REVIEW
A Dark-Matter Spike at the Galactic Center?
Astrophysics · Submitted 26 Jan 2001 · 19 references
Pith's verdict: The off-center seed channel is a real loophole in Gondolo-Silk, but the Fig. 3 inspiral boundary that carries the quantitative claim is quoted at the wrong radius and with an un-contracted halo.
T0 · AI review
Why Pith says this
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Referee report
The paper
The paper claims
The claimed dark-matter spike at the Galactic center is not a generic prediction: it requires the central black hole to have grown slowly, from a near-zero seed, exactly at the center of a cuspy halo made of very cold orbits, and realistic黑
The reading
What carries the argument
The argument rests on adiabatic invariants in a spherical potential: the angular momentum $L$ and the radial action $J_r$ are conserved when the black hole grows slowly, so the distribution function is carried over unchanged, $f_f(E_f,L)=f_i(E_i,L)$. For an initial power-law cusp $rho_i propto r^{-gamma}$ this gives the spike slope $A=(9-2gamma)/(4-gamma)$, i.e. $2.25 < A < 2.5$ for $0<gamma<2$, and a circular-orbit toy model reproduces the same scaling from angular-momentum conservation alone. The competing piece of machinery is the dynamical-friction inspiral time, which sets whether a seed can reach the center at all and therefore decides which regime the Galaxy is in.
Extended reading notes
Core claim
The paper's central claim is that the Gondolo-Silk very-dense spike, with a dark-matter density profile steeper than $r^{-2}$, is an artifact of an idealized setup rather than a robust consequence of black-hole growth. Reproducing the standard adiabatic-contraction machinery, the authors confirm that a black hole grown slowly at the exact center of an NFW cusp does produce a spike with slope $A=7/3$, matching the earlier result. But they then show the spike is built entirely from particles that were initially on very cold orbits within roughly the inner 50 pc, the region enclosing about the black-hole mass. If the seed black hole forms off-center, it must sink by dynamical friction, and the Chandrasekhar inspiral time exceeds a Hubble time unless the seed is already at least a significant fraction of the present black-hole mass. A seed that heavy heats and evacuates the inner cusp as it sinks, leaving a shallow $r^{-0.5}$ profile instead of a spike; a seed light enough to preserve the spike cannot arrive in time. The subsequent at-the-center growth of the black hole squeezes the remaining halo only mildly, whether that growth is adiabatic or instantaneous.
Load-bearing premise
The verdict hinges on the dynamical-friction inspiral time computed with Chandrasekhar's formula, which the authors themselves note depends on the Coulomb factor and orbital eccentricity, and whose threshold falls only a factor of a few from the Hubble time at the relevant 100 pc scale.
Editorial extensions
If this is right
- Null searches for neutralino annihilation radiation from the Galactic center cannot be used to exclude neutralino dark matter, because the predicted flux depends on a spike that need not be there.
- Likewise, such null searches do not constrain whether the Milky Way's dark halo has a central cusp, since the cusp can be heated away by the black hole's own inspiral.
- The existence of a dark-matter spike becomes a probe of black-hole formation history: a detected spike would favor slow growth from a tiny seed placed essentially at the halo center.
- For a seed to sink to the center within a Hubble time it must be at least roughly a tenth of the present black-hole mass, which in turn means the cusp is destroyed rather than amplified.
- Any annihilation signal predicted for the Galactic center should be computed with a shallow, inspiral-heated profile rather than the steep adiabatic spike.
Reading between the lines
- The paper turns a dark-matter prediction into a black-hole-formation discriminator: the presence or absence of a spike measures where and how fast the seed formed, which is otherwise hard to observe.
- The same reasoning should apply to other galaxies with measured black-hole masses: the spike, and hence the annihilation flux, should be suppressed wherever the black hole shows evidence of having merged or sunk into place rather than grown in situ.
- If the inspiral threshold is really a factor-of-a-few boundary around the Hubble time, then a modest improvement in the inner potential from baryonic compression could flip individual galaxies between the spike and no-spike regimes, making the prediction environment-dependent rather than universal.
- An independent handle would be a direct measurement of the central dark-matter profile slope on 10-100 pc scales, which would test whether the cusp survives to the radii where the spike would have to be built.
Original abstract
The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. We compute this effect in realistic growth models of the present (2-3)*10**6 solar mass BH from a low-mass seed BH, with special attention to dynamical modeling in a realistic galaxy environment with merger and orbital decay of a seed BH formed generally outside the exact center of the halo. An intriguing ``very-dense spike'' of dark matter has been claimed in models of Gondolo and Silk with density high enough to contradict with experimental upper bounds of neutralino annihilation radiation. This ``spike'' disappears completely or is greatly weakened when we include important dynamical processes neglected in their idealized/restrictive picture with cold particles surrounding an at-the-center zero-seed adiabaticly-growing BH. For the seed BH to spiral in and settle to the center within a Hubble time by dynamical friction, the seed mass must be at least a significant fraction of the present BH. Any subsequent at-the-center growth of the BH and steepening of the central Keplerian potential well can squeeze the halo density distribution only mildly, whether the squeezing happens adiabatically or instantaneously.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. We compute this effect in realistic growth models of the present (2-3)*10**6 solar mass BH from a low-mass seed BH, with special attention to dynamical modeling in a realistic galaxy environment with merger and orbital decay of a seed BH formed generally outside the exact center of the halo. An intriguing ``very-dense spike'' of dark matter has been claimed in models of Gondolo and Silk with density high enough to contradict with experimental upper bounds of neutralino annihilation radiation. This ``spike'' disappears completely or is greatly weakened when we include important dynamical processes neglected in their idealized/restrictive picture with cold particles surrounding an at-the-center zero-seed adiabaticly-growing BH. For the seed BH to spiral in and settle to the center within a Hubble time by dynamical friction, the seed mass must be at least a significant fraction of the present BH. Any subsequent at-the-center growth of the BH and steepening of the central Keplerian potential well can squeeze the halo density distribution only mildly, whether the squeezing happens adiabatically or instantaneously.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. | background 0.99 | 0.08 | 0.09 | speculative 0.89 |
| s1 | We compute this effect in realistic growth models of the present (2-3)*10**6 solar mass BH from a low-mass seed BH, with special attention to dynamical modeling in a realistic galaxy environment with merger and orbital decay of a seed BH formed generally outside the exact center of the halo. | method 0.60 | 0.94 | 0.05 | asserted 0.95 |
| s2 | An intriguing ``very-dense spike'' of dark matter has been claimed in models of Gondolo and Silk with density high enough to contradict with experimental upper bounds of neutralino annihilation radiation. | background 0.99 | 0.04 | 0.05 | asserted 0.85 |
| s3 | This ``spike'' disappears completely or is greatly weakened when we include important dynamical processes neglected in their idealized/restrictive picture with cold particles surrounding an at-the-center zero-seed adiabaticly-growing BH. | result 0.97 | 0.84 | 0.75 | asserted 1.00 |
| s4 | For the seed BH to spiral in and settle to the center within a Hubble time by dynamical friction, the seed mass must be at least a significant fraction of the present BH. | result 0.93 | 0.58 | 0.08 | asserted 0.99 |
| s5 | Any subsequent at-the-center growth of the BH and steepening of the central Keplerian potential well can squeeze the halo density distribution only mildly, whether the squeezing happens adiabatically or instantaneously. | result 0.98 | 0.80 | 0.52 | asserted 0.96 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:astro-ph/0101481 by the authors.
References
How later papers used it
127 later papers cite it
2 later papers by other authors are listed below: 2 used its method or tool.
Uses its method or tool 2 of 4 papers with this label
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Followed this paper to give the probability of finding a particle at radius r after collapse for an orbit specified by energy and angular momentum.
Dark Matter Mounds: towards a realistic description of dark matter overdensities around black holes (2024) · 0.92 · paraphrased: the licence does not allow quoting
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Computed its instability quantities numerically following this paper's prescription for each profile.
Multi-TeV dark matter density in the inner Milky Way halo: spectral and dynamical constraints (2023) · 0.99 · paraphrased: the licence does not allow quoting
How the literature uses it
111 arXiv papers cite this in 178 sentences
Papers citing it · 149 sentences without a confident label
Builds on it 2 papers
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The picture sketched in [ref] and [ref] has been further refined in [ref] , where a time-evolution analysis of the cusp formation is performed, including the effects of self annihilations, scattering of dark matter particles by stars, and capture in the black hole.
Multi-wavelength signals of dark matter annihilations at the Galactic center · A few benchmark scenarios · 0.85
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In order to compute the evolution of dark matter after collapse, we have introduced a new method, based on a Monte Carlo procedure, which generalises the results of Ref. [ref] to non-circular orbits, and includes the relativistic corrections to the inner cut-off from Ref. [ref] .
Dark Matter Mounds: towards a realistic description of dark matter overdensities around black holes · Introduction · 0.90
Uses its method or tool 1 paper
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Following Ref. [ref] , for an orbit specified by energy $ℰ$ and angular momentum $L$, the probability of finding after collapse the particle at a radius $r$ is given by: [equation] where $T(ℰ, L) = 2 ∫_r_min^r_max ṽ_r^-1 r$ is the period of the orbit.
Dark Matter Mounds: towards a realistic description of dark matter overdensities around black holes · Introduction · 0.92
Uses its data or values 1 paper
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For the Milky Way, the mass is $M_B ≃4×10^6 M_⊙$, while the mass within the central parsec can reach $∼10^7$-$10^8 M_⊙$, depending on the assumed density profile [ref] .
A metric solution for rotating black holes embedded in dark matter halos with central spikes · Numerical results and discussions · 0.83
Compares with it 1 paper
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The halo parameters we estimated are reasonable in the sense that they are similar to those of the Milky Way galaxy [ref] , which is known to host a SMBH with similar mass to that in NGC 1068 [ref] .
NGC 1068 constraints on neutrino-dark matter scattering · Fixing spike parameters · 0.83
Cites it as support 2 papers
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But again, the evolution of the host galaxy drives a suppression of the spike, due to cumulative mergers [ref] and possible off-center BH formation [ref] .
Black Holes as Dark Matter Annihilation Boosters · Conclusions · 0.96
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Even small (compared with $r_h$) and temporary displacements of the SMBH from its central location are sufficient to inhibit the growth of a spike or to destroy it after it has formed [ref] .
Dark matter at the centers of galaxies · Black hole adiabatic growth models · 0.98
Cites it as background 21 papers
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The formation of a DM spike is contingent on several conditions, detailed for example in [ref] and [ref] .
Black Holes, Dark Matter Spikes, and Constraints on Simplified Models with $t$-Channel Mediators · Dark Matter Spike Near the Supermassive Black Hole · 0.91
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The accretion of DM onto the SMBH has been widely studied in the literature, e.g., Refs. [ref] .
NGC 1068 constraints on neutrino-dark matter scattering · Dark matter spike profile · 1.00
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The spike profile has the form [equation] where $ρ_sp = ρ_NFW(r_sp)$, and the exponent $γ$ is subject to astrophysical uncertainties [ref] , including evolution during the merger [ref] .
Self-interacting dark matter solves the final parsec problem of supermassive black hole mergers · Introduction · 0.86
Discussion
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