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arXiv · 2510.25830

Extended Components of Little Red Dots in the Rest-Frame Optical

Yiyang Zhang·Xuheng Ding·Lilan Yang·Erini Lambrides·Hollis Akins·Andrew J. Battisti·Caitlin M. Casey·Chang-hao Chen·Isa Cox·Andreas Faisst·Maximilien Franco·Aryana Haghjoo·Luis C. Ho·Kohei Inayoshi·Shuowen Jin·Mitchell Karmen·Anton M. Koekemoer·Jeyhan S. Kartaltepe·Kai Liao·Ghassem Gozaliasl·Masafusa Onoue·Vasily Kokorev·Namrata Roy·R. Michael Rich·John D. Silverman·Takumi S. Tanaka·Bei You·Hassen M. Yesuf·Jorge A. Zavala
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Abstract

Recent JWST observations have revealed a population of red, compact, high-redshift objects called Little Red Dots (LRDs), whose host components have remained largely unconstrained, possibly due to their extreme compactness. Current morphological studies suggest the presence of extended emission in LRDs at rest-frame ultraviolet wavelengths. However, in the rest-frame optical regime, investigations have been limited by small sample sizes and insufficient imaging depth, hindering reliable separation between point-like and potential extended components. Here we perform the image stacking analysis of 217 LRDs in four NIRCam bands, a large and homogeneous sample observed with the COSMOS-Web survey. Our results reveal the detection of faint extended emission in the F444W band, with a typical size of ~200 parsecs and magnitude of ~27.7 AB at z~6.5. We perform four-band photometric spectral energy distribution fitting based on galaxy templates and derive an average stellar mass of log(M*/M_sun) = 9.02 +0.20/-0.18. Given this stellar mass, the host galaxy is compact, that is, ~2.5 times smaller than star-forming galaxies of similar mass at comparable redshifts. This work provides direct observational evidence for the existence of LRD host galaxies at rest-frame optical wavelengths and offers new insights into the stellar buildup of these systems within the first billion years after the Big Bang.

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Yiyang Zhang, Xuheng Ding, Lilan Yang, Erini Lambrides, Hollis Akins, Andrew J. Battisti, Caitlin M. Casey, Chang-hao Chen, Isa Cox, Andreas Faisst, Maximilien Franco, Aryana Haghjoo, Luis C. Ho, Kohei Inayoshi, Shuowen Jin, Mitchell Karmen, Anton M. Koekemoer, Jeyhan S. Kartaltepe, Kai Liao, Ghassem Gozaliasl, Masafusa Onoue, Vasily Kokorev, Namrata Roy, R. Michael Rich, John D. Silverman, Takumi S. Tanaka, Bei You, Hassen M. Yesuf, Jorge A. Zavala. 2025-10-29. Extended Components of Little Red Dots in the Rest-Frame Optical. https://doi.org/10.1038/s41550-026-02945-z

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