The Astrophysical Journal Letters (Jan 2024)

The First Robust Evidence Showing a Dark Matter Density Spike Around the Supermassive Black Hole in OJ 287

  • Man Ho Chan,
  • Chak Man Lee

DOI
https://doi.org/10.3847/2041-8213/ad2465
Journal volume & issue
Vol. 962, no. 2
p. L40

Abstract

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Black hole dynamics suggests that dark matter would redistribute near a supermassive black hole (SMBH) to form a density spike. However, no direct evidence of a dark matter density spike around an SMBH has been identified. In this Letter, we present the first robust evidence showing a dark matter density spike around an SMBH. We revisit the data of the well-known SMBH binary OJ 287 and show that the inclusion of the dynamical friction due to a dark matter density spike around the SMBH can satisfactorily account for the observed orbital decay rate. The derived spike index ${\gamma }_{\mathrm{sp}}={2.351}_{-0.045}^{+0.032}$ gives an excellent agreement with the value γ _sp = 2.333 predicted by the benchmark model assuming an adiabatically growing SMBH. This provides a strong verification of the canonical theory suggested two decades ago modeling the gravitational interaction between collisionless dark matter and SMBHs.

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