Valeria Alvarez Vergara
The impact of bars in active galactic nuclei galaxies
Nuclear activity is associated with internal disturbances that move gas towards the central regions of galaxies. Galactic bars are considered a key factor in this phenomenon, as their presence can lead to angular momentum loss, resulting in the redistribution of gas and its concentration in the galactic nucleus. To examine how bars affect the activity of active galactic nuclei (AGN), a sample of spiral galaxies with active nuclei and visible bars at z<0.1 was compiled using morphological data provided by Galaxy Zoo DECaLS. Similarly, a control group of AGN galaxies without bars, with comparable characteristics in stellar mass, magnitude, and redshift, was selected.
Properties such as stellar mass, color, and the Dn4000 index were evaluated in relation to L[OIII] and the accretion rate R, both robust indicators of nuclear activity. The results showed that galaxies with bars exhibit higher values of L[OIII] and R compared to the control group. Moreover, the proportion of galaxies with intense AGNs is significantly higher in those possessing bars, particularly in galaxies with younger and bluer stellar populations.
Yamila Daniela Burrafato
The chemical abundances of galaxies as tracers of their feedback histories
The chemical properties of galaxies provide essential insights into their formation, evolution, and the physical processes occurring during diverse cosmic epochs. This study examines the evolution of the global metallicity and individual elements (e.g. C, N, O, Mg, Si and Fe) in galaxies, with a special focus on the stellar component. In particular, we analyze the impact of feedback processes such as those associated with supernovae (SNe) and Active Galactic Nuclei (AGN), and how these processes influence the relationship between the stellar component and different gas phases. For this work, we used the EAGLE (Evolution and Assembly of GaLaxies and their Environments) suite of cosmological hydrodynamic simulations, comparing results obtained from different feedback models. According to our findings, the stellar metallicity shows a strong connection with the chemical enrichment of the star-forming gas, whereas the metallicity of non-star-forming gas seems to have a weak relation with the former ones. The chemical properties of the aforementioned galaxy baryonic components can be strongly affected by feedback, whose effects depend on the mass of the galaxy. We conclude that the joint characterization of the gas and stellar chemical properties of galaxies could provide important clues to constrain their formation paths.
Bruno Martin Celiz
Characterizing the accreted mass and stellar haloes in simulated dwarf galaxies
In a LCDM Universe, structure formation proceeds hierarchically, which implies that galaxies have an accreted stellar component built through successive mergers.
Consequently, it is possible to find old stars with long dynamical times in the outskirts, as it has been observed in massive galaxies, but its presence in low-mass galaxies is less well understood. Using the TNG50 cosmological hydrodynamic simulation we study the accreted mass component and the stellar halo as a function of both stellar mass and virial mass in isolated central galaxies with 2 x 10^10 M_sun < M_200 at redshift z = 0.
We find that i) Accreted mass strongly correlates with the galaxy’s stellar halo mass; ii) In dwarf galaxies the accreted mass corresponds to, statistically, between 1%-5% of the total stellar mass; iii) Accreted mass fraction decreases with virial mass rather than the stellar mass; and iv) The accreted component is more concentrated in galaxies that have higher accreted mass at a given virial mass, which also had late mergers. In LCDM simulations, dwarf galaxies can have an accreted component and, although in a smaller fraction, a diffuse stellar halo populated by old stars that were born ex-situ.
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