(Re)solving the Complex Multiscale Morphology and V-shaped Spectral Energy Distribution of a Newly Discovered Strongly Lensed Little Red Dot in A383

Le résumé fourni par la source

Abstract We present a luminous “little red dot” (LRD) at z = 6.027, doubly imaged by the galaxy cluster A383 and observed with the James Webb Space Telescope (JWST) NIRCam. Owing to its large magnifications, μ ∼ 11 for image A383-LRD1A and μ ∼ 7 for A383-LRD1B, 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, the blue and red dots have rest-frame UV and optical sizes of ∼60 pc and ≲150 pc, respectively, while extended emission traced most clearly in F356W ([O III ]+H β ) reaches scales of order ∼1 kpc. Spatially resolved spectral energy distribution (SED) analysis reveals that the characteristic V-shaped SED arises from the superposition of a flat UV continuum from the blue dot, consistent with a young stellar population, and a steep red SED from the red dot, which, based on Hubble Space Telescope+JWST photometry alone, admits a straightforward stellar interpretation as a massive, heavily dust-attenuated component. However, this interpretation is challenged by Atacama Large Millimeter/submillimeter Array dust continuum upper limits, suggesting a nonstellar origin such as dense gas configurations. Separated by only ∼300 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 begin unraveling the physical nature of this population.

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