Resumen:

I will present our latest models to explain the formation of the luminous component of the smallest ultra-faint dwarf spheroidal galaxies, which according to standard cosmology should be the very first galaxies in our Universe and the basic building blocks for any larger galaxy. In our models we assume a low star formation in the central part of the dark matter halo forming stars in a fractal distribution, similar to what we see in larger star forming regions in our Milky Way. We follow the dynamical evolution of these stellar distributions for several Gyr until we see a similar luminous component emerging as we have observed with the ultra-faint population of dwarf spheroidal galaxies around our Milky Way.

Resumen:

Barred structures are hosted by a considerable fraction of galactic discs, spanning diverse environments and galaxy luminosities. The environment likely exerts a significant influence on bar formation, with tidal interactions leading to the emergence of elongated features resembling bars within galaxy discs. It is plausible that the structural parameters of bars resulting from tidal interactions in high-density galactic environments differ from those formed through internal disc instabilities in isolated galaxies. To test this scenario, a viable approach is to compare the structural parameters of bars in galaxies situated within distinct environments. We present the comparison between the two key structural parameters of bars, strength and radius, derived using a Fourier analysis on SDSS r band images, in galaxies situated within the Virgo cluster spanning a wide range in luminosities and galaxies of comparable luminosities found in environments characterized by lower galaxy densities. The analysis reveals that the bar radius exhibits a correlation with galaxy luminosity, indicating that larger bars are typically found in more luminous galaxies. When comparing galaxies with fixed luminosities, the field galaxies display larger bar radii compared to those in the Virgo cluster. However, when the bar radius is scaled by the size of the galaxy, the disparity diminishes. This is because galaxies of similar luminosities tend to be larger in the field environment compared to the cluster. Consequently, the scaled bars in the Virgo cluster and the field exhibit similar sizes. The findings of this study indicate that the size of galaxies is the parameter that is influenced by the environment, while the bar radius remains independent of the environment when scaled by the galaxy size. These results support the notion that the internal dynamics and intrinsic characteristics of galaxies play a dominant role in the formation and evolution of bars, regardless of the surrounding environment.

Resumen:

Early-type dwarf galaxies (ellipticals and lenticulars) represent the numerically dominant population of galaxies in the central regions of rich groups and clusters in the local Universe. As for their origin, several authors postulate that they are the result of the transformation of disk galaxies that fall into these groups and clusters, and that this transformation is due to the interaction with the intracluster medium and the other surrounding galaxies. However, the presence of low-luminosity early-type galaxies in low-density environments poses a challenge to this scenario, and the origin of these galaxies in such environments remains unclear. It is therefore crucial to study these stellar systems in poor groups and the field, with a focus on exploring their morphology, dynamics, stellar populations, and observational properties, all of which can help trace their evolutionary history. In this context, we present a comprehensive photometric and spectroscopic analysis of the lenticular dwarf galaxy CGCG014-074, located at a distance of 14 Mpc, using excellent quality data obtained by the Gemini Observatory. Our study entails an exploration of the photometric properties, stellar formation history, and internal kinematics of CGCG014-074 in order to discuss the evolutionary past of the galaxy and the possible genetic link it shares with its neighbour, the massive lenticular galaxy NGC4546.

Resumen:

Relic galaxies are massive, compact, quiescent objects observed in the local Universe that have not experienced any significant interaction episodes or merger events since about z = 2, remaining relatively unaltered since their formation. On the other hand, massive and compact Early Type Galaxies (cETGs) in the local Universe appear to show similar properties to Relic galaxies, despite having substantial accretion history. Relic galaxies, with frozen history, can provide important clues about the intrinsic processes related to the evolutionary pathways of ETGs through cosmic times. Through them, one may infer the role that mergers play in their evolution. Using the high-resolution cosmological simulation TNG-50 from the Illustris Project, we investigate the assembly history of a sample of massive, compact, old, and quiescent subhalos split by satellite accretion fraction. Relic galaxies are defined as subhaloes which present less than 10% of satellite accretion, while compact ETGs are the remaining ones. We compare the evolutionary pathways at three cosmic times, at z=2, z=1.5, and z = 0, using the orbital decomposition numerical method to investigate the stellar kinematics of each galactic morphological component and their environmental correlations. Our preliminary results indicate that compact ETGs and Relic galaxies’ dynamic pathways present differences at z=2 in all morphological components (disk, bulge, and halo). From z=1.5 to z=0 the stellar dynamics remain similarly consistent among the sample. Relics and cETGs do not show a clear preference for high or low-density environments, within the volume explored at TNG50, although progenitors of Relic galaxies were shown to be located in high density since z = 2.

Resumen:

It has been shown that low-mass central galaxies inhabiting the outskirts of massive systems can lead to a strong two-halo conformity signal, which is the correlation in color or SFR between the central galaxy and their neighbors. Recent studies suggest that this signal at z~0 could be strongly influenced by backsplash galaxies, which were satellite galaxies in the past but are identified as central galaxies in their halos at present. However, there is no certainty whether these galaxies can produce all the signal or if another large-scale environmental effect could also produce the conformity. Throughout this talk, I will present results from the evolution of parameters like host halo mass and star formation for low-mass central galaxies using the IllustrisTNG300 hydrodynamical simulation, as well as assessing the role of backsplash galaxies in the conformity signal at different epochs.

Resumen:

One of the interesting things to study in galaxies is the surface density of the star formation rate (SFR) and how although a galaxy can have a lot of star formation it could be inefficient. The star formation efficiency per free-fall time can tell us if the star formation rate is low compared to what is expected if all of the gas converts rapidly into stars. Also, another important thing to study is where exactly in the galaxy the star formation efficiency per free-fall time is high or low and which regions have a high or low star formation rate. I have measured the star formation efficiency per free-fall time in NGC 3256 using a method published by Utomo et al. (2018). NGC 3256 was chosen because this galaxy is the merger of two gas-rich galaxies. The method consists in dividing the galaxy into a map of hexagons and calculating average values in each hexagon. I calculated the free-fall time, depletion time, and star formation rate in order to finally calculate the efficiency per free-fall time. With the star formation rate and efficiency in every hexagon, it is possible to understand the specific characteristics of every part of the galaxy and to see where the galaxy is more efficient at forming stars. The result is different maps and plots that help to understand the star-forming behavior of NGC 3256 and detect if some regions are affected by the jet of the galaxy. This project is part of the Globalink Research Internship from Mitacs under the supervision of Dr. Christine Wilson from McMaster University in Canada. Mitacs is a Canadian not-for-profit organization that encourages research and innovation.

Resumen:

The chemical properties of the baryonic components of galaxies encode crucial information about the formation and evolution of the structure in the Universe. In this work, we study the chemical evolution of galaxies since early cosmic times until the present by using state-of-the-art numerical cosmological simulations. We analyze the evolution of nuclei abundances of galaxies inhabiting halos of different masses, considering physical models corresponding to different feedback scenarios. We pay particular attention to the connection between the chemical properties of different baryonic phases in galaxies (e.g. cold gas, hot gas, stellar component) and try to determine the existence of scaling relations between them which can be compared with observational data.

Resumen:

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.

Resumen:

Ultra diffuse galaxies (UDGs) are a subset of low surface brightness (LSB) galaxies characterized by their large effective radii $ r_e > 1.5$ kpc and low surface brightness. These galaxies have been found in a variety of environments, including the field, groups, and clusters of galaxies. The different properties of UDGs and their globular clusters across environment have raised the question about the role of the environment on UDGs evolution and the effects of environment on their globular cluster (GC) population. In this presentation, we will discuss our ongoing work studying the properties of UDGs and their GCs in different environment's and our preliminary work in the detection of UDGs and their GCs in the Fornax cluster. We are using data from the S-PLUS Fornax Project (S+FP) to study the galaxy population in Fornax and its outskirts, Utilizing SourceXtractor++ to detect UDGs in the clusters and their corresponding globular clusters. By using their GCs as tracer particles to constrain their origins, UDGs found in this work will help us to understand their formation and evolution in different environments by increasing the sample size of cluster UDGs and their GCs.

Resumen:

The evolution of galaxies presents a significant challenge due to the non-linear physics involved. Various approaches, such as semi-analytic models, have been made. These models use N-body simulations or the Press-Schechter formalism to generate merger trees and then add a baryonic description of the main physical processes. We use two semi-analytic models, GALACTICUS and SAGE, with the aim of comparing their results and understanding their agreement or divergence. We use the Millennium run, an N-body simulation, as input, we employ a minimal set of physical processes to analyze the performance of the models focusing on statistical analyses. We examine key aspects including black hole population and galaxy properties, seeking to unravel their strengths and weaknesses. This research contributes to the advancement of our knowledge in the galaxy evolution providing insights into the complex processes involved.

Resumen:

Faint and ultra-faint dwarf spheroidal galaxies, discovered in recent years, are a subclass of classical dwarf spheroidal galaxies with remarkably similar physical properties. These galaxies typically exhibit fainter luminosities ($L_{V}$ $\sim$ $10^{3}-10^{4}$ $L_{\odot}$) compared to classical dwarf spheroidal galaxies, and they are among the most dark matter-dominated systems known. Spectroscopic analyses have revealed the presence of extremely metal-poor stars within them, with metallicities as low as [Fe/H] = -4.0 dex. In a number of cases they also show distorted shapes probably due to the tidal interactions with the MW. These galaxies form in relatively dense background environments and are thought to be the building blocks of larger galaxies, making them useful probes of galaxy formation at the smallest scales. We perform numerical simulations using AMUSE and the direct N-body integrator ph4 to study a star formation scenario for faint and ultra-faint dwarf spheroidal galaxies based on the dissolving star cluster scenario, using Ursa Major II as an example. We consider the evolution for 5 Gyr of 4000 stars initially in virial equilibrium and randomly placed in different fractal distributions, within the central region of an analytical dark matter halo with a cored form, building up the luminous component of the galaxy. We conclude from the first simulations that after 2 Gyr there is no more evolution and everything comes to more stable state. Therefore, we don’t need to re-simulate for another 5 Gyr, as it would be the same as simulating for 12 Gyr. On the other hand, our results indicate a strong dependence on the scale-length of the dark matter halo, which could be deduced by measuring the half-mass radius from the luminous component at 2 Gyr.

Resumen:

It is well known that galaxy properties depend on their environment, with overdense regions having a low fraction of star-forming ($f_{SF}$) galaxies. However, it is unclear how galaxy properties such as velocity dispersion ($\sigma$), stellar mass ($M_*$), group halo mass ($M_h$), AGN activity, etc., collectively influence the $f_{SF}$ galaxies along the clustercentric distance ($R/r_{vir}$). Fortunately, large-scale surveys have provided an increase in the amount of reliable extragalactic data, which can shed light on these questions. In this context, we use a complete sample of galaxies in the Sloan Digital Sky Survey's Data Release DR18 along with a logistic regression model to account for the ten different galaxy properties across their entire range of values without binning to investigate how the $f_{SF}$ varies with galaxy properties as a function of $R/r_{vir}$ up to 20 virial radii. Also, we explore the effect of two different star formation rate (SFR) measurements in the $f_{SF}$ galaxies: one using H$\alpha$ emission line and the other using UV/optical spectral energy distribution (SED). Our results show that, in general, $f_{SF}$ galaxies increases with clustercentric distance, with $\sigma$ and AGN activity playing a more important role in determining how the $f_{SF}$ varies. Furthermore, when various galaxy properties are taken into account, the dependence of $f_{SF}$ on $R/r_{vir}$ is significantly smaller, being important only for non-AGN galaxies and galaxies with intermediate $\sigma$ values ($ 1.9 < \log_{10} \sigma < 2.1$). Although the trends in the result are maintained, the extent and variations of $f_{SF}$ depend significantly on the different SFR estimation methodologies.

Resumen:

The properties of most galaxies in the universe follow certain scaling relations. For example, there are scaling relations between the stellar mass of early-type galaxies and their neutral hydrogen (HI) content. Based on these scaling relations we can identify unusual galaxies, such as HI-deficient galaxies with relatively low HI content and HI-excess galaxies with relatively high HI masses compared to their stellar mass. The possible reasons for the latter could be either recent gas accretion or an inefficient conversion of the HI to molecular gas. Since recent gas accretion is difficult to prove conclusively, we are investigating the molecular gas content of five extremely HI rich galaxies from the HIX galaxy sample (Lutz et al. 2018). The carbon monoxide is a good tracer of the molecular gas content of galaxies through its spatial distribution. Therefore, we use recent CO observations of five sample galaxies from the Atacama Large Millimeter Array (ALMA) to calculate the mass and the distribution of the molecular gas. Then we analyze the kinematics of this molecular gas and compare it to the HI, as well as the stellar and star formation properties of the galaxies. We find that our sample galaxies have relatively regular rotating molecular gas disks.

Resumen:

The Neighbourhood Watch is a survey to complete a census of all baryonic structures out to at least the virial radius in a sample of galaxy groups within 18 Mpc in the optical filters u'g'r'i' and H-alpha with CTIO/DECam and in the NIR J,K filters with ESO/VIRCAM. The observations reach unprecedented point source depths of 2.5 magnitudes beyond the peak of the globular cluster luminosity function (GCLF) which will detect $>99\%$ of all compact objects, i.e. globular clusters (GCs) and ultra-compact dwarf galaxies (UCDs), and reveal all low-surface brightness baryonic structures down to $\sim 28 \text{mags/arcsec}^2$. This dataset will allow us for the first time: to derive a complete GCLF out to the virial radius for these galaxies, search for spatial over-densities and unique age/metallicity distribution functions (ADF/MDF) in the GC population, detect 10-100 new low-surface brightness dwarf galaxies for each target group to test current state-of-the-art cosmological simulations and measure their luminosity function in different environments, and probe the complex interaction/merger/accretion history of these groups.  Survey targets the NGC2997, NGC3115, NGC6744, and NGC4594 groups, complementing the CenA group (Taylor et al. 2017), the Virgo Cluster (NGVS, Ferrarese et al. 2012), and the Fornax Cluster (NGFS, Munoz et al. 2015; Ordenes-Briceno et al. 2018).  Given the DECam community pipeline’s inability to properly determine the sky levels around large galaxies, a custom data reduction pipeline is being designed for this particular dataset to fulfil the aforementioned objectives. The preliminary findings indicate that utilising a multi-step approach that employs a combination of techniques (convolution masking for image artifacts, distortion reduction in chip gap, and better sky modal) leads to the retrieval of low surface brightness dwarf galaxies that are observable in the final stacks. This poster will provide an overview of the survey and present the initial outputs from data reduction process.

Resumen:

The correlations between nuclear star clusters (NSCs) and their host galaxy indicate a fundamental connection between the formation of NSCs and their parent galaxy. A recent study by the Next Generation Fornax Survey (NGFS; Ordenes-Brice\~no et al. 2018) shows the presence of relatively massive nuclei in the faint dwarf at lower galaxy mass regime $log(M_gal/M_Sun) < 9.5$, which could be due to recent or ongoing star formation activity that contributes to an earlier build-up of nuclei relative to the rest of the galaxy. The NUV-optical-NIR colour-colour diagram also indicates the presence of young stellar populations (less than 2 Gyr). Extending the SED coverage beyond the Balmer break to FUV allows us to determine the age and mass fraction of these young stellar components more accurately by combining data from NGFS. So, we obtained FUV data of two massive NSCs from Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat through a successful proposal in the current observing cycle. I will present preliminary results from this current observation.