First MATISSE L-band observations of HD 179218. Is the inner 10 au region rich in carbon dust particles?

TL;DR

This study uses MATISSE VLTI observations to investigate the presence and distribution of solid carbon dust in the inner 10 au of the protoplanetary disk around HD 179218, revealing insights into carbon reservoirs in planet-forming regions.

Contribution

First application of MATISSE L-band interferometry to spatially resolve and analyze solid carbon dust in the inner disk of HD 179218, combining IR continuum modeling with potential for future spectral feature detection.

Findings

Inner disk region contains carbonaceous material emitting in L-band

Temperature-gradient model fits IR continuum emission

Potential detection of carbon features with higher spectral resolution

Abstract

Carbon is one of the most abundant components in the Universe. While silicates have been the main focus of solid phase studies in protoplanetary discs (PPDs), little is known about the solid carbon content especially in the planet-forming regions ($\sim $0.1 to 10 au). Fortunately, several refractory carbonaceous species present C-H bonds (such as hydrogenated nano-diamond and amorphous carbon as well as polycyclic aromatic hydrocarbons (PAHs)), which generate infrared (IR) features that can be used to trace the solid carbon reservoirs. The new mid-IR instrument MATISSE, installed at the Very Large Telescope Interferometer (VLTI), can spatially resolve the inner regions ($\sim$ 1 to 10 au) of PPDs and locate, down to the au-scale, the emission coming from carbon grains. Our aim is to provide a consistent view on the radial structure, down to the au-scale, as well as basic physical properties and the nature of the material responsible for the IR continuum emission in the inner disk region around HD 179218. We implemented a temperature-gradient model to interpret the disk IR continuum emission, based on a multiwavelength dataset comprising a broadband spectral energy distribution (SED) and VLTI H-, L-, and N-bands interferometric data obtained in low spectral resolution. Then, we added a ring-like component, representing the carbonaceous L-band features-emitting region, to assess its detectability in future higher spectral resolution observations employing mid-IR interferometry.