parameters, etc.) are surprisingly similar to those in spiral galaxies. For our own Milky Way centre, a new ALMA large programme has mapped the central molecular zone (CMZ) at unprecedented spatial (sub-pc) and spectral (0.2 km/s) resolutions. Here, we found evidence of galactic shear effects and magnetic fields driving gas structure morphologies. I will conclude by summarising the physical drivers of molecular gas properties at different scales and in different environments.

Nearby low-metallicity dwarf galaxies are excellent laboratories to study astrophysical processes in the first galaxies at high redshift. I will present the initial results of our multiwavelength study of the dwarf galaxy KUG 1138 + 327 at 24.5 Mpc and its group environment. This galaxy shows an unusual tadpole morphology as a result of a very young starburst with extremely low (6\% solar) metallicity. We obtained Chandra X-ray observations as well as a JVLA continuum and HI survey of the region in several array configurations. The Chandra data reveal a dominant point-like source with an average 0.3-10 keV luminosity of $10^{40.3}$ erg/s and a variability by a factor of $\sim 2$ over months. This extremely luminous X-ray source is apparently associated with the young central cluster of the starburst and has an elongated nonthermal radio continuum counterpart of the order of $\sim 200$~pc. The radio, optical, and X-ray results suggest that the X-ray source could well be an intermediate-mass black hole undergoing sub-Eddington accretion. This scenario also explains the prominent emission lines [He\texttt{II}]$\lambda$4658 and [Ar\texttt{IV}]$\lambda$4711 in the starburst spectrum. These findings provide insights into questions such as: What is the radiation environment produced by the first generation of stars? What are the feedback processes in high-z star-forming regions at very low metallicity? We also find that KUG 1138+327 is associated with two additional far-UV bright dwarf galaxies, a rare phenomenon in the local Universe. The HI morphology of these galaxies strongly suggests that they have undergone tidal interactions, which may explain the recent low-metallicity gas feeding and starburst in KUG 1138+327.

The interstellar medium (ISM) is highly structured and multiphase, and our knowledge of it stems from multi-wavelength radiation dictated by ISM chemistry. Hydrodynamical simulations coupled with chemistry networks have been our primary tools for predicting these observables. However, interstellar dust, the catalyst of ISM chemistry, is commonly treated as a non-evolving species. In reality, dust is constantly created, destroyed, and reformed, with significant spatial variations in its abundance. In this talk, I will discuss recent progress in resolved galaxy-scale simulations of low-metallicity dwarf galaxies coupled with a dust-evolving chemistry network where dust evolution is followed explicitly rather than treated in a sub-grid fashion. I will demonstrate how dust evolution helps explain the observed CO luminosity at low metallicity, which has important implications for galaxies in the early universe observed by JWST. I will also discuss the survival of dust in galactic outflows and its role in the observed molecular outflows, whose origin remains a puzzle.

Galaxy survey analyses often infer lower values of two cosmological parameters, omega_matter and sigma_8, compared to the constraints from the cosmic microwave background. Is that a hint of new physics? Before any such conclusion we need to robustly probe this tension using novel and independent techniques. Moreover, ongoing and upcoming surveys of galaxies will contain an immense wealth of information in the smallest scales, which is under-utilised in most cosmological analyses. Vast amounts of information is often discarded because the smallest scales in survey data are most affected by systematics such as baryonic feedback, and because of the inherent difficulty involved in modelling the fully nonlinear regime. Because of these two key motivations, we developed Basilisk, a new Bayesian hierarchical forward-modelling technique to optimally extract maximum information from the smallest and fully non-linear scales of redshift survey data. It uses that complementary information to constrain galaxy-halo connection with extreme precision, and to constrain cosmological parameters in a completely novel approach that is free of halo assembly bias systematics and incorporates baryonic effects. I will discuss the methodology behind the new probe, the key results with SDSS data, and what can be achieved with upcoming galaxy surveys.

Upcoming spectroscopic surveys like PFS and DESI are beginning to release their first data, revealing an unprecedented three-dimensional view of the cosmic large-scale structure through the spatial distribution of (billions of) galaxies. Such surveys hold the potential to unveil key insights into the nature of dark matter, dark energy, and gravity—but fully realizing this potential requires extracting the maximal (reliable) information from galaxy maps. Traditional analyses compress such maps into summary statistics, while uncertainties in galaxy formation and evolution further complicate interpretation.
I will introduce the field-level inference program, which directly models the full galaxy maps on scales where astrophysical complexities can be robustly marginalized over. I will also discuss ongoing efforts to apply FLI to DESI and PFS data, including developments to account for observational systematics. If time allows, I will highlight how FLI can contribute to studies of galaxy formation and evolution through cross-correlation analyses.

Turbulence in protoplanetary disks affects dust evolution and planetesimal formation. The vertical shear instability (VSI) is one of the candidate turbulence-driving mechanisms in the outer part of the disks. Since the VSI requires rapid gas cooling, dust particles in disks can influence and potentially control VSI-driven turbulence. However, VSI-driven turbulence has strong vertical motion, causing vertical diffusion of dust particles. We perform global two-dimensional hydrodynamical simulations of an axisymmetric protoplanetary disk to investigate how the VSI drives turbulence and maintains a balance between dust settling and diffusion. These simulations account for the dynamic interplay between dust distribution, cooling rates, and VSI-driven turbulence. We find that VSI mixing, dust settling, and the local dust cooling reach an equilibrium, forming a thick dust layer with a dimensionless vertical mixing coefficient of approximately $10^{-3}$. The ability of VSI to sustain this equilibrium depends on dust size and dust-to-gas mass ratio. Larger grains or lower mass ratios weaken the turbulence, leading to dust settling. Our results suggest that in VSI-dominated disks, dust grows under turbulence with intensity varying by dust size. Finally, I will talk about the application of the early disk stage and further planet formation.

The presence of supermassive black holes (SMBHs) in galaxies is well known. But why most of them remain silent in today's Universe is poorly understood. Sgr A* at the center of our Milky Way Galaxy is an asymptotic example of such a low-luminosity SMBH. The proximity of Sgr A* provides a unique opportunity to observe and understand the dynamics of black hole activity and its interplay with its Galactic nuclear environment. Based primarily on deep X-ray observations and computer simulations, I will discuss what Sgr A* has been doing recently and how this interplay may have determined the life cycle of black hole activity and other galactic nuclear processes that profoundly affect the structure and evolution of our Galaxy. Such studies, complemented by observations of other nearby SMBHs and their environments, provide insights into the functioning of galactic ecosystems and astrophysical processes under extreme conditions.

1. Reference HOPS Calibration Pipeline for millimetre-VLBI Arrays
We present a new version of the EHT-HOPS calibration pipeline (Blackburn et al. 2019), designed to process data from the evolving EHT array, for handling both current and future configurations. This updated pipeline supports the calibration of multiple years of EHT data and similar VLBI arrays, accommodating changes in instrumentation, frequency bands, and array configurations (with and without ALMA). The refactored pipeline improves performance, code integration, and usability, features updated diagnostics, and supports hybrid polarization bases, tested using 2017 M87 data. Planned future developments include complex bandpass and full polarization calibration, parallel processing, and integration with new data formats to generate standardized calibrated data products for all EHT campaigns.

2. Interpol: A Polarized Imaging and Calibration Code for Heterogeneous VLBI Arrays
Very Long Baseline Interferometry (VLBI) has paved the way for groundbreaking astrophysical discoveries, such as black hole jets, planet formation, and imaging of the shadow of a black hole. However, transforming the raw VLBI data into an interpretable image is a formidable challenge. VLBI imaging requires modeling an entire image from a sparse sampling of Fourier components and the complicated instrument response to the incident electric field. While the instrument response and image are traditionally analyzed separately, distinguishing instrumental effects from source structure is complex and non-linear for heterogeneous VLBI arrays such as the EHT or GMVA. In this talk, I will present Interpol, a novel Bayesian simultaneous imaging and calibration algorithm implemented in the VLBI software Comrade. Interpol can reconstruct the full Stokes polarized image and instrumental response for circular, linear, and mixed feed arrays. We demonstrate Interpol on various VLBI arrays, including the VLBA, Event Horizon Telescope, and VLBA sources, demonstrating improved image resolution with fewer image artifacts and discuss its place relative to Polconvert, a common tool used to convert ALMA data from linear to a circular feed basis.

I will discuss a perspective on counting and locating the majority of our Universe's baryons from the scant signatures imprinted on the light and signals of distant sources (quasars and fast radio bursts). These data offer what I consider the most robust measurement of a cosmological parameter (the baryonic mass density) and I'll describe previous and ongoing efforts to establish where the majority of this matter resides. If time permits, I'll briefly detail my new adventure to measure – again in silhouette – the constituents of our Earth's oceans (e.g. phytoplankton).

Transneptunian Automated Occultation Survey (TAOS II) is a blind occultation survey with the primary goal to measure the size distribution of small (~1 km diameter) Trans-Neptunian Objects (TNOs). Such events are extremely rare (< 0.001 per star per year) and very short in duration (~200 ms). To enable serendipitous discovery many stars must be monitored simultaneously at high cadence. TAOS II will monitor 2,000 to 10,000 stars simultaneously at a cadence of 20 Hz using three 1.3 meter F/4 telescopes operating at San Pedro Mártir Observatory (SPM) in Baja California, Mexico. Over five years of operations, the TAOS II dataset will collect ~3 PB of multi-telescope 20 Hz lightcurve data for hundreds of thousands of objects. This unique dataset will provide ample opportunity for science outside of the primary goal to measure the TNO size distribution. TAOS II will achieve first light in Spring 2025. The current status and the near future plan will be presented in this talk.

Stable isotope measurements of natural samples over the past 80 years have been applied to numerous systems across space and time. Oxygen isotopes for example are used in polar ice and oceanic foraminifera to determine global temperatures from yearly to millions of year time scales. Atmospheric greenhouse gases stable isotope measurements are used to track sources and sinks of molecules and to define their chemistry. Meteorite isotope measurements identify pre solar system species such as grains of stardust to define their stellar sources and also to resolve the formation of the solar system chemical processes These applications require high level physical chemical understanding of the processes. Of note are those involved with photodissociation. Most recently we have partnered with Raphy Levines theory group in Jerusalem and made synchrotron measurements to develop the most complete isotopic theory to date, which will be presented.

Observational constraints on gas surface density in protoplanetary disks are crucial for understanding planet formation. However, directly measuring it is challenging due to the lack of a robust tracer, leading to uncertainties of orders of magnitude even in total disk mass estimates. To address this issue, we propose using the pressure broadening of CO emission lines. Since pressure-broadened CO lines are sensitive to hydrogen volume density, they enable a direct determination of the total gas surface density. We applied this method to three transition disks and successfully constrained their gas surface density profiles for the first time. By comparing these profiles with dust surface density distributions, we directly demonstrate that dust grains are trapped at gas pressure maxima in these disks. Additionally, our estimates of total gas mass exceed the minimum-mass solar nebula, suggesting that further planet formation remains quantitatively feasible.

We derive an effective equation and action for the propagation of gravitational waves (GW), encoding the effects of interaction and self-interaction in a time, frequency and polarization dependent effective speed.This effective approach generalizes the effective theory of dark energy and allows to make model independent predictions of observable quantities. We discuss how the frequency and polarization dependence of the GW-EM distance ratio and time delay provide a new test of general relativity and its modifications, and more in general of the interaction of GWs with other fields. As an application, consistent with the effective theory of dark energy, we show that for a luminal modified gravity theory, the gravitational-wave propagation and luminosity distance are the same as in general relativity, but depending on the matter gravity coupling, the electromagnetic luminosity distance can be modified w.r.t general relativity.

Cosmological hydrodynamical simulations are essential for understanding the interplay between dark matter and baryons, yet they remain computationally expensive and struggle to fully reproduce observational constraints. At the same time, tensions in key cosmological parameters, such as σ₈, raise the question of whether new fundamental physics or baryonic feedback effects are responsible. Recent advances in machine learning and differentiable modeling offer new approaches to improving these simulations and connecting them to observations, from GPU acceleration to field-level inference techniques that bypass traditional summary statistics. In this talk, I will explore how integrating ML and related optimization techniques with hydrodynamical simulations can enhance our ability to extract cosmological information, discuss the challenges and limitations of these methods, and outline the path toward a more efficient and robust framework for large-scale structure inference.

Over the past decade, advanced wide-field and multi-messenger transient surveys have revolutionized our ability to watch stellar explosions in real time. Coupled with rapid follow-up observations and extensive numerical models, I will highlight recent breakthroughs — such as the first robust electron-capture supernova at the boundary between white dwarf formation and iron core collapse, mysterious yet ubiquitous mass-loss activity in the final stages of massive stars, and kilonova emission from a binary neutron star merger detected in gravitational waves — that reshape our understanding of stellar evolution and explosion physics. I will also discuss their wide-ranging implications, including nucleosynthesis, galactic chemical evolution, and compact object populations. Finally, I will conclude with the promises in the coming golden decade of time-domain astronomy with the Vera C. Rubin Observatory’s LSST, Nancy Grace Roman Space Telescope, LIGO-Virgo-KAGRA’s fifth observing run, and the Bustling Universe Radio Survey Telescope in Taiwan.

XRISM (X-Ray Imaging and Spectroscopy Mission) is an X-ray observatory led by JAXA and NASA. XRISM carries two X-ray observing systems, called Resolve and Xtend. Resolve consists of an X-ray mirror and an X-ray microcalorimeter, while Xtend combines an X-ray mirror with an X-ray CCD. Resolve has high energy resolution of 5 eV at 6 keV X-ray photons, and it is effective even for spatially extended objects since it is a non-dispersive spectrometer. Xtend has a wide field of view of more than 900 arcmin2 (larger than the full moon!). XRISM was successfully launched in September 2023. However, due to a gate valve in front of the microcalorimeter failing to open, Resolve is unfortunately unable to observe X-ray photons below 2 keV. Nevertheless, XRISM observations are yielding exciting results. In this talk, I will present some of the recent results from XRISM.

Relativistic jets throughout the Universe transport energy from a galaxy's central supermassive black hole to extragalactic distances. Many jets, including the spectacular jet from the giant elliptical galaxy M87, are thought to be launched via the Blandford-Znajek (BZ) mechanism, where magnetic fields extract the black hole's spin energy. However, BZ energy extraction has never been confirmed observationally. In this talk, I will discuss how resolved images of supermassive black holes from the Event Horizon Telescope (EHT) are addressing long-standing questions about black hole accretion, magnetic fields, and jet launching. I will discuss how we obtain direct black hole images and how we interpret them with both analytic models and large-scale simulations. Connecting images to simulations indicates that in both M87 and the Galactic Center black hole Sgr A* the accreting plasma is arrested by strong coherent magnetic fields. I will show how the pattern of linear polarization in black hole images directly probes the direction of electromagnetic energy flux and encodes the black hole spin. I will also discuss how recent advances in simulating magnetically arrested accretion around black holes – including better coupling of gas-dominated and magnetically-dominated plasma and self-consistent electron-ion thermodynamics – are improving our ability to make sense of near-horizon images while raising new puzzles. I will show how future observations with the expanding EHT and the Black Hole Explorer (BHEX) space mission will increase the resolution and sensitivity of near-horizon images, expanding the sample of resolved black hole shadows and enabling precision measurements of black hole spin and jet launching in M87. Advances in horizon-scale theory and data over the next few years present an unprecedented opportunity to directly map out black hole magnetospheres and determine whether or not jets are powered by black hole spin energy extraction.

The submillimetre JCMT Transient Survey was the first dedicated monitoring of deeply embedded protostars on years timescales. Initially devised as a pilot program to determine the potential for observing variability associated with mass accretion, the survey has been a resounding success, revealing clear brightness variations from more than 20 sources, 30% of the relevant sample, during the earliest stages of formation! From these humble beginnings, the survey team has expanded its investigations using a myriad of ground-based submillimetre and space-based mid-infrared observatories. This past weekend at SNU the team celebrated the many successes thus far and contemplated the future. Along with the venerable JCMT, there are two additional ground-based submillimetre telescopes that will be important for time domain astronomy, and protostellar variability in particular. CCAT will achieve first-light by the end of this year and soon be scanning the sky nightly, primarily as a cosmology instrument. Its wavelength range, however, will reach to 350 microns, making it the ideal ground-based observatory for monitoring protostars. Furthermore, with its cadence of all sky observations CCAT, and dedicated time domain program, CCAT will reveal many additional submillimetre variables. Further into the future, the European (and Japanese) AtLAST aims to provide both an extremely large dish and an impressive state-of-the-art suite of instruments. This should allow for star formation variability studies across the Galaxy! In space, both JWST and SPHEREX will provide mid-infrared capabilities for the near future. However, NEOWISE, which produced excellent maps of the sky twice yearly recently reached the end of its lifetime and there is now a large gap in our ability to monitor protostars. We thus eagerly await NEO Survey, which is expected to launch in 2027. And, further out there is the possibility of a NASA Probe mission in the far infrared, PRIMA, which has been keeping time domain astronomy, and protostar monitoring, a key science driver. I look forward to discussing each of these opportunities with an emphasis on the their strengths in time-domain science, and protostellar variability in particular.

Understanding the evolution and behavior of interstellar ices is essential for interpreting molecular observations in astrophysical environments. This talk presents two complementary studies conducted at the Photoprocessing and Spectroscopy Laboratory, simulating space-like conditions using ultra-high vacuum and cryogenic technologies. The first study investigates how photon-induced desorption contributes to the presence of volatile molecules in the gas phase within dense molecular clouds. By examining the evolution of ices under energetic irradiation—from cold molecular clouds to protoplanetary disks—we highlight the critical role of absorption cross-sections in the solid phase. This perspective helps explain the discrepancies reported in photodesorption yields across different experimental groups. The second study focuses on the interaction between interstellar ices (CO, CO2, and H2O) and carbonaceous dust grains. Using temperature-programmed desorption (TPD), we found that porous amorphous carbon enhances molecular trapping and alters desorption dynamics, especially for CO and CO2. In contrast, H2O remains largely unaffected by substrate differences due to strong intermolecular hydrogen bonding. These findings underscore the importance of dust grain properties in shaping ice behavior and survival in cold astrophysical environments. These studies provide deeper insight into the physical and chemical processes governing interstellar ices, with implications for astrochemical modeling and observational interpretation.

(1) After summarizing the results of the GRBAlpha, GRBBeta, and VZLUSAT-2 nanosatellites that are detecting gamma-ray bursts, I will present the status and the science case of the Quick Ultra-Violet Kilonova surveyor - QUVIK mission. QUVIK is an ultra-violet (UV) space telescope on an approximately 200 kg small satellite with a moderately fast re-pointing capability and a real-time alert communication system, approved for a Czech national space mission. The satellite, which is expected to launch in five years, will provide key follow-up capabilities to increase the discovery potential of gravitational wave observatories and future wide-field multi-wavelength surveys. The primary objective of the mission is the measurement of the UV brightness evolution of kilonovae, resulting from mergers of neutron stars, to distinguish between different explosion scenarios. The mission, which is designed to be complementary to the Ultraviolet Transient Astronomy Satellite - ULTRASAT, will also provide unique follow-up capabilities for other transients both in the near- and far-UV bands. Between the observations of transient sources, the satellite will perform observations of other targets of interest for the scientific community, such as stars, stellar systems, and galactic nuclei.
(2) Four years after launch of the first prototype of a our nanosat-sized (75 cm^2) gamma-ray detector on board of GRBAlpha the number of similar devices on orbit is reaching a dozen, 4 of them operated by the team of Masaryk University (Brno, Czech Republic). A pair of identical detectors was sent to space in January 2022 as a secondary payload on board of a 3U CubeSat VZLUSAT-2 again on a SSO orbit. Both satellites has so far detected about 300 gamma-ray transients, including over 100 GRBs that are primary target of these mission, aiming at large constellations that could cover all sky with coarsely resolving triangulation. Besides this unexpectedly successful harvest long lifetime of both missions has allowed to analyze the degradation of the detector, especially silicon photomultipliers (SiPMs) that are known to be prone to radiation damage. Use of SiPMs as photon counters gains increasing popularity in space projects and this in-orbit aging and changes of their gain is highly important for design of next nanosatellite missions. A sequel called GRBBeta has been recently commissioned and bigger constellations like HERMES SP are finally in orbit. We will discuss possible improvements and prospects of joint efforts in GRB detections and an efficient downlink through a network of SatNOGS stations.

Our Solar system features outer giant planets and inner small planets. Long-term monitoring of Kepler and TESS systems is fueling a growing consensus that outer giant planets and inner small (rocky) planets seem to go together. But the cause of this correlation is unknown, as is the effect that the presence or absence of an outer giant has on the properties of the inner planets. To understand potentially Earth-like planets, we must understand their complete planetary systems. I present a program of research that addresses this science gap, taking advantage of exciting new ASIAA facility access to the Magellan, Giant Magellan, and ESO Extremely Large Telescopes. Key science questions include: How do the mass and radius of the inner planets vary with and without a giant companion? What is the composition of the inner planet's atmosphere? How does the outer giant influence the orbital properties (eccentricity, inclination, obliquity, etc.) or the multiplicity of the inner worlds? This project, led by ASIAA's exoplanet team in collaboration with key international partners, promises to deliver unprecedented new understanding of the composition, architectures, and atmospheres of planets orbiting nearby stars using the latest high-precision data from ground and space-based telescopes.

Taiwan’s geographic location provides a unique longitudinal advantage for time-domain astronomy, enabling coverage of critical time windows in global transient monitoring networks. Leveraging the flexibility of small-aperture telescopes, the 40 cm and 1 m telescopes at Lulin Observatory are routinely used for real-time follow-up of rapidly evolving transients, including kilonovae, fast blue optical transients (FBOTs), fast X-ray transients, gamma-ray bursts, and young supernovae. These efforts have resulted in the identification of multiple optical counterparts, particularly in response to Einstein Probe alerts, which are promptly reported to the community. The team is also actively involved in the ePESSTO+ and ZTF collaborations, and works with the ATLAS survey to capture the earliest phases of supernova explosions. Through the engagement of citizen scientists, the project aims to maximize the scientific return of these facilities and contribute meaningfully to the study of extreme transients.

Star formation in the early universe was characterized by the prevalence of massive stars, shaped by the thermal and chemical properties of low-metallicity gas. I will begin by discussing the formation of the first stars based on radiation hydrodynamics simulations, which show that they typically grow to tens to hundreds of solar masses, often forming in binary or multiple systems. Next, I will examine the gradual evolution of the initial mass function (IMF) with increasing metallicity. Dust-induced cooling becomes effective around 10^-5 to 10^-4 Zsun, allowing low-mass star formation, though massive stars still dominate. As metallicity increases, the IMF shifts toward a bottom-heavy distribution, approaching a Salpeter-like form near 0.1 Zsun. I will also discuss the role of CMB heating at redshifts z greater than 10, which suppresses gas cooling and leads to a more top-heavy IMF, increasing the number of supernovae by a factor of a few compared to the Chabrier IMF at Z around 0.1 Zsun. Finally, I will consider the implications for the unexpectedly large number of UV-bright galaxies observed by JWST at z greater than ~10. Our simulations suggest that star cluster formation at metallicities around 10^-2 to 10^-3 Zsun, where the IMF remains top-heavy and radiative feedback is not yet too strong, can account for the high UV luminosities, as the star formation efficiency remains sufficiently high.

The direct collapse scenario, which predicts the formation of supermassive stars (SMSs) as precursors to supermassive black holes (SMBHs), has traditionally been considered viable only in metal-free environments. However, the strong far-ultraviolet (FUV) radiation required to suppress fragmentation is more likely to occur in chemically enriched regions. In this talk, I will present results from radiation hydrodynamic simulations of star cluster formation in clouds with metallicities from Z = 10^-6 to 10^-2 Zsun, incorporating detailed thermal and chemical processes and stellar radiative feedback. Our simulations, extended to two million years, show that SMSs exceeding 10^4 solar masses can still form at Z less than about 10^-3 Zsun. Despite small-scale fragmentation, accretion flows are funneled into a few central stars through "super-competitive accretion." At higher metallicities (Z ~ 10^-2 Zsun), enhanced metal-line cooling induces large-scale fragmentation, suppressing SMS growth and instead forming dense clusters dominated by very massive (~10^3 Msun) stars. These clusters resemble young massive or globular clusters seen in both the early and local universe. Our results suggest that SMS formation remains viable below ~10^-3 Zsun, potentially increasing the number of massive seed black holes. Above this threshold, the same conditions naturally transition to dense stellar cluster formation, offering a unified framework for early SMBH and star cluster origins.

Ultra-high-energy cosmic rays (UHECRs) are the most energetic particles ever observed, reaching beyond 10^20 eV. Identifying their sources is complicated by magnetic deflections during propagation, but for the highest-energy, lightest particles, these effects are reduced—offering a path toward particle astronomy. Traditional analyses have focused on rejecting isotropic background rather than interpreting possible signals. In this talk, I will discuss how we can instead use our knowledge of UHECR acceleration, propagation, and detection to guide physically motivated source searches. I'll present results from two complementary methods that incorporate key aspects of UHECR phenomenology, offering new insights into source association at the highest energies.

The X-ray astronomy satellite XRISM, successfully launched in September 2023, is already providing valuable insights into the long-standing mystery of supernova explosion mechanisms. Our recent study of a nearby supernova remnant, Cassiopeia A, suggests that the internal structure of massive stars becomes unstable during the final decade before core-collapse, potentially leading to significant mass ejection --- a behavior unexpected from standard stellar evolution models. Direct evidence of such pre-explosion activity requires prompt follow-up observations within ~10 days of the supernova event. Since core-collapse supernovae emit a burst of precursor neutrinos prior to the explosion, these neutrinos can serve as an early warning to trigger immediate observations. Super-Kamiokande (SK), currently in operation, has the sensitivity to detect such neutrino bursts from supernovae occurring within our Galaxy or nearby satellite galaxies such as the Magellanic Clouds. However, due to SK’s limited angular resolution (a few degrees in radius), wide-field instruments are essential for effective localization. We propose to utilize Xtend, the wide-field soft X-ray imager onboard XRISM, for such rapid-follow-up observations. Xtend offers the largest field of view and effective area ever achieved for a single-focus X-ray imaging satellite, enabling a standby observation triggered by a neutrino alert. In this presentation, we outline the scientific goals and observational strategy of this novel program, and discuss in detail the technical coordination between Super-Kamiokande and XRISM/Xtend for real-time, multi-messenger observations of nearby supernovae.

Active galactic nuclei (AGN) feedback plays a fundamental role in regulating the evolution of galaxies, but the main driving processes and their contributions are still uncertain. We use SDSS/BOSS DR16 quasar spectra containing absorption features from CIV in quasar outflows to investigate the presence of the radiation-pressure signature dubbed line-locking, and to infer wind properties from stacked samples. We design software that will be publicly available to create mock CIV absorption troughs from quasar winds based on real spectra, and use it to confirm that the line-locking features observed in our outflow composite spectra are physical and not a product of line contamination or systematics. By making use of the composite mocks and real spectra, we then infer parameters characterizing the wind and the radiative power; assuming typical average outflow covering fractions above ~85%, we find a CIV line ratio > 1.5 and N_CIV ~1e14 cm-2, consistent with other literature results, and line locking to be present in over 50% of the absorption troughs in any case. Finally, we estimate that radiative pressure does play a major role in accelerating the winds, via the absorption of about 1% of the total quasar luminosity.

Based on https://arxiv.org/abs/2504.19562

The size of cool gas clouds in the circumgalactic medium (CGM) of galaxies holds information about the physical processes that shape this multiphase environment. We explore constraints on the size of cool gas clouds obtainable from the presence, or lack thereof, of refractive scattering in fast radio bursts (FRBs). We find that the bulk of low-redshift cool CGM gas, constrained to have densities of ne <∼10−2 cm−3, likely cannot produce two refractive images and, hence, scattering. It is only for extremely small cloud sizes ≲ 0.1 pc (about a hundred times smaller than the so-called shattering scale) that such densities could result in detectable scattering. Dense ne ≳ 0.1 cm−3 gas with shattering-scale cloud sizes is more likely to inhabit the inner several kiloparsecs of the low-redshift CGM: such clouds would result in multiple refractive images and large scattering times ≳ 1 − 10 ms, but a small fraction FRB sightlines are likely to be affected. We argue that such large scattering times from an intervening CGM would be a signature of sub- parsec clouds, even if diffractive scattering from turbulence contributes to the overall scattering.

High-z starbursts provide a unique laboratory to study ISM properties under extreme, gas-rich conditions compared to their low-z analogs. I will present observations and analysis of three distinct starbursts at z～1.5 using high-resolution (0.04 - 0.3") ALMA and JWST NIRCam/MIRI data. The molecular line CO J = 5-4 traces spatially resolved star formation and kinematics while the FIR continuum assesses the dust/gas content on scales of ~0.3-3 kpc. All systems exhibit dusty, gas-rich, centrally concentrated rotating disks with enhanced SF activity in their cores, likely growing bulges rapidly. In one merging pair, ALMA detects clear molecular outflows, potentially linked to strong SF feedback or interactions. The NIRCam data in multiple filters reveals diverse structures including highly obscured starbursting cores, unobscured tidal tails, clumps, and normal spiral features at redder wavelengths in two of the three starbursts. The latter indicates a minor merger or gas-rich disk instability may be as effective to trigger a starburst. Furthermore, within one dust-obscured starbursting core, the spatial profiles of the IR luminosity (L_IR) inferred by CO5-4 and the luminosity at 8μm (L_8) inferred by MIRI/F1800W are dissimilar thus leading to a significant deficit of mid-IR emission in the core. This may result from PAH destruction by intense ionizing radiation or a decrease of emissions from photodissociation regions, similar to SF regions in nearby galaxies and AGN host galaxies, aligning with the global properties of distant starbursts. These observations demonstrate the importance of spatially resolved studies on the physics of gas and stars and the evolution of compact distant starbursts.

With the Dark Energy Spectroscopic Instrument (DESI) well into its five-year run and first cosmology data from experiments like the Prime Focus Spectrograph (PFS), the Rubin Observatory (LSST), and Simons Observatory (SO) imminent, we are entering an unprecedented new regime in precision cosmology. Simultaneously, the past decade has seen significant advances in the modeling of cosmological structure formation from first principles, particularly by leveraging techniques from effective field theory (EFT) to consistently account for the impact of complex astrophysical effects in galaxy formation and evolution. Indeed, the so-called “EFT of Large-Scale Structure” has become the technique of choice for extracting fundamental physics from spectroscopic surveys like DESI. In this talk I will review some of these developments, including the analysis of DESI data, and argue that the same techniques can be extended beyond spectroscopic surveys to analyze upcoming data from weak lensing surveys like LSST, and beyond. I will also discuss synergies between these techniques and simulations-based methods in cosmology, and how both will be necessary to conduct the most optimal and robust searches for fundamental physics in upcoming data.

The standard inflationary model predicts that primordial perturbations are Gaussian random fields. For such fields the power spectrum (or equivalently, the two-point correlation function) serves as a sufficient statistic, which is why it plays a central role in cosmological analyses. However observables in the late-time universe exhibit significant non-Gaussianity due to nonlinear mode-coupling by gravity, making analyses based solely on the power spectrum potentially suboptimal. This naturally raises the question: how much information lies beyond the power spectrum? To address this I employ an optimal analysis technique, known as field-level inference. I demonstrate when and why the power spectrum becomes suboptimal and argue that a joint analysis using both the power spectrum and the bispectrum captures nearly all the information available through full field-level inference.

In the standard cosmological model, the matter content of the Universe is dominated by dark matter—an invisible component that governs the formation and evolution of cosmic structures. While dark matter cannot be observed directly, its gravitational influence can be detected through the deflection of light from background sources, a phenomenon known as gravitational lensing. In the first part of this talk, I will introduce the gravitational lensing effect in galaxy clusters and explain how it serves as a powerful probe for detecting dark matter and constraining its physical properties. In the second part, I will present a novel simulation-based inference framework for cluster cosmology. By integrating machine learning with forward modeling of weak lensing observables, this approach bypasses traditional likelihood-based methods and enables robust inference of cosmological parameters.

Core-collapse supernovae are the final explosions of massive stars with initial masses greater than ~10 solar masses. Through their feedback to the surrounding medium, they play a crucial role in driving the dynamical and chemical evolution of galaxies. However, many questions about the evolution of massive stars leading up to gravitational collapse remain unanswered. The development of unbiased optical transient surveys over the past couple of decades has enabled the detection of electromagnetic signals from these explosions within just a few to several tens of hours after the event. When combined with analytical and numerical modeling of their early light curves and spectra, these early signals offer valuable insights into otherwise hidden activity in massive stars during their final stages before core collapse. One key finding is the complex circumstellar environment of supernovae, shaped by mass-loss processes in their progenitors during the final centuries of evolution. In this talk, I will review recent observational advances in the study of core-collapse supernovae, particularly during their early phases, and present my efforts to address key open questions using numerical simulations.

Transient surveys across the electromagnetic spectrum have revolutionized our understanding of explosive astrophysical phenomena. While typical core-collapse supernovae are thought to be powered by neutrino emission from a proto-neutron star (the neutrino-driven explosion scenario), several classes of exceptionally bright and/or energetic supernovae challenge this standard model. Notable examples include broad-lined Type Ic supernovae associated with gamma-ray bursts and superluminous supernovae. These events are believed to be powered by more exotic central engines, such as fast-spinning magnetars or black hole accretion disks. Electromagnetic observations of this extreme supernova population offer a unique opportunity to probe their underlying physics and possibly identify their true power sources. In this talk, I will introduce these bright supernovae and present numerical studies I have conducted to investigate their origins and mechanisms.

Protoplanetary disks, the birthplace of planets, are expected to be gravitationally unstable in their early phase of evolution. IM Lup, a well-known T-Tauri star, is surrounded by a protoplanetary disk with spiral arms likely induced by gravitational instability. The IM Lup disk has been observed using various methods, but developing a unified explanatory model is challenging. Here we present a physical model of the IM Lup disk that offers a comprehensive explanation for diverse observations spanning from near-infrared to millimetre wavelengths. Our findings underscore the importance of dust fragility in retaining the observed millimetre emission and reveal the preference for moderately porous dust to explain the observed millimetre polarization. We also find that the inner disk region is probably heated by gas accretion, which provides a natural explanation for bright millimetre emission within 20 au. The actively heated inner region in the model casts a 100 au-scale shadow that aligns seamlessly with the observation of near-infrared scattered light. The accretion heating also supports the fragile-dust scenario in which accretion efficiently heats the disk midplane. Due to the fragility of the dust, it is unlikely that a potential embedded planet at 100 au formed through a standard pebble accretion model, which suggests that there are alternative pathways, such as outward migration or gravitational fragmentation.

The 4600-m altitude site and its suite of imaging and spectroscopic instruments covering the 70-300 GHz frequency range make the Large Millimeter Telescope (LMT) an excellent complement to the superb resolution and sensitivity of ALMA. I will review the scientific and technical areas where this synergy can be particularly important, including examples of imaging large, extended sources as well as large area surveys Future developments that could strengthen this synergy are also discussed.

Annular substructures are ubiquitous in protoplanetary disks; they serve as ideal venues for planetesimal formation. In the first part of this talk, I will present the physical mechanisms that can give rise to these substructures, with a focus on results from MHD simulations. In the second part, I will describe how planetesimals can form within rings via the Dusty Rossby Wave Instability. Finally, I will offer a theoretical perspective on turbulence in protoplanetary disks.

M-type stars, with masses ranging from approximately 0.01 to 0.5 Msun, are the most common stars in our galaxy, accounting for about 70% of the total stellar population. They serve as intriguing laboratories for investigating planet formation in extreme conditions characterized by low temperatures and densities. This interest arises from the observed higher frequency of Earth-sized planets in habitable zones around M-stars, as exemplified by notable cases like the TRAPPIST-1 system and Proxima Centauri b. Meanwhile, the population of giant planets around M-stars is less than a few percent of the detected exoplanets so far. The trends of exoplanet demographics may be reflected in the properties of the birth places of planets, a.k.a., protoplanetary disks, around M-stars. In the talk, I will review recent high-angular resolution ALMA observations of protoplanetary disks around M-stars, particularly very-low-mass stars with approximately 0.1 to 0.2 Msun.

I will focus on two instabilities that have the potential at concentrating dust grains in rings: the global streaming instability and the dusty Rossby wave instability.

I will summarize the current status and future plans for the world’s largest sub millimeter telescope, the JCMT. The JCMT provides a powerful suite of instruments for wide-field mapping, heterodyne spectroscopy, and very long baseline interferometry. These have been used extensively and with high impact including the discovery and characterization of sub millimeter galaxies, studies of star-formation and galaxy evolution, and the first images of the black holes in M87 and Sgr A* with the Event Horizon Telescope. New observing programs in the areas of VLBI, time domain science, and intensity mapping will play key roles in the future of the JCMT.

The observation of Cosmic Microwave Background (CMB) has a central role in modern cosmology. The Simons Observatory (SO) is a new project for CMB observations, which started taking data recently in Atacama, Chile. The SO will provide us with unprecedented sensitivities in CMB polarization measurements. A super-wide field of view and its large survey area allow the SO to perform various cross-correlation analyses with other projects, including the Rubin Observatory, DESI, Euclid, Roman, CCAT-Prime, and SPHEREx. The SO's super-wide survey will also lead to follow-up observation proposals at ALMA. In this talk, after a short review of CMB observations and future projects, I will describe rich astronomical and cosmological topics at the SO, including early universe, relic particles, neutrino mass, galaxy evolution, blazars, galactic science, planet 9, and transient sources. In the end, I will discuss a way for the Taiwanese astronomy/cosmology community to participate in and contribute to the science at the SO.

Cosmic dust plays an important role in galaxy evolution, providing chemically active regions to rapidly produce the base ingredients for new cycles of star formation. At the same time, this dust screen obscures over half of our view of cosmic star formation and our view of the bulk build up of stars across cosmic time. In this talk, I discuss the new insights of the dust obscured universe in the cosmic noon and dawn. With high resolution imaging of dusty galaxies at redshifts 2 to 5, I show the surprising diversity in dusty galaxies that are likely the progenitors of giant elliptical. A surprisingly warm lyman break galaxy at redshift 8 furthermore complicates our view of early dust build up, and by probing the limits from over 200 hours of ALMA time at z 8 to 15, I detail our best attempts at finding the start of dust emission in the Universe.

Mauve is a small satellite equipped with a 13-cm telescope and a UV-Visible spectrophotometer (with an operative wavelength range of 200-700 nm) conceived to measure the stellar magnetic activity and variability. It is scheduled for launch in October 2025 and is currently under construction. The Mauve science program will be delivered via a multi-year collaborative survey program, with thousands of hours each year available for long baseline observations of hundreds of stars, unlocking a significant time domain astronomy opportunity. Mauve’s mission lifetime is 3 years with the ambition of 5 years, and will cover a broad field of regard (–46.4 to 31.8 degrees in ICRS) during this period.

This facility was conceived to support pilot studies and new ideas in science and is fully dedicated to time-domain astronomy. The main surveys to be executed by Mauve are long baseline observations of flare stars, Herbig Ae/Be stars, exoplanet hosts, as well as contact binary variables (RS CVn variables, symbiotic stars, Algol-type stars, etc.). Besides these major science themes, the spectrometer data can be utilised to support and complement existing and upcoming facilities as a pathfinder, or conduct simultaneous/follow-up observations.

The discovery of exoplanets (planets outside of the Solar System) has revolutionized our understanding of planet formation and habitability. Particularly, it revealed the prevalence of close-in planets, which are absent in our own Solar System. How do these planets form, and how habitable are they? In this talk, we will discuss high-eccentricity migration, a key mechanism in the formation of close-in planets, and the coupling between planetary interior structural with orbital migration. We will show how a planet’s internal structure influences the migration process — and how migration, in turn, affects planetary structure. Additionally, we will explore the spin dynamics of close-in habitable zone planets, which may lead to chaotic day-night cycles and trigger snowball phases.

Substructures in protoplanetary Protoplanetary disk is one key feature for understanding planet formation. ALMA has revealed that many protoplanetary disks harbor rings, gaps and/or non-axisymmetric structures and the connection between such structures and planet formation and/or disk evolution is actively discussed. Yet, high resolution observations with ALMA requires long baseline observations that are expensive and therefore the number of disks that are fully resolved is still limited. Sparse modeling technique is a promising method for reconstructing a high spatial resolution image from data obtained with relatively short baseline. We present the results of our survey that has applied sparse modeling to a set of ALMA archival data of protoplanetary disks in Taurus and Ophiuchus regions. We discuss statistical properties of disk (sub)structures and indication on planet formation. We also present studies on some individual targets, if time allows.

Fast Radio Burst (FRB) is a millisecond burst in the radio frequency. The origin and mechanism of the FRB is yet a mystery. To better understand their origin, gathering a census of the FRB host galaxies and the local environment is an important first step. Such a task defies the design of existing facilities, and a new telescope is needed. BURSTT is a wide-field survey telescope in Taiwan that aims to detect and localize FRBs in the local universe. The telescope consists of a main array of dipole antennas for pulse detection and several smaller outrigger arrays for VLBI localization. The first stage of BURSTT has been built and is operational. Several hundreds of pulses from bright pulsars are being detected everyday. Recently, BURSTT has also detected its first FRB. I will briefly introduce a few science cases with coming observations of FRBs and pulsars using BURSTT and the synergy with research interests in IAA. Besides the studies related to FRBs and pulsars, BURSTT has also attracted interests from a variety of fields, e.g. cosmic ray, gravitational wave, solar radio bursts, lightning propagation, etc. These are potential opportunities to forge new collaborations with universities to add more values to BURSTT

Unrecognized blends are a class of objects that are mistakenly identified as a single object instead of multiple. For ground based surveys with large PSFs and seeing, unrecognized blends are an unavoidable problem that prevent precise measurements. It is expected that 20% of objects with 23 < i < 24.5 mags for the Vera Rubin Observatory will be an unrecognized blend. One of the best ways to identify unrecognized blends is through the use of space based data in deep fields. Using the COSMOS field we are able to label ground based measurements as unrecognized blends and train several machine learning algorithms to see if we are able to probabilistically label blends based on catalog values alone. I will also discuss extensions to this work and the on-going validation.
Paper: https://arxiv.org/abs/2503.16680

This talk will follow my research journey from studying Titan’s atmosphere to investigating the origins of organic matter in protoplanetary disks. During my PhD, I developed nanoscale laboratory techniques to characterize the material properties of Titan’s organic aerosols. These techniques are now being extended by my group to study organics relevant to the early Solar System and planet formation. We analyze sub-milligram quantities of organic matter extracted from carbonaceous chondrites, as well as synthetic analogs produced under various plausible disk conditions. These measurements reveal key physical properties, such as density, elasticity, and surface energy, that govern the role of organics in dust coagulation and the early stages of planetesimal growth. Our results challenge long-standing assumptions that organics enhance sticking efficiency and instead point to more limited growth pathways to form cm-sized dust particles. I will also discuss how these laboratory results help constrain the origin and evolution of organic materials in disks, and how they bridge to broader questions in planetary science and exoplanetary systems. I will also briefly highlight the potential for synergy between our lab-based approach and current efforts in meteorite analysis, disk modeling, and exoplanet atmosphere studies.

Classical Cepheids are well known cosmological yardsticks. The most accurate calibration of the Cepheid period-luminosity relation is obtained for the Cepheids which are located inside star clusters. The progenitors of Cepheids are thought to form in binaries, indicating that interactions between binary stars in clusters likely play an important role in the ability of mid-B stars to evolve to Cepheids. Using numerical modelling by the code NBODY6, we investigate the evolution of mid-B stars under the influence of star cluster dynamics for clusters of various initial masses. We find that the fraction of Cepheids located in clusters in our models (30 %) is noticeably larger than what is observed in the Local Group (around 9 %). Most clusters host at a given time at most one Cepheid and clusters with more Cepheids are rare. Cluster environment significantly increases the eccentricity of the binaries while other binaries are disrupted; in total approx. 42% of Cepheids is located in binaries, which is much less than the observed value (approx. 80%). We will discuss the nature of companions to Cepheids and also the implications for birth multiplicity of B type stars.

The importance of multi-band Deep Field observations to study distant galaxies has become evident during the last few decades. Among various wavelengths, rest-frame far-ultraviolet emission is particularly sensitive to both young stellar populations and interstellar dust in galaxies. I will first discuss how the UV imaging from the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat, combined with other observations, has helped us to disentangle the dust content and the nature of the attenuation law in star-forming galaxies at redshift ~ 0.5 - 0.8. I will also demonstrate how JWST MIRI imaging of galaxies in the AUDFs field is used to probe the 7.7 and 11.3 μm emission features of Polycyclic Aromatic Hydrocarbon (PAH) molecules under varying stellar radiation fields within the same redshift window. Overall, I will present key insights into interstellar dust in a relatively unexplored redshift range that bridges the cosmic noon and the present-day universe. I will also discuss the unique scope of the AUDF survey in discovering Lyman Continuum (LyC) leaking galaxies at redshift ~ 1 - 3, along with our recent finding of a z=2.9803 potentially LyC leaking galaxy (GNHeII~J1236+6215) showing a promising signature of PopIII-like star formation.

The nature of interstellar dust is a 100-year-old question. Though there has been progress towards an answer, basic properties of the dust - such as its chemical composition - remain highly uncertain. The wavelength dependence of dust extinction, typically parameterized by the variable R(V), is thought to reflect the grain-size distribution and composition of the dust, and is therefore one piece of evidence that can be used to empirically constrain the dust properties. Over the last decade, while there have been major advances in mapping dust density throughout our Galaxy, there have been comparatively few measurements of R(V). In this talk, I will discuss recent measurements of the dust extinction curve along 130 million sightlines in the Milky Way and Magellanic Clouds, using low-resolution, flux-calibrated BP/RP spectra from Gaia. Using these measurements, we have created the first large-scale, detailed map of R(V) variation in the Milky Way. This map contains hints that star formation plays a major role in shaping the dust grain population, and that polycyclic aromatic hydrocarbons (PAHs) drive much of the observed variation in R(V). We find that the optical extinction curve is not fully described by R(V), but rather contains at least three additional degrees of freedom, indicating more complex variations in dust chemistry. We also detect optical extinction features, which are of unknown origin. We find that the extinction curve is correlated with the strengths and shapes of various diffuse interstellar bands (DIBs), indicating that extinction features on different wavelength scales are connected. This large quantity of detailed measurements of extinction-curve variation throughout the Milky Way and Magellanic Clouds, enabled by Gaia, not only allows for more precise extinction corrections, but also provides a qualitatively new empirical basis for the development of dust models.

The observation of Cosmic Microwave Background (CMB) has a central role in modern cosmology. The Simons Observatory (SO) is a new project for CMB observations, which started taking data recently in Atacama, Chile. The SO will provide us with unprecedented sensitivities in CMB polarization measurements. A super-wide field of view and its large survey area allow the SO to perform various cross-correlation analyses with other projects, including the Rubin Observatory, DESI, Euclid, Roman, CCAT-Prime, and SPHEREx. The SO's super-wide survey will also lead to follow-up observation proposals at ALMA. In this talk, after a short review of CMB observations and future projects, I will describe rich astronomical and cosmological topics at the SO, including early universe, relic particles, neutrino mass, galaxy evolution, blazars, galactic science, planet 9, and transient sources. In the end, I will discuss a way for the Taiwanese astronomy/cosmology community to participate in and contribute to the science at the SO.

The preference for cored dark matter density profiles in dwarf disk galaxies has long stirred tensions over the internal structure of dark matter halos, further complicating the Cold Dark Matter (CDM) crisis at sub-galactic scales. Kinematic measurements of stars in the even more dark matter-dominated dwarf spheroidal (dSph) satellites of the Milky Way offer a promising, less baryon-contaminated avenue to revisit these issues. As data on individual member stars improve in both precision and sample size, dynamical estimates of their underlying mass distributions are becoming increasingly accessible. However, the inferred dark matter density profiles often stand in conflict with one another, revealing inconsistencies across galaxies.
We, therefore, attempt to extract more information contained in the non-uniform shape of the line-of-sight velocity distribution, which is assumed to be fixed in traditional Jeans modeling. This is achieved by invoking the stars’ higher-order velocity moments alongside their standard velocity dispersion. We demonstrate the model’s improved capacity for recovering dark matter density profiles and discuss its inherent limitations.
In addition, we explore the implications of our model within the context of fuzzy dark matter (FDM) theory, an alternative to CDM that gained growing attention for its potential to reconcile observations and theory. We provide preliminary constraints on the FDM particle mass necessary to address the core-cusp tension observed in classical Milky Way dSphs.

Recently it has become possible to numerically simulate large, representative volumes of the Universe. These cosmological (magneto)hydrodynamical simulations solve for the coupled evolution of gas, dark matter, stars, and supermassive black holes interacting via the coupled equations of self-gravity and fluid dynamics, all within the context of an expanding spacetime.

The IllustrisTNG simulations are the current state-of-the-art in this context. They simultaneously resolve tens of thousands, to millions, of individual galaxies - with properties and characteristics in broad agreement with observational data of real galaxy populations. This enables theoretical studies on galaxy formation and evolution, as well as large-scale structure and cosmology. We have also begun to go beyond TNG, with (i) the "Project GIBLE" simulations that resolve the circumgalactic medium (CGM) of galaxies to unprecedented levels, and (ii) the new "TNG-Cluster" simulation of the most massive virialized structures in the Universe: halos with total mass > 10^15 solar masses.

I will give a tour of the IllustrisTNG simulations, showcasing the information content and breadth of a virtual Universe. I will describe the modeling required for these simulations, both numerical and physical, and then touch on some recent scientific insights, from TNG, GIBLE, and TNG-Cluster, focusing on the interplay of galaxy formation, feedback, and the gaseous halos (i.e. CGM) of galaxies.

Massive stars are fundamental drivers of galactic evolution, exerting powerful feedback on their surroundings and shaping the ecology of their host galaxies. Over the past decade, high-resolution observations and state-of-the-art theoretical modeling have significantly advanced our understanding of their formation. In this talk, I will present recent theoretical and observational studies of massive star formation in both Galactic and low-metallicity environments, including collaborative work. I will focus on three key topics:
1. whether and how feedback regulates accretion onto very massive protostars;
2. dust evolution and gas chemistry in hot disks around massive protostars; and
3. new findings on massive protostars in low-metallicity environments such as the Magellanic Clouds, highlighting the potential diversity of star formation across different galactic contexts.

The cosmic microwave background (CMB), the faint afterglow of the Big Bang, is the oldest light we can observe in the Universe. Since its discovery by Penzias and Wilson in 1964, CMB observations have been central to the rise of modern precision cosmology. Together with other probes, they have revealed how the Universe began and evolved, what it is made of, and, at the same time, they have highlighted several fundamental questions that remain unanswered. In the coming decade, CMB observations are poised to take major steps forward. The Simons Observatory, the largest ground-based CMB experiment to date, has just begun observations with a particular focus on CMB polarization. Polarization measurements at degree angular scales will constrain primordial gravitational waves, probing cosmic inflation and quantum fluctuations of gravity. Fluctuations at arcminute scales, on the other hand, trace the growth of large-scale structure through gravitational lensing and galaxy cluster surveys, and can constrain so-called dark radiation—the relativistic degrees of freedom in the early universe. These rich data sets will drive substantial progress in our understanding of dark energy, neutrino masses, and the evolution of galaxies and clusters. In this talk, I will review the exciting scientific opportunities and experimental challenges of upcoming CMB measurements, and discuss how they may open new windows onto the physics of the early Universe.

The superb capabilities of the James Webb Space Telescope (JWST) have extended our view to the ultra-high-redshift universe (z > 12). Among numerous scientific discoveries enabled by JWST, some early deep extragalactic observations have unexpectedly revealed an abundance of massive galaxies, presenting significant challenges to conventional galaxy formation models. To address this cosmic puzzle, we utilize some well-established galaxy formation models in conjunction with state-of-the-art cosmological simulations to seek understanding of physical mechanisms that enabled extremely rapid star formation activities in the early universe. We investigated and quantified the impact of various sources of uncertainty, including a potentially evolving mass-to-light ratio driven by changes in the IMF, underestimated field-to-field variance, and significant uncertainties in photometric redshifts, among others. Our study also examines the number density of halo populations during this epoch, alongside the gas cooling rates and star formation efficiencies of galaxies. I will also present new simulated results for various alternative star formation and stellar feedback models and discuss the essential conditions required to reproduce the observed ultra-high-redshift galaxy populations.

We are at a unique time to study giant exoplanets. With more than 5000 exoplanets found and facilities like the James Webb Space Telescope that provide unprecedented data on their atmospheres, we moved from an era of discovery to an era of exoplanet characterisation. At the same time, precise measurements from missions like Juno and Cassini to Jupiter and Saturn, lead to a different way of looking at giant planet interior structures, that challenge traditional exoplanetary models.

This is an exceptional time to combine the detailed information on the solar system's giant planets with the large amount of data from exoplanets to get a better understanding of planetary physics and a better comprehension of planet formation and evolution. In this talk, I will explore how integrating data from our solar system's giants with the growing wealth of exoplanet observations leads to the derivation of more realistic interior structures, opening the door to a new generation of interior models for giant exoplanets and transforming our understanding of planetary physics, formation, and evolution.

Structures such as gaps and rings in ALMA observations of protoplanetary disks have long been hailed as signposts of planet formation. However, it is still not clear how common such substructures are, when they become apparent in disks and how they are linked to the formation of planets. In this talk I will describe the latest insights on the commonality and evolution of substructures in disks, as well as their connection with exoplanet populations. In particular, I will discuss the implications of the discovery of a new group of disks, which has only become apparent from ALMA observations at very high resolution: the compact disks with few or no gaps, with typical dust disk sizes of only a few au in radius. Such disks are primarily found around M dwarfs and can be connected directly with the formation of close-in super-Earths, through planet formation models including pebble drift and pebble accretion. Second, I will show the latest results on the role of jets and MHD-winds in protoplanetary disks as traced by free-free emission with ALMA and VLA, and their role in our understanding of the angular momentum transport in disks. Finally, I will demonstrate the combined impact of both ALMA and JWST observations on our perception of disk composition as the result of ice transport throughout the disk, and the consequences for planet composition.

The historical supernova SN 1181 remained unidentified for decades. In 2021, a strong candidate for its remnant was finally discovered, revealing several unique properties not seen in other supernova remnants (SNRs). Most notably, the SNR contains a white dward (WD) and the central WD is currently emitting a fast stellar wind at 15,000 km/s. This high-velocity wind is likely colliding with the ejecta of SN 1181, forming a termination shock. Consequently, the remnant exhibits a multi-layered X-ray structure: thermal X-ray emission is observed from both the shocked SNR and an inner emission region, as revealed by XMM-Newton. We analyzed Chandra X-ray data of this central emission and developed a theoretical model that reproduces the observed X-ray structure. Our analysis suggests that the fast wind from the WD began relatively recently, around 1990. To investigate this delayed wind onset, we performed WD evolution calculations using the stellar evolution code MESA, demonstrating that a delay of approximately 1,000 years is feasible. Furthermore, our calculations constrain the properties of the central WD, allowing us to constrain the progenitor system of SN 1181, which remains poorly understood.

The Terahertz Intensity Mapper (TIM) is a balloon-borne far-infrared (FIR) imaging spectrometer designed to characterize the cosmic star formation history and unveil the forces driving galaxy assembly over cosmic time. TIM has been optimized for a new observational technique called "line intensity mapping" (LIM), which has the potential to access unexplored and unique cosmological and astrophysical phase space. TIM will map the redshifted 158micron line of ionized carbon ([CII]) over the redshift range 0.5 < z < 1.7 (lookback times of 5-10 Gyr). TIM will spectroscopically detect galaxies, determine the star formation rate history over this time interval through LIM, and measure the stacked [CII] emission from galaxies in its well-studied target field (GOODS-S). Additionally, TIM will detect [OIII]88μm and [OI]63μm in high-redshift strongly lensed galaxies between 2 < z < 7, providing crucial insights into the evolution of FIR atomic transition lines into the epoch of reionization. Combining these measurements will be an important pathfinder for the survey techniques and observables necessary to probe the astrophysics of the first galaxies that re-ionized the universe at z>6. We are also studying the possibility of surveying the Galactic plane with CO and H2O. TIM consists of a 2-meter telescope feeding two grating spectrometers that cover 240-420 microns at R~250 across a 1-degree field of view, populated with 7200 kinetic inductance detectors. TIM will serve as an important scientific instrument, accessing wavelengths that cannot easily be studied from the ground, and as a testbed for future FIR space technology. This is crucial technology development for a future flagship FIR mission as well as a pathfinder for using LIM as a viable tool for astrophysics and cosmology. TIM is planning on an Antarctic science flight in the Austral Summer of 2026/27. I will provide an overview of TIM, the broader landscape for LIM.

The South Pole Telescope (SPT) has uncovered a population of high-redshift strongly gravitationally lensed starburst galaxies in a 2500 square degree cosmological survey. We have conducted the first ALMA spectroscopic survey for a complete sample of 81 of these systems, which range from 1.8 < z < 6.9. For the past decade, we have been studying these sources in great detail with ALMA in ionized carbon (C+), carbon monoxide (CO), and water (among others). Recently, we have been conducting observations of these sources with JWST, with both an ERS program, and GO programs in Cycles 1 and 2, targeting H-alpha, Pa-alpha, and PAH lines. I will present an overview, highlights, and the latest results from our observation programs with ALMA and JWST. I will also present new results from the 3rd generation SPT survey.

Abstract: Artificial intelligence is increasingly applied to analyze complex datasets, whether from Earth observation or astronomical instruments. In this talk, I will present recent work from the German Environment Agency using AI for environmental and climate challenges, including detecting radioactive elements via supervised dimensionality reduction, identifying wind turbines and solar panels from satellite imagery, and tracking illegal wildlife trade through automated online analysis: https://showcase.ai-env.de/en Many of the underlying methods are directly relevant to astronomy and physics. For example, dimensionality reduction techniques can improve element detection in spectra, while resource-efficient algorithms for object counting or data compression at the sensor can handle large-scale observational datasets. I will also highlight approaches for energy- and resource-efficient machine learning, demonstrating how to reduce computational cost without sacrificing accuracy. This talk illustrates how innovations in environmental AI can inform large-scale data challenges across scientific disciplines.

AI can be used to accelerate and even replace supercomputer simulations in astrophysics, turning complex models into easily accessible tools. I will introduce recent and ongoing work aimed at cosmology, including hybrid AI-physics codes, replacements of hydrodynamics solvers with graph neural networks, and ways to interface AI simulations with Large Language Models in multi-agent systems. I will show how such a system of agents can autonomously set up and run a complete hundred-million-particle three dimensional cosmological simulation in seconds. As a use case of this type of modelling, I will explore the Lyman-alpha forest of intergalactic absorption in high redshift quasars and how it can both be gravitationally lensed, and also used to make large-scale maps of the intergalactic radiation intensity. I will also briefly mention related simulation predictions for the "little red dot" galaxies seen by JWST at high redshift.

I will argue that if dark matter is produced via processes with subhorizon correlation length in the early universe, then there is a lower bound on the mass of dark matter particles [m > 10^(-19) eV]. For such dark matter, there is both (i) a free streaming suppression and (ii) white-noise enhancement in the dark matter density power spectrum. The absence of these in the existing observational data (for example, Ly-a) provides a bound on the mass. Beyond the bound, I will present a calculation framework for understanding the growth of structure where warmth and/or white noise are relevant. I will discuss nonlinear phenomenon (eg. solitons), resulting from the large initially isocurvature perturbations on small scales. Time permitting, I will include provide examples of growth of structure in multicomponent wave and particle dark matter.

The local burning front plays a crucial role in determining the global outcome of thermonuclear supernovae: success/failure, nucleosynthesis and ejecta morphology. Since the spatial scale of the flame front is much smaller than that of the WD system, even the state-of-the-art hydrodynamic simulations could miss its key aspects; insufficient resolution could in some cases lead to false success of explosion. We are currently pursuing the idea of theoretical descriptions and experimental observations to predict ignition and sustained propagation of detonation which are based on terrestrial burning physics and characteristic reaction scale known as the ‘cellular structure’. In the present talk, some key results will be provided demonstrating how effectively these theoretical/experimental frameworks serve as clues to the unresolved explosion mechanisms.

TBD

Since the evolution of molecular clouds regulates star formation, which in turn drives galaxy evolution, the topic has been actively discussed since the 1970s, when direct observations of molecular clouds first became possible. In recent years, thanks to ALMA, a large number of nearby galaxies have been observed with spatial resolutions sufficient to resolve giant molecular clouds (GMCs) down to scales below 100 pc. These observations have provided empirical evolutionary frameworks and timescales for GMCs across galactic disks (e.g., Chevance et al. 2020; Demachi et al. 2024). However, even with such progress, the internal structures of GMCs have not yet been fully resolved, and the key physical processes that drive their evolution remain open questions. To address this, we have returned our focus to the Milky Way, aiming to establish a unified evolutionary framework by combining (1) wide-field, low-resolution surveys that trace the empirical evolution of molecular clouds, and (2) high-resolution observations of individual clouds that reveal the underlying physical processes. For (1), we focused on the outer solar circle, where line-of-sight contamination is relatively low. Using CO data obtained with the CfA 1.2-m and NANTEN2 4-m telescopes, we smoothed the maps to match the spatial resolution of extragalactic ALMA observations (~40 pc) and identified molecular clouds. The results show that the evolution of molecular clouds can be described by a scenario similar to that in external galaxies: over timescales of about 10 Myr, clouds grow in mass from ~10⁴ M☉ to ~10⁵ M☉ while becoming increasingly active in star formation. Furthermore, comparison with H I data suggests that Taurus-like dark clouds may evolve into Orion-like GMCs through HI gas accretion (Yamada, Ph.D. Thesis 2025). These findings imply that the transition from atomic to molecular gas is a fundamental process governing cloud evolution. Regarding the recent observational findings, which proposed GMC formation via inflowing H I gas onto the Galactic disk, we focus on the Draco cloud for (2), where interactions between infalling gas and the Galactic disk within the last few Myr have been suggested. Finally, to bridge (1) and (2), we will discuss a comprehensive analysis strategy using the FUGIN archival data, as well as future observations of deuterated species with the Nobeyama 45-m telescope and the 7-BEam Element (7-BEEs) receiver.

The star formation rate is a very fundamental quantity that deeply influences the evolution of the Universe and which is only partly understood. In particular, its value in the Milky Way appears to be nearly two orders of magnitude lower than a simple estimate based on the freefall time, indicating that efficient supports are operating against gravity. Another remarkable relation is the so-called Schmidt-Kenicutt law which expresses the star formation rate as a function of the column density. In which conditions these two features can be reproduced? What are the physical processes explaining these observations? To answer these questions, I will present numerical simulations of self-regulated, stratified, star forming interstellar medium. I will show that stellar feedback plays a fundamental role to regulate star formation and can reproduce star formation rates compatible with the values observed in the Milky Way. However at larger column densities, the stellar feedback appears to be larger than the values inferred from the Schmidt-Kenicutt relations. I will propose that a large scale turbulent driving, possibly due to energy injected at the galactic scale, is required to bring the star formation rate to the observed values. Indeed, numerical simulations show that strong enough turbulence can very significantly reduce star formation. To understand exactly how this occurs, I will present an analytical model that relies on the turbulent support and show how turbulent support exactly operates. Comparisons with dedicated numerical simulations reveal good agreement with the predictions of the model.

Recent observations by James Webb Space Telescope discovered a number of distant galaxies that existed when the age of the Universe was just several hundred million years. The observational frontier is advancing toward exploring when the first stars and galaxies were formed, and even further back in time to when no luminous objects yet existed. We first review the physical cosmology focusing on the epoch called the Dark Age. A promising observational probe is the hydrogen 21cm line, and a number of observational efforts are underway, including those based on the far-side of the moon. We use state-of-the-art cosmological simulations with hydrodynamics, non-equilibrium chemistry and radiative transfer, to study in detail how small-scale structure develops in the early universe. Outstanding questions in the formation of the first stars and blackholes are discussed. Finally, we forecast for future low-frequency radio observations to probe the Dark Age and Cosmic Dawn and to test the standard cosmological model.

In 2024, DESI (Dark Energy Spectroscopic Instrument) reported the time variation of the Hubble parameter based on BAO (Baryon Acoustic Oscillation) observations, showing that it contradicts the predictions of standard cosmology predicted by CMB observation. One interpretation of the discrepancy is to introduce an appropriate time variation to dark energy without changing the cosmological model. We will consider another possibility based on the infrared galaxy surveys indicating that the Milky Way galaxy is located in a low-density region on a 300 Mpc scale. It turns out that a simple model of an inhomogeneous matter distribution explains the evolution of the Hubble parameter reported by DESI BAO observations as well as the Hubble tension.

Spectacular high-resolution imagery from the last decade has revealed that planet formation begins during the turbulent early stages of star formation, when stellar interactions profoundly shape protoplanetary disc structure. Observational evidence increasingly suggests that even apparently isolated stars bear the signatures of past stellar flybys -- encounters that leave lasting imprints on disc morphology and may trigger the onset of planet formation. With the majority of stars residing in binary or higher-order multiple systems, these interactions become even more significant. In such environments, circumbinary discs can become misaligned with the binary orbital plane, creating distinctive conditions for circumbinary (P-type) planet formation. Binary companions also truncate their circumstellar discs, directly affecting the formation efficiency of circumstellar (S-type) planets. Recent observations of circumtriple disc architecture further raise intriguing questions about the viability of circumtriple planet formation. I will demonstrate that stellar multiplicity is not merely incidental but fundamental to understanding disc evolution and the diverse pathways of planet formation throughout the galaxy.

Star formation and planet formation are genuinely intervowen processes. This tight interconnection largely occurs through the formation of circumstellar and protoplanetary disks. While it has since long been recognised that disks would naturally be explained by the conservation of angular momentum during the collapse of the dense core, several teams have recently stressed, that due to efficient magnetic braking, magnetic field is likely playing a crucial role regarding the formation of disks. How this exactly occurs, has however turned out to be rather complicated. This is because on the one hand, magnetic braking has been found to depend on the dynamical state of the collapsing dense core, namely the geometry and intensity of the magnetic field but also the strength of the turbulence. On the other hand, the efficiency of magnetic braking also depends on the ionisation degree and on the charge carriers, the dust grains. None of these processes are really well understood.

We will review the efforts carried out in the last 25 years to map the contribution of dust-obscured star-forming galaxies to the overall history of star formation. While the contribution of bright submillimeter galaxies in the Ultra Luminous Infrared Galaxy regime (L_IR > 10^12 L_sun) has been reasonably well characterized up to z~3, their contribution at larger redshifts is still a matter of debate. ALMA surveys have given us an initial view of the properties of dust obscuration in the Luminous Infrared Galaxy regime (L_IR > 10^11 L_sun), while the statistical characterization of the rise and fall of obscured star formation at these luminosities still awaits larger and deeper surveys. We will introduce the open-access Legacy Surveys that the 50m Large Millimeter Telescope new imaging and polarimetry camera TolTEC will carry out, that will address these issues and we show the predictions derived from cosmologically motivated simulations to illustrate the power and limitations we will face to derive the intrinsic properties of the population.

The Gravitational Instability (GI) is a dominant theory that explains angular momentum transport in young protoplanetary disks. Additionally, it is a key theory in planet formation, describing how a disk can fragment into clumps for efficient cooling. Most simulations characterizing GI have relied on a thin-disc (2D) approximation, employing either a zero or a finite smoothing length prescription for the gravitational potential. However, a finite smoothing length suppresses the Newtonian nature of gravity, potentially inhibiting gravitational collapse, and does not respect Newton’s third law. Conversely, a vanishing smoothing length, or solving a 2D Poisson equation, artificially amplifies gravity.

In the first part of my talk, I will introduce an analytically derived, exact 2D self-gravity prescription designed for use in 2D simulations. This prescription eliminates the need for smoothing length approximations. Specifically, I will demonstrate how it resolves the inherent issues of a Plummer potential, particularly the short-range suppression of Newtonian gravity. I will then discuss the broader implications of this work for the GI paradigm of planet formation, supported by 2D global simulations with the FARGO-CPT code. Specifically, I will show how this approach may address the long-debated ”convergence issue” in GI simulations with 2D grid-based codes. To conclude, I will present preliminary results from GI simulations in 2D shearing boxes, which suggest that stochastic fragmentation occurs less frequently than previously reported.

The Universe we observe holds many hidden wonders, most of which we are only beginning to understand. Astonishingly, only about 5% of the Universe consists of familiar "normal" matter, while the vast majority is dark energy and dark matter, whose origins and properties remain mysterious. This talk explores how studying the growth of cosmic structures, such as galaxies and galaxy clusters, provides crucial insights into these enigmatic components. What makes this exploration even more challenging is that much of the "normal" matter is also elusive. Computer simulations have long predicted that most of this "normal" matter exists as a diffuse, ionized gas within large-scale cosmic web structures. Electrons play a central role in probing this matter, as their interactions with light help reveal these structures. To accurately probe the dark universe, we must first disentangle the gravitational influence of this elusive normal matter from that of dark matter itself. Overcoming this is one of the central challenges in modern cosmology. I will show how the synergy between state-of-the-art computational modeling and machine learning offers a powerful solution. By training algorithms on virtual universes from our simulations, we can teach them to identify the subtle signatures of this gas in real telescope data. This synergy is essential for creating a complete cosmic map and tackling fundamental questions about the nature and composition of our Universe.

Cosmological field level inference (FLI) aims to extract maximal information from survey data using information encoded in the two point correlations and beyond. In recent years there has been a lot of development of AI powered solutions to FLI. Simulation Based Inference uses simulations and Neural Networks to learn the likelihoods, or the mapping between data and initial conditions, and this approach has been shown to extract more information than traditional two point correlation analysis. I will present examples to both weak lensing and galaxy clustering.

The interaction of galaxies is known to regulate the star-formation activities in the merging systems, or galaxy pairs, however, whether and how such activities interact with the central supermassive black hole, often manifested as active galactic nuclei---AGNs, is still under debate. Controversies exist as to whether AGN activities are enhanced or suppressed during the different merging phases. The answer to this question involves understanding of the physical properties of galaxy pairs in various scales, from the supermassive black hole at the galactic center to dust and gas of various phases---ionized, molecular, and atomic---throughout the galaxies and in the close vicinity. In this talk I will review some recent progresses made with IR-bright galaxies, and the combination of observations of significantly different scales and resolutions to connect AGNs and star formation activities in mergers, including new insights from JWST and ground based radio telescopes like FAST and NOEMA.

The discovery of thousands of exoplanets revealed a huge variety in the sizes, masses, and orbital properties of planets outside of our solar system. I will discuss how the physics of gas accretion and star-disk-planet interaction can shape the observed diversity, providing explanations for some of the puzzling demographic patterns that have emerged in exoplanet science while placing our solar system in the larger Galactic context.

Ultra-light bosons are well-motivated dark matter candidates with interesting phenomenology on galactic scales. In particular, wavelike behaviour of dark matter in the so-called "fuzzy" regime can help relieve potential problems for standard cold dark matter in galaxies, by producing central cores and suppressing the abundance of low-mass satellites. I will describe observational signatures of this wavelike behaviour, and will show how the smallest galaxies severely constrain ultra-light dark matter particle masses.

X-ray observations provide a powerful means of probing the vicinity of supermassive black holes (SMBHs) in active galactic nuclei (AGNs). In AGNs, a primary X-ray continuum is produced in a corona located near the SMBH and is subsequently reprocessed by surrounding structures, giving rise to a variety of diagnostic X-ray spectral features. High-resolution X-ray spectroscopy of these features with an X-ray microcalorimeter opens a new window on key topics in AGN research, including the structure of accretion disks, broad-line regions, and dusty tori; the physical properties of ionized absorbers and disk winds, including ultra-fast outflows (UFOs); and the connection between AGNs and their host galaxies. The X-Ray Imaging and Spectroscopy Mission (XRISM) was successfully launched on September 7, 2023. In orbit, the Resolve instrument achieves a high energy resolution of ~5 eV at 6 keV using the X-ray Mirror Assembly (XMA) and an X-ray microcalorimeter. In parallel, the Xtend instrument provides a wide field of view of 38' × 38' over the 0.4−12 keV energy range, employing the XMA and an X-ray CCD camera. In this presentation, I will give an overview of the XRISM mission, summarize recent AGN results obtained from XRISM observations, and discuss future prospects for AGN studies enabled by high-precision X-ray spectroscopy.