A Novel Method to Estimate the FUV Flux and a Catalogue for Star-Hosting Discs in Nearby Star-Forming Regions

TL;DR

This paper introduces a new method to estimate FUV flux at star-hosting discs using local star density distributions, improving accuracy over previous techniques, and provides a comprehensive catalogue for nearby star-forming regions.

Contribution

The paper presents a novel approach to infer 3D star-disc separations from 2D data, enabling more accurate FUV flux estimation in star-forming regions.

Findings

Discs near early-type stars experience significant FUV irradiation (10-100 G0).

Hints of a negative correlation between dust disc mass and FUV flux.

Median FUV fluxes are not heavily affected by interstellar dust extinction.

Abstract

Protoplanetary discs, when externally irradiated by Far Ultraviolet (FUV) photons from OBA-type stars, lose material through photoevaporative winds, reducing the amount of material available to form planets. Understanding the link between environmental irradiation and observed disc properties requires accurately evaluating the FUV flux at star-hosting discs, which can be challenging due stellar parallax uncertainties. In this paper, we address this issue proposing a novel approach: using the local density distribution of a star-forming region (i.e. 2D pairwise star separations distribution) and assuming isotropy, we infer 3D separations between star-hosting discs and massive stars. We test this approach on synthetic clusters, showing that it significantly improves the accuracy compared to previous methods. We compute FUV fluxes for a large sample of star-bearing discs in 7 regions within 200 pc, 6 regions in Orion, and Serpens sub-regions, providing a publicly accessible catalogue. We find that discs in regions hosting late-type B and early-type A stars can reach non-negligible irradiation levels for disc evolution (10-100 G0). We investigate dust disc masses relative to FUV fluxes detecting hints of a negative correlation when restricting to average region ages. However, we emphasize the need for more stellar and disc measurements at >10^2 G0 to probe the dependence of disc properties on the environmental irradiation. Including average interstellar dust extinction, median FUV fluxes are not significantly attenuated, though this result may change if high-resolution 3D dust extinction maps were available. The method presented in this work is a powerful tool that can be expanded to additional regions.