Eccentric debris disc morphologies II: Surface brightness variations from overlapping orbits in narrow eccentric discs

TL;DR

This paper investigates how free and forced eccentricities influence surface brightness patterns in narrow eccentric debris discs, revealing that observed glow features depend on disc width and resolution, challenging previous wavelength-only assumptions.

Contribution

It demonstrates that apocentre and pericentre glow phenomena are influenced by disc width and observational resolution, not just wavelength, providing new insights into debris disc morphology analysis.

Findings

Narrower discs show two radial brightness peaks, broader discs show one.

Brightness peaks merge with increasing disc width, first at apocentre then at pericentre.

Glow features depend on both disc width and observational resolution.

Abstract

We present Paper II of the Eccentric Debris Disc Morphologies series to explore the effects that significant free and forced eccentricities have on high-resolution millimetre-wavelength observations of debris discs, motivated by recent ALMA images of HD53143's disc. In this work, we explore the effects of free eccentricity, and by varying disc fractional widths and observational resolutions, show for a range of narrow eccentric discs, orbital overlaps result in dust emission distributions that have either one or two radial peaks at apocentre and/or pericentre. The narrowest discs contain two radial peaks, whereas the broadest discs contain just one radial peak. For fixed eccentricities, as fractional disc widths are increased, we show that these peaks merge first at apocentre (producing apocentre glow), and then at pericentre (producing pericentre glow). Our work thus demonstrates that apocentre/pericentre glows in models with constant free and forced eccentricities can be both width and resolution dependent at millimetre wavelengths, challenging the classical assertion that apocentre/pericentre glows are purely wavelength dependent. We discuss future high-resolution observations that can distinguish between competing interpretations of underlying debris disc eccentricity distributions.