The field of black hole accretion is seeing a renaissance in the last 5–10 years, thanks to the advent of wide-field, time domain surveys across the electromagnetic spectrum. These surveys monitor hundreds of thousands of AGN at unprecedented cadence, revealing the secrets AGN were keeping while we weren’t watching. Time domain surveys are changing what we thought we understood about standard AGN activity, and thus, evolving our picture of how supermassive black holes grow and affect their environments. In this talk, I will present some recent highlights on supermassive black hole transients, like Tidal Disruption Events, and a new phenomenon called Quasi-Periodic Eruptions, which are a totally unexpected X-ray phenomenon, where ~million solar mass black holes show extremely high-amplitude regular flares, which have been posited as due to the presence of an orbiting stellar mass object (also known as Extreme Mass Ratio Inspirals). We will discuss the current state of the field, and implications for future joint detections with the NewAthena, LISA Gravitational Wave Observatory and other multi-messenger facilities.

The Cold Dark Matter (CDM) paradigm remains the most successful framework for describing the formation and evolution of cosmic structure, yet its predictions on sub-galactic scales are still only weakly tested. A key prediction of CDM is the existence of a large population of low-mass dark matter haloes with a well-defined mass density profile, both as subhaloes within galaxies and as isolated structures along the line of sight. 

Since the majority of these objects are expected to be completely dark, strong gravitational lensing provides a unique opportunity to study them and to probe the nature of dark matter. 

In this talk, I will review the current status of the field and present the latest observational constraints from strong-lensing studies. Recent advances have pushed strong lensing into a previously inaccessible regime of halo mass and physical scale. In particular, Powell et al. (2025) reported the detection of a dark perturber with an enclosed mass of only 10^6M_sun identified through its effect on an exceptionally thin lensed arc observed with milli-arcsecond-resolution VLBI. This represents the lowest-mass object detected at cosmological distance through its gravitational influence and demonstrates, for the first time, that strong lensing can directly probe the million-solar-mass regime beyond the Local Group.

I will also present the latest constraints on the internal structure of the three currently known low-mass detections and show how their inferred properties compare with predictions from different dark matter models. I will then focus on the expected role of existing and upcoming observing facilities such as Euclid, ELTs, SKA, and the ngVLA in this field.

Metal-poor galaxies provide a unique window into the physical conditions and chemical enrichment processes that govern star formation in nearly pristine environments. A subset of these systems exhibit spectra with extremely strong high-ionization emission lines that cannot be reproduced by standard stellar population models and, therefore, offer an ideal laboratory for testing the physical mechanisms that produce unusually hard ionizing radiation fields and extreme emission. These extreme emission line galaxies (EELGs) are often modeled under simplified assumptions, such as the low-density limit, and are widely used as benchmarks for interpreting elemental abundances and ionizing spectra across cosmic time. However, growing empirical evidence suggests that more extreme conditions at the heart of these sources are biasing our interpretations.

I will present new empirical methods to constrain the ionizing continua of EELGs from the JWST CLASSYIR Treasury Survey, which combines ultraviolet (UV) through mid-infrared emission lines to map the high-energy ionizing spectrum. These observations reveal radiation fields that are significantly harder and more structured than predicted by standard stellar population models, pointing to additional contributions from very massive stars, ultra-luminous X-ray sources (ULXs), and obscured AGN. At the same time, I will show that nebular conditions in these galaxies are far from uniform. Density stratification, particularly in highly ionized gas, can lead to systematic biases in temperature measurements and subsequent abundance determinations when using traditional low critical-density optical emission lines. As a result, even the long-standing “gold-standard” of metallicity measurements, the direct method, will be significantly biased in extreme environments.

Fortunately, UV diagnostics provide access to the densities and physical conditions of the high-ionization gas, enabling more robust determinations of temperatures and abundances. By combining UV and optical measurements, we can establish a physically consistent framework for interpreting local EELGs and connect them to high-redshift galaxies observed with JWST, which exhibit even more extreme ionization conditions, elevated densities, and enhanced N/O ratios. I will discuss the physical pathways that can drive rapid enrichment in relative abundances, and the implications for interpreting both local and distant galaxy populations.

Together, these results demonstrate that metal-poor EELGs expose the interconnected physics linking ionizing spectra, nebular conditions, and chemical enrichment across cosmic time, but only when interpreted with a self-consistent UV+optical framework.

The intergalactic medium (IGM) represents the dominant reservoir of baryons at high redshift, traces the architecture of the cosmic web dominated by dark matter, and fuels on-going galaxy evolution. The IGM has been studied using Quasi-Stellar Objects (QSO) absorption lines including the Lyman alpha forest (LAF). But because of the low surface brightness and extended, diffuse distribution, direct detection of an emission equivalent to the absorption LAF has been challenging. Using KCWI, we have detected an emission Lyman α forest (ELAF). The emission forest is highly extended, shows filamentary morphology with filaments connecting galaxies, exhibits statistics like the absorption Lyman α forest, displays spectra resembling the absorption forest, and is correlated with galaxy-traced over-densities consistent with bias like dark matter. We conclude that the ELAF may provide a new tool for tracing a significant fraction of the cosmic web of baryons and dark matter. We have also discovered a virial scaling in the Circum-Galactic Medium of nearby galaxies, demonstrating a clear transition in CGM properties moving from lower mass, star forming galaxies, to higher mass galaxies that may be beginning to quench. I will present status of the Stratospheric Cosmic Web Imager (SCWI) program, a Brinson Exploration Hub balloon experiment, focused on emission from the Circum-QSO, the Circum-Galactic Medium, and the cosmic web. SCWI offers the opportunity to image the cosmic web in the local universe for the first time and compare its properties to those at high redshift

The first billion years of cosmic history mark the transition from the formation of the first galaxies to the emergence of the physical processes that shape galaxy evolution across cosmic time. In this early phase, galaxies grow rapidly through gas accretion, mergers, and feedback-regulated star formation, while their dark matter haloes assemble hierarchically. I will discuss how recent observations and theoretical work are changing our view of this galaxy formation epoch, with a focus on the connection between galaxies and their host haloes, the efficiency with which baryons are converted into stars, and the highly variable nature of early star formation. These bursty star-formation histories leave imprints on galaxy scaling relations, stellar populations, sizes, and morphologies, and may help explain the surprisingly abundant and diverse galaxy population now being revealed at high redshift. I will also explore how early galaxies begin to develop more ordered structures, such as disks, and how their growth gradually becomes more regulated. Together, these developments point toward a physical picture in which cosmic dawn is not only the era of first galaxy formation, but also the beginning of the evolutionary pathways that lead to the galaxies we observe today.

Relativistic cosmic-rays created by stellar and black hole feedback may play an important role in many aspects of structure formation. Cosmic-rays can drive outflows from galaxies and groups, and heat diffuse gas in the circumgalactic and intergalactic medium.  In this talk I will describe some of the possible impacts of cosmic-rays on galaxy formation, observational probes of their impact, and the theoretical uncertainities in our understanding of the role of cosmic rays in structure formation.

Spirals are iconic features of galaxies, and yet conventional theoretical models for how they emerge and evolve only partially capture their observed traits and their connections to their host disks.  Recent JWST observations of beautiful, regular spiral patterns at redshifts z~2 and beyond underscore the need to resolve these theoretical shortcomings.  I will present a new picture of spiral patterns as short-lived density waves, analytically bridging the gap between the conventional long-lived density wave picture and the model of spirals as transient material patterns.  This new view forces a wholesale revisioning of how spirals influence their host galaxies: rather than merely reflecting conditions in the underlying disk, collectively excited spirals actively shape it, producing widespread changes in galaxy structure through dynamical heating and changes in angular momentum.  I will describe how these widespread changes are the very ingredients that give rise to global spiral patterns and naturally lead to stellar bulge growth, radial gas inflows and an overall structural compaction over cosmic time.  The picture of global, collective spiral excitation also has implications for the kinematics and the rich structure of gas disks, as revealed by JWST/MIRI imaging of nearby galaxies. These structures suggest a simple unified model in which radial gas flows appear alongside dynamical heating, and the latter acts as an important source of turbulent motion to offset dissipation.

Binary black holes (BHBs) hold the promise of
"multi-messenger astrophysics": their detections in both gravitational
waves (GWs) and electromagnetic (EM) observations will help reveal
their astrophysical origin and yield novel probes of cosmology,
fundamental physics, and accretion physics.  This is true for massive
BHBs expected to be discovered by the future GW satellite LISA and by
pulsar-timing arrays, and for stellar-mass BHBs already detected by
ground-based detectors.  I will describe how circumbinary gas may
produce characteristic EM signatures for both massive and stellar-mass
BHBs, based on analytic models and hydrodynamical simulations and
discuss some binary candidates identified in optical surveys.

Since the revolutionary discovery of gravitational wave (GW) emission from a binary black hole merger in 2015, the remarkable GW detectors LIGO, Virgo and KAGRA have detected at least 220 compact object mergers. These events are transforming modern astronomy and physics. In particular, the first, and to date the only, binary neutron star merger, dubbed GW170817, was observed in both gravitational and electromagnetic radiation, thus opening up a new era in multi-messenger astrophysics. The multi-messenger characterisation of such an event has enabled major advances into diverse fields of modern physics from gravity, high-energy astrophysics, nuclear physics, to cosmology. In this talk, I will discuss our work in strong-field gravity astrophysics and how combining observations, theory and experiment have been key in making progress in this field. I will present the challenges and the opportunities that have emerged in multi-messenger astrophysics, particularly in the past decade, and what the future holds in this new era.

MeerKAT telescope has improved our understanding of various aspects of our radio universe ranging from stars, supernova remnant, pulsars, radio galaxies, Galaxy Clusters, and cosmology. In this talk, I will highlight some of the recent results from MeerKAT with particular focus on the South African Radio Astronomy Observatory (SARAO) MeerKAT Galactic Plane Survey (SMGPS) as it relates to star formation, and the influence of cluster environment to the evolution of radio galaxies as described below.

Intra-Cluster Magnetic field play a key role in the evolution of the cluster member galaxies. MRC 0600-399 is the second brightest member galaxy of the merging galaxy cluster Abell 3376 (redshift 0.0461). Elongated X-ray emission in the east–west direction shows a comet-like structure that reaches the megaparsec scale. MRC 0600-399 shows a 90-degree bend at the contact discontinuity, and the collimated jets extend over 100 kiloparsecs from the point of the bend. I will show the results of the polarization observations of MRC 0600-399 with MeerKAT to explore the properties of the magnetic fields of the galaxy.

Axions and other Weakly Interacting Sub-eV Particles (WISPs) are compelling candidates for physics beyond the Standard Model, offering solutions to the strong-CP problem and viable dark matter components. Astrophysical X-ray observations provide a powerful and complementary approach to searching for these particles through their conversion into photons in large-scale magnetic fields.Using data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), we pursue multiple strategies for axion detection. We search for axion–photon conversion in the Sun’s atmospheric magnetic field during the 2020 solar minimum, and for axion production via the nuclear M1 transition of 57Fe in the cores of nearby supergiant stars such as Betelgeuse. In addition, NuSTAR observations of Betelgeuse, following the work of Gianotti et al., probe axion production through the Primakoff process and axion–electron interactions, providing sensitivity to axion–photon, axion–nucleon, and axion–electron couplings. These studies yield the most stringent astrophysical constraints to date, improving previous solar and stellar limits by up to 1–1.5 orders of magnitude. Looking ahead, wide-field X-ray surveys such as eROSITA, with improved effective area and a complementary energy range, offer strong potential to further extend astrophysical axion searches across a broad range of masses and couplings. Together with laboratory experiments such as CAST and the forthcoming IAXO, these results underscore the growing role of X-ray astronomy in probing axions, WISPs, and the dark sector.

Advances in global magnetohydrodynamic (MHD) simulations have greatly promoted our understanding of astrophysical discs. Applications include compact X-ray binaries, discs in active galactic nuclei and entire galaxies, as well as outlining conditions for planet-formation in circumstellar discs. Depending on the overall degree of ionisation, several independent processes have been identified that may govern the transport of angular momentum. With few exceptions, magnetic fields are found to play the pivotal role in torquing the flow. One major goal in the field is to derive simplified long-term evolution models (e.g., for the disc surface density as a function of radius), and from those derive synthetic populations for comparison with the results found in big ALMA surveys. In the context of planet-formation theories, such models also serve as

the backdrop for planet-population-synthesis codes – governing the growth as well as orbital migration of the evolving planets, and discerning in-situ from ex-situ formation pathways. Irrespective of whether the plasma flow inside the disc remains laminar or becomes turbulent, the evolutionary processes are generally found to depend sensitively on the overall amplitude of the large-scale magnetic flux. This mandates to follow the magnetic flux evolution in tandem, either via non-ideal plasma effects, or –in the case of fully ionized discs– by means of a suitable mean-field description. Finally, we place these developments in the broader context of disc winds, mass loss, and observational diagnostics – highlighting how thermally driven and magnetically mediated outflows emerge from joint MHD and radiative-chemical modelling efforts and suggesting pathways toward directly linking theory to high-resolution disc observations.

The tidal breakup of binary stars by a massive black hole (MBH), known as the Hills mechanism, occurs when a binary approaches sufficiently close to the MBH. This well-known process produces a hyper-velocity star that escapes the galaxy and a captured star that is tightly bound to the black hole on a highly eccentric orbit.

In this talk, I explore what happens both before and after the Hills breakup. Prior to disruption, perturbations from the MBH over numerous pericenter passages can excite the inner binary orbit to high eccentricities, triggering strong tidal interactions between the two stars. We find that a significant fraction of initially wide binaries are driven into close configurations through tidal interactions in the chaotic regime, and subsequently undergo Hills breakup as close binaries.

After the breakup, the long-term evolution of the captured stars can produce a variety of nuclear transients. These include repeating partial tidal disruption events (TDEs) on timescales of years or longer and quasi-periodic eruptions (QPEs) with periods ranging from hours to months. We further show that collisions between Hills-captured stars and accretion disks formed by unrelated TDEs can efficiently circularize their orbits, providing a natural pathway for producing the shortest-period (sub-day) QPEs.

We have known for decades that magnetic fields and relativistic particles (cosmic rays) can play a key role in some astrophysical environments. But it has only recently become possible to model these directly including other key physics (like radiative cooling, self-gravity, star formation, etc.) in models of galaxies and super-massive black hole growth and “feedback.” Moreover those simulations have historically been limited to a very narrow dynamic range of scales being probed. I’ll discuss how a combination of new physics and new numerical methods has led to breakthroughs that now allow us to simulate problems like supermassive black hole growth, star and galaxy formation with truly unprecedented dynamic range reaching from the horizon to the intergalactic medium. These have revealed some major surprises. In particular, non-thermal physics may be vastly more important on both the smallest and largest scales, compared to previous assumptions. I’ll show how these simulations predict qualitatively new forms of strongly-magnetized accretion disks around supermassive black holes, that can resolve many decades-old observational puzzles and make new unique observational predictions. At the same time, the feedback from supernovae and black holes could be, on the largest (circum and intergalactic medium) scales dominated by cosmic rays. I’ll show how recent new observations of X-rays and the Sunyaev-Zeldovich effect, in particular, appear to be indicating that most of the pressure on these scales is not — as assumed in almost all models for decades — primarily thermal, but appears to be coming from cosmic rays. And I’ll show how new observations can probe this further over a range of galaxy mass scales.

Unraveling the planet formation process and the origin of the diversity of planetary systems require a comprehensive understanding of the planet-forming disks surrounding young stars. ALMA’s unprecedented spatial resolution and sensitivity have enabled a detailed examination of the physical and chemical structures of planet-forming disks (at ~10 au scale). The detections of gaps and rings in numerous disks have transformed our understanding of disk evolution and planet formation. I will first provide a summary on the detection and characterization of disk substructures, and discuss the exciting avenue of young planet search as guided by these disk features. While ALMA excels in probing the bulk disk property, the very innermost disk (within 1-3 au), remains elusive to its capabilities, which can now be well studied with JWST. In the second half of the talk, I will touch upon our expanding view of the inner disk chemistry, especially the interplay with substructures at large disk radii and for disks around very low-mass stars. By leveraging the capabilities of ALMA and JWST, we aim at establishing a global view of disk evolution, laying the groundwork for the development of a robust predictive model of planet formation.  

Bio: Feng Long is an Assistant Professor at the Kavli Institute for Astronomy and Astrophysics of Peking University. After receiving her PhD from Peking University in 2019, she spent three years as an SMA Postdoc Fellow at the Center for Astrophysics | Harvard & Smithsonian. From 2022 to 2025, she worked at the University of Arizona as a NASA Sagan Fellow. Her research uses advanced facilities like ALMA and JWST to study protoplanetary disk evolution and planet formation. 

The recently launched XRISM (JAXA/NASA/ESA) observatory has provided long-awaited high-resolution spectra of extended X-ray sources, including clusters of galaxies. These spectra enable direct measurements of gas kinematics in the intracluster medium (ICM). I will present XRISM results from observations of well-known bright galaxy clusters and discuss their implications for the physics of AGN feedback, ICM turbulence, cluster mergers and their assembly history, and cluster mass measurements for cosmology. Finally, I will compare these measurements with cosmological simulations, highlighting both what they reproduce and remaining challenges.

Thanks to the Hubble Space Telescope, combined with major ground-based facilities and gravitational lensing (“cosmic telescopes”), we have entered an era in which stellar clusters can be identified at cosmological distances. The James Webb Space Telescope (JWST) is now transforming this field -- and, more broadly, our view of the early Universe. With its exceptional sensitivity and angular resolution at infrared wavelengths, JWST, when coupled to strong gravitational lensing, can isolate individual star clusters even within the first half 0.5 Gyr of cosmic history. This lensing-enhanced spatial contrast enables the identification of candidate progenitors of present-day globular clusters and places them in the context of key questions, from the sources of ionizing photons during reionization to the emergence of extremely metal-poor (possibly near-pristine) star formation, and the possible connection to black-hole seeds. Looking ahead, ground-based facilities in the 2030s equipped with extreme adaptive optics (AO) -- most notably the ELT -- will consolidate these studies and push to even finer physical scales. The synergy between space and ground-based facilities will thus open an unprecedented window on the earliest stellar systems, connecting parsec-scale star formation to the assembly of galaxies and black holes in the reionization era.

James Webb Space Telescope (JWST) has opened a new window into the early universe, enabling sensitive, high-resolution images of the near-infrared sky and spectroscopy of faint, distant sources. The JWST Advanced Deep Extragalactic Survey (JADES) is a collaboration of the NIRCam and NIRSpec GTO teams pooling over 750 hours of JWST time to conduct an ambitious study of galaxy evolution in the Great Observatories Origins Deep Survey GOODS-South and GOODS-North fields. I will discuss exciting results from JADES observations about discoveries in the distant (z>12!) universe that provide new insight into the process of early galaxy formation and cosmic reionization. We discuss how our new constraints on star formation and galaxy growth at the very earliest times are rewriting the story of how the first galaxies form and evolve.

One of the most surprising results coming out of the first years of science operations with JWST is the unexpectedly high abundance of actively accreting black holes in the early Universe. Compared to the local population, many of these early black holes appear to differ in various aspects, such as their relation to their host galaxies or their multi-wavelength properties. These observational findings challenge our understanding of the past evolution of present-day supermassive black holes, and provide new ways to constrain theoretical models of black hole formation and growth. I will give an overview of recent observational results on massive black holes in the first few billion years, driven by the unprecedented capabilities of JWST to explore cosmic dawn, and with a focus on results from the GTO and GO NIRSpec-IFS surveys GA-NIFS and BlackTHUNDER.