VST Science Workshop 2026

9 Apr 2026, 09:30 → 10 Apr 2026, 17:00 Europe/Rome

Sala Cimmino (Monte Mario)

Enrichetta Iodice (Istituto Nazionale di Astrofisica (INAF))

Link for remote connection

Thursday 9 April

09:30 → 11:00 Opening Session

09:30 Welcome

09:35 Progress report from the VST Team

The members of the INAF Coordination Centre for the VST will report on the main activities, including observation tracking, data reduction, and data release.

Speaker: Enrichetta Iodice (Istituto Nazionale di Astrofisica (INAF))

10:20 The role of the VST within the panorama of INAF ground-based observing facilities

Speaker: Dr Marcella Marconi (Istituto Nazionale di Astrofisica (INAF))

10:40 The impact of the VST released data on the ESO Science Archive Facility

Speaker: Dr Martino Romaniello (ESO - Garching)

11:00 → 11:30 coffee-break

11:30 → 13:10 Session 1: Rubin-LSST in-kind@VST

11:30 Rubin-LSST@Italy, in-kind program status & perspectives

Speaker: Massimo Brescia (Istituto Nazionale di Astrofisica (INAF))

11:50 VST as a Facility for Rubin/LSST Follow-up

The advent of the Rubin Observatory Legacy Survey of Space and Time (LSST) will produce an unprecedented stream of transient and variable sources requiring rapid photometric follow-up. The VLT Survey Telescope (VST), with its wide field of view and imaging capabilities, is well suited to play a key role in this effort. In the context of the INAF in-kind contribution S18 to the Rubin Observatory, we explore the potential of VST as a facility for LSST follow-up observations. I will present the observing strategy and the level of interest from the community, including the number of proposals submitted in response to the recent NOIRLab call.

Speaker: Dr Felice Cusano (Istituto Nazionale di Astrofisica (INAF))

12:10 Unveiling the Transient Universe: VST Synergies with Euclid and Rubin

Time Domain Astronomy is living a golden era thanks to next-generation facilities extending our view of the transient Universe in a larger range of wavelengths and detecting hundreds of thousands of extra-galactic transients. Among all, the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory has recently begun circulating worldwide alerts for new transient and variable sources, and will soon commence its 10-year survey of the southern sky. At the same time, numerous spectroscopic surveys are preparing for follow-up observations (e.g. SOXS), while the time-domain community synchronizes multi-wavelength and multi-messenger facilities to characterize these events in unprecedented detail. To complement this framework, the ESA Euclid mission, launched on July 2023 and not explicitly designed for variability studies, is proving to be extremely valuable in detecting high-redshift and elusive transients, thanks to repeated observations in the Euclid Deep Fields (EDFs) with deep and high-resolution optical images, and additional near-infrared (NIR) photometry and slitless spectroscopy. One of these fields (EDF-S) has been chosen for additional monitoring with Rubin, and the upcoming Roman Space Telescope (scheduled for 2027) is also considering monitoring portions of this area through its dedicated high-redshift transient program.
Within this landscape, we proposed a VST monitoring of 4 square degrees in EDF-S, as an Italian in-kind contribution for LSST. Increasing the photometric coverage provides both pre- or post- discovery observations, and high-cadence light curves to improve the classification and characterization of the newly discovered sources. This is an indispensable requirement for cosmological,‬‭ progenitor, and diversity studies, as well as for the discovery of new classes of transients.‬ Combining simultaneous multi-band light curves from VST and LSST with high-resolution optical and NIR data from Euclid will allow us to investigate transients and their host-galaxy correlations with unprecedented precision. Although the LSST is just beginning, we started our monitoring one year earlier with the pilot project VESTA (Vst-Euclid Synergies for Time-domain Astronomy) designed to provide ground-based optical support for Euclid and get ready for the VST+Euclid+Rubin synergy. We present preliminary results from VESTA, describing our analysis pipeline and the strategic transition into the formal LSST in-kind program.

Speaker: Vincenzo Petrecca (Istituto Nazionale di Astrofisica (INAF))

12:30 The Timedomes project: building on the VST legacy in the time domain

I will present the status of the Timedomes project, started in 2021 and proposed as an in-kind contribution to the LSST collaboration. The program is targeting 4 sq.deg. of four of the LSST DDFs in two bands with 8 or more epochs each semester, in order to improve the temporal coverage of the fields up to the beginning of LSST observations. These data, complemented by all archival VST observations dating back to 2011, are allowing to build a legacy dataset of images and light curves to extend the DDF monitoring effort up to 20 years, with the aim of studying AGN properties and demographics, transient sources as well as provide deep reference templates.

Speaker: Prof. Maurizio Paolillo (Università degli Studi di Napoli Federico II)

12:50 Exploiting the synergy between LSST and VST to investigate the cosmos: the expansion rate and the geometry of the Universe measured through the time delays of strongly lensed variable sources

The Vera C. Rubin Observatory (LSST) will discover thousands of new multiply imaged quasars and supernovae (Oguri & Marshall 2010). In P3 and P4, we have proposed monitoring observations with the VST of quasars multiply lensed by galaxies and galaxy clusters, that will belong to the final LSST sample, to accurately measure the multiple image light curves, thus their time delays. We aim at using these time delays as an important and complementary tool to measure the expansion rate and the geometry of the Universe. In detail, we have performed a high-cadence and high S/N ratio monitoring campaign with the VST. Time-delay cosmography is based on well-know physics (General Relativity) and is a single-step technique that can yield competitive and independent estimates of the values of the cosmological parameters, without any complex calibration. I will give an overview of the status of the programme and will show the first promising results. The final outcomes of this study will help clarify whether the current, hotly debated tension on the value of $H_{0}$ must be ascribed to intriguing new physics or to significant systematic effects neglected so far, and improve by 40% the Figure of Merit of any stage-IV cosmological survey (LSST, Euclid, etc.). In addition, leveraging the large field of view of the VST, we will perform a search for Type Ia supernovae (SN Ia) exploding in cluster member galaxies. The daily sampling rate of the light curves will provide independent estimates of the luminosity distances of the SN Ia galaxy hosts, and thus of the lens clusters. Moreover, we will also estimate the rate of SNe Ia in galaxy clusters, which can shed light on the progenitors and physics of SNe Ia. Over the VST wide field of view, the same data will provide deep imaging, in good seeing conditions, that will allow us to build high-quality weak lensing mass maps and to detect serendipitous new transients. I will conclude with some examples of possible ancillary science, thanks to the measured light curves of several variable stars and AGNs identified in the targeted fields.

Speaker: Prof. Claudio Grillo (Istituto Nazionale di Astrofisica (INAF))

13:10 → 14:10 Lunch break

14:10 → 15:30 Session 2: Large Programs at VST

14:10 STEPping stones between the Clouds: the star formation history of the Magellanic Bridge

In the last decades, our understanding of dwarf galaxies has significantly advanced, driven by efforts to characterize their evolution and interactions with their surrounding environments. Ground-based observations, particularly those utilizing wide field-of-view telescopes like VST, have enabled detailed studies of both the central regions and the outer edges of the closer dwarfs, such as the Magellanic Clouds. In this context, we focus on the stellar populations of the Magellanic Bridge, likely formed during the last close encounter between the Magellanic Clouds approximately 150 Myr ago. Metallicity measurements from gas absorption lines indicate that the Bridge is predominantly composed of SMC material, with the interaction leaving imprints in its chemical enrichment and ongoing star formation. To investigate this encounter, we applied a color–magnitude diagram reconstruction technique to data from the STEP survey (The SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy), deriving the global Star Formation History (SFH) of the whole Magellanic Bridge. Thanks to VST's high photometric accuracy and deep magnitude limit, we reached the ancient main-sequence turn-off in the Bridge, reconstructing the SFH of this region with high age resolution. This allowed us to constrain the timing of the last close encounter between the Magellanic Clouds. When combined with the dynamical modeling of the system, our results may offer new insights into how tidal interactions have shaped the evolution of the Magellanic Clouds. These findings underscore the importance of understanding the complex interplay between star formation, chemical enrichment, and galaxy interactions in the low-mass regime.

Speaker: Francesco Ficara (Istituto Nazionale di Astrofisica (INAF))

14:30 The search for very nearby astrophysical transients with the VST

In this talk, we present the use of the VST to search for and study selected astrophysical explosions. The VST is one of the most powerful facilities for scanning wide regions of the southern sky and identifying transient phenomena. I will highlight several particularly interesting cases currently being pursued by the TNT group in Naples and describe our data reduction and analysis procedures, which have been specifically developed and optimized for transient studies with the VST

Speaker: Luca Izzo (Istituto Nazionale di Astrofisica (INAF))

14:50 From Autopsy to Diagnosis: Direct Detection of Episodic Mass Loss in SN Progenitors

Red Supergiants (RSGs) are the canonical progenitors of Type IIP/L supernovae. While standard stellar evolution models depict them as quiescent stars undergoing steady-state mass loss, this picture is increasingly challenged by evidence of complex, dense circumstellar material (CSM) surrounding the explosion site. These interaction signatures indirectly point to intense, episodic mass-loss events occurring shortly before core collapse, the physics of which remain an open question. In this talk, I discuss a shift in observational strategy: moving from the forensic "autopsy" of supernova light curves to the "diagnosis" of the living progenitor. I will present results from a targeted optical/NIR monitoring campaign with INAF facilities designed to detect these precursor outbursts, aiming to characterize the final evolutionary stages of massive stars before the terminal explosion.

Speaker: Fabrizio Bocchino (Istituto Nazionale di Astrofisica (INAF))

15:10 VST-SMASH: the outskirts of IC 5332 and the discovery of new satellite candidates in the field of NGC 5068

The VST Survey of Mass Assembly and Structural Hierarchy (VST-SMASH) program targets a volume-limited sample of 27 local galaxies within 11 Mpc and the Euclid survey footprint in g-, r-, and i-bands, achieving a surface brightness limit of μ ≥ 29 mag arcsec⁻² in g- and r-bands and shallower levels in i-band. VST-SMASH gives a unique opportunity to detect faint stellar streams, tidal remnants and satellites around local galaxies, allowing us to constrain the galaxy assembly across a wide range of masses and galaxy types through the comparison with theoretical models and cosmological hydrodynamic simulations. VST-SMASH will provide the only deep counterpart of galaxies at D < 11 Mpc in the south hemisphere for future Euclid data exploitation, anticipating the deep LSST images available in the next years.

I will discuss the current status of the program and present the first preliminary results, focusing on the outcomes of the two papers submitted to A&A and currently under revision. These papers address the structural properties of IC 5332, and the discovery of new dwarf galaxy candidates in the field of NGC 5068 and of the two Virgo galaxies NGC 5084 and NGC 5087. I will conclude by outlining the future plans for the project.

Speaker: Crescenzo Tortora (Istituto Nazionale di Astrofisica (INAF))

15:30 → 16:00 coffee-break

16:00 → 16:40 Session 2: Large Programs at VST

16:00 HAGRPS: an H-alpha narrow-band imaging survey of galaxy groups in the Local Supercluster

I will introduce HAGRPS, an H-alpha narrow-band imaging survey of galaxy groups in the Local Supercluster, which is a large observing program carried out with the VLT Survey Telescope (VST). 
H-alpha imaging data are gathered to study the role of the environment on galaxy evolution.
Indeed, H-alpha observations reveal the ionized hydrogen emission, which is a direct tracer of recent star formation, and are a powerful probe in the identification of perturbing mechanisms such as ram pressure stripping, tidal interactions, and starvation in dense regions.
Since these perturbing mechanisms acting on galaxies are expected to vary with the halo mass, observations must cover a wide range of environments, from massive clusters down to groups of M_halo ~ 10^13 Mo. 
This survey has been designed to extend previous narrow-band imaging studies of massive clusters down to intermediate mass groups.
I will present the progress of the observations and the scientific objectives of the survey, describe the development of a ad-hoc data reduction pipeline especially tailored for the reduction and calibration of the narrow band H-alpha imaging data and optimized for the detection of low surface brightness extended features such as those produced by the interaction of galaxies with the hostile surrounding environment.
I will also show the first results of the survey through the analysis of representative galaxies.

Speaker: Elena Sofia Mangola (LAM, Aix Marseille Université, CNRS)

16:20 VST-MAGNET: Mechanisms Affecting Galaxies Nearby and Environmental Trends with VST

The life of galaxies is regulated by the flow of gas in and out of galactic disks, hence a detailed understanding of how galaxies exchange material with their surroundings and what physical mechanisms can affect this flow is a key factor for understanding galaxy evolution. The environment in which galaxies reside plays an important role, as the effectiveness and importance of the different processes is ambient dependent. Nonetheless, while we recently made many fundamental steps forward in understanding what drives gas flows in galaxies hosted in clusters; we have not yet a solid ground to build up a complete understanding of environmental processes in less extreme environments, which are those hosting the vast majority of galaxies. The key question remains open: what is the importance of each of these processes in regulating the whole galaxy population, as a function of galaxy mass, redshift and position within the large-scale cosmic structure?

VST-MAGNET (Mechanisms Affecting Galaxies Nearby and Environmental Trends with VST) is a OmegaCAM Large Programme approved in P3. Its goal is to provide transformative new observational evidence on this open issue. We are carrying out a narrow-band imaging survey providing Hα emission at z between 0 and 0.04 on a 65 deg2 sky area that includes galaxy groups and associations in filaments of the cosmic web. These data will provide deep spatially resolved information of the distribution of the ionized gas and star forming regions in galaxies and will be used to shed unprecedented light on the efficiency of the different environmental mechanisms and of star-formation quenching for galaxies in a wide range of stellar masses (at least down to 1e8 solar masses).

I will present the status of the project, the strategies developed for the data reduction analysis of the VST data and some preliminary results.

Speaker: Marco Gullieuszik (INAF - OAPd)

16:40 → 18:00 Session 3: SP-Young programs

16:40 A VST survey of multiple populations inglobular clustes

It is now well established that globular clusters (GCs) host multiple stellar populations with distinct chemical compositions. However, the formation mechanisms responsible for the unique abundance patterns observed in these systems remain a major unresolved problem in stellar astrophysics. Although multiple populations are found in the majority of studied old and massive GCs, their incidence and properties vary significantly from cluster to cluster, producing diverse population patterns. This diversity highlights the need for extended and homogeneous surveys of these systems.

Among the key observational signatures of the phenomenon, the spatial distribution of the different populations is particularly important. While the Hubble Space Telescope (HST) has provided detailed information on multiple-population patterns in the cores of ~60 GCs, the outer regions remain poorly explored, with data currently available for less than half of the HST sample.

The VLT Survey Telescope (VST), thanks to its wide field of view, offers a unique opportunity to study multiple populations across the full radial extent of GCs. In this program (ID: 114.27TN, Cycle 3), we observed 47 Galactic GCs using the u, B, and i filters, which are well suited to disentangle chemically distinct stellar populations. By exploiting the VST’s large field of view, this survey enables the first complete and homogeneous mapping of multiple populations across the entire spatial extent of these clusters.

Speaker: Emanuele Dondoglio (Istituto Nazionale di Astrofisica (INAF))

17:00 The UMBREON project: revealing the invisible side of dark galaxies

In the ΛCDM cosmological framework, dark matter (DM) halos represent the building blocks for galactic structures. Galaxies are expected to form stars from their gas reservoirs in the gravitational potential of these DM halos, which are predicted to be more common with decreasing mass. But not all DM halos effectively convert this gas into stars, forming a galaxy. Gas may accumulate without undergoing star formation activity. Such galaxies are expected to be nearly dark due to the scarcity of stars, and in some cases, be completely dark due to the absence of stars. Such objects are named “dark galaxies” and their existence may contribute to solving the so-called “Missing Satellite
Problem, which has puzzled astronomers for decades.

Since dark galaxies contain a modest amount of cold neutral hydrogen (HI) gas, they are detectable with radio telescopes. We have collected deep imaging data with OmegaCAM@VST of five isolated “dark galaxies” candidates identified in the WALLABY ASKAP pilot survey to reveal the optical counterpart of these extreme objects. This will allow us to place a limit on how “dark” these galaxies truly are, thereby helping to clarify the nature of the HI emission and studying the structural properties of the mysterious class of galaxies.

In this talk, I will present recent results obtained by combining information on HI data with deep photometry from VST images.

Speaker: Chiara Buttitta (Istituto Nazionale di Astrofisica (INAF))

17:20 Into the jaws of darkness - Hunting for Dark Galaxies

The ΛCDM model successfully describes the hierarchical large-scale structure of the Universe, but it also predicts a much larger number of low-mass dark matter haloes than are actually observed. This tension can be explained by the fact that below a certain mass threshold, star formation is suppressed. However, these low-mass haloes should contain a significant amount of HI, which could be detectable through radio observations.
With the advent of high-sensitivity single-dish blind surveys (such as the FAST All-Sky HI Survey), several extragalactic HI sources with gas masses compatible with dwarf galaxies have been discovered, yet they do not present an optical counterpart even in the most sensitive optical surveys. These exotic objects are usually referred to as `dark galaxies'.
Using the FAST HI survey, we selected more than 3400 HI sources within 50 Mpc, the vast majority of which present a clear optical counterpart in the DESI Legacy Imaging Surveys, while 70 do not (Dark Galaxy Candidates, DGCs). Searching for extremely faint optical counterparts of these DGCs is crucial, since it allows us to place strict upper limits on their stellar mass and helps us understand why these systems exhibit extremely quenched star formation, or even no stars at all.
Taking advantage of the well-proven capability of the VST to detect extremely faint optical structures, we selected 12 promising DGCs to be observed with OMEGACAM@VST. With approximately 4-hour-long exposures in the g filter for each DGC under photometric conditions, we aim to reach a surface-brightness limit below 30 mag arcsec$^{-2}$. The VST's extremely wide field of view will also allow a detailed study of the environments in which these DGCs are located.
Both the detection and the non-detection of an optical counterpart will allow us to constrain the stellar mass or place an upper limit on it, and to link it with the HI properties. In the case of a detection, we will place these newly identified extremely faint dwarfs on the Tully–Fisher relation and compare their optical size with their HI mass.
In this talk, I will present an overview of the first five months of VST observations, the current status of the project, some preliminary results, and the next steps.

Speaker: Marco Monaci (Centre for Astrophysics and Supercomputing - Swinburne University of Technology)

Friday 10 April

09:30 → 10:50 Session 4: Normal Programs & ToO

09:30 YEARS: Young Exoplanet Analysis in Rich Stellar cluster

Exoplanet formation and their early evolution is still poorly understood
because of the paucity of known young planets at ages of less than 1 Gyr. Here I present the program YEARS (Young Exoplanet Analysis in Rich Stellar cluster, P.I. Ignazio Pillitteri) that aims at discovering new young exoplanets transiting the stars of the rich southern open cluster NGC 2516. The cluster has an age of about 100 Myr, and it is composed by more than 800 members concentrated within a field of view of about 1 degree. This is a perfect match for the FOV of Omegacam.
The program is designed to acquire sequences of exposures in Sloan 'r' and 'i' bands with OmegaCAM. The outcome of YEARS can increase the number of young exoplanets and allow their characterization of their atmospheres with respect to the effects of stellar activity and star-planet interaction at an age of about 100 Myr.
As a secondary outcome, the light curves will allow characterizing the stellar atmospheres with respect to their short term variability.

Speaker: Ignazio Francesco Pillitteri (Istituto Nazionale di Astrofisica (INAF))

09:50 Known by the Loss: Probing the Mass-Loss History of Supernova Progenitors through Circumstellar Interaction

The final stages of massive star evolution are strongly influenced by episodes of intense mass loss, which shape the circumstellar environment into which the supernova (SN) explosion expands. When the SN ejecta interact with this circumstellar material (CSM), the resulting radiation provides a unique diagnostic of the progenitor’s mass-loss history in the years to decades prior to explosion.

The Known by the Loss program is designed to investigate the structure and physical properties of the CSM around interacting supernovae through systematic observations and detailed modeling. By targeting supernovae exhibiting signatures of ejecta–CSM interaction, we aim to constrain the density profiles, mass-loss rates, and temporal variability of the progenitor winds or eruptive episodes that produced the surrounding material.

Our strategy combines multi-epoch observations with photometric analysis to trace the evolution of the interaction-powered emission and identify signatures of complex or episodic mass loss. These measurements will provide insights into the pre-supernova evolution of massive stars and help distinguish between steady winds and eruptive mass-loss scenarios.

The results from this program will contribute to a better understanding of the physical mechanisms driving late-stage stellar mass loss and their role in shaping the diversity of interacting supernovae.

Speaker: Fabio Ragosta (Istituto Nazionale di Astrofisica (INAF))

10:10 NEOVST: A survey of newly-discovered Near-Earth Objects through the VLT Survey Telescope

Near-Earth Objects (NEOs) provide a window into the smallest population of asteroids and comets that originated from different regions of the Solar System. As NEO discoveries increase – currently at about 3,000 objects per year – the majority are not followed up with physical characterization, which would provide insights into their formation and evolutionary processes. Such data can also help assess their potential as targets for future mining, exploration, and planetary defense missions.
Anticipating an increase in new discoveries with the start of LSST operations, we initiated a year-long, monthly photometric observation campaign of newly-discovered NEOs visible with the 2.61-m VLT Survey Telescope (VST) at Cerro Paranal, Chile. VST's 1-degree FoV enables the tracking of very fast-moving NEOs and also brings important collateral science: many other Small Solar System Bodies (SSSB) can be observed simultaneously.
The observations were carried out from February to September 2023, with two nights scheduled every month around the full Moon. The targets were observed by cycling through the SDSS r’i’z’g’r’ filters with exposure times of 10 to 30 s depending on the observational conditions. Every target was observed for 1 hour. In total, we acquired 5519 image cubes covering 72 NEAs, and likely 5 to 10 times that number of background SSSBs depending on the pointing region. The magnitude limit is estimated to be r’=21.5 for SNR=3 and exposure time of 20s. The data cubes are radiometrically calibrated in the Astro-WISE environment through the VST pipeline available by ARES cluster at INAF-OACN.
After calibration, the analysis is carried out by procedures in Python3 language and the use of Scikit-image, Astropy, Photutils, and Astroquery libraries. The steps are: 1. Querying SSSBs and Fixed Sources in the Field; 2. Moving Objects Locus Detection; 3. Target Tracking, Cube alignment, image stacking. 4. Aperture Photometry and lightcurve color analysis.
All data has been flux calibrated. To date, reduction and analysis have been completed for 107 SSSBs observed during the first 3 observing months. The obtained colors cluster in the typical bimodality between “S-like” and “C-like” asteroids, depending on the presence or absence of the 1-micron silicate band (i’-z’). Besides such more common asteroid types, we observe a significant diversity in the spectrophotometry of NEOs, suggesting the presence of rarer compositional types (e.g., A/L, Q and B/F) among our targets.
A new volley of monthly observations has been performed from February to September 2025. We focused on scattered monthly observations of newly discovered NEOs, with exposure times of 30s (r’), 40s (i’,g’) 50s (z’), and two 1-hour sequences per target. With this refined strategy, we aim to improve the signal of background stars for better astrometric positioning, and better sampling of phase and rotational curves. Data calibration down to April 2025 has been already carried out.

Speaker: Pedro Henrique Hasselmann (Istituto Nazionale di Astrofisica (INAF))

10:30 The unexpected stellar populations of the Milky Way's satellite Fornax dSph

Building upon the seminal work of Searle & Zinn (1978) and within the framework of the Λ-CDM paradigm, the Milky Way (MW) halo is understood to have formed through the progressive and ongoing accretion of smaller sub-galactic fragments. This hierarchical assembly can be empirically tested via Near-Field Cosmology, specifically by comparing theoretical structural predictions with star-by-star observations of extant MW satellites.

Among these satellites, the Fornax dwarf Spheroidal (dSph) is particularly significant; its substantial mass allows it to host its own system of globular clusters and complex, multi-modal stellar populations. While Fornax is known for its diverse metallicity and age distributions, it presents a striking anomaly for a dSph: an intermediate-age population (~1.5 Gyr) and a potential young component (~200 Myr). Recent KiDS (Kilo-Degree Survey) catalogues derived from VST imaging further suggest an even younger stellar population of approximately 100 Myr. To validate this, we have initiated an observational campaign to identify these extremely young stars and characterize their associated variable star populations, providing a definitive temporal record of Fornax's recent star-formation history.

Speaker: Massimo Dall'Ora (Istituto Nazionale di Astrofisica (INAF))

10:50 → 11:20 coffee-break

11:20 → 12:40 Session 4: Normal Programs & ToO

11:20 BEARD at the VST, characterising the low surface brightness features in Milky Way analogues

The Λ Cold Dark Matter (ΛCDM) cosmological model predicts that galaxies grow through frequent hierarchical mergers. While this framework competently explains many observed large structures, it undergoes challenges when accounting for bulgeless galaxies. These systems are dominated by their disk component and show no, or only negligible, bulges. In the ΛCDM picture, hierarchical mergers are expected to trigger central mass growth, producing massive bulges and often disrupting disks. Nevertheless, large samples of bulgeless galaxies are observed. Locally, observations of the Milky Way (MW), particularly from large spectroscopic surveys and the Gaia mission, indicate that it consists of a thin disk with four spiral arms, a thick disk, and a central boxy/peanut-shaped bar. Any classical bulge, if present, accounts for at most ~8% of the total Galaxy mass, suggesting the MW as our closest example of a bulgeless galaxy. The BEARD (Bulgeless Evolution And the Rise of Discs) program intends to explore the nature of bulgeless galaxies through systematically characterising their morphology, kinematics, and stellar populations. BEARD is designed as a multi-facility project combining broadband and narrowband Hα imaging with long-slit and integral-field-unit spectroscopy, providing an unprecedentedly detailed and homogeneous view of the formation and evolution of these systems. The program focuses on a volume-limited sample of 66 nearby MW analogues: bulgeless galaxies with stellar masses greater than 10^10 M⊙ and bulge-to-total ratios lower than 0.1.
In P3, we aimed to follow up 18 southern and equatorial BEARD galaxies with the VST. By exploiting OmegaCAM's large field of view (~1 deg²) and excellent image quality, we extend deep photometry well beyond the target galaxies. Observations for six of the eighteen targets have been completed, while three additional systems have been partially covered. All observations follow a common strategy: five dithered Obs of 300 s each in the g and r bands. Through these observations, we will investigate the following goals. First, we aim to trace low-surface-brightness features—such as tidal tails, shells, and stellar streams—which constrain the merger history of the host galaxies. Second, we will detect and measure stellar halos and connect their mass fraction to the formation history of the hosts. Third, we map the distribution of satellite galaxies, offering insight into the large-scale environments and revealing the structural properties and formation mechanisms of the targets. In particular, we will pay special attention to the faintest satellites, for which deep imaging and the large VST field of view are particularly useful. Having observed a subsample, we are now able to develop and test the data analysis pipeline in preparation for a future completion run. During this meeting, I will present the current status of data reduction and discuss the resulting image quality. The reduced images reach surface brightness depths of ~28.7 mag arcsec⁻² in the g band and ~28.1 mag arcsec⁻² in the r band, at 3σ within a one-arcsecond aperture. Even deeper limits can be achieved using isophotal averaging.

Speaker: Edoardo Borsato (Istituto Nazionale di Astrofisica (INAF))

11:40 INTERBARS, characterising bar formation driven by galaxy interaction

Stellar bars play an important role in regulating the evolution and morphology of disk galaxies and are very common, appearing in about 70% of local massive disk galaxies. Through their rotation, they redistribute stars and gas toward the central regions, feeding central black holes and contributing to the bulge growth. Over time, the angular momentum transferred from the bar to its host galaxy alters the galaxy's structure, and, at the same time, causes the bar to grow, strengthen, and slow down. Two main pathways have been proposed for bar formation. First, formation in isolation through internal secular processes. In this scenario, disk instabilities trigger stellar migration towards the central region of the galaxy naturally forming a bar. This mechanism has been widely studied and is relatively well understood. However, bar formation in isolation alone cannot reproduce all observed properties of barred galaxies. Second, bar formation triggered by galaxy interactions. A wide range of merger configurations can lead to bar formation. Bars may appear after major mergers, where galaxies of comparable mass merge into a single structure, after fly-bys or weak interactions, or before minor mergers with similarly oriented galaxies. Up to now, this scenario has been mostly investigated through Hydrodynamical simulations. The same studies suggest that a way to distinguish between bars formed in isolation and those triggered by interactions is to examine the spatial distribution of ionised gas and star formation. Galaxies evolving in isolation are expected to show relatively homogeneous, undisturbed star formation across their disk and bar regions. In contrast, merger-induced bars may display enhanced activity in the central regions and at the bar ends. They may show lower star formation along the bar length and a generally more asymmetric, disturbed distribution over the disk.
The INTERBARS program (PI V. Cuomo) observed a sample of 34 interacting barred galaxies using broadband g, r, and narrowband Hα filters with OmegaCAM at the VST. The sample was initially selected from Galaxy Zoo 2 by identifying barred galaxies. A second selection step isolated systems with at least one merger classification, indicating an interaction. From this parent sample, a redshift cut (z < 0.03) was applied. The candidates were then visually inspected to confirm the presence of the bar and to characterise the interaction type (pre-merger, post-merger, fly-by, or merger). Finally, were selected the galaxies observable during semester 2023B and with available deep LegacySurvey (LS) imaging. The VST Hα maps will allow us to characterize the resolved star formation distribution of the targets isolating the disk, bar and central regions. The structural parameters will be derived from the LS imaging and related to the star-formation. Lastly, we will investigate the larger environments around the sample galaxies thanks to the large VST FOV.
Of the 34 targets, 27 were observed, and 3 were only partially covered. I will present ongoing work on data reduction and continuum subtraction, along with preliminary results on the Hα distribution for a subsample of reduced observations.

Speaker: Edoardo Borsato (Istituto Nazionale di Astrofisica (INAF))

12:00 A MAGNHIFFIC view of nearby AGN, their circum-galactic medium and low-surface brightness satellites

The delicate balance between material accreting from the intergalactic medium and gas expelled from galaxies regulates their evolution. The accretion of gas onto their central supermassive black holes (SMBHs) and the subsequent ejection of highly energetic winds and jets (AGN feeding and feedback processes) play a crucial role in maintaining or disrupting this balance. The HI 21-cm line is an excellent tracer of his complex gas cycle, as low-density HI clouds (N$_{\rm HI} <10^{20}$ cm$^{−2}$) have been linked to both inflows fueling the SMBH and AGN outflows.
MAGNHIFFIC is an ongoing survey leveraging ultra-deep MeerKAT and VST observations to study feeding and feedback phenomena in 15 nearby jetted and radiative AGN spanning a wide range of ages, energetic outputs and environments. A primary challenge in this project is determining the nature of the atomic gas flows in these AGN: are they associated with stellar streams and tidal remnants, or do they represent condensations of pristine gas? Furthermore, how do HI flows contribute to sustaining the nuclear activity? By perfectly matching MeerKAT’s large field of view ($\sim 1$ deg$^2$) with deep OmegaCAM@VST optical photometry ($\mu_r \sim27$ mag arcsec$^{−2}$), we can clearly interpret the nature of the HI features and obtain a complete picture of the stellar properties of our targets and their companions. In this talk, I will focus on three MAGNHIFFIC AGN where deep MeerKAT and OmegaCAM@VST deep observations shed new light on their interaction history and the HI flows fueling the AGN.

Speaker: Filippo Maccagni (Istituto Nazionale di Astrofisica (INAF))

12:20 Nuclear activity and star formation in the HYPER-MAX fields J231 and J1342

We will present the first results on the co-evolution of active galactic nuclei (AGN) and their host galaxies using the first data from the HYPER-MAX survey, an intermediate-redshift program conducted with the VST telescope on fields from the HYPERION survey. Our analysis focuses on two fields. Stellar masses and star-formation rates (SFRs) are derived from multi-wavelength photometry through spectral energy distribution fitting with the CIGALE code, while AGN accretion rates are obtained from HYPERION X-ray data. From these measurements we estimate the probability density function of the Eddington ratio using kernel density estimation and investigate its relation with the SFR.

Speaker: Demetra De Cicco (Università degli Studi di Napoli "Federico II")

12:40 → 13:00 Fantastic images and where to find them

This talk presents some of images based on VST observations that have been distributed to the general public over the past couple of years. This includes also images of peculiar galaxies from the famous Arp catalogue, as part of the Arp@Vst project.

Speaker: Claudia Mignone (Istituto Nazionale di Astrofisica (INAF))

13:00 → 14:00 Lunch break

14:00 → 15:20 Session 5: Overview of the planned and new instrument developments at the VST

14:00 VSTPol

Speaker: Pietro Schipani (Istituto Nazionale di Astrofisica (INAF))

14:20 Science cases for VSTPOL: the first large survey telescope for optical polarimetry

VSTPOL is a polarimetric optical camera to be mounted on the VST. It will represent a major upgrade for the VST. Its design and manufacturing is supported by the national PNRR CTA+ project funded by the EU. Thanks to its wide field of view, VSTPOL is particularly well suited for observations of large sky areas and for follow-up studies of variable sources. Among the most promising targets are galactic and extra-galactic TeV emitters, which often exhibit a significant degree of optical polarization. I will highlight potential science cases, target classes, and observing strategies aimed at maximizing the scientific output of VSTPOL.

Speaker: Gianluca Castignani (Istituto Nazionale di Astrofisica (INAF))

14:40 Determination of Classical Cepheids distances in the Magellanic Clouds using polarimetric analysis

Classical Cepheids (DCEPs) are the most important standard candles of the extragalactic distance scale thanks to the Leavitt Law, which is a relationship between period and luminosity (PL) of DCEPs.
Once calibrated using independent distances based on geometric methods such as trigonometric parallaxes, eclipsing binaries, and water masers, these relations constitute the first step in forming the cosmic distance scale, as they calibrate secondary distance indicators.
An alternative method of estimating distances is using a polarimetric analysis of light echoes produced by the dust nebula around long-period DCEPs.
In this talk, I will illustrate the scientific case and present a preliminary observational strategy for extending this technique to the Magellanic Clouds, already used as anchors of the cosmic distance scale, which host over 10,000 Classical Cepheids.
Current statistics indicate that more than 50 long-period DCEPs are promising candidates for polarimetric distance measurements. Geometric distances derived for these objects would provide robust results for the distance scale of the Large and Small Magellanic Clouds and, consequently, for the extragalactic distance ladder. Furthermore, the resulting absolute luminosities will offer valuable constraints on Cepheid pulsation and stellar evolution models.

Speaker: Erasmo Trentin (Istituto Nazionale di Astrofisica (INAF))

15:00 A VST/OmegaCAM Large Programme for DESI-II: 1000 deg$^2$ medium-band imaging with a custom M5168 filter

DESI-II is the planned second phase of the Dark Energy Spectroscopic Instrument, with survey operations expected from 2029 and science goals spanning dark energy, inflation, and dark matter. A key requirement for the high-redshift component of DESI-II is new medium-band imaging able to identify Ly$\alpha$ emitters and Lyman-break galaxies at $z \gtrsim 2$ with much higher efficiency and photometric-redshift precision than is possible from existing broad-band data alone. Within the wider DESI-II imaging effort, we are developing a VST/OmegaCAM Large Programme designed to provide an independent and complementary data set over about 1000 deg$^2$ of the equatorial footprint using a custom 26-nm-wide M5168 filter centered at 516.9 nm.

The proposed survey will deliver six-pass imaging to a stacked depth of about 25 AB mag, matching the DESI-II imaging baseline while taking advantage of VST's wide field and flexible scheduling across a broad right-ascension range. In addition to strengthening target selection for the DESI-II high-redshift survey, the VST data will provide an important cross-check on photometric systematics, calibration stability, and field-to-field uniformity relative to the DECam, CFHT, and Subaru imaging programmes. The project also offers a strong legacy component for the VST community: the VST observations would be released as part of the wider DESI-II medium-band imaging effort, alongside the ongoing CFHT and Subaru programmes, following the successful model established by the public DECaLS releases. We will present the science case and applications, survey design, observing strategy, current instrument requirements for installing the new filter in OmegaCAM, and the role of VST within the broader international DESI-II imaging programme.

Speaker: Dr Giuseppe D'Ago (Institute of Astronomy, University of Cambridge)

15:20 → 15:50 Concluding Remarks