PROGRAM

Chile, Universidad Andrés Bello

The role of galaxy cluster in the mass-metallicity relation

Abstract:
Evolution of the MZR at z~0.3 with star forming galaxies in the AC114 galaxy cluster. The mass-metallicity relation (MZR) and its evolution is understood very well. However, the construction of this correlation is generally done with field galaxies. Therefore the physical processes studied involve only the intrinsic properties of galaxies. In this work, we study the evolution of the MZR by using star-forming galaxies of the AC114 galaxy cluster located at z~0.3. We study the role of galaxy clusters in the MZR. We found a change in the slope of the MZR with respect to the constructed with field galaxies at the same redshift. This feature can be the result of the quench of the star-formation rates when galaxies interact with the intra-cluster medium.

Argentina, IAFE

X-ray binary feedback over the interstellar and intergalactic media

Abstract:
The properties of the first generations of stars formed at the Cosmic Dawn (10^8 − 10^9 yr after the Big Bang) and their influence on the subsequent evolution of galaxies are fundamental research topics in extragalactic astrophysics. Several authors have suggested that X-ray binaries (XRBs) may have contributed significantly to the energy feedback into their environment at that epoch, participating in the regulation of the cosmic star formation and the ionization state of the intergalactic medium [1, 2, 3]. The determination of the properties of XRB populations in the Early Universe is therefore important. This can be done by exploring XRB populations in low-metallicity galaxies at redshift zero, which are assumed to be the local analogs of those prevailing at Cosmic Dawn [4, 5, 6]. To this aim, we investigated the correlations between X-ray luminosity, star formation rate, mass and metallicity of a sample of local galaxies in which XRBs have been detected. We compared them with the general sample of local galaxies [7, 8, 9], finding a bias towards low metallicity in the former. After homogenizing the data we discarded the possibility of the bias being caused by some systematics. We modelled XRB populations using cosmological hydrodynamical numerical simulations of galaxy formation and evolu- tion [8, 9], coupled to our XRB population synthesis model, to determine the origin of this bias. In this poster we show our preliminary results which suggest that the bias may arise in the effect of the metallicity dependence of XRB evolution on the properties of the population, in agreement with previous results.

[1] I. F. Mirabel, et al., 2011A&A…528A.149M
[2] M. C. Artale, et al., 2015MNRAS.448.3071A
[3] V. M. Douna, et al., 2018MNRAS.474.3488D
[4] V. M. Douna, et al., 2015A&A…579A..44D
[5] Lehmer B. D., et al., 2019, ApJS, 243, 3
[6] Lehmer B. D., et al., 2021, ApJ, 907, 17
[7]Mannucci, F., et al. 2010MNRAS.408.2115M
[8] Pillepich, A., et al., 2019MNRAS.490.3196P
[9]Schaye, J., et al., 2015MNRAS.446..521S

Argentina, Facultad de Ciencias Astronomicas y Geofisicas

The assembly process of massive ellipticals in colours: optical/IR photometry of NGC 1395.

Abstract:
Massive elliptical galaxies are known to host ancient and metal-rich stellar populations, and also are found in the densest regions of the Universe. Those stellar populations are considered equivalent to fossil records of the star formation history and the chemical evolution of the ISM during the early stages of the Universe. This early epoch was also the time of the formation of globular clusters (GC). Being a good approximation to single stellar populations, it is believed that they store recoverable information about the environmental conditions at the time and place of their formation. In such a context, the existence of distinct subpopulations of GC holds clues to the star formation history, assembly and evolution of the galaxies that host them.
This poster presents the analysis of the assembly process of the massive early-type galaxy NGC 1395. To do so, we have combined optical and near-infrared GC photometry obtained with the Gemini-South telescope. Different subpopulations of GC candidates are identified in several colour planes. Special emphasis is placed on the combination of different photometric bands in an attempt to minimise the effects that horizontal branch stars may have on the age-metallicity degeneracy. The spatial distribution of the identified subgroups is also studied. These results are analysed in the context of the two-phase formation scenario of massive elliptical galaxies.

Bolivia Instituto de Astrofísica – Pontificia Universidad Católica de Chile (IA-PUC)

Perturbation effects and the evolution of giant Low Surface Brightness Galaxies: the case of Malin 1

Abstract:
Low surface brightness galaxies (LSBGs) dominate the volume density of galaxies in the universe; however, given their low surface brightness, they are difficult to detect, introducing biases in the statistical analysis of galaxy populations. A correct and complete theory of galaxy formation and evolution should include them. Giant low surface brightness disk galaxies (gLSBGs), on the other hand, have extended neutral Hydrogen. One of the most impressive gLSBGs is Malin 1, given its 200 kpc stellar disk with giant spiral arms, a flat rotation curve, low star formation, low dust, and a possible giant dark matter halo. Its environment shows at least three possible interacting galaxies, exo-Malin 1, Malin 1A and Malin 1B. Also, it is apparent a giant stellar stream extending from Malin 1 centre to a galaxy located to the NE, the so-called galaxy exo-Malin 1. Finally, a possible hole or cavity within its disk is observed at the south of the disk of Malin 1. These features could be evidence of past or current perturbations in Malin 1. In this work, we are proposing to study perturbation effects and their impact on the evolution of this type of galaxies, all focused on Malin 1. To do that, we will use N -body simulations constrained by observations. This will allow us to model the internal and orbital evolutionary histories of Malin 1 and its satellite candidates, which will in turn allow us to improve the galaxy formation and evolution models for gLSB galaxies in general.

Argentina, Instituto de Astronomía y Física del Espacio (IAFE) – UBA

Cosmic Rays at the Epoch of Reionization

Abstract:
The reionization of the intergalactic medium (IGM) during the Cosmic Dawn is an important open problem in Cosmology. The radiation produced by the first galaxies would not have been enough to maintain the ionization fraction of the IGM at large scales, therefore complementary ionization agents have been proposed, including cosmic rays (CR) that escape from those galaxies. In this poster, we investigate the ionization of the IGM produced by the electromagnetic cascades initiated by CR electrons, emphasizing the contribution of secondary photons, which has not been extensively explored yet. We simulated the transport of all the particles comprising the cascades and calculated the rate of ionization and the distribution of energy between the particles and the IGM. Our results show that high energy electrons carry energy far away from the source while ionizing the medium in their path, whilst those with kinetic energies lower than a few keV cool completely via ionization within a distance of kiloparsecs, reinforcing the results of previous works and extending their predictions to higher energy electrons and farther distances from the source. In addition, we show for the first time that photoionization by secondary photons produced in high-energy cascades may contribute significantly to the ionization of the IGM. This particular result implies a significant ionization rate in the far IGM that has not been considered by previous works. Finally, we evaluate the ionization rate at any point in the IGM in terms of the properties of the galaxy population present during the Cosmic Dawn as predicted by cosmological simulations of galaxy formation.

Argentina, FaMAF – UNC

Galactic Stellar Haloes in ΛCDM simulations

Abstract:
Using the cosmological hydrodynamic simulation TNG50-1 we characterize stellar haloes (SHs) of galaxies with stellar mass in the range 8.0 < log M*/M☉ < 11.0 in a ΛCDM Universe. Defined as the stellar component at distances between twice the stellar half-mass radius (2r*) and the virial radius (r200), we studied the stellar mass (MSH), the size (rvir/2r*) and the spherically averaged density profile (ρ(r)) of isolated central galaxies’ SH at redshift z = 0 and analyzed their relation to intrinsic properties of the galaxy. We calculate the density profile’s logarithmic slope α, finding values -10 < α < -2 and that: i) strongly correlates with the SH mass fraction (fM); ii) is inversely proportional to the galaxy rotational support κrot; and iii) unlike what is reported in the literature, we do not find a tendency between the SHs slope α and the virial mass M200 for dwarfs galaxies. These results aim to predict and compare simulated and observed SHs properties for galaxies with mass lower than the Milky Way or Andromeda, suggesting that outer regions of galaxies could be good estimators of their intrinsic properties in a wide mass range.

Argentina, CASLEO (CONICET-UNLP-UNC-UNSJ) & FCAG (UNLP)

Sersic’s Law in dwarf elliptical galaxies: a history more than 30 years long

Abstract:
Driven by the widespread use of CCD detectors starting in the mid eighties of last century, surface photometry of galaxies experimented a noticeable expansion, alongside a significant increase in precision. This allowed, for the first time, detailed studies of low-surface brightness objects, such as dwarf elliptical galaxies (dE). While the surface brightness profiles of luminous elliptical galaxies (E) used to be fit with a de Vaucouleurs law, the Exponential Law was used for dEs, in analogy to stellar disks. It was soon evident that both mathematical expressions gave adequate fits just for particular cases of profiles that, in reality, display a continuous curvature distribution. Sersic’s Law was thus rescued from oblivion, showing its powerful ability to properly quantify different profile curvatures, in a
way that opened the possibility of studying, on a firm basis, the relationships between different structural parameters of early-type galaxies. We present here a brief review of our work with Sersic’s Law and dwarf galaxies along 30 years, including the controversy that arised regarding its usefulness as a distance indicator.

Argentina, IATE

Gravitational effects in galaxy pairs

Abstract:
In this work, we use photometric data from the ODIN (One-hundred-deg2 DECam Imaging in Narrowbands) survey and spectroscopic data from the DESI (Dark Energy Spectroscopic Instrument) to study galaxies in pairs. We aim to investigate the interactions of galaxies at high redshift to learn about the gravitational effects of neighboring galaxies on the central ones. Our study will complement knowledge about the dynamics of disc galaxies, enriching our understanding of gravitational effects and environments.

Brazil, Valongo Observatory, UFRJ

Stellar mass distribution in barred galaxies through multi-band decomposition in the mid-IR

Abstract:
Observing galaxies in the Local Universe, we frequently identify an elongated central structure composed of gas and stars, called a bar – present in ∼ 65% of spirals. This structure strongly transforms its host galaxy, causing intense movement of gas and stars, breaking the axisymmetric disk dynamics and affecting its evolution. We choose the mid-infrared to focus on lower mass stars – which are the majority – and avoid obscuration caused by dust. We aim to study the amount of stellar mass involved in this structure, and how it might influence the galaxy as a whole. For this we use data for 371 barred galaxies
from the Spitzer Survey of Stellar Structure in Galaxies (S4G). S4G consists of imaging in the 3.6 and 4.5 μm bands for more than 2300 nearby, large and bright galaxies obtained by the Spitzer Space Telescope. The S4G team made a publicly available GALFIT-based decomposition in the 3.6 μm band. This 2D image decomposition fits different stellar components — including bulge, disk, bar, nuclear point source and/or secondary disk — resulting in a final decomposition model with 1-4 components for each galaxy. Knowing the flux contained in each component from the decomposition, we can estimate the stellar mass of such structures. We compared samples of galaxies with different global masses and found that there seems to be a trend towards more massive galaxies, and with a bulge in the galaxy model, with bars with a higher relative mass. We found that bars are less present in lower mass galaxies (M∗ < 10^9 M⊙, about 38%). This is consistent with bar fraction studies that suggest that lower-mass galaxies are still acquiring and growing their bars. We are working to include the 4.5 μm band, with a multi-band decomposition of the bands 3.6 and 4.5 μm using GALFITM – GALFIT’s version that allows simultaneous multi-band decomposition – to build a model for our galaxies. As we advance in our multi-band decomposition, we will be able to draw more accurate conclusions on how the stellar mass contained in the bar influences other global properties of the host galaxy.

Brazil, IF(UFRJ)

Recovering the origin of lenticular galaxies by studying their multi-wavelengths Sersic index profiles, for different bins of mass and star formation

Abstract:
Lenticular galaxies account for more than 50% of massive galaxies in the local Universe; yet their formation mechanisms are still unclear, specifically which is the role of the galaxy mass and the surrounding environment in the formation of lenticular galaxies and if some low mass S0s could be primordial objects. Recent (and not so recent) works have pointed out that S0 galaxies could be a group of very different objects, sharing a similar isophotal profile. Indeed, a clear definition of the properties of lenticular galaxies is still missing in the astronomical community. In this work we make use of SPLUS multi-wavelengths data to define the main photometric parameters characterizing S0 galaxies, using GALFITM to fit the 5 broad and 7 narrow bands. Moreover, performing a SED fitting using Lephare, we can obtain galaxy masses and specific star formation rate (sSFR). We study the relation between Sersic index, bulge-over-total (B/T) light ratio, colour, masses and star formation rate for a sample of ~400 lenticular galaxies in the Stripe 82. Among others, we find a correlation between B/T and the sSFR, which suggests a correlation between bulge growth and star formation quenching. We aim at connecting this findings with environmental measures, obtained using S-PLUS photometric redshifts and/or available in the literature.

Brazil, IF (UFRJ)

Multiwavelegths analysis of galaxies’morphologies and their internal structure

Abstract:
We will present preliminary results obtained analysing a sample of bright galaxies in the AEGIS field with GALFITM ( a multiwavelength implementation of GALFIT – to perform parametric fits of galaxy images), using the 54 narrow and 4 broad band miniJPAS images. GALFITM allows us to decompose the galaxy light into its different components, such as bulge, disk and AGN, when present. We study the wavelength variation of the recovered morphological parameters, especially the Sersic index and effective radius, for different galaxy morphologies and sub-components. For a subsample of galaxies we investigate the radial variation of galaxies’ properties, such as stellar mass density and specific star formation rate, for different Sersic indexes of the bulge. Finally, we are now exploring the multi wavelengths residual images.

Argentina, IAETE – OAC

Properties of disks and spheroids in the Illustris-TNG and EAGLE simulations

Abstract:
Galaxies are complex stellar systems formed by several overlapping stellar components (bulge, disk, bar, etc.) whose formation and evolution process is inherently related to the individual processes undergone by each of them. We study the properties of discs and spheroids by applying two dynamical decomposition methods to a sample of galaxies with stellar masses > 10^10 M⊙ identified in the EAGLE and IllustrisTNG cosmological numerical simulations. In agreement with observational results, we find that the stellar mass fraction in the spheroidal component fsph increases systematically with galaxy stellar mass M∗ from fractions of 50% for galaxies of M∗ ∼ 10^10 M⊙ to 90% for M∗ ∼ 10^12 M⊙, although with a fair amount of scatter. For galaxies with stellar masses similar to that of the Milky Way (M∗ ∼ 10^10.6 M⊙) and applying isolation criteria we find fsph ∼ 0.2 at best which is only slightly higher than the lowest values estimated observationally for local galaxies fsph ∼ 0.15. This would indicate that the cosmological volume simulations are capable of reproducing a population of disk galaxies comparable to those observed. In addition, we perform the extension and analysis of the scaling relations between mass, specific angular momentum and characteristic velocity of disks and spheroids and how they compare with those of full galaxies and those obtained observationally, such as the Tully-Fisher and Faber-Jackson relations. In addition, the dimensionless spin parameter of the halo and the stellar components are analyzed, finding that there seems to be no correlation between them. These results show how closely the formation and evolution history of the galaxy is linked to that of each of its components.

Brasil, Instituto de Astronomia, Geofísica e Ciências Atmosféricas
What drives the corpulence of galaxies?

Abstract:
Dwarf galaxies have a variety of sizes (stellar half-mass radii), at given stellar mass, in the present-day Universe. This suggests different scenarios of evolution according to their final size. In this work, we compare the evolution of compact and normal dwarf galaxies in the Illustris TNG50 cosmological hydrodynamical simulation. We denote Compact those dwarf galaxies (log(M/M⊙) between 8.3 and 9.3) that end up in the low-size (r1/2 < 450 pc) branch at z=0. We then compare the median evolution of relevant physical parameters and radial profiles to understand the different evolution of the Compact population. In TNG50, Compact galaxies are rounder at z = 0 and their current environments are fairly similar. However, at z ∼ 1, the sizes (half-mass radii of the stellar component) of their most massive progenitors begin to decrease relative to those of normals, while their gas half-mass-radii and stellar masses evolve similarly to those of normal galaxies. This is related to star formation concentrated (suppressed) in the inner (outer) region of the galaxy, which is due to efficient gas infall associated with the lower density environment and fewer interactions for the Compact galaxies that otherwise pump angular momentum into normal galaxies. In TNG50, the formation of Compact galaxies is driven by the lack of mergers and interactions, in contrast with the popular idea of merger-driven compaction at high redshift for more massive compact star-forming galaxies.
Also, we find that external contributions through interaction are important for dwarf galaxies to have larger sizes and become diffuse.

Chile, Universidad de Valparaíso/IFA
Abundance of Primordial Black Holes from Optical and X-ray Quasar Microlensing Observations: Constraints to the Dark Matter Fraction

Abstract:
Quasar microlensing is a very powerful tool that allows us to estimate the mass and the abundance of any kind of compact object in the lens galaxies. According to the mass range considered for the compact objects and the size of the source, we are able to account for the effect of the microlenses to each macro image of the source and obtain the corresponding magnification maps. Recent results coming from GW experiments (LIGO/Virgo) raised again the interest in studying other candidates of BHs to be part of the elusive DM nature. I present the results of using optical (Esteban-Gutierrez et al. 2022a, 2022b) and X-ray (Esteban-Gutierrez et al. 2023) microlensing magnification measurements and computing magnification maps taking into account a population of stars and PBHs in the simulations. Then, we apply a Bayesian analysis to calculate the Probability Density Functions (PDFs) for the individual abundances of PBHs and stars, to see if the PBH fraction obtained could explain the observed amount of DM in these lens galaxies. The mass range explored from planetary to intermediate-mass PBHs (∼10−3Msun – 60Msun) provides an additional constraint to the DM fraction and establishes the strongest bounds according to other microlensing studies (Esteban-Gutierrez et al. 2023).

Argentina, UNSJ-CONICET

Nuclear Rings in Simulated and Observed Galaxies: A Comparative Analysis between TNG-50 and SDSS-DR14.

Abstract:
In this study, we investigate the presence and properties of nuclear rings in the TNG-50 simulation and compare them with their observational counterparts from the SDSS-DR14 catalog. Nuclear rings are intriguing astronomical structures, the understanding of which provides valuable insights into galaxy formation and evolution.

Using data from the TNG-50 simulation, we identify and characterize a sample of nuclear rings in galaxies at different stages of their evolution. We analyze various properties to gain a better understanding of their dynamics and the physical processes that give rise to them. Subsequently, we conduct a comparative study with data from the SDSS-DR14 to verify whether the properties of nuclear rings in TNG-50 align with real observations. We evaluate their similarities and differences, highlighting the utility of cosmological simulations like TNG-50 in enhancing our understanding of these structures.

Argentina, Famaf-IATE

Low-frequency Radio Astronomy and Gravitational Waves in the study of Primordial Supermassive Black Holes

Abstract:
The formation of the first galaxies marks a significant transition in the evolution of structure in the Universe. These same galaxies with their zero metallicity Population III stars, second generation Population II stars, and black hole-driven sources (mini-quasars, x-ray binaries, etc.) transformed the intergalactic medium (IGM) from neutral (XHI) to ionized (XHII)—this process known as the Epoch of Reionization (EoR).

We analyze the evolution of neutral Hydrogen (HI) through semi-numerical simulations (21cmFAST, BEoRN, 21cmTOOLs, etc.) generating tomographies in a comoving volume (Lightcone). Because the 21cm HI signal is approximately five orders of magnitude smaller than the Foreground, generated by the synchrotron radiation of the galaxy and different astrophysical sources (galaxies, quasars, etc.).

Quasars are the most luminous non-transient sources in the epoch of cosmological reionization and are powerful probes of the intergalactic medium (IGM) at that time. This work covers current efforts to identify high-redshift quasars and how they have been used to constrain the reionization history.

We analyze the new data (CEERS, JADES, GLASS) from JWST (AGN type1, 5 < z < 16) and

Finally, we aim at characterizing the cross-correlation signal between Line intensity mapping (LIM) and Gravitational Wave (GWs),focusing on the LIM of the neutral hydrogen (HI) from the proposed 21cm IM survey with the SKAO and on resolved GW events from the merger of BBHs as detected by the EinsteinTelescope (ET). A cross-correlation signal is expected because both HI and GWs trace the cosmic density field.

Chile, Universidad de La Serena

Low X-ray Luminosity Clusters in the eROSITA Era: The Special Case of AS555

Abstract:
Galaxy clusters are the largest gravitationally bound structures in the universe, and they are considered excellent laboratories for studying galaxy evolution and the large-scale structure (LSS) of the universe. Following this idea, great efforts have been made to study these systems at multiple wavelengths. For example, in X-rays using ROSAT space observatory, the intracluster medium (ICM) of these clusters has been detected over the whole sky, but with a bias towards more massive systems due to instrumental limitations.
Considering this, galaxy clusters of low X-ray luminosity are defined as those having Lx < 10^44 erg/s in the [0.1-2.4 keV] band, and currently, with the instrumental capabilities of eROSITA, even more of these systems can be detected, and therefore we can study them with greater statistical significance.
In this work, we present results of a detailed study of the nearby cluster (z = 0.044) Abell S555 (AS555), using optical images from DECaLS DR10, eROSITA X-ray catalogs and information obtained from the literature (e.g. BCG integral field spectroscopy). This cluster meets the definition of low X-ray luminosity considering the ROSAT data and qualitatively appears to have a relaxed dynamical state in the optical. However, eROSITA detected 3 peaks of its ICM, which could indicate active gas dynamics. Consequently, this study will serve as the kickoff for an even larger one, using the large volume of data from the DEROSITAS survey.

Argentina, UNSa

Evolution of dynamically identified stellar components in simulated galaxies.

Abstract:
Galaxies are complex systems that result from the combination of various stellar components, which interact with each other as they coexist spatially and temporally, such as the disk, the stellar halo, the nucleus, etc. Therefore, understanding how each of them evolves is essential to grasp the evolution of the galaxy as a whole. In this work, we present an advancement of the undergraduate special project, where we dynamically decompose and study the properties of both the disk and the spheroid of a simulated galaxy generated from ad-hoc initial conditions and evolved to reach equilibrium using the GADGET-2 code. Subsequently, we evolve the merger of two galaxies with similar stellar masses until the system reaches equilibrium. We dynamically decompose the resulting galaxy and compare the properties of the new components with those of the original components.

Argentina, IATE – FaMAF

The impact of orbital history on star formation

Abstract:
It has been observed that internal and external factors significantly influence the star formation of galaxies, depending on both their stellar mass and the environment in which they have evolved. In this work, we present a preliminary analysis of the conditions that lead to the quenching of star formation in groups of galaxies using the hydrodynamical cosmological simulations IllustrisTNG 300-1. Our focus is on the population of galaxies in transition, known as the Green Valley, as well as those galaxies that have completed an orbit around the system and are currently outside the virial radius, referred to as backsplash galaxies.

Argentina, IALP

Analysis of disc instabilities in barred galaxies using the TNG50 simulation

Abstract:
Bars are very common structures of galaxies, observed in a large fraction of disc galaxies. However, the underlying mechanisms that determine why certain galaxies develop bar structures while others of comparable mass and morphology do not are not fully understood, remaining a subject of debate.
The aim of this work is to identify the physical processes involved in the formation of bars, using the TNG50 simulation. For the barred galaxies, we calculate the bar strength and formation time and we assess the ability of different dynamical processes, such as interactions and fusions with nearby galaxies (external processes), to give place to the formation of bars. Finally, we evaluate the efficiency of different instability criteria in predicting bar formation.

Chile, Universidad de La Serena

NIR Analysis of Milky Way X-ray Sources in the Zone of Avoidance using Machine Learning Tools

Abstract:
Automated methods for classifying extragalactic objects in extensive surveys offer significant advantages over manual approaches in terms of efficiency and consistency. However, the presence of dust extinction near the Galactic disc poses additional challenges. Few studies have explored the application of machine learning (ML) in the Zone of Avoidance (ZoA), characterized by high extinction levels, star crowding, and limited data and studies. One recent study (Daza et al., 2023) employed ML to classify Galaxy and non-Galaxy objects in the VVV and VVVx surveys. Another study (Zhang et al., 2021) used ML to classify STAR/GALAXY/QSO in the 4XMM-DR9 survey, which includes the ZoA.

In this research, we investigate the challenges and benefits of using ML tools for galaxy classification in the ZoA and explore the implications of environmental factors on classification results and their reliability. We address the hypothesis that the analysis area should have conditions similar to the training set, which is not the case in the ZoA. Our analysis reveals significant differences between the sample galaxies and those found throughout the Galactic disc, mainly due to the lack of information on galaxies in the Galactic plane in the training set. Some chosen regions of interest within the ZoA exhibit a high probability of being a galaxy in X-ray data but closely resemble extended Galactic objects.

Our findings emphasize the complexities of using ML for galaxy classification in the ZoA and underscore the importance of considering environmental factors and data distribution to enhance the reliability and accuracy of future studies in this challenging region.

Chile, Universidad de La Serena

Galaxy Clusters candidates in the Zone of Avoidance

Abstract:
Here we present our results about to identify galaxy overdensities and characterize galaxy clustering in the Zone of Avoidance. We use different clustering algorithms to identify galaxy overdensities: the Voronoi tessellations, the minimum spanning tree, and the ordering
points to identify the clustering structure. We studied the membership, isolation, compactness, and flux limits to identify compact groups of galaxies. Each method identified a variety of galaxy systems across the Galactic plane that are publicly available. We also explore the probability that these systems are formed by concordant galaxies using mock catalogues. 19 galaxy systems were identified in all of the four methods. They have the highest probability to be real overdensities. We stress the need for spectroscopic follow-up observations to confirm and characterize these new structures.

Argentina, IATE-OAC

Structure, kinematics and chemical evolution of the SMC

Abstract:
Star clusters can help to understand the dynamic and chemical history of their host galaxy, and viceversa. Our group has been systematically analyzing the SMC star clusters in order to understand how the interaction of this galaxy with (mainly) de LMC has driven its structure, kinematics, star formation and chemical enrichment processes. For this we have used the observational information provided by the photometric survey VISCACHA (http://www.astro.iag.usp.br/~viscacha/index.html) and its GMOS/GEMINI spectroscopic follow-up. In this work we will present a summary of the main results obtained by these international collaborations between Brazil, Chile, Argentina and Mexico.

Argentina, IATE

Vorticity and angular momentum in cosmological filaments

Abstract:
Cosmic filaments are anisotropic environments that influence the angular momentum (AM) evolution of dark matter halos. Anisotropic tidal torque theory (ATTT) proposes a mechanism for acquiring AM based on geometry, and has been used to explain the alignment of AM with filaments (spin-flip phenomenon) observed in simulations. This work contrasts the ATTT model predictions with measurements of dark matter halos and filaments in IllustrisTNG simulations.
We find that the vorticity field in these environments closely aligns with the ATTT predictions. Furthermore, it is found that the shape of the filament and the direction of the most massive node create a coordinate system that facilitates the constructive summation of vorticities from different environments. Although a correlation is detected between the AM orientation of the halos and the local vorticity, the AM-filament alignment does not follow the same patterns as the vorticity-filament alignment, suggesting a weak or non-existent causal relationship between the two phenomena.

Argentina, FaMAF

Simulated BCGs: the interplay between their SMBHs  and the formation of stars over time

Abstract:
We study the relationship of nuclear activity (AGN) and star formation in the brightest galaxies of galaxy clusters (BCGs) exploiting a set of hydrodynamic simulations. Throughout the evolution of this set of galaxies, there can be found periods in which the black hole accretion rate and the star formation rate are correlated, as well as periods with no evident correlation. We study the evolution of this correlation and its possible relation with the onset of the radio mode in the accretion of the central SMBHs.

Argentina, UNSJ CONICET

Characterising the HOD in filamentary structures

Abstract:
The standard paradigm for the formation of the Universe suggests that large structures are formed from hierarchical clustering by the continuous accretion of less massive galaxy systems through filaments. In this context, filamentary structures play an important role in the properties and evolution of galaxies by connecting high-density regions, such as nodes, and being surrounded by low-density regions, such as cosmic voids. The halo occupation distribution (HOD) is a powerful tool for linking galaxies and dark matter halos, allowing constrained models of galaxy formation and evolution. In this work we combine the advantage of halo occupancy with information from the filament network to analyse the HOD in filaments and nodes.

Mexico, IRyA – UNAM

Star formation histories of cluster galaxies at high- and
low-redshift

Abstract:
The observed properties of galaxies are strongly dependent on both their total stellar mass and their morphology. Furthermore, the environment is known to play a strong role in shaping them. The galaxy population in the local universe that is located in virialized clusters is found to be red, poorly star-forming, and mostly composed of early morphological types. Towards a holistic understanding of the mechanisms that drive
galaxy evolution, we exploit data from the WINGS/OmegaWINGS local (0.04 < z < 0.07) galaxy cluster survey and the spectrophotometric code
Sinopsis, to study the role of both the local and global environments affecting stellar properties of galaxies such as star formation rate and
star formation histories. We attempt to disentangle their effects from the intrinsic characteristics of the galaxies, in shaping the star
formation activity at fixed morphological type and stellar mass.
Using data from the EDisCS (0.4 < z < 1.0), we compare our main results at low-z with those at intermediate-high redshift. We confirm some known findings, such as the morphological evolution through cosmic time and the larger star formation rate on the main sequence at higher redshift.
We also determine that clusters may have been more efficient in quenching star formation in the past, and we propose that the general
higher star formation activity in galaxies at these redshifts may explain the Butcher-Oemler effect.

Argentina, Famaf-IATE

A CMB lensing analysis of the extended mass distribution of clusters

Abstract:
Abstract: We study the anisotropic weak lensing signal associated with the mass distribution of massive clusters of galaxies using the Cosmic Microwave Background data. For this purpose, we stack patches of the Planck Collaboration 2018 CMB lensing convergence map centered on SDSS DR8 redMaPPer clusters within the redshift range [0.4, 0.5].
We obtain mean radial profiles of the convergence parameter k finding strong signals at scales as large as 40 Mpc/h. By orienting the clusters along their major axis defined through the galaxy member distribution, we find a significant difference between the parallel and perpendicular oriented convergence profiles. From a model with an anisotropic surface mass density, we obtain a suitable agreement for both mass and ellipticities of clusters compared to results derived from weak lensing shear estimates, finding strong evidence of the correlation between the galaxy cluster member distribution and the large-scale mass distribution.

Argentina, Famaf-IATE

Title: Spatial orientation of planetary nebulae in the Milky Way

Abstract:
Planetary nebulae (PN) are remnants of intermediate-mass stars, which consist of an expanding envelope of low-density ionized gas that is very susceptible to change by electromagnetic effects within galaxies. These can be produced by, i.e., charged dark matter particles, effects of long duration such as the magnetic field of the galaxy or even interactions with the interstellar medium. PN present disparate morphologies, mostly non-spherical, which allows us to define an angle between their major-axis and some point of reference within our galaxy. However, the challenge in studying PN orientations lies in the fact that astronomical observations are two-dimensional projections of three-dimensional distributions on the celestial sphere. Thus, it is non-trivial to distinguish a real oriented distribution from a random one.  In this work we used Montecarlo simulations to study the signal given by a flux limited sample of PN distributed with the density profile of a spiral galaxy. We analyzed two samples: one with a preference for pointing towards the galaxy’s center and another with a random orientation. We investigated how the signal varied under different scenarios and compared the results with observational data. We found that with the current data, random orientation cannot be ruled out yet.

Argentina, Facultad de Ciencias Astronómicas y Geofísicas, UNLP

The chaotic recent past of NGC 4546 vs. the peaceful life cycle of the stars.

Abstract:
NGC 4546 is an S0 galaxy, located in a low-density environment that hosts a Low-Luminosity Active Galactic Nuclei (LLAGN) of the LINER (Low-Ionization Nuclear Emission Region) class. Its very central region (200pc) was studied by means on GMOS/IFU data and it’s thought that the LINER is surrounded by an old stellar population whose embedded gas emission mimics that of the LLAGN itself. Such a scenario is known as the HOLMES (HOt Low-Mass Evolved Stars) emission.
However, the galaxy shows signs of having undergone an efficient accretion process as a consequence of a rather recent minor merger with a dwarf galaxy, whose tidally disrupted core (the Ultra Compact Dwarf NGC4546-UCD1) is kinematically decoupled from the NGC 4546 disk. That is, its non-negligible gas content is clearly detected at kpc scales, and is counter-rotating with respect to the stellar population. The gas, however, rotates in almost the same direction as NGC4546-UCD1, from which the galaxy has accreted some globular clusters (in the context of the two-phase mechanism of assembly process of early-type galaxies).
Since this merger took place a few Gyr ago, we are dedicated to reanalyse the circumnuclear stellar population to finally unveil if the gas emission we see is due the HOLMES phenomenon, as suspected, or it is related to a younger episode of star formation, triggered by the merger.

Argentina, IATE-OAC

Full Spectrum Fitting of Globular Clusters

Abstract:
The pixel-to-pixel technique for spectral fitting has been proved to be very effective to infer stellar populations in extragalactic objects. Here we apply synthesis techniques to a sample of Globular Clusters observed in the optical, to obtain reddening, Ages, metallicities and mass. We also discuss the possibility of multiple populations in those objects.

Chile, Universidad de La Serena

Morphological Study of Galaxies in Clusters as Function of their Dynamical State

Abstract:
In the context of the standard cosmological model ΛCDM, massive galaxy clusters form hierarchically through merging and smooth accretion. The model predicts that numerous clusters of galaxies are in some stage of merging at any epoch. These processes are the most powerful events in the universe after the Big Bang, releasing energy at 10⁶⁴ erg/s, making them unique laboratories to study galaxy evolution. Under such conditions, galaxies may undergo violent processes that alter their physical properties and morphology. In this work, we present results on the characterization and estimation of the dynamical state of 12 clusters in the redshift range of 0.10 < z < 0.35. We study its influence on the morphology of their populations using parametric and non-parametric methods.

Chile, Universidad Andres Bello

High-Mass X-ray Binaries in Milky way/Andromeda type Galaxies

Abstract:
High-Mass X-ray Binaries (HMXBs) are systems composed of a massive star and a compact object (neutron star or black hole). Understanding their properties in the context of their host galaxies is crucial for unraveling their evolutionary history and contribution as progenitors of gravitational wave sources. Here we combine the stellar evolution synthesis code SEVN with the Milky way/Andromeda type galaxies catalogues from IllustrisTNG50 to model the formation and evolution of HMXBs within their host galaxies. In this talk, we present our preliminary results on the HMXB properties such as the mass of the compact object and companion star and their luminosity distributions and compare them with observations of HMXBs in the Galaxy. Finally, we will discuss how these findings can be extended to other galaxy populations in the future.

Argentina, Facultad de Ciencias Astronomicas y Geofisicas, La Plata (FCAGLP)

The color behavior of the Blazar PKS 2155-304: analysis of two decades of data taken at Argentine facilities

Abstract:
Blazars are a subclass of Active Galactic Nuclei (AGNs). Based on their emission and absorption line features at the optical range, they are divided into BL Lac and Flat Spectrum Radio Quasars (FSRQ). One of the main features of blazars is the presence of temporal variability in their flux across the entire electromagnetic spectrum. According to the color-brightness behavior, BL Lac objects tend to become bluer as the source’s brightness increases (Bluer when brighter, BWB), while FSRQs are more like redder when brighter (RBW). However, recent results have shown that both BWB and RBW objects tend to stabilize their color as their brightness increases even further, calling them Bluer-stable when brighter (BSWB) and Redder-stable when brighter (RSWB). Through the detailed study of the optical flux behavior in blazars it is possible to infer the conditions under which the observed emission is generated in the source.

In this work, we present the results obtained for the blazar PKS 2155-304, a BL Lac at z = 0.116. This object has been detected from Radio to TeV energies, being one of the brightest in the southern hemisphere. Our research group has observed this source at different Argentine astronomical facilities (e.g., CASLEO, Bosque Alegre), with data spanning over more than two decades. Using these photometric data, in this work we present the results of a detailed analysis of the V- and R-band behavior of PKS 2155-304, with emphasis on the spectral index changes. These results are compared with those reported in the literature.

Argentina, Instituto de Astronomía y Física del Espacio (IAFE)

The Role of Effective Yields as Feedback Tracers in EAGLE Galaxies

Abstract:
Feedback mechanisms, such as those driven by supernovae and active galactic nuclei, play a central role in regulating star formation and shaping the properties of galaxies. However, quantifying the impact and efficiency of these feedback processes remains an ongoing challenge in astrophysics. In this study, we use the EAGLE suite of cosmological hydrodynamical simulations to investigate the effects of implementing various feedback models on the formation and evolution of model galaxies. We focus on the analysis of effective yields, testing their capability to provide insight into the impact of feedback processes during the evolution of galaxies. By studying their role in 2D and 3D scaling relations, we analyze the connection between effective yields and different feedback scenarios. In this sense, our study contributes to advancing the understanding of the intricate interplay between feedback processes and galaxy evolution.