Boundary-supported radial layering in Hoag-like ring galaxies

TL;DR

This paper proposes a boundary-supported radial-layering mechanism in Hoag-like ring galaxies, explaining their structure through a shell deformation model and identifying parameters consistent with observed galaxies.

Contribution

It introduces a novel shell-deformed Kepler model to explain the formation of gaps and rings in Hoag-like galaxies, supported by Monte Carlo simulations.

Findings

The model reproduces observed gap-to-ring ratios in several Hoag-like galaxies.

Localized boundary-supported candidates do not contain ordered interior minima-maxima-minima sequences.

The mechanism explains the formation of detached rings and gaps in these galaxies.

Abstract

Clean Hoag-like ring galaxies are often characterized by an old compact central component, a depleted gap, and a detached outer ring. We identify a boundary-supported radial-layering mechanism in a shell-deformed Kepler control model. A compact inner boundary supplies the core state, while a localized effective shell deformation, interpreted as the reduced imprint of externally supplied material settled near a finite circularization radius, needs to create only an internal maximum and a subsequent outer minimum. These act as the gap barrier and ring-supporting well. The onset of this structure is organized by a saddle-node threshold of the critical-point equation. In a 10^4-point Monte Carlo scan, shell-localized boundary-supported candidates occupy finite parameter volume under the adopted priors, and none of the localized candidates contains an ordered interior minimum--maximum--minimum subsequence. The same branch gives a scale-free gap-to-ring interval overlapping representative ratios for Hoag's Object, UGC 4599, and PGC 1000714, but not for the environmentally processed comparison object JO171.