X-ray View of Little Red Dots: Do They Host Supermassive Black Holes?

The discovery of Little Red Dots (LRDs) -- a population of compact, high-redshift, dust-reddened galaxies -- is one of the most surprising results from JWST. However, the nature of LRDs is still debated: some studies suggest that these galaxies host accreting supermassive black holes (SMBHs), while others conclude that the near-infrared emission primarily originates from intense star formation. In this work, we utilize ultra-deep Chandra observations and study LRDs residing behind the lensing galaxy cluster, Abell~2744. We probe the X-ray emission from individual galaxies but find that they remain undetected and provide SMBH mass upper limits of (1. 5-16) 10^6~M_ assuming Eddington limited accretion. To increase the signal-to-noise ratios, we conduct a stacking analysis of the full sample with a total lensed exposure time of 87~Ms. We also bin the galaxies based on their stellar mass, lensing magnification, and detected broad-line H emission. All but one stacked sample remains undetected with SMBH mass upper limits of 2. 510^6~M_. We obtain a tentative, 2. 6 detection for LRDs exhibiting broad-line H emission. Taking this detection at face value, the inferred mean SMBH mass is 3. 210^6~M_ assuming Eddington-limited accretion, about 1. 5 orders of magnitude lower than that inferred from JWST data. Our results imply that LRDs do not host over-massive SMBHs and/or accrete at a few percent of their Eddington limit. The significant discrepancy between the JWST and Chandra data hints that the scaling relations used to infer the SMBH mass from the H line and virial relations may not be applicable for high-redshift LRDs.