A Unified Explanation for JWST Little Red Dots and High-Redshift Low-Mass Disk-like Galaxies: Prolate Galaxies Viewed End-on vs Side-on

TL;DR

This paper proposes that high-redshift, low-mass galaxies and the rare Little Red Dots observed by JWST can be explained by many being intrinsically prolate galaxies viewed end-on, with their observed properties resulting from orientation effects.

Contribution

The study introduces a unified geometric model linking prolate galaxy shapes to observed high-redshift galaxy morphologies and LRD features, explaining their rarity and properties without new physics.

Findings

Prolate galaxies viewed end-on appear as compact, reddened sources matching LRD characteristics.

The model predicts a 1-3% fraction of near end-on systems, consistent with JWST observations.

Orientation effects can account for the observed diversity in high-redshift galaxy morphologies.

Abstract

Recent JWST surveys have revealed two puzzling high-redshift phenomena: (1) an unexpectedly large abundance of flattened, disk-like galaxies at z > 3, and (2) a rare population of compact, extremely red sources at z ~ 4-9 ("Little Red Dots," LRDs) that often show V-shaped SEDs and very broad Balmer lines. These findings lack a consensus interpretation and have motivated models ranging from dusty starbursts to obscured AGN and more exotic scenarios. We propose that both phenomena are linked by a simple geometric consequence of a third clue: mounting evidence from structural modeling and axis-ratio statistics indicates that many low-mass galaxies at z > 3 are intrinsically prolate (cigar-like), not oblate rotation-supported disks. In this picture, a substantial fraction of the flattened, disk-like morphologies reported at z > 3 arise from side-on and intermediate-angle projections of prolate systems, while the rare near end-on views appear extremely compact and high-surface-brightness, and are preferentially reddened by the maximal line-of-sight column, naturally matching key elements of LRD selection. The expected fraction of near end-on systems, $P_{\text{end}} = 1 - \cos(\theta_{\text{max}})$, is ~1-3% for $\theta_{\text{max}}$ ~ 10{\deg}-15{\deg}, consistent with LRD demographics in wide JWST fields. This orientation-based framework does not exclude AGN or starburst activity; rather, it explains LRD rarity as an orientation effect and provides a natural route to the large columns of gas/dust and scattering depths inferred in recent dense-gas and electron-scattering interpretations of LRD spectra, without fine-tuned new physics. The model makes falsifiable predictions to validate or rule out this geometric interpretation.