Benedetta Vulcani

The JWST’s view on star formation in cluster galaxies

The goal of this project is to get unprecedented insights on the mechanisms that regulate star-formation in galaxies at z=0.1-1, exploiting for the first time integral and spatially resolved fluxes of some critical near infrared lines obtained with revolutionary space-based observations. The student will exploit data acquired with the James Webb Space Telescope (JWST), the most powerful space observatory ever built, which will open a new window, offering unprecedented resolution and sensitivity from the visible through the mid-IR range.
 The proposed analysis will based on one of the first ever observations obtained with JWST, taken in the context of the JWST Director’s Discretionary Early Release Science (ERS) Program. Specifically, the student will exploit the data of the Grism-Lens Amplified Survey from Space (GLASS)-ERS to investigate the Paschen and Balmer emission line fluxes in star forming galaxies in different environments to characterize the dust, gas and  star-formation rate distributions. Paschen lines suffer minimal extinction due to their longer wavelength than the Balmer ones and are optimal SFR tracers. The student will investigate the integrated and spatially resolved  star-formation rate for log M*/Msun>7 galaxies. Variations in the line ratios within and across galaxies would indicate a modification of the intrinsic ratio by reddening. Exploiting also ancillary FIR data that constrain the thermal dust emission the student will derive the dust properties and detect deviations from the typical relations, and eventually pin down an appropriate theoretical model for the hydrogen-emission-line region. Comparisons between galaxies in the different environments will shed light on the physical processes at work. Complementary studies of morphologies and structural parameters, obtained on ultra-deep imaging, will give additional insight on the galaxy assembly histories. The student will be immediately inserted in a vibrant international environment, and join the ERS team.

​

​

 

Characterizing the physical processes affecting galaxies in filaments. 

 Understanding galaxy evolution requires a detailed characterization of how galaxies interact with their environment, particularly how they exchange material and what physical mechanisms influence this exchange. The environment in which galaxies are embedded plays a crucial role, as the effectiveness and significance of different processes vary depending on local conditions.

We are seeking a highly motivated PhD student that will work within the framework of MAGNET (Mechanisms Affecting Galaxies Nearby and Environmental Trends), a cutting-edge multiwavelength program aimed at providing definitive insights into the relative importance and effectiveness of various mechanisms influencing galaxy properties across different environments in the local universe. Specifically, this project focuses on understanding the role of cosmic filaments in shaping galaxy characteristics, primarily through high-resolution zoom-in simulations. The student will learn to set up and run their own zoom simulations, so they can choose to zoom individual galaxies and/or of larger regions of interest within the large scale structure. Simulations will be run using the adaptive mesh refinement code, Ramses, enabling the student to vary subgrid physics, in order to better understand the interaction between galaxies and the surrounding gas of the cosmic web. Only with the high resolution provided by the zoom simulation, can we understand the consequences of location within the large scale structure for galaxy properties such as morphology, gas content, angular momentum, and alignment.

The PhD student will have the unique opportunity to integrate theoretical findings with observational data gathered by the MAGNET team. The student will also be part of an international collaboration, with the possibility of spending several months working with Prof. Smith at the Universidad Técnica Federico Santa María (Chile).

 

​

Exploring the baryon cycle at cosmic noon with JWST

We are seeking a highly motivated PhD student to explore the baryon cycle in galaxies during cosmic noon—the period in the universe's history when star formation activity peaked. This project leverages cutting-edge observations from the James Webb Space Telescope (JWST), the most powerful space-based observatory ever built, to gain unprecedented insight into the processes that regulate star formation in galaxies. The research will be based on data from two major and complementary slitless spectroscopy surveys: PASSAGE (Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution, PI: Malkan) and POPPIES (Public Observation Pure Parallel Infrared Emission-Line Survey, PI: Kartaltepe). Together, these surveys provide a rich dataset across a wide range of redshifts, enabling the study of galaxies with stellar masses as low as 10⁷ M☉—a regime largely unexplored until now. The student will investigate key physical properties of galaxies, including star formation rates, gas ionization conditions and metallicity. Using emission lines such as Hα, Paα, and PAH, the project will trace both unobscured and obscured star formation, for the first time in a statistically robust sample. The analysis will also explore SFR distributions and gradients within galaxies, offering insights into their internal structure and star formation histories. This research will shed light on how galaxies assembled during a pivotal epoch in cosmic history—when galaxies transitioned from irregular, turbulent systems to more structured disks. The findings will provide crucial observational constraints on "inside-out" galaxy formation scenarios, in which bulges form early, followed by disk growth.

The successful candidate will become part of a vibrant and collaborative international research environment and will be integrated into the PASSAGE and POPPIES survey teams, offering valuable opportunities for collaboration and co-authorship on high-impact publications.

​

​

The assembly of galaxy clusters through the cosmic time

Galaxy clusters are the largest known gravitationally bound structures in the Universe and contain up to thousands of galaxies. We currently have at least a broad-brush understanding of how local massive clusters affect their members, both via tidal and hydrodynamic processes. However, our knowledge is much more limited at higher redshift (z > 1-2), when structures are younger and still in formation and gas densities and star formation (SF) rates were much higher. Studies of the highest redshift progenitors of local clusters — called proto-clusters — are currently very sparse and limited. The goal of this project is to characterize the population of galaxies in protoclusters, either from a theoretical or observational point of view. 

Following a theoretical oriented approach, the PhD candidate will exploit the GAEA semi-analytic model to study the assembly of clusters through the cosmic time (from z=4 to 0), tackling the challenge of linking the high and low universe. The student will investigate the properties of galaxies in the different environments and at different epochs, to guide future observational requests. This analysis will be very important as it will assist the interpretation of observational results. From an observational point of view, the student will use archival and proprietary ALMA and JWST data to investigate the gas content and distribution, metallicity and star forming properties of galaxies in different environments.

By characterizing how star formation activity and mass assembly vary in different environments the student will be able to establish how environment primarily act when the Universe was a few billion years old. These results will pave the way to a physical understanding of how environment drives galaxy evolution in the early Universe.

​

 

A few StePS forward in unveiling the complexity of galaxy evolution
One of the major goals of extragalactic astrophysics is to understand the physical processes that cause the formation and evolution of luminous structures. Recently, ground-breaking progress has been made in the low-redshift Universe in describing how the main galaxy properties vary with both galaxy mass and host halo mass. However, detailed observations of the evolutionary changes of galaxy properties as a function of look-back time are needed to establish which mechanisms dominate galaxy evolution, what drives the star formation history of galaxies and their mass assembly in the different environments. We propose a thesis to characterise in detail the stellar and gas content of galaxies at intermediate redshift in the different environments making use of the data of StePS, one of the eight surveys that will be carried out during the first five years of WEAVE operations. The main goals of the project are to understand 1) what physical mechanisms drive the star formation histories of galaxies and its quenching over two thirds of the life of the Universe? 2) what is the role of environment vs. intrinsic galaxy properties in this evolution? 3) how do galaxies assemble their mass during the last 7 Gyr?
The project will benefit from the high quality of StePS spectra that will allow to derive galaxy stellar ages, star-formation timescales, stellar and gas metallicities, and dust attenuation, and infer the past evolution of galaxies at different masses and redshift, relating their star formation histories to their intrinsic (e.g., stellar mass, galaxy morphology) and environmental properties. These spectra will also provide gas kinematics and stellar velocity dispersions, which will allow us to perform a dynamical classification of our galaxies and make a link between star formation history, mass assembly history and dynamics.
The student will be immediately inserted in a broad international context and will have the possibility to collaborate with other team members both in Italy and abroad.