Examinando por Autor "Gómez, F."

Mostrando 1 - 2 de 2
  • Miniatura
    Ítem
    Chemodynamics of barred galaxies in cosmological simulations: On the Milky Way’s quiescent merger history and in-situ bulge
    (Oxford University Press, 2020-04) Fragkoudi, F.; Grand, R.J.J.; Pakmor, R.; Blázquez-Calero, G.; Gargiulo, I.; Gómez, F.; Marinacci, F.; Monachesi, A.; Ness, M.K.; Pérez, I.; Tissera, P.; White S.D.M., S.D.M.
    We explore the chemodynamical properties of a sample of barred galaxies in the Auriga magnetohydrodynamical cosmological zoom-in simulations, which form boxy/peanut (b/p) bulges, and compare these to the Milky Way (MW). We show that the Auriga galaxies which best reproduce the chemodynamical properties of stellar populations in the MW bulge have quiescent merger histories since redshift z ∼ 3.5: their last major merger occurs at tlookback > 12 Gyr, while subsequent mergers have a stellar mass ratio of ≤1:20, suggesting an upper limit of a few per cent for the mass ratio of the recently proposed Gaia Sausage/Enceladus merger. These Auriga MW-analogues have a negligible fraction of ex-situ stars in the b/p region (< 1 per cent), with flattened, thick disc-like metal-poor stellar populations. The average fraction of ex-situ stars in the central regions of all Auriga galaxies with b/p’s is 3 per cent – significantly lower than in those which do not host a b/p or a bar. While the central regions of these barred galaxies contain the oldest populations, they also have stars younger than 5 Gyr (>30 per cent) and exhibit X-shaped age and abundance distributions. Examining the discs in our sample, we find that in some cases a star-forming ring forms around the bar, which alters the metallicity of the inner regions of the galaxy. Further out in the disc, bar-induced resonances lead to metal-rich ridges in the Vφ − r plane – the longest of which is due to the Outer Lindblad Resonance. Our results suggest the Milky Way has an uncommonly quiet merger history, which leads to an essentially in-situ bulge, and highlight the significant effects the bar can have on the surrounding disc. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
  • Miniatura
    Ítem
    Influence of Physical-Chemical Soil Parameters on Microbiota Composition and Diversity in a Deep Hyperarid Core of the Atacama Desert
    (Frontiers Media S.A., 2022-02) Fuentes, B.; Choque, A.; Gómez, F.; Alarcón, J.; Castro-Nallar, E.; Arenas, F.; Contreras, D.; Mörchen, R.; Amelung, W.; Knief, C.; Moradi, G.; Klumpp, E.
    The extreme environmental conditions and lack of water on the soil surface in hyperarid deserts hamper microbial life, allowing only highly specialized microbial communities to the establish colonies and survive. Until now, the microbial communities that inhabit or have inhabited soils of hyperarid environments at greater depths have been poorly studied. We analyzed for the first time the variation in microbial communities down to a depth of 3.4 m in one of the driest places of the world, the hyperarid Yungay region in the Atacama Desert, and we related it to changes in soil physico-chemical characteristics. We found that the moisture content changed from 2 to 11% with depth and enabled the differentiation of three depth intervals: (i) surface zone A (0–60 cm), (ii) intermediate zone B (60–220 cm), and (iii) deep zone C (220–340 cm). Each zone showed further specific physicochemical and mineralogical features. Likewise, some bacterial phyla were unique in each zone, i.e., members of the taxa Deinococcota, Halobacterota, and Latescibacterota in zone A; Crenarchaeota, Fusobacteriota, and Deltaproteobacterium Sva0485 in zone B; and Fervidibacteria and Campilobacterota in zone C, which indicates taxon-specific preferences in deep soil habitats. Differences in the microbiota between the zones were rather abrupt, which is concomitant with abrupt changes in the physical-chemical parameters. Overall, moisture content, total carbon (TC), pH, and electric conductivity (EC) were most predictive of microbial richness and diversity, while total sulfur (TS) and total phosphorous (TP) contents were additionally predictive of community composition. We also found statistically significant associations between taxa and soil properties, most of which involved moisture and TC contents. Our findings show that under-explored habitats for microbial survival and existence may prevail at greater soil depths near water or within water-bearing layers, a valuable substantiation also for the ongoing search for biosignatures on other planets, such as Mars.