Examinando por Autor "Tissera, P.B."
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Ítem Assembly of spheroid-dominated galaxies in the EAGLE simulation(Astronomy and Astrophysics, 2019) Rosito, M.S.; Tissera, P.B.; Pedrosa, S.E.; Rosas-Guevara, Y.Context: Despite the insights gained in the last few years, our knowledge about the formation and evolution scenario for the spheroid-dominated galaxies is still incomplete. New and more powerful cosmological simulations have been developed that together with more precise observations open the possibility of more detailed study of the formation of early-type galaxies (ETGs). Aims. The aim of this work is to analyse the assembly histories of ETGs in a Λ cold dark matter cosmology, focussing on the archeological approach given by the mass-growth histories. Methods: We inspected a sample of dispersion-dominated galaxies selected from the largest volume simulation of the EAGLE project. This simulation includes a variety of physical processes such as radiative cooling, star formation (SF), metal enrichment, and stellar and active galactic nucleus (AGN) feedback. The selected sample comprised 508 spheroid-dominated galaxies classified according to their dynamical properties. Their surface brightness profile, the fundamental relations, kinematic properties, and stellar-mass growth histories are estimated and analysed. The findings are confronted with recent observations. Results: The simulated ETGs are found to globally reproduce the fundamental relations of ellipticals. All of them have an inner disc component where residual younger stellar populations (SPs) are detected. A correlation between the inner-disc fraction and the bulge-to-total ratio is reported. We find a relation between kinematics and shape that implies that dispersion-dominated galaxies with low V/σL (where V is the average rotational velocity and σL the one dimensional velocity dispersion) tend to have ellipticity smaller than ∼0.5 and are dominated by old stars. On average, less massive galaxies host slightly younger stars. More massive spheroids show coeval SPs while for less massive galaxies (stellar masses lower than ∼1010M⊙), there is a clear trend to have rejuvenated inner regions, showing an age gap between the inner and the outer regions up to ∼2 Gyr, in apparent contradiction with observational findings. We find evidences suggesting that both the existence of the disc components with SF activity in the inner region and the accretion of satellite galaxies in outer regions could contribute to the outside-in formation history in galaxies with low stellar mass. On the other hand, there are non-negligible uncertainties in the determination of the ages of old stars in observed galaxies. Stronger supernova (SN) feedback and/or the action of AGN feedback for galaxies with stellar masses lower than 1010 M⊙ could contribute to prevent the SF in the inner regions.Ítem Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations(Institute of Physics Publishing, 2018) Hayes, C.R.; Majewski, S.R.; Shetrone, M.; Fernández-Alvar, E.; Prieto, C.A.; Schuster, W.J.; Carigi, L.; Cunha, K.; Smith, V.V.; Sobeck, J.; Almeida, A.; Beers, T.C.; Carrera, R.; Fernández-Trincado, J.G.; García-Hernández, D.A.; Geisler, D.; Lane, R.R.; Lucatello, S.; Matthews, A.M.; Minniti, D.; Nitschelm, C.; Tang, B.; Tissera, P.B.; Zamora, O.We find two chemically distinct populations separated relatively cleanly in the [Fe/H]-[Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities [Fe H] < -0.9) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the Sloan Digital Sky Survey. These two stellar populations show the most significant differences in their [X/Fe] ratios for the α-elements, C+N, Al, and Ni. In addition to these populations having differing chemistry, the low metallicity high-Mg population (which we denote "the HMg population") exhibits a significant net Galactic rotation, whereas the low-Mg population (or "the LMg population") has halo-like kinematics with little to no net rotation. Based on its properties, the origin of the LMg population is likely an accreted population of stars. The HMg population shows chemistry (and to an extent kinematics) similar to the thick disk, and is likely associated with in situ formation. The distinction between the LMg and HMg populations mimics the differences between the populations of low- and high-α halo stars found in previous studies, suggesting that these are samples of the same two populations.Ítem Field spheroid-dominated galaxies in a Λ-CDM Universe(EDP Sciences, 2018) Rosito, M.S.; Pedrosa, S.E.; Tissera, P.B.; Avila-Reese, V.; Lacerna, I.; Bignone, L.A.; Ibarra-Medel, H.J.; Varela, S.Context. Understanding the formation and evolution of early-type, spheroid-dominated galaxies is an open question within the context of the hierarchical clustering scenario, particularly in low-density environments. Aims. Our goal is to study the main structural, dynamical, and stellar population properties and assembly histories of field spheroid-dominated galaxies formed in a Λ-cold dark matter (Λ-CDM) scenario to assess to what extent they are consistent with observations. Methods. We selected spheroid-dominated systems from a Λ-CDM simulation that includes star formation (SF), chemical evolution, and supernova feedback. The sample is made up of 18 field systems with MStar ≤ 6 × 1010M⊙ that are dominated by the spheroid component. For this sample we estimated the fundamental relations of ellipticals and compared them with current observations. Results. The simulated spheroid galaxies have sizes that are in good agreement with observations. The bulges follow a Sersic law with Sersic indexes that correlate with the bulge-to-total mass ratios. The structural-dynamical properties of the simulated galaxies are consistent with observed Faber-Jackson, fundamental plane, and Tully-Fisher relations. However, the simulated galaxies are bluer and with higher star formation rates (SFRs) than the observed isolated early-type galaxies. The archaeological mass growth histories show a slightly delayed formation and more prominent inside-out growth mode than observational inferences based on the fossil record method. Conclusions. The main structural and dynamical properties of the simulated spheroid-dominated galaxies are consistent with observations. This is remarkable since our simulation has not been calibrated to match them. However, the simulated galaxies are blue and star-forming, and with later stellar mass growth histories compared to observational inferences. This is mainly due to the persistence of extended discs in the simulations. The need for more efficient quenching mechanisms able to avoid further disc growth and SF is required in order to reproduce current observational trends. © ESO 2018.Ítem Morphology of galaxies with quiescent recent assembly history in a Λ-CDM universe(EDP Sciences, 2014-07) Pedrosa, S.E.; Tissera, P.B.; De Rossi, M.E.Context. The standard disc formation scenario postulates that the disc forms as the gas cools and flows into the centre of the dark matter halo, conserving the specific angular momentum. Major mergers have been shown to be able to destroy or highly perturb the disc components. More recently, the alignment of the material that is accreted to form the galaxy has been pointed out as a key ingredient to determine galaxy morphology. However, in a hierarchical scenario galaxy formation is a complex process that combines these processes and others in a non-linear way so that the origin of galaxy morphology remains to be fully understood. Aims. We aim at exploring the differences in the formation histories of galaxies with a variety of morphologies, but quite recent merger histories, to identify which mechanisms are playing a major role. We analyse when minor mergers can be considered relevant to determine galaxy morphology. We also study the specific angular momentum content of the disc and central spheroidal components separately. Methods. We used cosmological hydrodynamical simulations that include an effective, physically motivated supernova feedback that is able to regulate the star formation in haloes of different masses. We analysed the morphology and formation history of a sample of 15 galaxies of a cosmological simulation. We performed a spheroid-disc decomposition of the selected galaxies and their progenitor systems. The angular momentum orientation of the merging systems as well as their relative masses were estimated to analyse the role played by orientation and by minor mergers in the determination of the morphology. Results. We found the discs to be formed by conserving the specific angular momentum in accordance with the classical disc forma tion model. The specific angular momentum of the stellar central spheroid correlates with the dark matter halo angular momentum and determines a power law. Our results suggest that gas accretion to rebuild the disc component is a necessary but not sufficient ingredient for a disc-dominated galaxy in a hierarchical clustering scenario. The survival of the discs is tightly linked to their subsequent history of accretion, as previously reported. Minor mergers play an important role. It is more likely that they will destroy the disc and feed the central spheroid if their angular momentum is misaligned with respect to that of the main galaxy. Conversely, if they are aligned, they can contribute to the disc formation.Ítem Redshift evolution of the dark matter haloes shapes(Oxford University Press, 2023-08-01) 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. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Ítem Stellar feedback from high-mass X-ray binaries in cosmological hydrodynamical simulations(Artale, M.C., 2015-04) Artale, M.C.; Tissera, P.B.; Pellizza, L.J.We explored the role of X-ray binaries composed by a black hole and a massive stellar companion [black hole X-ray binaries (BHXs)] as sources of kinetic feedback by using hydrodynamical cosmological simulations. Following previous results, our BHX model selects metal-poor stars (Z = [0, 10-4]) as possible progenitors. The model that better reproduces observations assumes that an ~20 per cent fraction of low-metallicity black holes are in binary systems which produces BHXs. These sources are estimated to deposit ~1052 erg of kinetic energy per event. With these parameters and in the simulated volume, we find that the energy injected by BHXs represents ~30 per cent of the total energy released by Type II supernova and BHX events at redshift z ~ 7 and then decreases rapidly as baryons get chemically enriched. Haloes with virial masses smaller than ~1010M{bull's eye} (or Tvir ≤105 K) are the most directly affected ones by BHX feedback. These haloes host galaxies with stellar masses in the range 107-108 M{bull's eye}. Our results show that BHX feedback is able to keep the interstellar medium warm, without removing a significant gas fraction, in agreement with previous analytical calculations. Consequently, the stellar-to-dark matter mass ratio is better reproduced at high redshift. Our model also predicts a stronger evolution of the number of galaxies as a function of the stellar mass with redshift when BHX feedback is considered. These findings support previous claims that the BHXs could be an effective source of feedback in early stages of galaxy evolution. © 2015 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.Ítem The central spheroids of Milky Way mass-sized galaxies(Oxford University Press, 2018-01) Tissera, P.B.; Machado, R.E.G.; Carollo, D.; Minniti, D.; Beers, T.C.; Zoccali, M.; Meza, A.We study the properties of the central spheroids located within 10 kpc of the centre of mass of MilkyWay mass-sized galaxies simulated in a cosmological context. The simulated central regions are dominated by stars older than 10 Gyr, mostly formed in situ, with a contribution of ~30 per cent from accreted stars. These stars formed in well-defined starbursts, although accreted stars exhibit sharper and earlier ones. The fraction of accreted stars increases with galactocentric distance, so that at a radius of~8-10 kpc, a fraction of~40 per cent, on average, is detected. Accreted stars are slightly younger, lower metallicity, and more α-enhanced than in situ stars. A significant fraction of old stars in the central regions come from a few (2-3) massive satellites (~1010M⊙). The bulge components receive larger contributions of accreted stars formed in dwarfs smaller than ~109.5M⊙. The difference between the distributions of ages and metallicities of old stars is thus linked to the accretion histories - those central regions with a larger fraction of accreted stars are those with contributions from more massive satellites. The kinematical properties of in situ and accreted stars are consistent with the latter being supported by their velocity dispersions, while the former exhibit clear signatures of rotational support. Our simulations demonstrate a range of characteristics, with some systems exhibiting a co-existing bar and spheroid in their central regions, resembling in some respect the central region of the Milky Way. © 2016 The Authors.