Benítez-Llambay, A.
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The recent discovery of a starless dark matter halo
In recent years, our theoretical understanding of what establishes the onset of galaxy formation on small scales has become increasingly mature, to the point that the halo occupation fraction, namely, the fraction of halos that host a luminous galaxy in their centre is now well understood in terms of the interplay between dark matter halo mass assembly histories and the existence of a redshift-dependent ""critical mass"" for galaxy formation. This enables predictions regarding the count of faint nearby dwarfs and some of their properties, including their gas fraction, neutral hydrogen content, and star formation histories, among others. Interestingly, these models also predict the existence of a population of starless halos with masses just under the critical mass. These starless halos elude the complexities associated with star formation and the subsequent supernova feedback and contain enough neutral hydrogen to produce a significant emission in 21 cm.
In this talk, I will discuss these systems in the context of a recent detection of extended 21 cm emission consistent with a starless dark matter halo carried out with the Five-hundred Aperture Radio Telescope (FAST). I will also discuss how these observations can be used to constrain the nature of dark matter, the LCDM, and galaxy formation models at the smallest scales. I will end by discussing current uncertainties, ongoing observational programmes, and future theoretical and observational directions that may lead to further improvements.
Domínguez Romero, M.
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A determination of the LMC dark matter subhalo mass using the MW halo stars in its gravitational wake
Our goal is to study the gravitational effects caused by the passage of the Large Magellanic Cloud (LMC) in its orbit on the stellar halo of the Milky Way (MW). We employed the Gaia Data Release 3 to construct a halo tracers data set consisting of K-Giant stars and RR-Lyrae variables. Additionally, we have compared the data with a theoretical model to estimate the DM subhalo mass. We have improved the characterisation of the local wake and the collective response due to the LMC orbit. On the other hand, we have estimated for the first time the dark subhalo mass of the Large Magellanic Cloud, of the order of $2times 10^{11}$ M$_{odot}$, comparable to previously reported values in the literature.
Yaryura, Y.
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A new method for tracing the cosmic web
It is well established that galaxies exhibit distinct intrinsic properties across varying environments, highlighting the significant role of the environment in galaxy formation and evolution. The cosmic web, characterized by the intricate arrangement of galaxies in large-scale structures, is commonly classified into four types: knots, filaments, walls, and voids. However, defining these categories poses a challenge due to the various methods by which these systems can be distinguished from one another. Moreover, considering the intricate nature of the Universe's large-scale structure, rigidly compartmentalizing galaxies into four discrete categories appears to lack the flexibility inherent in the cosmic web itself. One prevalent method for categorization involves utilizing the eigenvalues of the Hessian matrix derived from the matter distribution. By examining the ratios of these eigenvalues, we demonstrate statistically that there exists no distinct set of four characteristic values delineating discrete compartmentalized environments. Instead, a continuous distribution of these ratios reveals a complex and continuous network of environmental conditions. We apply these findings to a semi-analytical model of galaxy formation integrated with dark matter-only simulations, elucidating how galaxy intrinsic properties dynamically respond to environmental variations.
Granato, G. L.
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Modelling Molecular Hydrogen in Hydro-Simulations
In the metal-enriched interstellar medium, the abundance of molecular gas is primarily governed by the formation of H2 on dust grains, as well as its self-shielding and shielding by dust against photo-dissociation by the interstellar radiation field. The upcoming presentation intends to describe a sub-resolution model for forming molecular hydrogen in hydrodynamic simulation with dust description and encouraging results in predicting the properties of galaxies in cosmological boxes.
Rodríguez-Medrano, A.
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The evolutionary path of void galaxies
Cosmic voids represent unique environments for studying galaxy evolution. Due to their low matter density, voids offer an opportunity to investigate galaxy evolution in the absence of mergers and interactions, serving as proxies for an "in situ" evolution of galaxies. In this talk, we will present observational findings and results from numerical simulations that evaluate these concepts. By combining observational data with state-of-the-art numerical simulations, we aim to shed light on the role of cosmic voids in shaping the evolution of galaxies. Our findings contribute to a deeper understanding of the complex interplay between cosmic structures and the evolution of galaxies within them.
Schivazappa, F.
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Automatic exploration of the correlation between cosmic void tracers in cosmological simulations
In the present work, we aim to explore the hypothesis that there is a relationship between the abundance curves of cosmic voids identified in halos and in matter. This would allow us to overcome the obstacle posed by the bias relationship when analyzing the distribution of matter in the Universe. We use cosmic voids surveys obtained from cosmological simulations with Ω=[0.1;0.5], with a step of Ω=0.025, and halo densities ranging between 0.001, 0.002, and 0.004. To test the hypothesis, we explore the relationship between the curves using three types of regressors: a linear regressor, a random forest regressor, and a Gaussian regression. The aim is to establish whether training an algorithm with information about the abundance of voids identified with both tracers can predict the behavior of the abundance curve in matter when the only data provided is from the abundance curve in halos.
Paz, D.
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Probing cosmology with voids in the large scale structure
We present an analysis of the abundance of void regions identified across various simulations with different cosmological parameters and gravity models. In particular, our study investigates the dependence of void shapes on fundamental cosmological parameters, such as matter density and sigma_8 within the framework of LCDM simulations. Additionally, we explore modified gravity models, including the chameleon-screened Hu-Sawicki f(R) model and the normal-branch Dvali-Gabadadze-Porrati (nDGP) model, to understand their impact on void statistics.
Utilizing a model emulator, we delve into the constraining power of studying void abundance and shape within the context of redshift surveys. Through this research, we aim to gain valuable insights into the interplay between void properties and cosmological parameters, shedding light on the potential implications for modified gravity theories.
Stasyszyn, F.
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Are cosmological voids magnetised enough?
We study the magnetization of cosmic voids by galaxies and from primordial origins. Star-forming galaxies within the voids, a part of a voids volume is expected to be filled with magnetic field.
Lunch
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Wolovick, N.
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Cómo armar un HPC Latinoamericano
¿Existe el HPC en Latinoamérica? ¿Cómo es? ¿Cuál es su futuro? ¿Para qué tenerlo?
Desde el CCAD-UNC armamos algo que creemos que es interesante. Una forma distinta de hacer HPC en Argentina y en Latinoamérica. Está pensada para y por nosotros. Detectamos los problemas de otras estrategias y vamos exactamente para el otro lado.
En esta charla intentaré contarles estas ideas que construimos muchas personas, a lo largo de más de 14 años de trabajo continuo.
Tal vez se puedan extrapolar, o mejor dicho, este es nuestro deseo.
Colazo, P.
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Structure formation with PBHs to alleviate early star formation tension revealed by JWST
This letter explores the potential role of primordial black holes (PBHs) to address cosmological tensions as the presence of more massive than expected galaxies at high redshifts, as indicated by recent James Webb Space Telescope observations. Motivated by inflation models that enhance power at scales beyond the observable range that produce PBHs with Schechter like mass functions, we aim to explain the excess of high redshift galaxies via a modification of the $Lambda$ Cold Dark Matter power spectrum that consists in adding (i) a blue spectral index $n_b$ at $k_{text{piv}}=10/$Mpc and (ii) Poisson and Isocurvature contributions from massive PBHs that only make up $0.5%$ of the dark matter. We simulate these models using the SWIFT code and find an increased abundance of high-redshift galaxies in simulations that include PBHs. We compare these models to estimates from James Webb Space Telescope observations.Unlike the $Lambda$ Cold Dark Matter model, the inclusion of PBHs allows us to reproduce of the observations with reasonable values of star formation efficiency. Furthermore, the power spectra we adopt potentially produce PBHs that can serve as seeds for SMBHs with masses $7.57 times 10^4 M_{odot}$.
Padilla, N.
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Coulomb to Gravitational force ratio and galaxy formation
A small imbalance of electric charge of a few in ~1e36 particles is expected for a gas in hydrostatic equilibrium, as first noted by Rosseland (1924). This imbalance equals the ratio of gravitational to Coulomb forces between two protons, and it allows electrons which are significantly less massive, to remain bound to a galaxy. This charge excess is small enough that it can be safely ignored in most cases. On the other hand, the origin of cosmic magnetic fields is still unresolved, as it requires a seed field for which there are several contending proposals. Using current knowledge of galaxy formation we estimate the net charge for a rotating protogalaxy to produce the required seed. The resulting charge represents an imbalance that is consistent with Rosseland's. We will describe this and other possible consequences of a Rosseland charge imbalance for galaxy formation and evolution.
Fabris, J.
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Newtonian theory with variable G
We construct a consistent Newtonian theory with variable G. Some astrophysical and cosmological implications are described. In particular, solutions exhibiting accelerated expansion of the universe are possible due to the variation of the gravitational coupling.