---
_id: '17585'
abstract:
- lang: eng
  text: Recent gravitational wave (GW) observations by LIGO/Virgo show evidence for
    hierarchical mergers, where the merging BHs are the remnants of previous BH merger
    events. These events may carry important clues about the astrophysical host environments
    of the GW sources. In this paper, we present the distributions of the effective
    spin parameter (χeff), the precession spin parameter (χp), and the chirp mass
    (mchirp) expected in hierarchical mergers. Under a wide range of assumptions,
    hierarchical mergers produce (i) a monotonic increase of the average of the typical
    total spin for merging binaries, which we characterize with χ¯typ≡(χ2eff+χ2p)1/2¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯,
    up to roughly the maximum mchirp among first-generation (1g) BHs, and (ii) a plateau
    at χ¯typ∼0.6 at higher mchirp. We suggest that the maximum mass and typical spin
    magnitudes for 1g BHs can be estimated from χ¯typ as a function of mchirp. The
    GW data observed in LIGO/Virgo O1--O3a prefers an increase in χ¯typ at low mchirp,
    which is consistent with the growth of the BH spin magnitude by hierarchical mergers,
    at ∼2σ confidence. A Bayesian analysis suggests that 1g BHs have the maximum mass
    of ∼15--30M⊙ if the majority of mergers are of high-generation BHs (not among
    1g-1g BHs), which is consistent with mergers in active galactic nucleus disks
    and/or nuclear star clusters, while if mergers mainly originate from globular
    clusters, 1g BHs are favored to have non-zero spin magnitudes of ∼0.3. We also
    forecast that signatures for hierarchical mergers in the χ¯typ distribution can
    be confidently recovered once the number of GW events increases to ≳O(100).
article_processing_charge: No
article_type: original
author:
- first_name: Hiromichi
  full_name: Tagawa, Hiromichi
  last_name: Tagawa
- first_name: Zoltán
  full_name: Haiman, Zoltán
  id: 7c006e8c-cc0d-11ee-8322-cb904ef76f36
  last_name: Haiman
- first_name: Imre
  full_name: Bartos, Imre
  last_name: Bartos
- first_name: Bence
  full_name: Kocsis, Bence
  last_name: Kocsis
- first_name: Kazuyuki
  full_name: Omukai, Kazuyuki
  last_name: Omukai
citation:
  ama: Tagawa H, Haiman Z, Bartos I, Kocsis B, Omukai K. Signatures of hierarchical
    mergers in black hole spin and mass distribution. <i>Monthly Notices of the Royal
    Astronomical Society</i>. 2021;507(3):3362-3380. doi:<a href="https://doi.org/10.1093/mnras/stab2315">10.1093/mnras/stab2315</a>
  apa: Tagawa, H., Haiman, Z., Bartos, I., Kocsis, B., &#38; Omukai, K. (2021). Signatures
    of hierarchical mergers in black hole spin and mass distribution. <i>Monthly Notices
    of the Royal Astronomical Society</i>. Oxford University Press. <a href="https://doi.org/10.1093/mnras/stab2315">https://doi.org/10.1093/mnras/stab2315</a>
  chicago: Tagawa, Hiromichi, Zoltán Haiman, Imre Bartos, Bence Kocsis, and Kazuyuki
    Omukai. “Signatures of Hierarchical Mergers in Black Hole Spin and Mass Distribution.”
    <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press,
    2021. <a href="https://doi.org/10.1093/mnras/stab2315">https://doi.org/10.1093/mnras/stab2315</a>.
  ieee: H. Tagawa, Z. Haiman, I. Bartos, B. Kocsis, and K. Omukai, “Signatures of
    hierarchical mergers in black hole spin and mass distribution,” <i>Monthly Notices
    of the Royal Astronomical Society</i>, vol. 507, no. 3. Oxford University Press,
    pp. 3362–3380, 2021.
  ista: Tagawa H, Haiman Z, Bartos I, Kocsis B, Omukai K. 2021. Signatures of hierarchical
    mergers in black hole spin and mass distribution. Monthly Notices of the Royal
    Astronomical Society. 507(3), 3362–3380.
  mla: Tagawa, Hiromichi, et al. “Signatures of Hierarchical Mergers in Black Hole
    Spin and Mass Distribution.” <i>Monthly Notices of the Royal Astronomical Society</i>,
    vol. 507, no. 3, Oxford University Press, 2021, pp. 3362–80, doi:<a href="https://doi.org/10.1093/mnras/stab2315">10.1093/mnras/stab2315</a>.
  short: H. Tagawa, Z. Haiman, I. Bartos, B. Kocsis, K. Omukai, Monthly Notices of
    the Royal Astronomical Society 507 (2021) 3362–3380.
date_created: 2024-09-05T12:30:08Z
date_published: 2021-08-13T00:00:00Z
date_updated: 2024-09-19T11:50:46Z
day: '13'
doi: 10.1093/mnras/stab2315
extern: '1'
intvolume: '       507'
issue: '3'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.1093/mnras/stab2315
month: '08'
oa: 1
oa_version: Published Version
page: 3362-3380
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
  issn:
  - 0035-8711
  - 1365-2966
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: Signatures of hierarchical mergers in black hole spin and mass distribution
type: journal_article
user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345
volume: 507
year: '2021'
...