Browsing by Author "Rosas-Guevara, Yetli"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Milky Way-like galaxies: stellar population properties of dynamically defined discs, bulges and stellar haloes
    (2022) Ortega-Martinez, Sara; Obreja, Aura; Dominguez-Tenreiro, Rosa; Pedrosa, Susana E.; Rosas-Guevara, Yetli; Tissera, Patricia B.
    The formation of galaxies can be understood in terms of the assembly patterns of each type of galactic component. To perform this kind of analysis, it is necessary to define some criteria to separate those components. Decomposition methods based on dynamical properties are more physically motivated than photometry-based ones. We use the unsupervised Gaussian Mixture model of galactic structure finder to extract the components of a sub-sample of galaxies with Milky Way-like masses from the eagle simulations. A clustering in the space of first- and second-order dynamical moments of all identified substructures reveals five types of galaxy components: thin and thick discs, stellar haloes, bulges and spheroids. We analyse the dynamical, morphological and stellar population (SP) properties of these five component types, exploring to what extent these properties correlate with each other, and how much they depend on the total galaxy stellar and dark matter halo masses. All galaxies contain a bulge, a stellar halo and a disc. In total, 60 per cent of objects host two discs (thin and thick), and 68 per cent host also a spheroid. The dynamical disc-to-total ratio does not depend on stellar mass, but the median rotational velocities of the two discs do. Thin discs are well separated in stellar ages, [Fe/H] and alpha-enhancement from the three dispersion-dominated components, while thick discs are in between. Except for thin discs, all components show correlations among their SP properties: older ages mean lower metallicities and larger alpha-enhancement. Finally, we quantify the weak dependence of SP properties on each component's dynamics.
  • No Thumbnail Available
    Item
    Revealing the properties of void galaxies and their assembly using the EAGLE simulation
    (2022) Rosas-Guevara, Yetli; Tissera, Patricia; Lagos, Claudia del P.; Paillas, Enrique; Padilla, Nelson
    We explore the properties of central galaxies living in voids using the EAGLE, cosmological hydrodynamic simulations. Based on the minimum void-centric distance, we define four galaxy samples: inner void, outer void, wall, and skeleton. We find that inner void galaxies with host halo masses < 10(12) M-circle dot have lower stellar mass and stellar mass fractions than those in denser environments, and the fraction of galaxies with star formation (SF) activity and atomic hydrogen (H I) gas decreases with increasing void-centric distance, in agreement with observations. To mitigate the influence of stellar (halo) mass, we compare inner void galaxies to subsamples of fixed stellar (halo) mass. Compared to denser environments, inner void galaxies with M-* = 10([9.0-9.5]) M-circle dot have comparable SF activity and H I gas fractions, but the lowest quenched galaxy fraction. Inner void galaxies with M-* = 10([9.0-10.5]) M-circle dot have the lowest H I gas fraction, the highest quenched fraction and the lowest gas metallicities. On the other hand, inner void galaxies with M-* > 10(10.5) M-circle dot have comparable SF activity and H I gas fractions to their analogues in denser environments. They retain the highest metallicity gas that might be linked to physical processes that act with lower efficiency in underdense regions such as AGN (active galaxy nucleus) feedback. Furthermore, inner void galaxies have the lowest fraction of positive gas-phase metallicity gradients, which are typically associated with external processes or feedback events, suggesting they have more quiet merger histories than galaxies in denser environments. Our findings shed light on how galaxies are influenced by their large-scale environment.
  • No Thumbnail Available
    Item
    The evolution of the oxygen abundance gradients in star-forming galaxies in the EAGLE simulations
    (2022) Tissera, Patricia B.; Rosas-Guevara, Yetli; Sillero, Emanuel; Pedrosa, Susana E.; Theuns, Tom; Bignone, Lucas
    We analyse the evolution of the oxygen abundance gradient of star-forming galaxies with stellar mass M-* >= 10(9)M(circle dot) in the EAGLE simulation over the redshift range z = [0, 2.5]. We find that the median metallicity gradient of the simulated galaxies is close to zero at all z, whereas the scatter around the median increases with z. The metallicity gradients of individual galaxies can evolve from strong to weak and vice versa, since mostly low-metallicity gas accretes on to the galaxy, resulting in enhanced star formation and ejection of metal-enriched gas by energy feedback. Such episodes of enhanced accretion, mainly dominated by major mergers, are more common at higher z and hence contribute to increasing the diversity of gradients. For galaxies with negative metallicity gradients, we find a redshift evolution of similar to -0.03 dex kpc(-1)/delta z. A positive mass dependence is found at z <= 0.5, which becomes slightly stronger for higher redshifts and, mainly, for M-* < 10(9.)(5) M-circle dot. Only galaxies with negative metallicity gradients define a correlation with galaxy size, consistent with an inside-out formation scenario. Our findings suggest that major mergers and/or significant gas accretion can drive strong negative or positive metallicity gradients. The first ones are preferentially associated with disc-dominated galaxies, and the second ones with dispersion-dominated systems. The comparison with forthcoming observations at high redshift will allow a better understanding of the potential role of metallicity gradients as a chemical probe of galaxy formation.