Abstract

JWST has revealed a new high-redshift population called little red dots (LRDs). Since LRDs may be in the early phase of black hole growth, identifying them in the early Universe is crucial for understanding the formation of the first supermassive black holes. However, no robust LRD candidates have been identified at z > 10, because commonly used NIRCam photometry covers wavelengths up to similar to 5 mu m and is insufficient to capture the characteristic V-shaped spectral energy distributions (SEDs) of LRDs. In this study, we present the first search for z greater than or similar to 10 LRD candidates using both NIRCam and MIRI imaging from COSMOS-Web, which provides the largest joint NIRCam-MIRI coverage to date (0.20 deg(2)). Taking advantage of MIRI/F770W to remove contaminants, we identify one robust candidate, CW-LRD-z10 at z(phot)=10.5(-0.6)(+0.7) with MUV=-19.9(-0.2+0.1)mag . CW-LRD-z10 exhibits a compact morphology, a distinct V-shaped SED, and a nondetection in F115W, all consistent with being an LRD at z similar to 10. Based on this discovery, we place the first constraint on the number density of LRDs at z similar to 10 with MUV similar to -20 of 1.2(-1.0)(+2.7)x10(-6)Mpc-3mag-1 , suggesting that the fraction of LRDs among the overall galaxy population increases with redshift, reaching similar to 3% at z similar to 10. Although deep spectroscopy is necessary to confirm the redshift and the nature of CW-LRD-z10, our results imply that LRDs may be a common population at z > 10, playing a key role in the first supermassive black hole formation.