Active Galactic Nuclei (AGNs) are black holes in the centres of galaxies that undergo phases of growth, in the form of accreting gas. To better understand how this happens in detail, understanding the AGN structure remains a major objective since their discovery 60 years ago. This can be achieved by monitoring small-scale AGN variability to map the structure (the so-called broad-line region, or "BLR") with light echoes, or directly resolving the BLR size which has become feasible only with recent developments at the VLT interferometer.
The other big question that remains is how does the gas get there to begin with? The BLR is up to tenthousand times smaller that the host galaxy, with timescales and gas dynamics being decoupled from each other. The relevant mechanisms must describe multiple time, temperature and density scales to bridge distance before it is accumulated on the accretion disc and eventually disappears behind the black hole's event horizon. What host galaxy properties promote the AGN phase? How do the stellar and gas kinematics in the host galaxy affect AGN activity and vice versa? What role does the host galaxy star formation play on different spatial and time scales? With my research I try to contribute bringing us closer to answering these questions.
Highlights
Gravitational Torques from a Lopsided Young Stellar Component Sustain High Black Hole Accretion Rates in NGC 4593
A prominent one-armed molecular gas spiral transports cold gas inward from 1.3 kpc to near the sphere of influence of NGC 4593's central black hole. Taken from Winkel et al. (2025b).
In our most recent work, we identify a key mechanism that may explain how supermassive black holes (SMBHs) grow without the need for galaxy collisions. We studied the galaxy NGC 4593, selected for its high central gas content and black hole accretion rate - typical of the galaxies that have driven most SMBH growth in the last 10 billion years of the Universe. We discovered a prominent one-armed spiral of molecular gas funnelling material from galactic scales directly toward the black hole. This inflow is likely driven by a lopsided central stellar component and is capable of sustaining black hole growth for tens of millions of years. Our findings provide evidence that this long-lived, internal process-predicted by theory but rarely observed - could be a major contributor to SMBH growth across cosmic time. Upcoming surveys will be able to test how common this mechanism is.
Calibrating the Black Hole Mass - Host Galaxy Scaling Relations in AGNs
After matching the distribution in black hole mass, AGNs (blue data points) and inactive galaxies (grey contours) follow the same MBH-σ⋆ relations (stripes). Taken from Winkel et al. (2025a).
Active galactic nuclei (AGNs) provide a unique chance to study SMBH growth and measure their masses beyond the local Universe.
However, measuring galaxy properties like stellar velocity dispersion (σ⋆) and dynamical mass (Mdyn) in AGN hosts is challenging due to AGN contamination, observational limitations,
and galaxy diversity. We analyzed a sample of AGNs with highly accurate SMBH mass measurements using advanced techniques like reverberation mapping and
VLTI/GRAVITY imaging.
By mapping stellar motion across these galaxies, we discovered that SMBH mass correlates best with σ⋆ measured within the galaxy's bulge.
Importantly, we showed that AGNs follow the same SMBH-host galaxy scaling laws as inactive galaxies. This indicates the AGN phase doesn’t significantly alter SMBH mass over time. These findings support using the established virial factor (log f = 0.65) to estimate SMBH masses in distant AGNs, enhancing our understanding of SMBH growth throughout cosmic history.
Tracing the Circumnuclear Star Formation in Mrk 1044
Illustration of the MUSE NFM-AO data of Mrk1044's centre covering the innermost ~2kpc. A prominent star-forming ring is detected in Hα and [NII] emission.
This study focusses on the host galaxy conditions that allow rapid growth of supermassive black hole. The target is Mrk 1044, a narrow-line Seyfert 1 (NLS1) galaxy, an AGN class that have high specific black hole accretion-rates, may help us understand how black hole activity begins. Using 3D spectroscopy obtained with ESO/MUSE NFM-AO, we mapped Mrk 1044’s stars and gas from galaxy-wide scales down to its central regions. We found a compact, star-forming region near the nucleus that remains unaffected by the AGN’s activity, indicating that Mrk 1044’s AGN phase likely began recently. This aligns with the idea that NLS1 galaxies are in an early AGN stage, where star formation and black hole growth are closely linked. The animation on the right shows the flux density maps (top panel) of the ionized gas emission from the host galaxy on galaxy scales (left) and nuclear scales (right). Traversing the emission lines of Hα and the forbidden [N II] doublet, the maps show the disk-like rotation pattern of the host galaxy.
A parsec-scale multi-phase outflow in the heart of Mrk 1044
We explored the geometric alignment of two spatially runresolved Ly-α absorbers and [O III] emitters close (< 1pc) to Mrk 1044's AGN. Taken from Winkel et al. (2023).
Following our work on nuclear star formation in Mrk 1044, we conducted an in-depth analysis of its core region. Using spectroastrometry - a technique that traces emission lines at sub-pixel resolution- we identified and located multiple components of outflowing ionized gas. These AGN-driven winds are compact, exhibit relatively high gas densities, and were launched only recently (within the past 10,000 years). Given the substantial circumnuclear star formation, our findings suggest that Mrk 1044’s AGN phase began recently enough that the ionized gas outflow has not yet significantly impacted the host galaxy's ISM near the nucleus.
The Imprint of Cosmic Web Quenching on Central Galaxies
Illustration of the metric used for determining gradients with respect to the galaxy's position in the cosmic web. Taken from Winkel et al. (2022).
In this project, we investigated how the cosmic web influences the properties central galaxies the Sloan Digital Sky Survey. We focus on how properties like star formation rate, age, metallicity, and element ratios vary with a galaxy’s distance from cosmic web structures -nodes, walls, and filaments- identified using the DisPerSE tool. Controlling for factors such as galaxy mass and local density (field vs. group settings), we find that galaxies closer to these cosmic features tend to have lower star formation rates, are older, richer in metals, and show higher [α/Fe] ratios. These trends hold true in both field and group environments, supporting the idea that the cosmic web influences galaxy evolution through environmental effects like ram pressure stripping or the intrinsic properties of the cosmic web itself.
