Browsing by Author "Gomez, Facundo A."

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Exploring the outskirts of the EAGLE disc galaxies
    (2022) Varela-Lavin, Silvio; Tissera, Patricia B.; Gomez, Facundo A.; Bignone, Lucas A.; Lagos, Claudia del P.
    Observations show that the surface brightness of disc galaxies can be well-described by a single exponential (TI), up-bending (TIII), or down-bending (TII) profiles in the outskirts. Here we characterize the mass surface densities of simulated late-type galaxies from the eagle project according to their distribution of mono-age stellar populations, the star formation activity, and angular momentum content. We find a clear correlation between the inner scale lengths and the stellar spin parameter, lambda, for all three disc types with lambda > 0.35. The outer scale lengths of TII and TIII discs show a positive trend with lambda, albeit weaker for the latter. TII discs prefer fast rotating galaxies. With regards to the stellar age distribution, negative and U-shape age profiles are the most common for all disc types. Positive age profiles are determined by a more significant contribution of young stars in the central regions, which decrease rapidly in the outer parts. TII discs prefer relative higher contributions of old stars compared to other mono-age populations across the discs whereas TIII discs become progressively more dominated by intermediate age (2-6 Gyr) stars for increasing radius. The change in slope of the age profiles is located after the break of the mass surface density. We find evidence of larger flaring for the old stellar populations in TIII systems compared to TI and TII, which could indicate the action of other processes. Overall, the relative distributions of mono-age stellar populations and the dependence of the star formation activity on radius are found to shape the different disc types and age profiles.
  • No Thumbnail Available
    Item
    Lopsided galaxies in a cosmological context: a new galaxy-halo connection
    (2023) Varela-Lavin, Silvio; Gomez, Facundo A.; Tissera, Patricia B.; Besla, Gurtina; Garavito-Camargo, Nicolas; Marinacci, Federico; Laporte, Chervin F. P.
    Disc galaxies commonly show asymmetric features in their morphology, such as warps and lopsidedness. These features can provide key information regarding the recent evolution of a given disc galaxy. In the nearby Universe, up to & SIM;30 per cent of late-type galaxies display a global non-axisymmetric lopsided mass distribution. However, the origin of this perturbation is not well understood. In this work, we study the origin of lopsided perturbations in simulated disc galaxies extracted from the TNG50 simulation of the IllustrisTNG project. We statistically explore different excitation mechanisms for this perturbation, such as direct satellite tidal interactions and distortions of the underlying dark matter distributions. We also characterize the main physical conditions that lead to lopsided perturbations. 50 per cent of our sample galaxy have lopsided modes m = 1 greater than & SIM;0.12. We find a strong correlation between internal galaxy properties, such as central stellar surface density and disc radial extension with the strength of lopsided modes. The majority of lopsided galaxies have lower central surface densities and more extended discs than symmetric galaxies. As a result, such lopsided galaxies are less self-gravitationally cohesive, and their outer disc region is more susceptible to different types of external perturbations. However, we do not find strong evidence that tidal interactions with satellite galaxies are the main driving agent of lopsided modes. Lopsided galaxies tend to live in asymmetric dark matter haloes with high spin, indicating strong galaxy-halo connections in late-type lopsided galaxies.
  • No Thumbnail Available
    Item
    Lopsidedness as a tracer of early galactic assembly history
    (2023) Dolfi, Arianna; Gomez, Facundo A.; Monachesi, Antonela; Varela-Lavin, Silvio; Tissera, Patricia B.; Sifon, Cristobal; Galaz, Gaspar
    Large-scale asymmetries (i.e. lopsidedness) are a common feature in the stellar density distribution of nearby disc galaxies both in low- and high-density environments. In this work, we characterize the present-day lopsidedness in a sample of 1435 disc-like galaxies selected from the TNG50 simulation. We find that the percentage of lopsided galaxies (10 percent-30 percent) is in good agreement with observations if we use similar radial ranges to the observations. However, the percentage (58 percent) significantly increases if we extend our measurement to larger radii. We find a mild or lack of correlation between lopsidedness amplitude and environment at z = 0 and a strong correlation between lopsidedness and galaxy morphology regardless of the environment. Present-day galaxies with more extended discs, flatter inner galactic regions, and lower central stellar mass density (i.e. late-type disc galaxies) are typically more lopsided than galaxies with smaller discs, rounder inner galactic regions, and higher central stellar mass density (i.e. early-type disc galaxies). Interestingly, we find that lopsided galaxies have, on average, a very distinct star formation history within the last 10 Gyr, with respect to their symmetric counterparts. Symmetric galaxies have typically assembled at early times (similar to 8-6 Gyr ago) with relatively short and intense bursts of central star formation, while lopsided galaxies have assembled on longer time-scales and with milder initial bursts of star formation, continuing building up their mass until z = 0. Overall, these results indicate that lopsidedness in present-day disc galaxies is connected to the specific evolutionary histories of the galaxies that shaped their distinct internal properties.
  • No Thumbnail Available
    Item
    Machine learning for galactic archaeology: a chemistry-based neural network method for identification of accreted disc stars
    (2022) Tronrud, Thorold; Tissera, Patricia B.; Gomez, Facundo A.; Grand, Robert J. J.; Pakmor, Ruediger; Marinacci, Federico; Simpson, Christine M.
    We develop a method ('Galactic Archaeology Neural Network', gann) based on neural network models (NNMs) to identify accreted stars in galactic discs by only their chemical fingerprint and age, using a suite of simulated galaxies from the Auriga Project. We train the network on the target galaxy's own local environment defined by the stellar halo and the surviving satellites. We demonstrate that this approach allows the detection of accreted stars that are spatially mixed into the disc. Two performance measures are defined - recovery fraction of accreted stars, f(recov) and the probability that a star with a positive (accreted) classification is a true-positive result, P(TP). As the NNM output is akin to an assigned probability (P-a), we are able to determine positivity based on flexible threshold values that can be adjusted easily to refine the selection of presumed-accreted stars. We find that gann identifies accreted disc stars within simulated galaxies, with high f(recov) and/or high P(TP). We also find that stars in Gaia-Enceladus-Sausage (GES) mass systems are over 50 per cent recovered by our NNMs in the majority (18/24) of cases. Additionally, nearly every individual source of accreted stars is detected at 10 per cent or more of its peak stellar mass in the disc. We also demonstrate that a conglomerated NNM, trained on the halo and satellite stars from all of the Auriga galaxies provides the most consistent results, and could prove to be an intriguing future approach as our observational capabilities expand.
  • No Thumbnail Available
    Item
    Too dense to go through: the role of low-mass clusters in the pre-processing of satellite galaxies
    (2022) Pallero, Diego; Gomez, Facundo A.; Padilla, Nelson D.; Bahe, Yannick M.; Vega-Martinez, Cristian A.; Torres-Flores, S.
    We study the evolution of satellite galaxies in clusters of the c-eagle simulations, a suite of 30 high-resolution cosmological hydrodynamical zoom-in simulations based on the eagle code. We find that the majority of galaxies that are quenched at z = 0 (greater than or similar to 80per cent) reached this state in a dense environment (log(10)M(200)[M-circle dot] >= 13.5). At low redshift, regardless of the final cluster mass, galaxies appear to reach their quenching state in low-mass clusters. Moreover, galaxies quenched inside the cluster that they reside in at z = 0 are the dominant population in low-mass clusters, while galaxies quenched in a different halo dominate in the most massive clusters. When looking at clusters at z > 0.5, their in situ quenched population dominates at all cluster masses. This suggests that galaxies are quenched inside the first cluster they fall into. After galaxies cross the cluster's r(200) they rapidly become quenched (less than or similar to 1 Gyr). Just a small fraction of galaxies (less than or similar to 15 per cent) is capable of retaining their gas for a longer period of time, but after 4 Gyr, almost all galaxies are quenched. This phenomenon is related to ram pressure stripping and is produced when the density of the intracluster medium reaches a threshold of rho(ICM) similar to 3 x10(-5) n(H) (cm(-3)). These results suggest that galaxies start a rapid-quenching phase shortly after their first infall inside r(200) and that, by the time they reach r(500), most of them are already quenched.