The discovery of the "little red dots" with the James Webb Space Telescope has revealed a host of surprises about this mysterious class of high-redshift objects. Their physical nature remains hotly contested. I will argue that little red dots trace the initial phase of supermassive black holes that predates the formation of their host galaxies. As such, they offer a uniquely valuable...
We investigate the morphology from UV to optical of eight little red dots (LRDs) selected from the JWST UNCOVER survey, applying a new technique (GalfitS) to simultaneously fit the morphology and spectra energy distribution using multiband NIRCam images covering ~ 1-4 ${\mu m}$. For the majority of LRDs (7/8) in our sample, the morphology in all bands are dominated by an unresolved point...
The early growth of high-redshift quasars and their host galaxies raises critical questions about their cosmic evolution. We exploit the angular resolution and sensitivity of NIRCam to investigate the host galaxies of 31 quasars at $4\lesssim z\lesssim7$ drawn from multiple JWST surveys. Using a new multi-band forward-modeling code (\textsc{GalfitS}) that incorporates physically motivated...
The Einstein Probe (EP) is a newly launched space mission dedicated to the X-ray all-sky survey and characterization of all kinds of high-energy transients. During the first few months of in-orbit operation, EP has discovered dozens of new X-ray transients with intriguing properties. In this talk, I will present a few typical examples of TDE candidates discovered by EP since its launch,...
Tidal disruption events (TDEs) have been thoroughly examined within the local universe using diverse observations and theoretical frameworks. However, the study of TDEs at high redshifts has been relatively scarce. The imminent launch of advanced high-resolution, wide-field surveys facilitated by telescopes such as LSST, Nancy Grace Roman Space Telescope (Roman) and Ultrasat is set to...
A tidal disruption event (TDE) occurs when a star ventures too close to a massive black hole. Initially, the angular momentum of the star's orbit may not coincide with the black hole's spin axis, resulting in the formation of a tilted accretion disk relative to the black hole. The Lense-Thirring effect then sets this disk into precession. In this study, we have constructed a precessing...
TDEs provide a valuable probe for studying the dynamics of stars in the nuclear environments of galaxies. Recent observations show that TDEs are strongly overrepresented in post-starburst or “green valley” galaxies, although the underlying physical mechanism remains unclear. Considering that galaxy mergers may trigger starbursts and AGN activity, the TDE rate may also be related to the...
Tidal Disruption Events (TDEs) host galaxies are known to exhibit distinct characteristics, such as high central stellar concentration and an overrepresentation in E+A (post-starburst) galaxies, which has led to the hypothesis that recent merger events may play a significant role in their evolution. However, the underlying mechanisms driving these characteristics remain unclear. This study...
Directly resolving the gas distribution in galactic nuclei are challenging, but radio‑bright nuclear transients—especially tidal disruption events (TDEs)—offer a powerful indirect probe. Our three‑dimensional hydrodynamic simulations show that the interaction between a TDE outflow and the circumnuclear medium (CNM) produces radio light curves whose shapes reveal the CNM density profiles....
A growing number of transient phenomena in galaxy nuclei have recently begun to shed new light on SMBH demographics and the physics of gas accretion onto these objects, tracing events where this accretion has drastically intensified, diminished, and/or otherwise disturbed, over surprisingly short timescales. These phenomena include “changing look AGN” and other, poorly understood flares from...
AGN are known to show flux variability over all observable timescales and across the entire electromagnetic spectrum. Over the past decade, a growing number of sources have been observed to show dramatic flux and spectral changes, both in the X-rays and in the optical/UV. Such events, commonly described as “changing-look AGN”, can be divided into two well-defined classes. Changing-obscuration...
Accurate supermassive black hole (SMBH) mass measurements are essential for understanding their formation and coevolution with host galaxies. Recent advances with the GRAVITY instrument on the Very Large Telescope Interferometer have revolutionized our ability to study active galactic nuclei (AGNs) and luminous quasars at unprecedented angular resolution. In this talk, I will present GRAVITY...
Super-Eddington accretion happens in various astrophysical systems. For example, it is currently believed that super-Eddington accretion onto black holes powers tidal disruption events (TDEs), little red dots (LRDs) and a large fraction of ultra-luminous X-ray sources (ULXs). In this work, we conduct a series of 3D general relativistic radiation magnetohydrodynamics (GRRMHD) simulations of...
Bowen lines, such as NIII4640 and NIII4100, were predicted to be detectable in supermassive black holes decades ago. However, they were only recently discovered in 2019 through extreme events such as tidal disruption events (TDEs), Changing Look AGNs, and Bowen Fluorescent Flare. The Bowen mechanism employs resonant absorption, EUV emission and outflows to account for the relatively strong...
I will talk about preliminary results from EP-FXT follow-up observations of previously known tidal disruption events.
