Impact of planetesimal eccentricities and material strength on the appearance of eccentric debris disks

Abstract

Context. Since circumstellar dust in debris disks is short-lived, dust-replenishing requires the presence of a reservoir of planetesimals. These planetesimals in the parent belt of debris disks orbit their host star and continuously supply the disk with fine dust through their mutual collisions. Aims. We aim to understand effects of different collisional parameters on the observational appearance of eccentric debris disks. These parameters are the eccentricity of the planetesimal belt, dynamical excitation, and the material strength.Methods. The collisional evolution of selected debris disk configurations was simulated with the numerical code ACE. Subsequently, selected observable quantities are simulated with our newly developed code DMS. The impact of the eccentricity, dynamical excitation, and the material strength is discussed with respect to the grain size distribution, the spectral energy distribution, and spatially resolved images of debris disk systems. Results. The most recognizable features in different collisional evolutions are as follows. First, both the increase of dynamical excitation in the eccentric belt of the debris disk system and the decrease of the material strength of dust particles result in a higher production rate of smaller particles. This reduces the surface brightness differences between the periastron and the apastron sides of the disks. For very low material strengths, the "pericenter glow" phenomenon is reduced and eventually even replaced by the opposite effect, the "apocenter glow". In contrast, higher material strengths and lower dynamical excitation of the system result in an enhancement of asymmetries in the surface brightness distribution. Second, it is possible to constrain the level of collisional activity from the appearance of the disk, for example, the wavelength-dependent apocenter-to-pericenter flux ratio. Within the considered parameter space, the impact of the material strength on the appearance of the disk is stronger than that of dynamical excitation of the system. Finally, we find that the impact of the collisional parameters on the net spectral energy distribution is weak.

Constraining the detectability of water ice in debris disks

“…In summary, we considered grain sizes from 0.1 to 1000 µm with the above steady-state grain size distribution. We note that the nongravitational forces acting on grains particularly in the range of tens to hundreds of micrometers in diameter may further modify the size distribution (Krivov et al 2000;Krivov et al 2006;Plavchan et al 2005;Löhne et al 2017;Kim et al 2018). However, this effect has not been taken into account in the current study.…”

“…The simulation of observables of debris disks We used a newly developed software tool called debris disks around mainsequence stars (DMS; Kim et al 2018), which is optimized for simulating observables of debris disks, or in other words, optically thin systems. In particular, it allows us to simulate scattered light and thermal dust reemission images, the continuum spectral energy distribution (SED), and scattered light polarization images.…”

Demographics of young stars and their protoplanetary disks: lessons learned on disk evolution and its connection to planet formation

“…Swept-back "wings" in edge-on systems have been variously attributed to interactions with the ISM or eccentric planets, but the presence of millimeter emission in the haloes favors a dynamical explanation (like an eccentric planet) over gas drag that should act more strongly on smaller grains . The phenomenon of "apocenter glow" at millimeter wavelengths, due to the pileup of material that orbits more slowly at apocenter than at pericenter, has been definitively observed and is now being used as a tool to probe dust grain properties and the orbital properties of putative planets sculpting debris disks (Pan et al 2016;MacGregor et al 2017;Regály et al 2018;Kim et al 2018;Faramaz et al 2019).…”

Deep ALMA search for CO gas in the HD 95086 debris disc

“…Whilst the variations in spectral index across the disc seen in figure 7 are not found to be significant due to the low sensitivity of the band 3 and 7 data and the low resolution of the band 3 data, with deep resolved maps at multiple ALMA wavelengths, such methods could be used to determine such variations. Variations are expected, for instance, in the case of an eccentric disc, where a difference in size distribution is expected between the pericentre and apocentre due to it being easier to remove small grains by radiation pressure at the pericentre than at the apocentre (Löhne et al 2017;Kim et al 2018).…”