Pulsar Timing Array Constraints on the Merger Timescale of Subparsec Supermassive Black Hole Binary Candidates

We estimate the merger timescale of spectroscopically selected, subparsec supermassive black hole binary (SMBHB) candidates by comparing their expected contribution to the gravitational-wave background (GWB) with the sensitivity of current pulsar timing array (PTA) experiments and in particular, with the latest upper limit placed by the North American Nanohertz Observatory for Gravitational Waves. We find that the average timescale to coalescence of such SMBHBs is «tevol» > 6 × 104 yr, assuming that their orbital evolution in the PTA frequency band is driven by emission of gravitational waves. If some fraction of SMBHBs do not reside in spectroscopically detected active galaxies, and their incidence in active and inactive galaxies is similar, then the merger timescale could be ∼10 times longer, «tevol» > 6 × 105 yr. These limits are consistent with the range of timescales predicted by theoretical models and imply that all the SMBHB candidates in our spectroscopic sample could be binaries without violating the observational constraints on the GWB. This result illustrates the power of the multimessenger approach, facilitated by the PTAs, in providing an independent statistical test of the nature of SMBHB candidates discovered in electromagnetic searches.

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Work Title Pulsar Timing Array Constraints on the Merger Timescale of Subparsec Supermassive Black Hole Binary Candidates
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Open Access
Creators
  1. Khai Nguyen
  2. Tamara Bogdanović
  3. Jessie Runnoe
  4. Stephen Taylor
  5. Alberto Sesana
  6. Michael Eracleous
  7. Steinn Sigurdsson
Keyword
  1. Active galactic nuclei
  2. Galaxy mergers
  3. Gravitational waves
  4. Supermassive black holes
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Astrophysical Journal Letters
Publication Date September 15, 2020
Publisher Identifier (DOI)
  1. https://doi.org/10.3847/2041-8213/abb2ab
Deposited January 26, 2024

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Version 1
published

  • Created
  • Added 2006.12518-1.pdf
  • Added Creator Khai Nguyen
  • Added Creator Tamara Bogdanović
  • Added Creator Jessie Runnoe
  • Added Creator Stephen Taylor
  • Added Creator Alberto Sesana
  • Added Creator Michael Eracleous
  • Added Creator Steinn Sigurdsson
  • Published
  • Updated Keyword Show Changes
    Keyword
    • Active galactic nuclei, Galaxy mergers, Gravitational waves, Supermassive black holes
  • Updated