INVITED SPEAKERS

Numerical simulations for large-scale structure cosmology
Abstract: One of the most pressing issues in theoretical cosmology today is how to optimally interpret the data from future observations of the large-scale structure of the Universe. In this talk, I will discuss a framework based on cosmological N-body simulations that provides accurate predictions as a function of cosmological parameters and astrophysics. The method is a result of several recent advances in computational cosmology regarding the modelling of dark matter, gas, and baryonic effects, galaxy formation, as well as the development of neural networks that enable the delivery of theory predictions in a fraction of a second. The approach I will discuss has the potential to significantly increase the amount of cosmological information extracted from surveys such as EUCLID, and thus about the nature of dark energy, dark matter, and the mass of neutrinos.

It’s time of the intracluster light: how hydrodynamical simulations help study the most extended stellar systems of the Universe
Abstract: The development of sophisticated observational technologies and the implementation of massive observational programs are making it possible to study, in number and depth, the very diffuse and extended light of galaxy clusters, the so-called intracluster light (ICL), like never before. This is a stellar component mainly associated with the gravitational potential of the entire cluster, where dark matter dominates. To understand the nature and origin of these huge but diffuse stellar systems, it is crucial to properly separate this component from the brightest central galaxy (BCG) and characterize its surface brightness distribution (e.g., a Sérsic law), as well as its kinematics. To our aid come hydrodynamical cosmological simulations of galaxy clusters, which must be post-processed to assign spectra to stellar particles and to obtain synthetic observations comparable to real observations. I will present a review of progress in this direction, the state of the art in understanding the origin of the ICL, the challenges we still have, and inferences about the distribution of dark matter that could be made from ICL observations. I will also present some preliminary results from our group on analysis and comparison with observations from post-processed lllustris-TNG300 cluster simulations.

The dark matter density profile of clusters of galaxies
Abstract: Dark matter (DM) has been originally discovered in clusters of galaxies by Zwicky (1933). These systems currently remain excellent laboratories for probing DM properties through gravitational lensing, and the dynamical equilibrium of cluster visible components (intra-cluster plasma and galaxies). Comparison of the shape of cluster mass density profiles with predictions from cosmological simulations are used to constrain the properties of DM. Particularly useful in this respect is the determination of the inner slope (gammaDM) of the dark matter (DM) density profile. Cold DM cosmological simulations predict gammaDM~1. While significantly flatter slopes have been obtained in the literature, our new results, based on the CLASH-VLT data with MUSE follow-up observations, appear to reconcile the observational determinations of gammaDM with predictions from LambdaCDM cosmological simulations.

Barred galaxies in the simulated and in the real Universe.
Abstract: I will first review our current  theoretical understanding of
how bar structures form and evolve within disc galaxies, focusing
particularly on results based on the analysis of the hydrodynamical
cosmological simulations IllustrisTNG.
I will then discuss the potential of the J-PAS photometric survey to
study the evolution of bars and the properties of the host galaxies.
J-PAS is a survey featuring 54 narrow bands covering the full optical
range, effectively delivering a low-resolution spectrum for every pixel
observed.  Its filter system, combined with its large field of view,
makes J-PAS an ideal survey to study galaxy properties and
morphological features in a wide variety of environments.

Galaxy spectral modeling in the JWST era
Abstract: I will review galaxy spectral modeling in the context of the exploration of the distant Universe with JWST.

When do disks form bars?
Abstract: Using high-resolution N-body simulations, we have investigated a stellar disk’s stability to a bar mode. To date, there is no convincing global criterion regulating the formation of bars in disk galaxies. Here we do not assume that the disk is purely self-gravitating but exists in the potential of an external force field and its self-gravity. The simulations show that two global
dimensionless parameters in our study appear to control the instability to m=2 modes. Our analysis shows that these two parameters define a plane with regions of stable and unstable disks to the bar formation. Unlike the Toomre Q parameter, which regulates the disk stability locally, the identified parameters in our study are global and play a crucial role in the stability of a broad class of disks to bar formation at all scales. The criterion should be applicable to
high redshift disks.

The CMB Cold Spot as predicted by foregrounds around nearby galaxies
Abstract: The non-Gaussian Cold Spot (CS) surrounded by its hot ring is one of the most striking features of the CMB. It has been speculated that either new physics or ISW effect induced by the presence of a cosmic void at high redshift can account for the observations. Here we investigate if the systematic decrease in CMB temperature in the neighbourhood of nearby galaxies may create such a strong temperature depression. In particular, we note that the Eridanus supergroup and its neighbouring groups, is in the CS area. Our goal is to analyse observational galaxy data to characterise the neighbourhood of the CS, explore the properties of these galaxies and thereby make a prediction of the CMB temperature decrement in this region. We use the Planck SMICA maps and the galaxy catalogues 2MRS, 6dF and HIPASS as foreground tracers. We apply mean temperature profiles to model the temperature decrement from the galaxies in the CS area. Even after correcting for the mean low temperature of the CS region, we find that the temperature decrement around galaxies is significantly stronger than the mean decrement in other parts of the sky. We discuss whether this could be attributed to the fact that the CS area coincides with one of the regions populated by the most HI deficient galaxies. Modelling the foreground temperature profile, we find a particularly strong temperature decrement due to the presence of the late-type overabundant largest group complex in the nearby universe. A CS shape, which to a large degree overlaps with the CMB CS, is observed. We conclude that the coincidence of the only nearby spiral rich group complex located in the CS region, and the success of the modelling performed, adds strong evidence to the existence of a local extragalactic foreground which could account for the observed temperature depression, alleviating the tension with an otherwise Gaussian field expected in the CMB.

A primer on dust evolution in galaxy formation models
Abstract: I will briefly review the reasons to incorporate dust formation and evolution in cosmological galaxy formation models, the processes to be considered, and the activity of our group in this field.

Galactic Phylogenetics: using evolutionary biology to understand galactic histories.
Abstract: Today, almost every evolutionary study use phylogenetic trees to reconstruct histories. These are graphs that illustrate the shared evolutionary history among a dataset, allowing us to understand the hierarchical pattern of ancestry and decent which connects all of the observations. Phylogenetic methods can reconstruct ancestral relationships as long as there is a shared history and a heritable process linking the data objects. These objects are normally individuals, species and higher taxa in biology, where methods to analyse them have been developed, but they are applicable more broadly. By making the hypothesis that the stars in galaxies come from the same but evolving interstellar medium (ISM), and that the evolutionary marker (i.e. the heritable component) of the ISM is the chemical composition, we can use the chemical abundances of stars as fossil records for building phylogenetic trees. In this talk I will present our latest results and lessons learnt in what happen when we borrow tools from other disciplines to contribute to galaxy evolution studies.

But we know very little about the Milky Way
Abstract: We have made a lot of progress in the study of the MW. But much of our Galaxy remains unknown, in spite of the recent progress made with near-IR surveys like the VISTA Variables in the Via Lactea (VVV) and its extension VVVX. Some amazing breakthroughs await to be made in the exploration of the Galactic center and the far side of the Galaxy. In particular, the Galactic extinction horizon is a fundamental difficulty, and it is my aim here to discuss
how profound is our ignorance, and also to try to suggest ways for improvement with future facilities.

The intriguing lives of galaxies lacking dark matter
Abstract: The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and Sérsic indices). Here we show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. Moreover, these encounters occur when the satellite is still gas-rich, suggesting that gas-rich interactions may explain the peculiar globular cluster populations in these galaxies. We predict that ∼30% of massive central galaxies (with at least 10e11 solar masses in stars) harbour at least one dark-matter-deficient satellite (with 10e8 -10e9 solar masses in stars). This distinctive class of galaxies provides an additional layer in understanding how tidal stripping and star formation triggering unfolds under these extreme conditions. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.

Galaxy density profiles: significance and origins
Abstract: I will discuss possible explanations for the origin of the density profiles of galaxies and dark matter halos, their physical significance, and applications. Aside from some historical notes, I aim to show simple examples of how stellar density profiles may be used to track the importance of Galactic tides on the evolution of the dwarf spheroidal satellites of the Milky Way. Such tidal effects may also be used to distinguish between faint star clusters and dark matter-dominated dwarfs: a recent application suggests that we may have recently identified the faintest, smallest, and densest galaxy ever discovered. These findings have important consequences for the LCDM paradigm and alternative dark matter theories.

The co-evolution between galaxies and dark matter halos
Abstract: The current cosmological paradigm posits that dark matter halos provide the gravitational scaffolding for galaxy formation through a combination of hierarchical structure formation and non-linear local astrophysical processes. As a result, the growth and assembly history of dark matter halos are expected to influence the assembly history of galaxies which can leave observable imprints on their properties. This close and interdependent relationship between
galaxies and halos is commonly referred to as the galaxy-halo connection. While the stellar mass of galaxies has been found to be strongly correlated with the mass of their dark matter halos, it is essential to note that the galaxy-halo connection is actually a multivariate distribution of galaxy and halo properties, which can be constrained using data from astronomical observations and simulations, the so-called semi-empirical modelling. In this talk, I discuss the semi-empirical model for the galaxy-halo connection. In particular, I will
discuss EMPIRE which utilizes the assembly histories of dark matter halos and the multivariate distribution between galaxy and halo properties to infer the star formation histories of galaxies, galaxy sizes, as well as the accretion histories of their host supermassive black holes.

Evolution mapping: an approach to describe the non-linear density field
Abstract: In this presentation, I introduce the concept of “evolution mapping” as a powerful tool for simplifying the description of the non-linear matter density field. This approach exploits the fact that cosmologies with identical linear power spectra exhibit strikingly similar non-linear evolutions. This inherent degeneracy drastically reduces the number of parameters required to characterize statistics of the non-linear density field. Among other applications, this offers the opportunity to construct emulators for Large-Scale Structure (LSS) statistics whose predictions are applicable across a broad range of cosmologies and redshifts. The evolution mapping degeneracy also provides a straightforward avenue for comprehending the cosmological information content of all clustering statistics. In this context, I will demonstrate how this concept can be used to decode the information embedded in large-scale anisotropic two-point clustering measurements.

A photometric estimator of galaxy cluster masses
Abstract: We model the cumulative galaxy number profile of SDSS clusters of galaxies with a Sérsic profile plus a two-halo term, using photometric redshifts to ascribe cluster membership. The fitted parameters allow us to obtain the splashback radii of the clusters. Using masses obtained by weak lensing for calibration, we show that we are able to estimate cluster masses from the splashback radii with a dispersion of 0.12 dex. The results are robust with
respect to the magnitude limit adopted for the analysis and show that we are able to estimate cluster masses with good accuracy by using photometric information only.

Made in Córdoba; Sersic-Pastoriza galaxies
Abstract: This intriguing class of galaxies called Sersic-Pastoriza after the Sersic and Pastoriza 1965 seminal paper, appear in galaxies from different morphological classes and with different degrees of nuclear activity, all of them displaying a  circumnuclear ring of star formation. Their study helps setting constraints for different aspects of galaxy formation and evolution, in particular it allows to investigate the conditions for star formation present in  high metallicity environments. In my talk I will concentrate on this aspect, emphasising on new methods devised in order to study these extreme regimes.

Mapping the Hubble flow from z~0 to z~7.5 with HII galaxies
Abstract: I will discuss the tight relation between ionized gas velocity dispersions and Balmer emission line luminosities  in HII galaxies and Giant HII regions, its implications and its use as distance indicator to trace the expansion of the Universe up to z ~ 9 with JWST. This approach yields tight independent constraints on H0, Ωm and the Dark Energy equation of state parameter w. The concordance between our determinations of H0, Ωm and w with those from SNIa, BAO and Planck provides empirical support for a universal IMF.

Unraveling the History of Galaxies through Chemical Signatures
Abstract: The chemical abundances found in stellar populations and the interstellar medium of galaxies offer invaluable information regarding their assembly histories and the mechanisms that influence star formation and element mixing.
In this presentation, we will present the comprehensive analysis results of chemical abundances in star-forming regions of galaxies, investigating how these characteristics vary concerning their merger and accretion histories. Furthermore, we will explore the information preserved by young stars to unveil the effects of significant events on the recent history, utilizing hydrodynamical cosmological simulations.