Theoretical Insights into Star Formation: from the Early to the Present Day Universe

6 May 2025, 08:30 → 9 May 2025, 18:00 Europe/Rome

Pisa

Marco Padovani (INAF- Osservatorio Astrofisico di Arcetri)

Star formation is the fundamental process by which galaxies took shape, from the primordial conditions of the early universe to the complex structures we observe today. By examining theoretical perspectives across different epochs, we gain insights into how stars form, how they evolve, and how they impact the interstellar medium.

 

Starting with the latest developments in the field of star formation, this conference is expected to bring together theorists and observers from different disciplines to share their insights into this crucial area of astrophysics.

 

The planned sessions aim to provide a broad overview of star formation, covering the key areas of Galactic star formation, Magnetic fields, Cosmic rays and Astrochemistry. The discussion will also focus on the Early Universe followed by Chemical evolution and Nucleosynthesis, to explore the enrichment of elements underlying the diversity of stars and galaxies. A final session on the History of Astronomy will consider the last centuries of discoveries, relating historical developments to current theoretical knowledge.

 

This conference brings us together to acknowledge the career of Daniele Galli, whose work has advanced research on these topics, contributing to our knowledge of star formation in its many facets.

 

Participants who have registered for the conference will soon receive a link to pay the registration fee of €200, including coffee breaks and the aperitif on May, 8th.

 

This event has received funding from INAF and from the Minigrant 2025 ENERGIA: ExploriNg low-Energy cosmic Rays throuGh theoretical InvestigAtions at INAF (PI Marco Padovani).

 

Tuesday 6 May

Registration

Welcome

Session 1a: Galactic Star Formation (1)

1 The first steps of star and planet formation

Extremely low temperatures and relatively low densities characterize the interstellar clouds precursors of stars and planets. In these early stages, fundamental chemical and physical processes affect each other, ultimately regulating clouds' dynamical evolution toward the formation of stellar systems like ours, where at least one habitable planet is present. Here, I'll present a journey from clouds to planets, which started in Arcetri with the help of outstanding scientists, including one from Pisa, highlighting the open questions and future perspectives.

Speaker: Prof. Paola Caselli (Max Planck Institute for Extraterrestrial Physics)

2 From Psuedodisk Formation in Magnetized Collapse to the Interplay with Multi-faced Outflow Phenomena

A plethora of new enigmatic phenomena in the innermost parts of protostellar systems associated with jets and outflows have been revealed by ALMA and JWST. These jets and outflows, along with the streamers from their magnetically collapsing prenatal envelopes, are integral parts of the physical processes that assemble the systems. We review the characteristics of these enigmatic, powerful phenomena that constitute telltale signs of the underlying fundamental physics revealed by generations of radio and optical telescopes. The unprecedented revelation of the fine, nested kinematic and morphological structures is consistent with theoretically predicted features of magnetized bubbles blown by magnetized winds from the innermost regions and the pseudo-disks formed inside the large magnetically supported envelopes. The ubiquitous characteristics of the coupled nested velocity and emission components finds a natural explanation in the unique combination of jet–outflow–envelope systems. Tomographic projection of the morphological and kinematic structures naturally connect to high-angular resolution and high-sensitivity observations of the magnetically-interplayed inflow and outflow, enriched by chemical diversity.

Speaker: Dr Hsien Shang (Institute of Astronomy and Astrophysics, Academia Sinica)

3 Characterizing the emission of molecular clouds using a sampling technique

Characterizing the molecular emission from whole molecular clouds is critical to identify the physical and chemical processes that act at different spatial scales and lead to the formation of stars. It is also needed to connect spatially-resolved observations of galactic clouds with extragalactic observations that do not resolve the clouds.

The traditional approach of characterizing the emission of clouds using mapping techniques is very time consuming since it requires fully sampling the emission over many square degrees in the sky, and for this reason, it can only be carried out over a very limited sample of clouds. As an alternative to mapping, we have developed a new technique of characterizing the multi-line emission from clouds using statistical sampling. Our method uses available extinction maps to select a relatively small sample of cloud positions that cover the full range of column densities in the cloud, and that can be observed with only a modest investment of telescope time

We present the results of applying our sampling technique to the three nearby clouds California, Perseus, and Orion A, for which we have used the IRAM 30m telescope to cover the full 3mm wavelength band. Although the clouds present very different rates of star formation, their emission properties are remarkable similar, and the intensity of all their tracers correlates strongly with the amount of column density. The observed similarities in the emission suggest that despite their star-forming differences, the clouds have a similar underlying physical structure and a chemical composition dominated by a few critical ingredients that include outer photodissociation, inner freeze out, and localized stellar feedback.

Speaker: Mario Tafalla (Observatorio Astronomico Nacional (Spain))

4 Poster session (1)

Marie-Anne Carpine, Alessandro Coletta, Noé Brucy, Pedro R. Rivera-Órtiz

10:50 Coffee Break

5 Gas infall via accretion disk feeding Cepheus A HW2

Located at the edge of the Cepheus Bubble, the massive star-forming region Cepheus A hosts HW2, a very young star growing more than dozen times the mass of our Sun - and the second closest of its kind to us. Using sensitive VLA observations, we have finally imaged its debated accretion disk in hot ammonia at centimeter wavelengths. We have resolved the accretion disk within a few hundred au of HW2, showing that circum-stellar gas is collapsing nearly in free-fall and slowly orbiting at 40% the Keplerian velocity down to 200 au. At this distance from the star, gas piles up at very high infall rates of 0.002 Solar masses per year. I will discuss both state-of-the-art simulations and a toy model which reproduce our observations in detail, commenting on (1) how these new findings advance our knowledge of (proto-)stellar disks at large and (2) how they can drive future observations in the field.

Speaker: Alberto Sanna (Istituto Nazionale di Astrofisica (INAF))

6 The accretion/ejection properties of Class 0 protostars studied with near-infrared spectroscopy

Sun-like stars are thought to accrete most of their final mass during the protostellar phase, where the protostellar embryo is surrounded by an infalling dense envelope. The so-called Class 0 phase designates the youngest protostellar stage, where the accretion is the most vigorous. Because these objects are highly embedded, it is difficult to retrieve direct diagnostics from the accretion, whose observational imprint lie at small wavelengths, in the near-infrared and below. Therefore, little is known about the accretion properties and mechanisms occurring in the Class 0 phase because of high extinction. However, in rare cases the blueshifted cavity created by the outflow is sufficiently close to pole-on to liberate enough near-infrared scattered light for us to probe the immediate surroundings of the central object.

We present NIR observations of Class 0 protostars recently observed with Keck MOSFIRE and/or JWST NIRSpec. Bry, several H$_2$ and CO overtone/fundamental ro-vibrational emission lines are detected and analyzed.
The analysis of the numerous H$_2$ lines reveal the wind and shocks structures along the jet, which allow comparisons with shock models and robust estimation of the mass ejection rate. CO fundamental ro-vibrational emission lines seem to coincide with the base of the wind/jet system. Stellar CO overtone lines are seen in absorption in several sources either suggesting recent vigorous accretion episodes, or quiescent protostars. They also allow for the first time the exploration of the photospheric properties of these young protostellar embryos. CO overtone is seen in emission in half of the sources, tracing the dense inner accretion disk. Comparing these results with archival sample of Class I K-band spectra, we find that the CO and Bry emission lines are systematically more luminous in Class 0s, suggesting the accretion is on average more vigorous in the Class 0 phase. Typically associated with the heated inner accretion disk, the much higher detection rate of CO overtone emission in Class 0s indicate also that episodes of ExOr-type high accretion activity are more frequent in Class 0 systems. We modeled the CO overtone emission bands with analytical model of circumstellar disks and found the kinematics of the Class 0 CO overtone emission is consistent with either an accretion-heated inner disk, or material directly infalling onto the central nascent stellar embryo. The CO emission seems to be confined close to the central object surface (1-5 stellar radius). These results could point toward an accretion mechanism of different nature in Class 0 systems than the typical picture of magnetospheric accretion.

The sensitivity and wavelength coverage of JWST of these sources allow for much more precise extinction measurements, analysis of the excitation of molecular and atomic gas, and spatial mapping of the different spectral lines associated to the ejected and accreted material. These near- and mid-IR spectroscopy capabilities shall quantify the actual accretion/ejection properties of the youngest protostars.

Speaker: Valentin Le Gouellec (ICE-CSIC)

7 ALMAGAL: Evolutionary study of high-mass protocluster formation in the Galaxy

Stars form preferentially in clusters deeply embedded inside massive molecular clouds. Some of these clusters contain high-mass stars that influence their immediate environment through gravitational, mechanical and radiative interactions, and eventually through supernova explosions. Therefore, a comprehensive understanding of star formation requires characterizing the formation and early evolution of (high-mass) stellar clusters. The ALMA Large Program ALMAGAL has observed over 1000 high-mass star forming regions distributed throughout the Galaxy, sampling different evolutionary stages and environmental conditions. For the first time, a large sample has been observed at high spatial resolutions (1000 au) and mass sensitivities (0.1 Msun), enabling statistically relevant studies. In this talk, we will present the ALMAGAL project. This includes the observation strategy and main challenges during the data reduction process, as well as a glimpse to the first scientific results and the potential and legacy value of the project. Overall, ALMAGAL aims at providing answers to key questions of the star formation process such as: What are the processes that govern fragmentation and allow the formation of star clusters? How do the different cluster members gain mass, and how feedback may influence the process? How does chemistry evolve in time during the star formation process?

Speaker: Alvaro Sanchez-Monge (Institute of Space Sciences (ICE, CSIC))

8 Rotation and angular momentum transport mechanisms in molecular clouds and filaments

For many years, evidence of large-scale velocity gradients has been found in molecular clouds and filaments, which are commonly associated with rotation. It is known that during the collapse and fragmentation of these structures, a process of redistribution and loss of angular momentum is involved, such that the fragments possess less angular momentum per unit of mass than their parent structures. The mechanisms responsible for transporting angular momentum out of the fragments are still a matter of debate. Therefore, studying this redistribution process is essential to understand both the star formation process and (since at some point the mechanism responsible for transporting angular momentum at cloud scales should be inefficient on small scales) disks formation.

In this work we focus on the study of the residual angular momentum and the 3D velocity field in and around molecular clouds and filaments. We analyze numerical simulations including turbulence, gravity, and magnetic fiel, and define numerical samples of clumps and filaments. In particular, we address the following issues:

1. Turbulent viscosity: dominant mechanism for transferring angular momentum at molecular cloud scales? Are gravity and magnetic field necessary to reproduce angular momentum scaling in clumps and cores?
2. Angular momentum measurements in filaments: what is the best way to measure it? Do filaments follow the same angular momentum scaling as clumps and cores? And more importantly, do filaments rotate?
3. Filament dynamics: what is the 3D velocity and magnetic field around and inside filaments? Properties of turbulence in filaments? Is the angular momentum of clumps and cores determined by these properties?

Work in progress with openness to discussion and collaboration.

Speaker: Griselda Arroyo-Chavez (Steward Observatory - University of Arizona)

9 Poster Session (2)

Pierre Dumond, Adnan Ali Ahmad, Valentin Vallucci-Goy, Ashley Bemis, Ilseung Han

12:50 Lunch

Session 1b: Galactic Star Formation (2)

10 How we think planet formation disks are forming? The past, the present and the future

Protoplanetary disks are fundamental objects for our understanding of planet formation. Whereas they are in essence a consequence of angular momentum conservation, the exact amount of mass and angular momentum which are delivered towards the proto-star remain largely unknown. Indeed, this process seems to be largelly controlled by magnetic field and more specifically by magnetic braking. However the outcome sensitivelly depends on the ionisation degree as well as the charge carriers, which appear to be not only the electrons and the ions but also the dust grains. This adds considerable complexity in the problem.
During the talk, I will review our understanding of the protoplanetary disk formation process, adopting an historical perspective and stressing what are the important steps for the future.

Speaker: Prof. Patrick Hennebelle (CEA)

11 Theoretical models for filamentary structures and collapse of pre-stellar cores

Molecular are the sites of star formation, made by networks of filaments (e.g., Andre’ et al. 2014, Hacar et al. 2023).
Individual filaments composing a molecular cloud accumulate mass by accretion from the parental cloud, until they become gravitationally unstable and fragment into cores, that eventually collapse into stars and stellar clusters. The candidates for supporting the clouds are large-scale magnetic fields and turbulence (e.g., Pattle et al. 2023).
In a contest where these processes are interplaying at different time- and length-scales, is crucial to understand their role in the equilibrium and in the dynamical evolution of molecular clouds as well as how the gravitational collapse can affect them.

In this talk, I will present an analysis of the stability and contraction of molecular clouds both in the hydrodynamical and magnetohydrodynamical case, in the quasi-static and dynamical phase of evolution. Under the hypothesis that the observed filaments and
cores can be represented by a sequence of hydrostatic or magnetostatic models, I will analytically study their radial density profiles and stability properties (Toci & Galli 2015 a,b).
However, molecular clouds must contract and fragment in order to form stars.
I will show an analysis of the growth of small-scale density perturbation during the hydrodynamical collapse of a molecular core, simulated using a modified version of the ECHO (Del Zanna et al.2017) code to include a generic anisotropic metric that allows stretching in all directions. I also analytically estimated the transition time to non-linear regime in analogy with the Burgers equation. The results point out that the formation of shocks and the subsequent dissipation prevents the onset of gravitationally unstable perturbations, thus other kind of mechanism are needed to explain the process of fragmentation in cores (Toci et al. 2021).

Speaker: Dr Claudia Toci (European Southern Observatory (ESO))

12 Accretion disks and massive stars: New light on an ancient history

Investigating the formation of the most massive stars has since ever been a theoretical challenge and a difficult observational task. Substantial progress has been made recently on both fronts and it appears that circumstellar accretion disks (and the associated jets) are key to explain how these stars form. We will report on our contribution to this topic in the last twenty years, with special attention to the most recent results obtained with the Atacama Large Millimeter and submillimeter Array.

Speaker: Riccardo Cesaroni (Istituto Nazionale di Astrofisica (INAF))

13 Clusters, Associations and the Stellar Mantle

As a stellar group forms within its parent molecular cloud, new members first appear in the deep interior. Theory suggests, and observations confirm, that these crowded stars continually diffuse outward. I suggest that they also leak out of the cloud, to form an expanding envelope which I call the ``stellar mantle." In a nascent OB association, the mantle remains nested deep inside the Galactic tidal radius. In smaller stellar groups, the tidal force erodes the mantle, and determines whether the group becomes a T association or a gravitationally bound open cluster.

Speaker: Steven Stahler (U. C. Berkeley)

14 Poster Session (3)

Pedro R. Rivera-Órtiz, Basmah Riaz, Gabriel Verrier, Shingo Nozaki, Vianey Camacho

16:10 Coffee Break

15 Investigating the origin of stellar masses with ALMA-IMF

The origin of stellar masses and the link between core and stellar mass distributions (CMF and IMF respectively) are a central open issue in astrophysics. I will present the ALMA-IMF Large Program, whose goal is to determine if and how the origin of the IMF depends on the cloud characteristics and evolution. We surveyed 15 massive protoclusters covering a wide variety of Galactic environments and evolutionary stages (Motte et al. 2022; Galvan-Madrid et al. 2024). ALMA-IMF provides the community an homogeneous database of about 1000 cores (Louvet et al. 2024), 25% of which qualify as protostellar as they drive outflows (Nony et al. 2023) and hot cores (Bonfand et al. 2024).
ALMA-IMF results indicate that the mass distributions of cores in these massive environments of the Milky Way present an excess of high-mass cores with respect to the canonical IMF (Pouteau et al. 2022; Louvet et al. 2024). We propose that the CMF deviates from the canonical IMF form when and where a burst of star formation develops (Nony et al. 2023; Pouteau et al. 2023; Armante et al. 2024). Based on the combined analysis of the core distribution (CMF, mass segregation) and cloud structure (PDF), we propose an evolutionary sequence of massive protoclusters, which is in line with the dynamical scenarios of cloud and star formation (e.g., Motte et al. 2018a; Vazquez-Semadeni et al. 2019).

Speaker: Thomas Nony (Istituto Nazionale di Astrofisica (INAF))

16 Exploring Accretion Variability via Jet Evolution in G023.01-00.41

A complete understanding of high-mass (> 8 M$_{Sun}$) star formation, including the overall process of jet emission and its behavior, remains elusive. Whether or not the accretion variability broadly observed in low-mass star formation is also a common process regulating the formation of massive stars has been highly debated in the last decade. We have recently discovered that the 1.3 cm continuum brightness of the massive protostellar jet G023.01$-$00.41 has decreased by ~50% since 2008 (Rodriguez et al., submitted). Follow up observations confirm a brightness variation is found throughout the radio spectrum, and the jet morphology appears to have changed as well. The implications of our results will be discussed in the context that changes in jet emission, which are expected to be directly related to accretion outbursts, may be common during high-mass star formation.

Speaker: Tatiana Rodriguez (University of Cologne)

17 Dusty protostellar collapses simulations in 3D with dust growth

Dust grains are essential ingredients in star formation and play a significant role in gas/dust dynamics, chemical reactions, and radiative transfer. The efficiency of all these physical processes depends on the grain-size distribution and how it evolves in time. Thus, accurate dust modeling is a much needed feature of star formation simulations. Dust growth and fragmentation are mathematically described by the Smoluchowski coagulation and the fragmentation equations. Solving these equations accurately while preserving tractable computational costs is a tremendous numerical challenge, yet critical for understanding the formation of stars, disks and planets. In particular, low-order schemes do strongly overestimate the formation of large particles. We present a novel high-order discontinuous Galerkin algorithm (Lombart+,2021,2022,2024) that addresses all these issues. We aim to perform the first 3D simulations of dusty protostellar collapses that include realistic dust growth/fragmentation.

Speaker: Anaëlle Maury (Institute of Space Sciences (Barcelona) & CEA Astrophysics department (Paris-Saclay))

18 Core Formation in Molecular Clouds: Evidence Favoring Turbulent Over Gravitational Fragmentation

Stars form within dense cores embedded in turbulent molecular clouds. In this study, we investigate the cloud fragmentation process in Galactic molecular clouds with various star formation acttivity. Using astrodendro, we identified over $10^4$ dense cores across both nearby molecular clouds and high-mass star-forming clumps. Our central hypothesis is that core mass and separation provide key insights into cloud fragmentation mechanisms.

Our analysis reveals that in nearby clouds, core masses and separations are significantly smaller than those predicted by gravitational fragmentation but agree well with the expectations of turbulent fragmentation. In contrast, in high-mass SF clumps, cores formed via turbulent fragmentation tend to be gravitationally unstable, suggesting that self-gravity plays an increasingly dominant role in higher-density environments.

These findings indicate that turbulent fragmentation is the primary mechanism driving core formation across diverse cloud conditions, with gravitational effects becoming more significant as density increases.

Speaker: Dr Fumitaka Nakamura (NAOJ)

19 Poster Session (4)

Chiara Mininni, Alice Nucara, Leonardo Berti

Wednesday 7 May

Session 2: History of Astronomy

20 Giovan Battista Donati and the birth of a new physics for stars

In the second half of the 19th century, Italian astronomers made a fundamental contribution to the birth of astrophysics through the first spectroscopic analysis of stellar light. These were the dawn of spectroscopy and astrophysics, transforming our scientific knowledge of the universe through the study of the intrinsic characteristics of stars (chemical composition, temperature, density, velocity), a prospect previously considered unthinkable.
Angelo Secchi and Lorenzo Respighi in Rome, Giuseppe Lorenzoni in Padua, Pietro Tacchini in Palermo, and Giovan Battista Donati in Florence were pioneers in this field. These scientists were protagonists of essential results such as the first spectral classification of stars, the first spectrum of a comet, the development of solar physics, and the establishment of the first scientific society devoted to astrophysical studies.
This talk retraces the key milestones of this extraordinary turning point in Italian astronomy, with a particular emphasis on the Pisan astronomer Giovan Battista Donati, founder of the Arcetri Observatory.

Speaker: Dr Mauro Gargano (Istituto Nazionale di Astrofisica (INAF))

21 The life and time of a Pisan Astronomer

While we celebrate our friend Daniele from Pisa, I will talk about another great Pisan
astronomer, Giovanni Battista Donati (1826-1873), pioneer of Astrophysics and founder
of the Arcetri Observatory. Despite his many achievements, Donati had received little
attention by Italian science historians in the past. In the last two decades, however, the
situation has changed, thanks to Daniele, who spent countless night hours to read and
transcribe letters and other documents regarding his personal hero (a.k.a. "Bista").
I will illustrate the human aspects of Bista that emerged from Daniele's work (and the fun we had in this research!).

Speaker: Simone Bianchi (Istituto Nazionale di Astrofisica (INAF))

22 Beyond Academic Boundaries: Scientific Collaboration and Friendship in the Lorenzoni-Abetti Partnership

The scientific relationship between Giuseppe Lorenzoni (1843-1914) and Antonio Abetti (1846-1928) is one of the most significant and enduring partnerships in late 19th-century Italian astronomy. Despite their similar ages, Abetti always regarded Lorenzoni as his Master, a respect that fostered rather than hindered their productive scientific collaboration. Their deep personal bond, which extended to include their families, had an important impact on the scientific development of Italian astronomical research of the time. A prime example of their collaborative work was the expedition to India to observe the transit of Venus across the Sun, of which Lorenzoni was one of the principal organizers and in which Abetti took an active part. The correspondence exchanged between them during this extensive journey provides valuable insights into their close relationship, illuminating both the scientific endeavors and the personal dynamics that characterized their partnership, a collaboration that made remarkable contributions to astronomical advancement in the newly unified Italy.

Speaker: Valeria Zanini (Istituto Nazionale di Astrofisica (INAF))

10:40 Coffee break

Session 3: Magnetic Fields

23 Magnetized star formation

Molecular clouds have a tiny fraction of ions, but high enough to make them to be dynamically sensitive to the presence of the interstellar magnetic field. The role of the magnetic field in the dynamics of the molecular clouds at all scales, and in the process of the star formation, have been a source of vivid debate for the last 3 decades. A relatively strong magnetic filed can prevent fragmentation and removes efficiently the angular momentum through the magnetic braking process. The magnetic field can also play an important role in the formation of planet-forming disk and their early evolution. However, there are several physical processes that can diminish its importance, such as ambipolar diffusion, Ohmic dissipation, the Hall effect or turbulence reconnection. Measuring the properties of magnetic fields relies mostly on the linear polarization of aligned aspherical dust grains, in the Zeeman effect of species such OH and CN, and in the Goldreich-Kylafis effect in molecular lines. In this talk, I will also talk about the recent progress done since ALMA offered polarization capabilities in some frequency bands. There have been various attempts to better characterize the properties of the magnetic fields at core scales (<0.1 pc) in various surveys such as MagMaR (Magnetic Fields in Massive Star-forming Regions), BOPS (B-field Orion Protostellar Survey) o ALPPS (ALMA Perseus Polarization Survey). The first results of these works will also be presented here.

Speaker: Josep M Girart (Institut de Ciències de l'Espai, CSIC)

24 Formation and structure of magnetized protoplanetary disks

Protoplanetary disks are thought to form through the gravitational collapse of magne-
tized, rotating dense cores. In this talk, I will review work conducted during an enjoyable
and fruitful collaboration with Daniele Galli on the gravitational collapse phase and the
structure of magnetized protoplanetary disks.
To enable the formation of rotationally supported disks, the magnetic flux from the
natal cloud must be lost to prevent catastrophic magnetic braking. During this process,
accretion disks threaded by a poloidal magnetic field and irradiated by the central star
are expected to emerge. The poloidal field induces sub-Keplerian gas rotation in the disk,
which can accelerate planet migration and enhance disk stability against gravitational per-
turbations. Additionally, magnetic compression reduces the disk scale height compared to
nonmagnetic disks. The mass-to-flux ratio, λ, is the key parameter governing these effects.
Models of magnetized disks around young YSOs such as HL Tau and TW Hya suggest λ∼
20 – 30, significantly higher than the values of the natal cloud, indicating substantial flux
loss during disk formation. Determining λ observationally is crucial for understanding this
process. Polarized dust emission from protoplanetary disks is primarily dominated by dust
scattering rather than emission from grains aligned with the magnetic field. Consequently,
measuring disk magnetization requires Zeeman splitting observations with ALMA and the
VLA. These measurements are essential for advancing our understanding of protoplanetary
disk formation and evolution.

Speaker: Susana Lizano

25 Planets Formation via Gravitational Instability: Magnetic Fields, Opacity Limited Fragmentation, and the Mass Distribution

This talk revisits the mass scales for planets that form through the action of gravitational instability in circumstellar disks. After including the effects of magnetic fields, we show that several alternate ways to specify the mass of forming planets converge to the same result under the constraint that the parental disks are marginally stable (with stability parameter Q=1). Next we show that the well-known constraint that the formation of secondary bodies requires rapid cooling is equivalent to that of opacity limited fragmentation. These results are then used to derive a mass function for planets forming through disk instability. The resulting distribution is relatively narrow, with gaussian-like shape and a characteristic mass scale of order 10 Jovian masses.

Speaker: Fred Adams (University of Michigan)

26 Self-similarity of the magnetic field in G31.41+0.31 from cloud to circumstellar scales

In this presentation, I will discuss the magnetic field properties at all spatial scales (cloud, core, disk) of one of the best studied high-mass star-forming regions, the massive protocluster G31.41+0.31. Dust polarization observations of this massive core carried out with the SMA at 870 microns and 1” (3750 au) have revealed one of the most clear examples up to date of an hourglass-shaped magnetic field in the high-mass regime. ALMA observations at higher angular resolutions have revealed that the magnetic field maintains its hourglass-shaped morphology down to circumstellar scales (~300 au). All this is supported by the modelling of the polarized emission, which confirms the poloidal shape of the magnetic field. Recent JCMT polarization observations of the cloud indicate that the orientation of the hourglass B-field observed at core and circumstellar scales is preserved at large scales. This self-similarity in the B-field orientation suggests that the field is connected from cloud to circumstellar scales despite the difference in density and spatial scales.

Speaker: Maite Beltrán (INAF-Osservatorio Astrofisico di Arcetri)

27 Poster Session (5)

Luca Moscadelli, Hua-Bai Li, Indrani Das, David Whitworth, Diego Falceta-Gonçalves, Ya-Chi Wang

12:50 Lunch

28 Origin of fossil fields in Ap/Bp-type stars

Among 10% of intermediate mass stars, particularly the group of chemically peculiar Ap/Bp-type stars, have very strong magnetic fields of order 1 kGauss or even above. As the stars are radiative,, the magnetic fields are difficult to explain via a dynamo, but are often considered to possible have an origin of fossil fields from the interstellar medium. In this talk, we assess this possibility, considering the available magnetic fields in the interstellar medium and their evolution during gravitational collapse. A crucial phase concerns then the protostellar evolution, which may be convective or radiative depending on the accretion rate of the protostars. We will show that it is very difficult for magnetic fields to survive in the convective phase, but more likely in the radiative one, and will show some representative cases for the possible protostellar evolution. We suggest that at least in some cases, suitable protostellar evolution histories can be obtained to explain the origin of magnetic fields in Ap/Bp-type stars.

Speaker: Dominik Schleicher (Sapienza University of Rome)

29 Magnetic fields in prestellar cores: a new perspective from meter-wavelength radio data

Magnetic fields in starless, prestellar cores are crucial for understanding the formation of stars, as these cores mark the initial gravitationally bound stage in the star-formation process. Typically, these cores accumulate gas from their molecular cloud environments until they overcome magneto-turbulent support and collapse into protostellar objects. Traditional studies of magnetic fields in these cores have primarily used indirect methods, such as infrared dust polarization and molecular-line Zeeman splitting. However, these methods have significant limitations, including large uncertainties and issues like magnetic-field dilution due to beam averaging.

In this talk, I propose a novel technique complementary to the infrared band, utilizing non-thermal synchrotron emission detectable in the radio spectrum to trace magnetic fields in prestellar cores. This approach builds on theoretical studies suggesting that cosmic-ray electrons interacting with magnetic fields can produce detectable synchrotron radiation at low radio frequencies (Padovani+2018). I will present an extensive statistical analysis using the LOFAR telescope at 144 MHz, focusing on the median stacking of a large sample of more than 300 prestellar cores in the Perseus molecular cloud (Bracco+2025). While we only achieved upper limits on magnetic field strengths on the order of 100 uG—due to current telescope sensitivity—this method promises a new avenue for studying magnetic fields in molecular clouds with upcoming advanced radio telescopes like the Square Kilometer Array, which could detect such emissions within a few hours of observation.

Speaker: Andrea Bracco (Istituto Nazionale di Astrofisica (INAF))

30 Magnetized Clustered Star Formation in Orion

Interferometric polarization observations have revealed that magnetic fields are crucial in the star formation process. However, their relative importance in different environments and their role in stellar multiplicity remain poorly understood. The B-field Orion Protostellar Survey (BOPS) recently observed 870 $\mu$m dust polarization observations of 61 young protostars in the Orion molecular cloud, probing scales from 400 to 2000 au. The observations reveal standard hourglass magnetic field morphologies in collapsing cores, highlighting the interplay between magnetic fields and gravity, while misaligned or twisted fields indicate the growing influence of rotation and turbulence. Our findings suggest that magnetic fields play a key role in regulating fragmentation within dense envelopes: strong magnetic fields suppress fragmentation by stabilizing against gravitational instabilities, whereas weaker fields allow the formation of binary or multiple star systems. We also find that the magnetic field affects disk formation through magnetic braking, that significant misalignment between the magnetic field and outflow axes tends to reduce magnetic braking, leading to the formation of larger disks.

Speaker: Bo Huang (Institute of Space Sciences (ICE-CSIC))

15:30 Coffee break

31 Signatures of magnetic braking in Class 0 protostars: Exploring the gas kinematics in magnetized models of low-mass star formation

Only indirect evidence of the role of magnetic braking in regulating gravitational collapse and the formation of circumstellar disks, such as compact disk sizes and the launching of high-velocity collimated protostellar jets, has been found from observational work.

More direct tests of the magnetic braking shaping the angular momentum of the gas in Class 0 protostars are crucially needed to confirm and make progress on the magnetically regulated disk formation scenario.

In the present work we used nonideal magnetohydrodynamic models of protostellar collapse and synthetic observations of molecular gas spectral emission, from the radiative transfer post-processing of these models. We analyzed the synthetic observations to test whether possible kinematic signatures of the magnetic braking in the gas velocity field can be captured from maps of the molecular gas emission in protostellar envelopes.

By comparing the 3D specific angular momentum of models with varying turbulent energy and magnetization, we show that, in the numerical models of protostellar evolution explored, the increase in magnetization and its consequences on the spatial redistribution of angular momentum modifies the shapes of the radial profiles of specific angular momentum probed along the equatorial plane. However, various analysis of gas kinematics from the synthetic observations of molecular line emission mostly fail to capture the magnitude and differences in radial profiles of specific angular momentum due to different magnetization. Finally, we compare our synthetic observations to observational datasets from the literature to discuss possible magnetic braking signatures in protostellar envelopes.

Our analysis suggests that the detection of symmetric patterns and organized velocity fields in the moment 1 maps of the molecular line emission, and monotonous radial profiles of the specific angular momentum showing a power law decline, should be suggestive of a less magnetized scenario. Protostellar cores where efficient magnetic braking is at work are more likely to present a highly asymmetric velocity field, and more prone to show complex radial profiles of their specific angular momentum measured in the equatorial plane.

Speaker: Nacho Añez-Lopez (CEA Paris-Saclay)

32 Dust Properties of Taurus Protostellar Twins in a Magnetized Environment

The evolution of astrophysical dust during early star formation phases is crucial for understanding planet formation and the magnetic fields have a role in regulating this process. Theoretical models mainly proposed two dominant mechanisms of dust polarization with mm/sub-mm wavelengths; dust alignment due to the magnetic fields (e.g., Lazarian 2007) and self-scattering of dust grains (e.g., Kataoka et al. 2015). It is, however, still unclear how to distinguish the dominant mechanisms in observations due to the entanglement of many factors, requiring more polarization observational samples to constrain it.
IRAS 04166+2706 (K66) and IRAS 04169+2702 (K69) are young protostars within the B213 filament in the Taurus molecular cloud. These sources provide ideal laboratories for studying dust evolution and the role of magnetic fields in the early stages of star formation because they share similar ages born within the common dusty region where previous observations presented configurations of the magnetic fields at the filament scale. Here, we will present our ALMA program towards this unique system, and discuss the properties of polarized dust emission, obtained at unprecedented spatial resolutions from ~20 au to 1000 au, resolving for the first time both the protoplanetary disks and the surrounding envelopes.
Our data reveals striking differences between the two sources, despite them being embedded and born in the same environment. In particular, K66 likely has hourglass-shaped B-fields at >200au scales, and both the B-fields and self-scattering are dominant at the 20 au scale. K69 likely has compact toroidal B-fields at >200au scales and the self-scattering is dominant at the 20au scale. In this talk, I will discuss implications of these differences between the twins, focusing on dust evolution and the role of magnetic fields in shaping the star formation there.

Speaker: Asako Sato (Institut de Ciències de l’Espai, CSIC)

33 Unveiling the magnetized path of massive star formation with MAGMA

Magnetic fields play a dynamically crucial role in massive star formation. Models of massive star formation suggest that the magnetic field could significantly prevent fragmentation, cloud and core collapse, and influence the formation of accretion disks and jets. However, there are many aspects that ultimately lead to the formation of massive stars and star clusters that still remain uncertain, including the relative importance of magnetic fields in setting the large-scale initial conditions, fragmentation and infall properties. Two possible methods to make progress in resolving these open questions are (i) to conduct multi-scale studies to characterise the magnetic field properties (morphology, strength and dynamical importance) from cloud to core to disk/jet scales and/or (ii) to statistically probe the magnetic field properties of a large sample of star-forming regions in different environments, which can help not only to better understand the its role in crucial processes such as star formation, but also to gain insights into their origin and evolution. In this talk I will summarise the preliminary results of the MAGnetic field in MAssive star formation (MAGMA) survey, which combines both methods by accurately characterising the magnetic field properties from cloud to disk scales over a statistically significant sample of high-mass star-forming regions. These preliminary results have already provided crucial insights into the role and relative importance of the magnetic field in high-mass star formation.

Speaker: Chi Yan Law (Istituto Nazionale di Astrofisica (INAF))

Thursday 8 May

Session 4: Galaxy formation and evolution

34 From Island Universes to Noisy Neighborhoods: the chemical evolution of galaxies

One of the fundamental astronomical discoveries just a century ago, was that the Milky Way is one of a vast number of "islands" within the cosmic sea. One of the great challenges of this century is to understand why they are neither isolated nor monolithic. The pollution of the gaseous, baryonic component by stellar nucleosynthesis is the unique evidence remaining over cosmic time to trace the populations and dynamics of galaxies. The study of the large scale abundance gradients and isotopic compositions is essential for constraining the history of star formation and galactic growth. The talk will review the changing perspectives and significance of the underlying astrophysical assumptions from the first structureless closed box models to the current generation of cosmological numerical simulations, and the new perspective regarding the stochasticity and inherent heterogeneity of that evolution.

Speaker: Steven N. Shore (Dipartimento di Fisica, Universita di Pisa)

35 Star formation history of the Milky Way thick and thin discs from chemical evolution models

I will discuss the formation and evolution of the Milky Way thick and thin discs from the point of view of detailed Galactic chemical evolution models. To model the evolution of these two components and explain the observed bimodality in the [$\alpha$/Fe] vs. [Fe/H] plot, two different approaches can be adopted. In particular, (i) a sequential scenario called two-infall approach where the thick disc forms fast and before the thin disc and by means of a fast gas accretion episode, whereas the thin disc forms by means of a second accretion episode on a longer time-scale; (ii) a parallel approach, where the two discs form in parallel but at different rates. By means of chemical evolution models, I will show new results for the star formation history of the Milky Way thick and thin discs in the light of recent data for abundance patterns, metallicity distributions and age distributions of thick and thin disc stars.

Speaker: Valeria Grisoni (Istituto Nazionale di Astrofisica (INAF))

36 Revisiting the Milky Way’s Star Formation Rate: A New and Improved Estimate

This presentation explores three methods for estimating the total star formation rate (SFR) of the Milky Way, two of which leverage Herschel far-infrared imaging observations. The first method derives SFRs by positioning Hi-GAL star-forming clumps on the luminosity–mass diagram, incorporating a variable gas-to-dust ratio that varies with Galactocentric distance. The second method, inspired by extragalactic studies, introduces a novel approach that estimates SFRs based on the total 70 µm emission in Hi-GAL maps. The third method examines molecular clouds identified through CO emission lines, adjusting masses and SFRs according to Galactocentric radius and applying a star formation efficiency per free-fall time that depends on the cloud's virial parameter.
All three approaches yield not only a global SFR estimate for the Milky Way but also its Galactocentric profile and a detailed 2D face-on projection. While the methods show overall consistency, some intercalibration differences and localised discrepancies persist, which will be discussed. Additionally, the presentation includes a test of the Kennicutt-Schmidt relation using Milky Way regions, providing a valuable link to extragalactic studies.

Speaker: Davide Quintino Elia (Istituto Nazionale di Astrofisica (INAF))

37 Bar-spiral interaction produces star formatin bursts

Central bars and spirals are known to strongly impact the evolution of their host galaxies, both in terms of dynamics and star formation. Their typically different pattern speeds cause them to regularly overlap, which induces fluctuations in bar parameters. I will show, using both numerical simulations and observations, how bar-spiral physical overlap produces both migration and star formation boosts on the timescale of their beat-frequency. On the one hand, this mechanism can send stars from the bar radius out to the solar neighborhood on cold orbits. On the other end, it can enhance star formation by a factor of up to 4 when the bar and the spiral are connected, depending on the strength of the spiral structure. This is in agreement with observational studies seeing a revival of star formation rates at the end of the bar, compared to its decrease along the bar major axis. The bursts do not always happen simultaneously at the two sides of the bar, hinting at the importance of odd spiral modes. Various pieces of evidence seem to show the relevance of non-bisymmetric spiral structure in the MW. Such a phenomenon could be investigated thanks to resolved observations of nearby face-on galaxies, by comparing star formation rates from the two sides of the bar.

Speaker: Lea Marques (Leibniz-Institut fur Astrophysik Potsdam, Germany (AIP))

38 Poster session (6)

Enrique Vázquez Semadeni, Stevie King

10:35 Coffee break

Session 5: Primordial Universe

39 Back where it all begins: the formation of the first stars and black holes

The formation of the first stars and black holes marked a fundamental transition in cosmic history, from the cosmic dark ages to cosmic dawn. This event laid the foundation for the Universe as it appears today and shaped the evolution of the first galaxies and active galactic nuclei. The launch of JWST has enabled an unprecedented leap forward in exploring these distant cosmic epochs, raising new and compelling questions. In this talk, I will review our current theoretical understanding of the properties of the first stellar populations and black holes, discussing the many open questions and the prospects of future facilities in the electromagnetic and gravitational wave bands for providing a consistent picture of cosmic dawn.

Speaker: Raffaella Schneider

40 A 'low' redshift mode of Population III star formation during the Epoch of Reionization

Thanks to JWST, we are now in an era where observing campaigns to discover Population III stars has become a possibility. Over the past 3 years, multiple JWST proposals on Pop III stars have secured time, but no definitive detections have emerged. The two most pertinent challenges are: 1.) if most Pop III stars were massive, they would have not survived for a time window long enough for JWST to capture them, and 2.) if they formed at redshifts > 15, which even with the sensitivity of JWST remains notoriously hard to observe. Recent works suggest that Pop III star formation could have continued down to 'low' redshifts, during the Epoch of Reionization (EoR, z ~ 6). If realistic, this could be a game changer since the natural expectation is that such Pop III stars would have been less massive, lived to a longer time period, and are located at cosmological distances within the reach of JWST. Motivated by these possibilities, we carry out the first 3D radiation magnetohydrodynamics simulations of Pop III star formation during the EoR. We find significant differences in the mass, multiplicity, radiation and cluster properties of Pop III stars between z = 6 and z > 15. Contrary to expectations, even though the gas is colder at z = 6, there is less fragmentation within the pristine cloud due to the combined effects of magnetic fields and radiation feedback. Differences in protostellar accretion rates at z = 6 and z > 15 lead to very distinct stellar evolution, which changes the amount of ionizing and dissociating photons produced, and subsequent escape fractions. The differences are even more dramatic when a background Lyman-Werner radiation appropriate at z = 6 is included. By providing realistic, full physics-guided estimates of the mass and radiation properties of these stars, our simulations provide much needed benchmarks for designing Pop III observing campaigns with JWST towards the end of the first billion years.

Speaker: Lisanne van Veenen (Leiden University)

41 The POPSICLE project: star cluster formation at cosmic dawn

The era of cosmic dawn began with the first stars that formed in the Universe a mere 200 - 300 million years after the Big Bang. These stars produced the first supernovae and black holes, enriched the interstellar medium (ISM) with metals, were the building blocks of the first galaxies, and significantly contributed to cosmic reionization. However, compared to star formation and feedback in metal-rich environments today, the lack of direct observations at low metallicities as well as high redshifts has posed a significant challenge for understanding the physics behind their formation and evolution. In this talk, I will introduce POPSICLE, a new framework for high resolution simulations that caters to star formation and feedback in low metallicity environments reminiscent of redshift > 10 galaxies. I will describe how incorporating the full spectrum of ISM physics coupled to stellar evolution is crucial to constrain the stellar initial mass function (IMF) and feedback in such environments. I will particularly focus on the impacts of non-equilibrium chemistry, cosmic rays, and cooling in these environments, and discuss the interplay between different physicochemical mechanisms that govern the IMF, feedback and black hole growth in the early Universe. I will conclude by showcasing the capability of GPU-accelerated simulations to revolutionize our understanding of the astrophysics of cosmic dawn, and bring theory at par with state of the art observations from JWST.

Speaker: Dr Piyush Sharda (Leiden University)

42 Dust Attenuation of Star-Forming Galaxies in the Early Universe with JWST

Dust plays a fundamental role in shaping the formation and evolution of galaxies, regulating star formation through absorption and scattering of stellar light. The dust attenuation curve provides key insights into dust properties and their connection to the interstellar medium (ISM), yet its characteristics in the early Universe remain poorly constrained.

Using JWST/NIRSpec spectroscopy, we analyze a large sample of galaxies at z ~ 2–12, applying a customized SED-fitting approach to simultaneously characterize dust attenuation and global galaxy properties. We find evidence for a significant evolution in attenuation curves with redshift, suggesting changing dust grain compositions and production mechanisms. Additionally, we detect UV bump features in ~30 galaxies, including the most distant case at z = 7.55, placing new constraints on early dust enrichment. Our results provide crucial insights into the link between dust, star formation, and chemical evolution, shedding light on the earliest stages of galaxy assembly.

Speaker: Vladan Markov (FMF, University of Ljubljana, Slovenia)

43 Poster Session (7)

Stefano Ciabattini, Gian Luigi Granato

12:45 Lunch

14:25 Free Afternoon

Social event and Aperitivo: Social event

Friday 9 May

Session 6: Cosmic Rays and Astrochemistry

44 Cosmic rays and star formation

Cosmic rays (CRs) play a crucial role in the physics and chemistry of the interstellar medium (ISM). At the high densities found in molecular clouds, they represent the main ionising agent of the gas, affecting its heating and evolution. CRs ionise molecular hydrogen, quickly producing H3+, setting the gas ionisation fraction. The latter affects the timescale of ambipolar diffusion —the drift of neutral matter across the magnetic field lines— a mechanism that allows the collapse of subcritically magnetised prestellar cores. Furthermore, CRs initiate the rich chemistry of molecular ions in molecular clouds. In this regard, it is of particular importance the formation of H2D+, the precursor of deuterated species in the gas phase, and that of He+, the first step towards ammonia formation. In my review talk, I will describe the different physical and chemical properties of star-forming regions that are affected by CRs. I will focus, in particular, on how we can observationally measure their impact through the CR ionisation rate (CRIR), discussing the different methodologies used in recent years, and I will show the most recent results in these regards. I will conclude with a few details on the future perspective regarding the study of cosmic rays especially from an observational point of view.

Speaker: Dr Elena Redaelli

45 Interpretable Machine Learning for Astrochemistry

Machine learning is revolutionizing astrochemistry by providing new ways to analyze complex datasets and accelerate computationally expensive models. However, interpretability remains a key challenge, especially when extracting physical insights from data-driven approaches. In this talk, I will present recent advancements in applying interpretable machine learning techniques to astrochemical problems, focusing on two case studies. First, I will discuss how neural networks and SHapley Additive exPlanations (SHAP) can be used to identify spectral features that retain key physical information in synthetic observations of prestellar cores. Second, I will showcase a novel approach that leverages autoencoders and optimization techniques to reduce the dimensionality of large chemical networks while maintaining accuracy and interpretability. These methods not only enhance our understanding of astrochemical processes but also provide practical tools for improving the efficiency of numerical simulations. I will conclude by discussing the broader implications of interpretable machine learning for astrophysical modeling and future directions for the field.

Speaker: Tommaso Grassi

46 NEGATIVE ION CHEMISTRY AMONG STARS AND CLOUDS : MOLECULAR PROCESSES IN THE INTERSTELLAR MEDIUM

The last ten years or so have witnessed a tremendous growth
on the detection and observation of charged molecular species in the interstellar medium (ISM), especially within the special environments provided by interstellar and circumstellar clouds. Further observations within the atmospheres of the exoplanets have confirmed the marked ubiquity of these most diverse chemical species in the rather hostile environments of the interstellar space and identified specific regions that are considered to be the most efficient laboratories for molecular formation processes involving molecular anions. In the present talk I shall draw examples from our recent works on the study of molecular mechanisms presiding over ion-molecule reactions which lead to those anionic molecular products which have already been astronomically observed. We have been investigating the most efficient paths which can guide the formation of the recently observed carbon-rich molecular anions and on a variety of possible molecular quantum processes which can take place in the Diffuse and Dark regions of the interstellar clouds and in the atmospheres of some of the exoplanets.
1. F.A. Gianturco et al., Phys. Rev.Lett. 127, 043001 (2021).
2. F.A.G. et al., Phys. Rev. Lett.,131,183002 (2023).
3. F.A.G. et al., The Astrophys. J. 897,75-88 ,(2020)
4. F.A.G. et al., Faraday Disc., 212, 117 (2018).
5. F.A.G. et al.,The Astrophys. J., 850, 42 (2017).
6. F.A.G. et al., J. Chem. Phys. 153, 184309 (2020.
7. F.A.G. et al., MNRAS, 522 , 5775-5787 (2023).
8. F.A.G. et al., The Astrophys. J.,960, 40-52 (2023).
9. F.A.G. et al., The Astrophys. J., 973, 17 (2024)

Speaker: Francesco Gianturco (Institute of Ion Physics, Innsbruck University, Innsbruck Austria)

47 Cosmic ray ionization in the local Milky Way: How well do we understand it?

I will present recent advances in understanding properties of low-energy CRs in molecular clouds.

In the first part of my talk I will summarize results of reevaluation of CR ionization rate (CRIR) derived from available measurements. Previous estimates of CRIR for these measurements relied on model-dependent assessments of the gas density along the probed sight lines. Now, we utilized the recently developed 3D dust extinction maps that allowed us to precisely identify the location of molecular clouds probed in each measurement, and also to derive the gas density in these clouds. This helped us to evaluate CRIR in each cloud without involving any model-dependent assumption about the environment. Our results indicate that (i) values of CRIR probed in individual diffuse molecular clouds in the local Galactic environment may vary by an order of magnitude from cloud to cloud, and (ii) the average CRIR value is a factor of 5-10 smaller than that derived previously.

I will also discuss resent theoretical development in understanding dominant mechanisms that govern attenuation of Galactic CRs penetrating molecular clouds. Apart from regular attenuation mechanisms, associated with ionization energy losses, penetrating CRs may also be scattering on self-generated turbulence excited in diffuse envelopes of the clouds. We found that significant self-modulation of non-relativistic CRs may already operate in clouds with the gas column density of a few times 10^21 cm−2, while for a few times 10^22 cm-2 the effect becomes strong for GeV protons. The obtained results are in excellent quantitative agreement with recent Fermi LAT observations of nearby giant molecular clouds.

Speaker: Dr Alexei Ivlev (MPI for extraterrestrial physics)

10:40 Coffee Break

48 Impacts of Energetic Particles from T Tauri Flares on Inner Protoplanetary Discs.

T Tauri stars are known to be magnetically active stars subject to strong flares observed in X-rays. These flares are likely due to intense magnetic reconnection events during which a part of the stored magnetic energy is converted into energetic supra-thermal particles.
Since T Tauri stars are surrounded by accretion discs, these particles may influence the disc dynamics and chemistry. The talk will discuss our methods for modelling particle acceleration in T Tauri flares. We will then examine the ionization rate produced by these flares, relying on data from the Chandra X-ray survey of nearby young stellar objects.
Our work indicates that energetic particles from flares significantly contribute to the ionisation of the disc. The talk will also address the consequences of this additional ionisation source on the inner disc, focusing on its impact on accretion rates, chemical complexity, heating rates, and potential observables by the James Webb Space Telescope.

This talk will provide new insights about the interactions between young stars and the discs surrounding them.

Speaker: Valentin Brunn (Istituto Nazionale di Astrofisica (INAF))

49 Transport of spectrally-resolved cosmic-ray protons and electrons in the multiphase interstellar medium

Modeling cosmic-ray (CR) transport on galactic scale is a challenging task due to the complex physical processes that couple CRs to the thermal gas, which are not yet fully understood. As a result, in most interstellar-medium (ISM) studies involving CRs, the interaction between CRs and their scattering waves, that is unresolved on macroscopic scales, is treated via a constant scattering coefficient, whose value is motivated by observational constraints. To improve upon this approach, we recently developed a physically-motivated prescription for the transport of CRs, in which the scattering coefficient varies with the properties of the ambient gas, with a functional form motivated by the theory of self-confinement. In this talk, I will present our application of this prescription to compute the transport of spectrally-resolved CR protons and electrons with energies between 1 and 100 GeV within the TIGRESS MHD simulations of star-forming galactic disks. I will discuss the evolution of the CR spectral distribution as these particles propagate through the multiphase, magnetized ISM, and compare our simulation results with direct observations in the solar neighborhood, highlighting the remarkable agreement we found.

Speaker: Lucia Armillotta (Istituto Nazionale di Astrofisica (INAF))

50 The Effect of Weak Cosmic Ray Heating Events on the Desorption of H2

Cosmic rays (CRs) have a large effect on the physical and chemical evolution of star-forming material. One particular aspect of this is desorption; CRs that impact dust grains deposit energy along their track, heating the grain transiently to a higher temperature. The grain then sheds the deposited energy via (partial) desorption of the ice mantle. This mechanism is arguably the most important means of desorbing icy material in regions well shielded from the interstellar radiation field. 

Earlier numerical models of CR-induced desorption have assumed that the grains are always heated to a transient maximum temperature of 70 K, stemming from the assumption that the CRs are iron nuclei and that the radius of the (spherical) grain is fixed at 0.1 microns. In reality, there is a spectrum of CRs, consisting of different particles coming in with a range of energies. This means that dust grains can be transiently heated to temperatures of a few tens of K, which is enough to desorb H2 for example, and in fact such heating events occur much more often than those heating the grains to 70 K.

We present the results of revised CR-induced desorption models where the effect of “weak heating events”, that is, those heating the grains to a few tens of K, on gas-phase and ice abundances in star-forming regions is examined. We direct particular attention to H2 ice, which is notorious for appearing in unrealistic amounts in chemical simulations. Surprisingly, we find that even the weak heating events are not enough to remove large quantities of H2 from the grains. The abundances of species other than H2 are however affected by the revision of the CR desorption model to various degrees depending on the physical conditions. We discuss the implications of our results on the understanding of (ice) chemistry in the interstellar medium.

Speaker: Olli Sipilä (Max-Planck-Institute for Extraterrestrial Physics)

51 Chemical signatures of a prestellar cluster in the Galactic Center

The Central Molecular Zone (CMZ) contains most of the mass of our Galaxy but its star formation rate is one order of magnitude lower than in the Galactic disk. This is likely related to the fact that the bulk of the gas in the CMZ is in a warm (>100 K) and turbulent phase with little material in the prestellar phase.
In this talk, I will first present D/H ratios of HCN, HNC, HCO$^{+}$, and N$_{2}$H$^{+}$ obtained toward the CMZ molecular cloud G+0.693-0.027 (Colzi et al. 2022). These observations clearly show, for the first time, the presence of a colder, denser, and narrow component, with a line width of about 9 km s$^{-1}$, in addition to the typical gas component of the CMZ, warm, less dense, and turbulent with a line width of about 20 km s$^{-1}$. For this new component D/H ratios > 10$^{-4}$ and excitation temperatures of 7 K for all molecules have been found, suggesting kinetic temperatures < 30 K and H$_{2}$ densities >5$\times$10$^{4}$ cm$^{−3}$. This new method indicates that the degree of deuteration of different molecules, such as N$_{2}$H$^{+}$ and HCO$^{+}$, and their line profiles can be used to reveal the different gas components in the line of sight to the CMZ.
Then, I will present HC$_{3}$N excitation-derived gas densities and temperatures of the gas components towards the same source, using multiple transitions coupled with spatially resolved HC$_{3}$N images of the source. This approach allows us to identify denser gas that possibly is on the verge of gravitational collapse and that will host future protostars in the CMZ (Colzi et al. 2024).

Speaker: Laura Colzi (Centro de Astrobiologia (CAB), CSIC-INTA)

52 Exploring the limits of chemical complexity in the interstellar medium: present and future

Following the initial detection of a molecule in the interstellar medium (ISM) in the late 1930s, more than 330 different species have been identified to date. The detection rate has increased in tandem with the enhancement of telescope sensitivity, particularly in the centimetre and (sub)millimetre ranges. Remarkably, the field has recently undergone a true revolution, with nearly 100 new species – constituting almost a third of the total number – being discovered in the last four years alone. The identified molecules are characterised by an increase in chemical complexity, as evidenced by the number of atoms and the diversity of their chemical composition. Of particular interest is the detection of species that are well-known precursors of prebiotic chemistry, i.e., the set of chemical processes that led to the emergence of life on early Earth. Consequently, we already know that the interstellar material from which stars and planets are formed contains at least some of the fundamental ingredients for life.

Complementarily, recent analyses of comets and asteroids using "in-situ" and sample-return space missions have revealed that our Solar System was formed in a parental cloud rich in prebiotic molecules, including a wide variety of amino acids and all five nucleobases present in RNA and DNA. However, these complex species have not yet been identified in the ISM, raising obvious questions: does our Solar System represent a unique case with a particularly rich (prebiotic) chemistry? Or alternatively, are the prebiotic ingredients widespread in many other places in the Galaxy, or even in other galaxies? In this talk, I will address these questions in the light of the latest results in the field. Firstly, I will summarise the state-of-the-art in the quest to detect new molecules of prebiotic interest in the ISM. Secondly, I will discuss new perspectives for the next years and decades thanks to the advent of a new generation of significantly more sensitive observational facilities.

Speaker: Dr Víctor M. Rivilla (Centro de Astrobiología (CAB, CSIC-INTA))

53 Poster session (8)

Álvaro Sánchez-Monge, Gan Luo, Lorenzo Branca, Nai Chieh Lin

Final remarks