(Re)solving the complex multi-scale morphology and V-shaped SED of a newly discovered strongly-lensed Little Red Dot in Abell 383

TL;DR

This study uses JWST observations of a strongly-lensed high-redshift galaxy to resolve its complex multi-scale morphology, revealing two distinct components that explain its characteristic V-shaped SED, offering insights into the nature of Little Red Dots.

Contribution

First spatially resolved analysis of a strongly-lensed Little Red Dot, revealing its internal structure and the origin of its V-shaped SED, advancing understanding of early galaxy populations.

Findings

The system shows two distinct components separated by ~300 pc.

The red component may be an evolved stellar population or an AGN.

The blue component is consistent with a young stellar population.

Abstract

We present a luminous Little Red Dot (LRD) at $z=6.027$, doubly imaged by the galaxy cluster Abell 383 and observed with JWST/NIRCam. The source shows the characteristic "V-shaped" SED and pronounced Balmer break that define the LRD population. Owing to its large magnifications, $\mu\sim11$ for image S1 and $\mu\sim7$ for S2, the system is exceptionally bright and highly stretched, providing a rare, spatially resolved view of an LRD. The images reveal a complex morphology with a compact red dot, a spatially offset blue dot, and faint emission bridging and surrounding the two. After correcting for lensing, we find that both dots are extremely small but resolved, with rest-frame UV sizes of $\sim 20$ pc (red) and $\sim60$ pc (blue). These compact dots are embedded in a more extended, line-dominated cloud traced most clearly in F356W ([OIII]+H$\beta$), which reaches scales of order $\sim$1 kpc. SED decomposition shows that the blue component has a flat UV continuum consistent with a young stellar population, whereas the red component has a steep red SED that can be interpreted as either an evolved stellar population with high stellar mass ($\log M_\star/M_\odot>10$) or a reddened AGN. If this object is representative of the LRD population, our results imply that the V-shaped SEDs of LRDs do not arise from individual compact sources but instead from the superposition of two physically distinct components. Separated by only $\sim300$ pc in the source plane, these components would blend into a single compact source in unlensed observations with the canonical LRD colors. This system therefore provides a rare opportunity to resolve the internal structure of an LRD and to gain direct insight into the physical nature of this population.