The imprint of satellite accretion on the chemical and dynamical properties of disc galaxies

Abstract

Aims. We study the effects of the cosmological assembly history on the chemical and dynamical properties of the discs of spiral galaxies as a function of radius. Methods. We made use of the simulated Milky Way mass, fully-cosmological discs from Ramses Disc Environment Study (RaDES). We analysed their assembly history by examining the proximity of satellites to the galactic disc, instead of their merger trees, to better gauge which satellites impact the disc. We presented stellar age and metallicity profiles, age-metallicity relation (AMR), age-velocity dispersion relation (AVR), and stellar age distribution (SAD) in several radial bins for the simulated galaxies. Results. Assembly histories can be divided into three different stages: i) a merger dominated phase, when a large number of mergers with mass ratios of ∼1:1 take place (lasting ∼3.2 ± 0.4 Gyr on average); ii) a quieter phase, when ∼1:10 mergers take place (lasting ∼4.4 ± 2.0 Gyr); and iii) a secular phase where the few mergers that take place have mass ratios below 1:100, which do not affect the disc properties (lasting ∼5.5 ± 2.0 Gyr). The first two phases are able to kinematically heat the disc and produce a disc that is chemically mixed over its entire radial extension. Phase 2 ends with a final merger event (at time t jump ) marking the onset of important radial differences in the AMR, AVR, and SAD. Conclusions. Inverted AMR trends in the outer parts of discs, for stars younger than t jump , are found as the combined effect of radial motions and star formation in satellites temporarily located in these outer parts. U-shaped stellar age profiles change to an old plateau (∼10 Gyr) in the outer discs for the entire RaDES sample. This shape is a consequence of inside-out growth of the disc, radial motions of disc stars (inwards and outwards), and the accretion of old stars from satellites. We see comparable age profiles even when ignoring the influence of stellar migration due to the presence of early in situ star formation in the outer regions of the galaxy.

Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal redistribution

“…We note that these trends are observed for the older stellar populations (second and third panels of Fig. 12), however the metallicity dispersion is larger owing to dynamical effects such as mergers (Ruiz-Lara et al 2016;Bustamante et al 2018) and radial migration that broaden the metallicity distribution (Minchev et al 2013, Di Matteo et al 2013, Grand et al 2015, Grand et al 2016b, Sánchez-Menguiano et al 2016, Loebman et al 2016, Kawata et al 2017. We defer a detailed analysis of the drivers of the stellar metallicity distribution to future work (Tronrud et al in prep).…”

The properties, origin and evolution of stellar clusters in galaxy simulations and observations

“…We do not provide much discussion of the evolution of the simulations as they are discussed elsewhere Ruiz-Lara et al 2016;Dobbs et al 2014), but we do give a brief summary here. In the isolated galaxy simulations, the gas arranges into dense clouds, preferentially along the arms, by a combination of gravitational instabilities, thermal instabilities and cloud-cloud collisions.…”

CALIFA, the Calar Alto Legacy Integral Field Area survey

“…vii) We studied the nature of the progenitors of SNe (Galbany et al 2014); viii) we explored star formation indicators for extended objects and the suitability of Hα as an SFR tracer (Catalán-Torrecilla et al 2015), as well as the spatially resolved SFR density across the Hubble sequence (González . ix) We studied oxygen abundance gradients in the gas, developing new calibrators (Marino et al 2013), finding a characteristic shape Sánchez-Menguiano et al 2016), and a weak dependence of the profile truncations on the gradient properties (Marino et al 2016) and the stellar populations (Ruiz-Lara et al 2016). x) We explored the mass-metallicity relation for both the stellar populations (González Delgado et al 2014a) and the gas oxygen abundance ).…”