Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Novel method to trace the dark matter density profile around supermassive black holes with AGN reverberation mapping

Mayank Sharma, Gonzalo Herrera, Nahum Arav, Shunsaku Horiuchi

TL;DR

This work introduces a novel RM-based method to constrain the dark matter density profile in the sub-parsec vicinity of distant SMBHs by leveraging mass inferences from multiple emission lines. By contrasting a constant-$M_{ m BH}$ model with a DM spike model and fitting for inner DM parameters $\rho_0$ and $\gamma$ (with $\gamma$ potentially universal), the study analyzes a 14‑AGN RM sample. It finds strong/positive evidence for a DM spike in two objects and identifies a global best-fit slope $\gamma\approx1.6$, though many results are limited by systematic uncertainties in RM mass estimates. The work highlights the potential of combining RM with interferometry and advanced BLR modeling to directly constrain sub-parsec DM structure, while stressing that current uncertainties necessitate caution and further observations with more emission lines.

Abstract

We propose a new method to determine the dark matter density profile in the vicinity of distant supermassive black holes (SMBH) using reverberation mapping (RM) measurements of active galactic nuclei (AGN). The mapping of multiple emission lines allows the measurement of the enclosed mass within different radii from the central SMBH, which can be used to infer or constrain the dark matter density profile on sub-parsec scales. We apply a toy model based on this method to a sample of fourteen AGN to test its feasibility based on current measurements. We find that for five objects, the observed enclosed mass does grow with radii, hinting towards the presence of a dark matter component at the 1-2 $σ$ level. For these sources, we find global evidence for a universal dark matter profile with a preferred radial steepness of index $γ\sim 1.6$, consistent with the scenario expected for a dark matter spike mildly relaxed by stellar heating processes. The enclosed dark matter mass, however, is found to be significantly larger than expected. We show that the current RM based mass measurements suffer from large systematic uncertainties, that limit the effectiveness of our method. Our work emphasizes the importance of applying the recent developments in mass determination techniques to target multiple emission lines with future RM and interferometry campaigns. This provides the most direct way of constraining the dark matter density in the sub-parsec regions around extragalactic SMBHs, which is crucial to our understanding of the dynamics and nature of dark matter.

Novel method to trace the dark matter density profile around supermassive black holes with AGN reverberation mapping

TL;DR

This work introduces a novel RM-based method to constrain the dark matter density profile in the sub-parsec vicinity of distant SMBHs by leveraging mass inferences from multiple emission lines. By contrasting a constant- model with a DM spike model and fitting for inner DM parameters and (with potentially universal), the study analyzes a 14‑AGN RM sample. It finds strong/positive evidence for a DM spike in two objects and identifies a global best-fit slope , though many results are limited by systematic uncertainties in RM mass estimates. The work highlights the potential of combining RM with interferometry and advanced BLR modeling to directly constrain sub-parsec DM structure, while stressing that current uncertainties necessitate caution and further observations with more emission lines.

Abstract

We propose a new method to determine the dark matter density profile in the vicinity of distant supermassive black holes (SMBH) using reverberation mapping (RM) measurements of active galactic nuclei (AGN). The mapping of multiple emission lines allows the measurement of the enclosed mass within different radii from the central SMBH, which can be used to infer or constrain the dark matter density profile on sub-parsec scales. We apply a toy model based on this method to a sample of fourteen AGN to test its feasibility based on current measurements. We find that for five objects, the observed enclosed mass does grow with radii, hinting towards the presence of a dark matter component at the 1-2 level. For these sources, we find global evidence for a universal dark matter profile with a preferred radial steepness of index , consistent with the scenario expected for a dark matter spike mildly relaxed by stellar heating processes. The enclosed dark matter mass, however, is found to be significantly larger than expected. We show that the current RM based mass measurements suffer from large systematic uncertainties, that limit the effectiveness of our method. Our work emphasizes the importance of applying the recent developments in mass determination techniques to target multiple emission lines with future RM and interferometry campaigns. This provides the most direct way of constraining the dark matter density in the sub-parsec regions around extragalactic SMBHs, which is crucial to our understanding of the dynamics and nature of dark matter.

Paper Structure

This paper contains 8 sections, 7 equations, 7 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Dark matter density profile around black holes
  3. Sample selection and Methodology
  4. Results
  5. Discussion
  6. Physical plausibility and implications of the derived DM spike parameters
  7. Uncertainty in RM based $M_{BH}$ determinations
  8. Conclusions

Figures (7)

  • Figure 1: Measurements of the enclosed mass within different radii for five sources presenting differing levels of evidence for a dark matter component: strong (3C 390), positive (NGC 7469) and weak (SBS 1116, MCG 0811, NGC 2617) evidence (see section \ref{['sec:results']} and Fig. \ref{['fig:confidencepositivestrong']}). For comparison, we show the best fit obtained for a flat constant mass (pink dashed), and the best fit for an increasing mass component (purple solid), which includes contribution from the dark matter component (shown in blue).
  • Figure 2: Confidence contours on the dark matter profile parameters---density $\rho_0$ and radial slope $\gamma$; see Eq. (\ref{['eq:parametrization']})---for AGN with strong (3C 390), positive (NGC 7469) and weak (SBS 116, MCG 0811, NGC 2617) evidence. For comparison, we show in horizontal markings the expected profile indexes for different theoretical expectations: a dark matter spike, a spike relaxed by stellar heating, an NFW profile, and a dark matter core.
  • Figure 3: Individual $\Delta \chi^2$ as a function of $\gamma$ for the objects in our analysis presenting preference for a DM component. We also show the combined $\Delta \chi^2$ for these objects, which has a well defined minimum at $\gamma \simeq 1.6$.
  • Figure 4: Dark matter density profiles from sub-pc to kpc scales from the sources in our sample presenting evidence for an inner dark matter component. The inner density profile parameters are the best-fit values from Table \ref{['table:BIC']}, and outer halo parameters are fitted to reproduce the total mass of the galaxy expected from the phenomenological relation in equation \ref{['eq:BH_Halo_Mass']}. The outer spike radius ($R_p$) is assumed to be 0.1 pc and 0.01 pc in the left and right panel, respectively.
  • Figure 5: Measurements of the enclosed mass within different radii for sources showing an increasing mass, but no preference for dark matter component.
  • ...and 2 more figures