Browsing by Author "Pedrosa, S. E."

Now showing 1 - 5 of 5
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    Application of dimensionality reduction and clustering algorithms for the classification of kinematic morphologies of galaxies
    (2023) Rosito, M. S.; Bignone, L. A.; Tissera, P. B.; Pedrosa, S. E.
    Context. The morphological classification of galaxies is considered a relevant issue and can be approached from different points of view. The increasing growth in the size and accuracy of astronomical data sets brings with it the need for the use of automatic methods to perform these classifications.Aims. The aim of this work is to propose and evaluate a method for the automatic unsupervised classification of kinematic morphologies of galaxies that yields a meaningful clustering and captures the variations of the fundamental properties of galaxies.Methods.We obtained kinematic maps for a sample of 2064 galaxies from the largest simulation of the EAGLE project that mimics integral field spectroscopy images. These maps are the input of a dimensionality reduction algorithm followed by a clustering algorithm. We analysed the variation of physical and observational parameters among the clusters obtained from the application of this procedure to different inputs. The inputs studied in this paper are (a) line-of-sight velocity maps for the whole sample of galaxies observed at fixed inclinations; (b) line-of-sight velocity, dispersion, and flux maps together for the whole sample of galaxies observed at fixed inclinations; (c) line-of-sight velocity, dispersion, and flux maps together for two separate subsamples of edge-on galaxies with similar amount of rotation; and (d) line-of-sight velocity, dispersion, and flux maps together for galaxies from different observation angles mixed.Results. The application of the method to solely line-of-sight velocity maps achieves a clear division between slow rotators (SRs) and fast rotators (FRs) and can differentiate rotation orientation. By adding the dispersion and flux information at the input, low-rotation edge-on galaxies are separated according to their shapes and, at lower inclinations, the clustering using the three types of maps maintains the overall information obtained using only the line-of-sight velocity maps. This method still produces meaningful groups when applied to SRs and FRs separately, but in the first case the division into clusters is less clear than when the input includes a variety of morphologies. When applying the method to a mixture of galaxies observed from different inclinations, we obtain results that are similar to those in our previous experiments with the advantage that in this case the input is more realistic. In addition, our method has proven to be robust: it consistently classifies the same galaxies viewed from different inclinations.
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    Baryons shaping dark matter haloes
    (2021) Cataldi, P.; Pedrosa, S. E.; Tissera, P. B.; Artale, M. C.
    In this work, we aim at investigating the effects of baryons on the dark matter (DM) haloes structure, focusing on the correlation between the presence and importance of stellar discs and the halo shapes. We study the properties of a subsample of DM haloes from Fenix and eagle cosmological simulations. We inspect the central regions of haloes in the mass range at z = 0, comparing the hydrodynamic runs and their dark matter only (DMo) counterparts. Our results indicate that baryons have a significant impact on the shape of the inner halo, mainly within similar to 20per cent of the virial radius. We find haloes to be more spherical when hosting baryons. While the impact of baryons depends on the mass of the haloes, we also find a trend with morphology which suggests that the way baryons are assembled is also relevant in agreement with previous works. Our findings also indicate that disc galaxies preferentially form in haloes whose DMo counterparts were originally more spherical and with stronger velocity anisotropy. The presence of baryons alter the orbital structure of the DM particles of the haloes, which show a decrease in their velocity anisotropy, towards more tangentially biased orbits. This relative decrease is weaker in the case of disc-dominated galaxies. Our results point out to a cosmological connection between the final morphology of galaxies and the intrinsic properties of their DM haloes, which gets reinforce by the growth of the discs.
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    Redshift evolution of the dark matter haloes shapes
    (2023) Cataldi, P.; Pedrosa, S. E.; Tissera, P. B.; Artale, M. C.; Padilla, N. D.; Dominguez-Tenreiro, R.; Bignone, L.; Gonzalez, R.; Pellizza, L. J.
    In this work, we aim at investigating the morphology evolution of Milky Way mass-like dark matter haloes selected from the cielo and IllustrisTNG projects. The connection between halo shapes and their environment has been studied in previous works at z = 0 but their connection remains yet to be fully understood. We focus on the evolution across cosmic time of the halo shapes and the relation with the infalling material, using hydrodynamical simulations. Our findings show that haloes tend to be more triaxial at earlier times as a consequence of stronger accretion in the direction of the filaments. As the haloes evolve towards a dominant isotropic accretion mode and relaxation, their shape at 20 per cent of the virial radius becomes more spherical. In agreement with previous results, baryons have an important effect within the inner regions of the haloes, driving them from triaxial to rounder shapes. We also find a correlation between the strength of the quadrupole infalling mode and the degree of ellipticity of the haloes: as the filament strength decreases steadily with redshift, the haloes became more spherical and less elliptical.
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    The metallicity gradients of star-forming regions store information of the assembly history of galaxies
    (2024) Jara-Ferreira, F.; Tissera, P. B.; Sillero, E.; Rosas-Guevara, Y.; Pedrosa, S. E.; De Rossi, M. E.; Theuns, T.; Bignone, L.
    The variations in metallicity and spatial patterns within star-forming regions of galaxies result from diverse physical processes unfolding throughout their evolutionary history, with a particular emphasis on recent events. Analysing MaNGA and EAGLE galaxies, we discovered an additional dependence of the mass-metallicity relation (MZR) on metallicity gradients (del((O/H))). Two regimes emerged for low- and high-stellar mass galaxies, distinctly separated at approximately M-star > 10(9.75)M(circle dot). Low-mass galaxies with strong positive del((O/H)) appear less enriched than the MZR median, while those with strong negative gradients are consistently more enriched in both simulated and observed samples. Interestingly, low-mass galaxies with strong negative del((O/H)) exhibit high star-forming activity, regardless of stellar surface density or del((O/H)). In contrast, a discrepancy arises for massive galaxies between MaNGA and EAGLE data sets. The latter exhibit a notable anticorrelation between specific star formation rate and stellar surface density, independent of del((O/H)), while MaNGA galaxies show this trend mainly for strong positive del((O/H)). Further investigation indicates that galaxies with strong negative gradients tend to host smaller central black holes in observed data sets, a trend not replicated in simulations. These findings suggest disparities in metallicity recycling and mixing history between observations and simulations, particularly in massive galaxies with varying metallicity gradients. These distinctions could contribute to a more comprehensive understanding of the underlying physics.
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    The role of AGN feedback in the structure, kinematics, and evolution of ETGs in Horizon simulations
    (2021) Rosito, M. S.; Pedrosa, S. E.; Tissera, P. B.; Chisari, N. E.; Dominguez-Tenreiro, R.; Dubois, Y.; Peirani, S.; Devriendt, J.; Pichon, C.; Slyz, A.
    Context. Feedback processes play a fundamental role in the regulation of the star formation (SF) activity in galaxies and, in particular, in the quenching of early-type galaxies (ETGs) as has been inferred by observational and numerical studies of Lambda -CDM models. At z=0, ETGs exhibit well-known fundamental scaling relations, but the connection between scaling relations and the physical processes shaping ETG evolution remains unknown.Aims. This work aims to study the impact of the energetic feedback due to active galactic nuclei (AGN) on the formation and evolution of ETGs. We focus on assessing the impact of AGN feedback on the evolution of the mass-plane and the fundamental plane (FP; defined using mass surface density) as well as on morphology, kinematics, and stellar age across the FP.Methods. The Horizon-AGN and Horizon-noAGN cosmological hydrodynamical simulations were performed with identical initial conditions, including the same physical processes except for the activation of the AGN feedback in the former. We selected a sample of central ETGs from both simulations using the same criteria and exhaustively studied their SF activity, kinematics, and scaling relations for z <= 3.Results. We find that Horizon-AGN ETGs identified at z=0 follow the observed fundamental scaling relations (mass-plane, FP, and mass-size relation) and qualitatively reproduce kinematic features albeit conserving a rotational inner component with a mass fraction regulated by the AGN feedback. We discover that AGN feedback seems to be required to reproduce the bimodality in the spin parameter distribution reported by observational works and the mass-size relation; more massive galaxies have older stellar populations, larger sizes, and are slower rotators. We study the evolution of the fundamental relations with redshift, finding a mild evolution of the mass-plane of Horizon-AGN ETGs for z< 1, whereas a stronger change is detected for z> 1. The ETGs in Horizon-noAGN show a strong systematic redshift evolution of the mass-plane. The FP of Horizon-AGN ETGs agrees with observations at z=0. When AGN feedback is switched off, a fraction of galaxies depart from the expected FP at all analysed redshifts owing to the presence of a few extended galaxies with an excess of stellar surface density. We find that AGN feedback regulates the SF activity as a function of stellar mass and redshift being able to reproduce the observed relations. Our results show the impact of AGN feedback on the mass-to-light ratio (M/L) and its relation with the tilt of the luminosity FP (L-FP; defined using the averaged surface brightness). Overall, AGN feedback has an impact on the regulation of the SF activity, size, stellar surface density, stellar ages, rotation, and masses of ETGs that is reflected on the fundamental relations, particularly on the FP. We detect a dependence of the FP on stellar age and galaxy morphology that evolves with redshfit. The characteristics of the galaxy distribution on the FP according to these properties change drastically by z similar to 1 in Horizon-AGN and hence this feature could provide further insight into the action of AGN feedback.