arXiv subjects

Maxime Roumesy

Publications and source records attributed to Maxime Roumesy.

4 recordsLinked to original sources

arXiv2026

Probing dust properties through polarized scattered-light images of a sample of ring-shaped protoplanetary disks

The evolution of protoplanetary disks, especially in the early stages of planetary formation, as dust grows, is the cornerstone of the birth of planets. The mechanisms involved in the growth of sub-micrometric dust grains into planetesimals within a very short time frame are a challenging field of study, while the initial conditions remain relatively undefined. One of the main challenges is to unambiguously identify the dust properties within the disk, and our goal is to break this barrier by investigating the light scattered by dust particles lying on the protoplanetary disk surface from many recent promising observations. In this study, we used a set of 30 polarized light images composed of new VLT/SPHERE observations to examine the light scattered by dust grains. For each ring-shaped system, we used the new DRAGyS tool to estimate the disk geometry using the substructures visible on the surface and to extract the limb-brightening-corrected scattering phase function, which encodes the dust grains' physical properties. Finally, we compared our results with the AggScatVIR database of numerical scattering phase functions of nonspherical dust. We combined our measurements of disk geometry to estimate an average disk flaring of about 1.357. First, we recovered the two categories of scattering phase functions based on their shape, as determined in previous studies. Category I is monotonically decreasing and can be explained by fractal organic aggregates with small monomers of 100nm, or compact aggregates with medium porosity and big monomers of 400nm. Category II is defined by a bell-shaped scattering phase function and can be explained by sub-micrometric irregular grains or compact aggregates with low porosity. This statistical study offers general trends about dust populations, but the degeneracy is too strong to apply this method to a unique disk analysis.

astro-ph.SR↗

arXiv2025

DRAGyS -- A comprehensive tool to extract scattering phase functions in protoplanetary disks

The early stages of planet formation, involving dust grain growth and planetesimals formation, remain shrouded in mystery. The analysis of the Scattering Phase Function (SPF) measured in disks surrounding young stars holds great potential for revealing crucial information about dust grain properties. Given the increasing number of high-quality datasets available, an efficient method to extract the SPF is required. DRAGyS is a tool designed for the quick and comprehensive analysis of ring-shaped protoplanetary disks. It directly estimates the disk geometry and extracts the total and polarized SPF from scattered light images, without requiring any radiative transfer modeling, a limitation of previous efforts. Key disk parameters (inclination, position angle, aspect ratio) are obtained by fitting ellipses to the disk intensity peaks from the ring surface, assuming the disks are circular. We validated the method using simulated disk images and then applied it to archival polarized-intensity images of nine images for six protoplanetary disks. DRAGyS provides a method to correct for the effect of limb brightening on the SPF. DRAGyS recovers well the injected geometry and the SPF from synthetic images where the parameters are known. When compared to previously published results extracted from images without considering limb brightening, DRAGyS yields similar results for the inclination, position angle, and SPF. We show that the effect of limb brightening on the SPF is significant, with consequences for the inference of dust properties. DRAGyS takes advantage of a fast and purely geometrical approach to estimate ringed-disk geometries. It allows the efficient extraction of SPF either globally or by sectors, allowing it to deal with disk asymmetries. By bypassing the need for a full modeling of the disk geometry before SPF extraction, DRAGyS is well suited to study large samples of disk images.

astro-ph.IM↗

arXiv2024

JWST Imaging of Edge-on Protoplanetary Disks. IV. Mid-infrared Dust Scattering in the HH 30 disk

We present near- and mid-infrared (IR) broadband imaging observations of the edge-on protoplanetary disk around HH 30 with the James Webb Space Telescope/Near Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI). We combine these observations with archival optical/near-IR scattered light images obtained with the Hubble Space Telescope (HST) and a millimeter-wavelength dust continuum image obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) with the highest spatial resolution ever obtained for this target. Our multiwavelength images clearly reveal the vertical and radial segregation of micron-sized and sub-mm-sized grains in the disk. In the near- and mid-IR, the images capture not only bi-reflection nebulae separated by a dark lane but also diverse dynamical processes occurring in the HH 30 disk, such as spiral- and tail-like structures, a conical outflow, and a collimated jet. In contrast, the ALMA image reveals a flat dust disk in the disk midplane. By performing radiative transfer simulations, we show that grains of about 3 $\mu$m in radius or larger are fully vertically mixed to explain the observed mid-IR scattered light flux and its morphology, whereas millimeter-sized grains are settled into a layer with a scale height of $\gtrsim1$ au at $100$ au from the central star. We also find a tension in the disk inclination angle inferred from optical/near-IR and mm observations with the latter being closer to an exactly edge-on. Finally, we report the first detection of the proper motion of an emission knot associated with the mid-IR collimated jet detected by combining two epochs of our MIRI 12.8-$\mu$m observations.

astro-ph.EP↗

arXiv2024

The grazing angle icy protoplanetary disk PDS 453

PDS 453 is a rare highly inclined disk where the stellar photosphere is seen at grazing incidence on the disk surface. Our goal is take advantage of this geometry to constrain the structure and composition of this disk, in particular the fact that it shows a 3.1 $\mu$m water ice band in absorption that can be related uniquely to the disk. We observed the system in polarized intensity with the VLT/SPHERE instrument, as well as in polarized light and total intensity using the HST/NICMOS camera. Infrared archival photometry and a spectrum showing the water ice band are used to model the spectral energy distribution under Mie scattering theory. Based on these data, we fit a model using the radiative transfer code MCFOST to retrieve the geometry and dust and ice content of the disk. PDS 453 has the typical morphology of a highly inclined system with two reflection nebulae where the disk partially attenuates the stellar light. The upper nebula is brighter than the lower nebula and shows a curved surface brightness profile in polarized intensity, indicating a ring-like structure. With an inclination of 80{\deg} estimated from models, the line-of-sight crosses the disk surface and a combination of absorption and scattering by ice-rich dust grains produces the water ice band. PDS 453 is seen highly inclined and is composed of a mixture of silicate dust and water ice. The radial structure of the disk includes a significant jump in density and scale height at a radius of 70 au in order to produce a ring-like image. The depth of the 3.1 $\mu$m water ice band depends on the amount of water ice, until it saturates when the optical thickness along the line-of-sight becomes too large. Therefore, quantifying the exact amount of water from absorption bands in edge-on disks requires a detailed analysis of the disk structure and tailored radiative transfer modeling.

astro-ph.SR↗