arXiv subjects

Simona Pirani

Publications and source records attributed to Simona Pirani.

4 recordsLinked to original sources

arXiv2026

Mercury-Ar$\chi$es: a high-performance n-body code for planet formation studies

Forming planetary systems are populated by large numbers of gravitationally interacting planetary bodies, spanning from massive giant planets to small planetesimals akin to present-day asteroids and comets. All these planetary bodies are embedded in the gaseous embrace of their native protoplanetary disks, and their interactions with the disk gas play a central role in shaping their dynamical evolution and the outcomes of planet formation. These factors make realistic planet formation simulations extremely computationally demanding, which in turn means that accurately modeling the formation of planetary systems requires the use of high-performance methods. The planet formation code Mercury-Ar$\chi$es was developed to address these challenges and, since its first implementation, has been used in multiple exoplanetary and Solar System studies. Mercury-Ar$\chi$es is a parallel n-body code that builds on the widely used Mercury code and is capable of modeling the growth and migration of forming planets, the interactions between planetary bodies and the disk gas, as well as the evolving impact flux of planetesimals on forming planets across the different stages of their formation process. In this work we provide the up-to-date overview of its physical modeling capabilities and the first detailed description of its high-performance implementation based on the OpenMP directive-based parallelism for shared memory environments, to harness the multi-thread and vectorization features of modern processor architectures.

astro-ph.EP↗

arXiv2021

How the formation of Neptune shapes the Kuiper belt

Inward migration of giant planets is predicted by hydrodynamical simulations during the gas phase of the protoplanetary disc. The phenomenon is also invoked to explain resonant and near-resonant exoplanetary system structures. The early inward migration may also have affected our Solar System and sculpted its different minor planet reservoirs. In this study we explore how the early inward migration of the giant planets shapes the Kuiper Belt. We test different scenarios with only Neptune and Uranus and with all the four giant planets, including also some models with the subsequent outward planetesimal-driven migration of Neptune after the gas dispersal. We find objects populating mean motion resonances even when Neptune and Uranus do not migrate at all or only migrate inwards. When the planets are fixed, planetesimals stick only temporarily to the mean motion resonances, while inwards migration yields a new channel to populate the resonances without invoking convergent migration. In these cases, however, it is hard to populate mean motion resonances that do not cross the planetesimal disc (such as 2:1 and 5:2) and there is a lack of resonant KBOs that cross Neptune's orbit. These Neptune crossers are an unambiguous signature of the outward migration of Neptune. The starting position and the growth rate of Neptune matters for the contamination of the classical Kuiper belt region from neighbouring regions. The eccentricity and inclination space of the hot classicals and the scattered disc region become much more populated when all the giant planets are included. The 5:2 resonance with Neptune becomes increasingly populated with deeper inward migrations of Neptune. The overall inclination distribution, however, is still narrower than from observations, as is generally the case for Kuiper belt population models.

astro-ph.EP↗

arXiv2019

On the inclinations of the Jupiter Trojans

Jupiter Trojans are are characterized by dark photometric colors, high inclinations and an asymmetry in number of bodies between the two swarms. Different models have been proposed to explain the high inclination of the Trojans and to interpret their relation with the TNOs, but none of them can also satisfactorily explain the asymmetry ratio. Recently it has been found that the asymmetry can arise if Jupiter has migrated inwards by at least a few au during its growth. The asymmetry and the dark colors of the Trojans are natural outcomes of this model, but simulations with massless unperturbed disc particles led to a flat distribution of the Trojan inclinations and a final total mass that was 3-4 orders of magnitude larger than the current one. In our work, we investigate the possible origin of the peculiar inclination distribution of the Trojans in the scenario where Jupiter migrates inwards. We analyze different possibilities: (a) the secular evolution of an initially flat Trojan population, (b) the presence of planetary embryos among the Trojans and (c) capture of the Trojans from a pre-stirred planetesimal population. We find that the secular evolution of the Trojans and Saturn do not affect the Trojan inclinations appreciably, nor is there any significant mass depletion. Embryos embedded in the swarms, in contrast, can stir the Trojan inclinations and can also deplete the swarms efficiently, but it turns out that it is very difficult to get rid of all of the massive bodies. We propose that the disc where Jupiter's core was forming was already excited by the presence of other embryos competing in Jupiter's core's feeding zone. We show that the trapped Trojans preserve their high inclination through the gas phase of the disc and that Saturn's perturbations are more effective on highly inclined Trojans, leading to a lower capture efficiency and to a substantial depletion of the swarms.

astro-ph.EP↗

arXiv2019

The consequences of planetary migration on the minor bodies of the early Solar System

Pebble accretion is an efficient mechanism able to build up the core of the giant planets within the lifetime of the protoplanetary disc gas-phase. The core grows via this process until the protoplanet reaches its pebble isolation mass and starts to accrete gas. During the growth, the protoplanet undergoes a rapid, large-scale, inward migration due to the interactions with the gaseous protoplanetary disc. In our work, we investigate how this early migration would have affected the minor body populations in our solar system. In particular, we focus on the Jupiter Trojans and the Hildas asteroids. We found that a massive and eccentric Hilda group is captured during the migration from a region between 5 and 8 au and subsequently depleted during the late instability of the giant planets. Our simulations also show that inward migration of the giant planets always produces a Jupiter Trojans' leading swarm more populated than the trailing one, with a ratio comparable to the current observed Trojan asymmetry ratio. The in situ formation of Jupiter, on the other hand, produces symmetric leading/trailing swarms. The reason for the asymmetry is the relative drift between the migrating planet and the particles in the coorbital resonance. The capture happens during the growth of Jupiter's core and Trojan asteroids are afterwards carried along during the giant planet's migration to their final orbits. The asymmetry and eccentricity of the captured Trojans correspond well to observations, but their inclinations are near zero and their total mass is 3-4 orders of magnitude higher than the current population. Future modelling will be needed to understand whether the dynamical evolution of the Trojans over billions of years will raise the inclinations and deplete the masses to observed values.

astro-ph.EP↗