Delayed Reconstruction of Gravitational Geometry in Dissociative Galaxy Cluster Mergers

Gravitational lensing observations of dissociative galaxy cluster mergers, such as the Bullet Cluster and El Gordo, exhibit spatial offsets between the peaks of the lensing mass distribution and the X-ray emitting intracluster gas. These offsets are commonly interpreted under the implicit assumption that gravitational geometry responds instantaneously to changes in the mass distribution.

In this work, that assumption is tested empirically. Using a small but well-constrained sample of dissociative galaxy cluster mergers spanning approximately 0.1–1 Gyr after first core passage, we demonstrate that the observed lensing–gas offsets systematically decrease with increasing time since merger. The data are well described by a minimal exponential relaxation law characterized by a reconstruction timescale of order τ ≈ 0.9 ± 0.3 Gyr.

The results indicate that gravitational geometry in large, violently perturbed systems is not realized instantaneously, but undergoes a delayed global reconstruction following major merger events. This behavior does not require any modification of local General Relativity and is consistent with standard local gravitational tests, while placing new empirical constraints on the interpretation of lensing observations in dynamically disturbed systems.