Interferometric Evidence for Quantum Heated Particles in the Inner Region of Protoplanetary Disks around Herbig Stars

TL;DR

This study provides interferometric evidence that quantum heated carbonaceous particles, such as PAHs, contribute significantly to the extended near-infrared flux observed in the inner regions of protoplanetary disks around Herbig stars, highlighting their role in planet formation environments.

Contribution

It demonstrates that quantum heating effects of very small carbonaceous grains are essential to explain the observed NIR flux, a novel insight into disk composition and heating processes.

Findings

Quantum heated particles explain extended NIR flux.

Correlation between PAH flux and NIR flux.

Small carbonaceous grains produce realistic SEDs.

Abstract

To understand the chemical composition of planets, it is important to know the chemical composition of the region where they form in protoplanetary disks. Due to its fundamental role in chemical and biological processes, carbon is a key element to trace. We aim to identify the carriers and processes behind the extended NIR flux observed around several Herbig stars. We compare the extended NIR flux from objects in the PIONIER Herbig Ae/Be survey with their flux in the PAH features. HD 100453 is used as a benchmark case to investigate the influence of quantum heated particles, like PAHs or very small carbonaceous grains, in more detail. We use the Monte Carlo radiative transfer code MCMax to do a parameter study of the QHP size and scale- height and examine the influence of quantum heating on the amount of extended flux in the NIR visibilities. There is a correlation between the PAH feature flux of a disk and the amount of its extended NIR flux. We find that very small carbonaceous grains create the observed extended NIR flux around HD 100453 and still lead to a realistic SED. These results can not be achieved without using quantum heating effects, e.g. only with scattered light and grains in thermal equilibrium. It is possible to explain the extended NIR emission around Herbig stars with the presence of carbonaceous, quantum heated particles. Interferometric observations can be used to constrain the spatial distribution and typical size of carbonaceous material in the terrestrial planet forming region.