Black Holes in the Red-sequence Elliptical Galaxies at Redshifts $\sim 0.7-2.5$: Not Dark Energy Source but Remanants of Little Red Dots

Lei Lei, Ze-Fan Wang, Yi-Ying Wang, Lei Feng, Yi-Zhong Fan

First listed 2025-06-24 | Last updated 2025-06-24

Abstract

The nature of dark energy remains one of the most profound mysteries in modern cosmology. One intriguing proposal is that black holes (BHs) could be the astrophysical source of dark energy through a cosmological coupling mechanism, and strong evidence has been claimed via analyzing the growth of the black hole masses in the red-sequence elliptical galaxies at redshifts $\leq 2.5$. In this work, with a group of very high redshift AGNs detected by the James Webb Space Telescope (JWST) in the red-sequence elliptical galaxies, we show that the possibility of BHs being the astrophysical source of dark energy has been rejected at a confidence level exceeding 10$σ$. Moreover, it turns out that the Little Red Dots recently discovered by JWST, characterized by the low accretion rates, can naturally evolve into the red-sequence elliptical galaxies hosting the relatively low mass black holes at the redshifts of $\sim 0.7-2.5$, without the need of black hole cosmological coupling.

Short digest

Uses a JWST-selected set of very high‑z AGNs in red‑sequence ellipticals to test black‑hole cosmological coupling via the MBH–M* fundamental plane. The sample aligns with the local relation and yields a posterior on the coupling strength that rejects the “BHs as dark energy” scenario at >10σ, contradicting earlier claims of strong coupling. Simulations and data further show that low‑accretion Little Red Dots can evolve into the z≈0.7–2.5 red‑sequence ellipticals hosting relatively low‑mass BHs, eliminating the need for cosmological coupling. This links JWST LRD demographics to later ETG BH masses while removing BHs as a viable dark‑energy source.

Key figures to inspect

• Figure 1: Compare JWST AGNs to the local MBH–M* relation and the blue dashed prediction for nonzero coupling; note that the high‑z points track the local plane rather than the coupled-growth track.
• Figure 2: Inspect the posterior for the coupling parameter; quantify how far the peak and credible intervals lie from the strong‑coupling value and note the >10σ exclusion relative to previous claims.
• Figure 3: Follow the simulated LRD evolutionary contours across redshift and see how they overlap both JWST LRD measurements and the red-/blue-point AGN samples, supporting an LRD→red‑sequence ETG pathway.