arXiv subjects

Camille Bergez-Casalou

Publications and source records attributed to Camille Bergez-Casalou.

4 recordsLinked to original sources

arXiv2026

Planetary system architectures in the final stages of planet formation

The processes in the last stages of planet formation determine the final assembly and composition of planets. After the protoplanetary discs dissipate, a system of planets and planetesimals -- analogues of the Asteroid and Kuiper Belts -- remains. Ongoing collisions between these bodies produce second-generation dust and gas that form a debris disc. Resolved images of such belts allow us to trace the dynamical history of these systems, including giant impacts and planet-belt interactions, during the crucial era from 10 to a few 100 Myr of terrestrial planet formation. High-resolution mm and optical/near-IR imagers have revolutionised our view of the brightest planetesimal belts, providing first glimpses of diverse structures, many of which show plausible planet imprints, while ALMA has revealed gas in a growing number of systems. Yet these results are strongly biased toward the brightest, mostly young belts around early-type stars, and even for these, crucial details remain undetectable at the required resolution due to their typically low surface brightness. A future (sub-)mm facility with an order of magnitude leap in continuum sensitivity and 10x higher line sensitivity would transform our understanding of late-stage planet formation by enabling the first statistically meaningful surveys of faint outer planetesimal belts across all spectral types, imaging planetary collisions in the inner regions of planetary systems, and gas measurements that trace volatile delivery to terrestrial planets. For the first time, this would reach the faint majority of belts, rather than only the rare bright discs accessible today.

astro-ph.IM↗

arXiv2026

Hydrogen Line Emission in Accreting Low-Mass Objects I: Spectral Analysis of Shock-Origin Narrow Component

Hydrogen lines are widely used as tracers of stellar and planetary accretion. In classical T~Tauri stars, hydrogen lines are usually interpreted as arising from magnetospheric accretion columns, whereas in lower-mass counterparts (subsolar-mass objects including brown dwarfs and gas giant planets), the post-accretion-shock region can directly emit a substantial fraction of the hydrogen-line luminosity. However, the boundary between non-shock-dominated and shock-dominated cases has remained unclear. In this study, we compare hydrogen-line profiles predicted by the shock emission model with 254 observations of 164 low-mass accreting objects ($\lesssim 0.5\,M_\odot$) in the VLT/X-Shooter archive. We simultaneously fit seven hydrogen lines (H$β$, H$γ$, H6, H8, H9, Pa$β$, and Br$γ$), testing both line profiles and flux ratios within a single framework, and introduce a phenomenological broad-component-subtracted fit for cases with mixed non-shock and shock contributions. We find that shock emission dominates the hydrogen-line emission at object masses $M\lesssim0.05\,M_\odot$ or free-fall velocities $v_\mathrm{ff}<175\,\mathrm{km\,s^{-1}}$, but becomes minor at $M \gtrsim 0.2\,M_\odot$. The inferred flow velocities at the shock front are often significantly smaller than the free-fall velocity from infinity, implying smaller truncation radii and surface dipole magnetic field strengths of sub-kG. The accretion luminosities inferred from the shock-emission fitting are systematically larger than literature values, often by orders of magnitude, likely because conventional estimates neglect line emission that is non-negligible in low-mass objects. We also confirm that H$α$ is more susceptible than the other hydrogen lines to additional non-shock components.

astro-ph.SR↗

arXiv2024

An impact-free mechanism to deliver water to terrestrial planets and exoplanets

To date, the most widespread scenario is that the Earth originated without water and was brought to the planet mainly due to impacts by wet asteroids coming from further out in space. However, many uncertainties remain regarding the exact processes that supply water to inner terrestrial planets. This article explores a new mechanism that would allow water to be efficiently transported to planets without impacts. We propose that primordial asteroids were icy and that when the ice sublimated, it formed a gaseous disk that could then reach planets and deliver water. We have developed a new model that follows the sublimation of asteroids and evolves the subsequent gas disk using a viscous diffusion code. We can then quantify the amount of water that can be accreted onto each planet in a self-consistent manner. We find that this new disk-delivery mechanism can explain the water content on Earth as well as on other planets. Our model shows most of the water being delivered between 20 and 30 Myr after the birth of the Sun. Our scenario implies the presence of a gaseous water disk with substantial mass for 100s Myr, which could be one of the key tracers of this mechanism. We show that such a watery disk could be detected in young exo-asteroid belts with ALMA. We propose that viscous water transport is inevitable and more generic than the impact scenario. We also suggest it is a universal process that may also occur in extrasolar systems. The conditions required for this scenario to unfold are indeed expected to be present in most planetary systems: an opaque proto-planetary disk that is initially cold enough for ice to form in the exo-asteroid belt region, followed by a natural outward-moving snow line that allows this initial ice to sublimate after the dissipation of the primordial disk, creating a viscous secondary gas disk and leading to the accretion of water onto the exoplanets.

astro-ph.EP↗

arXiv2022

Simultaneous gas accretion onto a pair of giant planets: Impact on their final mass and on the protoplanetary disk structure

Several planetary systems are known to host multiple giant planets. However, when two giant planets are accreting from the same disk, it is unclear what effect the presence of the second planet has on the gas accretion process of both planets. In this paper we perform long-term 2D isothermal hydrodynamical simulations (over more than 0.5 Myrs) with the FARGO-2D1D code, considering two non-migrating planets accreting from the same gaseous disk. We find that the evolution of the planets' mass ratio depends on gap formation. However, in all cases, when the planets start accreting at the same time, they end up with very similar masses (0.9 $<m_{p,out}/m_{p,in}<$ 1.1 after 0.5 Myrs). Delaying the onset of accretion of one planet allows the planets' mass ratio to reach larger values initially, but they quickly converge to similar masses afterward (0.8 $<m_{p,out}/m_{p,in}<$ 2 in $10^5$ yrs). In order to reproduce the more diverse observed mass ratios of exoplanets, the planets must start accreting gas at different times, and their accretion must be stopped quickly after the beginning of runaway gas accretion (less than 0.5 Myrs), for example via disk dispersal. The evolution of the planets' mass ratio can have an important impact on the dynamics of the system and may constrain the formation history of Jupiter and Saturn.

astro-ph.EP↗