Welcome by the Director of INAF-Osservatorio di Arcetri. Brief introduction to the workshop by the organisers.
Galactic studies are currently undergoing a renaissance, thanks to the wealth of data from the Gaia satellite and ground-based surveys. Previously unknown portions of the Galactic disc have been mapped, triggering new interest and questions into the physical mechanisms regulating the evolution of the Galaxy. Recent works based on field stars and open clusters revealed: (i) the segments of the...
With the unprecedented increase of known star clusters, quick and modern tools are needed for their analysis. In this work, we develop an artificial neural network trained on synthetic clusters to estimate the age, metallicity, extinction, and distance of Gaia open clusters. We implement a novel technique to extract features from the colour-magnitude diagram of clusters by means of the...
Gaia has revolutionised our ability to identify clusters and to use them as tracers of the Galactic structure. Our view is however severely limited when looking towards the inner regions of the Milky Way, where the clusters we do see are very young and very massive. The differences between the inner and outer disc are in part due to observational biases, but could also indicate that different...
The combination of photometric and astrometric data from Gaia with parameters derived by spectroscopic surveys, like Gaia-ESO, improved our knowledge of the properties of young star clusters and our understanding of the processes leading the cluster evolution until its dispersion.
However, current datasets suffer of two main shortcomings: they are mostly based on optical observations, so we...
The study of open clusters is a crucial element in the understanding of the processes that led to the formation of the disk in the Milky Way and in general in spiral galaxies. For this reason they have been targeted by all the recent spectroscopic surveys, providing radial velocities and chemical abundances. In the coming future, a number of spectroscopic surveys such as WEAVE and 4MOST will...
To study stellar clusters and be able to effectively use them to understand how stars and clusters form and evolve and to link this to the Galactic evolution, we need not only large samples, such as those provided by the spectroscopic surveys, but also high resolution and detailed analysis.
As part of the SPA (Stellar Population Astrophysics) Large Programme at the TNG, we observed a large...
Stars are primarily formed in clustered environments in giant molecular clouds. Stars are also primarily found in binary or higher order multiple systems. Therefore, there is a time during the formation of star clusters when both stellar dynamics and hydrodynamics are needed to describe the dominant populations, and we probably also need to care about radiation, chemistry, dust physics, and...
While some young stars are clustered, many other young stars are observed as dispersed,
non-gravitationally bound groups, or in complete isolation. Using N-body simulations,
we study dispersal of young open star clusters of a wide range of initial masses.
We find that observational data are consistent with the assumption that all stars form
in initially embedded star clusters, which loose...
In the last ~10 yrs, several young stellar clusters have been associated to diffuse gamma-ray emission in the energy range from ~1 GeV up to ~100 TeV. In particular in the region close to the association Cygnus OB2 photons up to the incredible energy od 1.4 PeV have been detected by LHAASO. The orginin of the non-thermal particles responsible for the gamma-ray emission is not completely clear....
The initial conditions of star-forming regions will dictate if they will disperse into the field or survive as bound open clusters. Methods have been developed to characterise star-forming regions and infer the initial conditions of them (i.e. initial density, degree of substructure and virial state). These methods have been used to quantify the spatial clustering of stars within star-forming...
In our quest to gain a deeper understanding of our Solar Neighborhood, Gaia has proven instrumental in elucidating the 3D spatial structure of the local interstellar medium (ISM) and the distribution of young stellar clusters. However, to unravel the origin and evolution of nearby young structures, a crucial dimension is the measurement of their 3D space motions. These motions allow us to...
We perform simulations of cluster formation in regions taken from galaxy scale simulations, including photoionization and supernovae feedback. We simulate regions with different densities, and from different galactic environments. In all our simulations, clusters undergo mergers and splits during their formation. More massive clusters form in regions of spiral arms with stronger converging...
Star formation is a fundamental process that impacts many fields of astrophysics, from the formation and evolution of planets to galaxies. The interaction between the natal cloud and the newborn stars is one of the least understood star formation processes and has an important impact on the final star-formation efficiency and cluster dynamics. I will present an innovative methodology to...
Young clusters are a formidable tool to study star formation, stellar evolution, binary stars, as well as the formation and evolution of clusters themselves. The availability of data from Gaia, coupled with additional ground-based data and clustering analysis methods, allow us for the first time to discover and study a wide range of clusters with unprecedented details. In the region around...
The EWOCS (Extended Westerlund 1 and 2 Open Clusters Survey) project has the objective of studying star and planet formation, and early stellar evolution, in super massive star clusters (SSCs). With a mass in excess of 10^4 solar masses, the very few SSCs known in the Milky Way represent the most accessible examples of starburst regions, which are very rare in our Galaxy today, but common in...
In just five years, Gaia has revolutionised the census of star clusters in the Milky Way - including allowing for the detection of thousands of new clusters. However, many of these clusters are much smaller and more dispersed than canonical open clusters like the Pleiades, and it is not clear how many of these clusters are actually gravitationally bound. This presents critical challenges when...
Accurate mass determinations for open clusters (OCs) are essential for
studying star formation as well as OC dissolution processes. Using the Gaia DR3 OC catalogue of Hunt & Reffert (2023), we construct an extensive sample of OC mass estimates. We analyze more than 2000 OCs within 2 kpc, estimating their tidal masses and fitting their mass functions where possible (including the effect of...
Deducing the masses and mass functions of stellar clusters (SCs) is an important step to understanding their formation and evolution and to comprehending the formation of the Galaxy. This contribution explores, how unresolved binaries affect not only the deduction of these parameters for SCs, but also for their tails. If the binaries in SCs and their tails cannot be resolved, their masses are...
Fluorine remains an enigmatic element in galactic archaeology, with a scarcity that camouflages its importance in understanding chemical and stellar evolution. Various astrophysical sites, including massive stars, AGB stars, Wolf-Rayet stars, and Novae, have been proposed as fluorine producers, yet the element's origins remain a subject of debate. To shed light on this, we have initiated a...
The recent detection of large diffuse $\gamma$-ray halos in coincidence with a dozen young massive stellar clusters (YMSCs) has strengthened the hypothesis of stellar clusters as cosmic ray factories and $\gamma$-ray sources. Noticeably, the observed $\gamma$-ray emission is, on average, remarkably extended (~1-3°) and of the same size as the dimension of the superbubble developed by YMSCs....
The stars in a galaxy form in compact embedded star clusters which expand after removal of their residual gas. The subsequent virialisation leads to a fraction of the stars condensing into an open star cluster. The open star cluster dissolves as it orbits in the potential of the hosting galaxy through the energy equipartition process. In the Newtonian gravitational theory, the ensuing tidal...
Compared to the globular clusters and their tidal tails, open cluster tails are ~1000 smaller in terms of star counts and must be found in an environment ~1000 times denser than the halo. Hence finding stars in tidal tails of open clusters is a difficult task even in the era of Gaia. I will present a probabilistic method where we start by simulating the dissolution of a cluster, which defines...
The tidal tails of stellar clusters are an important tool for studying the clusters’ birth conditions, their evolution, coupling, and interaction with the Galactic potential, and to understand how field stars populate the Milky Way. Thanks to Gaia, much progress has been accomplished in finding tails of open clusters. I will show here that such tidal tails are much longer than previously...
We study the kinematics of the young stars around the spiral arms in the Milky Way, using Gaia DR3. We first demonstrate that we can measure the circular velocity at the position of the Sun in the Milky Way using the young OB stars, but there is a clear sign of the impact of the Local arm. From the kinematics of these stars and also of old stars, we find that the Local arm is not a minor arm,...
I will discuss the results from numerical simulations of star cluster formation and evolution. I will review what has been learnt from numerical simulations regarding how the properties of low-mass stellar clusters and their stars depend on initial conditions, such as metallicity, molecular cloud density, magnetic fields, and turbulence. I will also discuss how these clusters may be expected...
Understanding the factors that influence the survival of open clusters within the Milky Way is a complex endeavor. This study delves into the role of key parameters such as mass, density, size, and the galactic environment, including the Galactic bar, spiral structures, and molecular clouds. Particular attention is given to how open clusters and field stars respond differently to...
The wealth and homogeneity of Gaia data have allowed the discovery of several open clusters with signs of disruption.
We do a morphological, kinematic and chemical analysis of the disrupting cluster UBC 274 (2.5 Gyr, d = 1778 pc), with the objective of studying its global properties.
A new membership study up to 50 pc from its center and un to magnitude G=19 using GaiaEDR3 data, shows that...
M67 is a cornerstone open cluster for stellar astrophysicists. It is the same age and metallicity as the Sun - indeed its stars are so similar to the Sun that some have speculated that the Sun may have been born there. Furthermore its location - relatively close to use but well above the plane of the Milky Way - makes it easy to distinguish from the background field population. However this...
Numerical and analytical evidences that collisionless and collisional relaxation processes work differently in Newtonian and modified Newtonian dynamics (MOND) theories of gravitation imply that processes such as the disruption of satellites falling onto the parent galaxy should, in principle, behave differently in the two scenarios. In particular, it is not clear whether a stronger...
The sun is located at a Galactocentric distance where the transition from Newtonian to MoNDian dynamics is expected to occur. Due to their proximity solar neighbourhood open star clusters are ideal kinematical laboratories to discriminate between the validity of Newtonian or MoNDian dynamics. Direct MoNDian N-body integrations of open star clusters embedded in an external field are performed...
I will discuss the upcoming survey that will make use of 4MOST at the VISTA ESO telescope. By exploiting the characteristics of such instrument, the survey will provide the most comprehensive characterization of the chemistry and kinematics of stellar clusters collected to date. It will target essentially all the Galactic Globular and Open Clusters and Star Forming Regions accessible 4MOST,...
Open clusters’ dynamical evolution is driven by stellar evolution, internal dynamics and external forces, which according to dynamical simulations, will evaporate them in a timescale of about 1 Gyr. However, about 10% of the known open clusters are older. They are special systems whose detailed properties are related to the dynamical evolution of clusters and the balance between mechanisms of...
Gaia has undoubtedly changed the way we look at the dynamics, morphology and evolution of star clusters. The exquisite spatio-kinematic dataset combined with sophisticated clustering tools allow us to observe not only the compact cores, but also extended regions beyond the tidal radius, where haloes, coronae and tails harbour an increasing fraction of the stellar mass as clusters dissolve with...
The spiral shape of the vertical phase diagram found by Antoja and collaborators is one of the most conspicuous of the many results provided by Gaia. This structure is observed over a wide range of galactocentric radii for disk stars with ages greater than 1 Ga. Alfaro et al. chose a sample of star clusters with ages less than 30 Ma finding a linear relationship between Vz and Z. We have...
