Galactic Nuclei: Nuclear Star Clusters and Massive Black Holes - - PowerPoint PPT Presentation

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Galactic Nuclei: Nuclear Star Clusters and Massive Black Holes - - PowerPoint PPT Presentation

May 26, 2023 112 likes •386 views

Supermassive Black Hole Formation in Galatic Nuclei: The Role of Intermediate-mass Black Holes Abbas Askar Carl Tryggers Postdoctoral Fellow at Lund Observatory Department of Astronomy and Theoretical Physics Lund University In Collaboration

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Compact Objects For All, Lund, Sweden 10th February, 2020

Supermassive Black Hole Formation in Galatic Nuclei:

The Role of Intermediate-mass Black Holes

Abbas Askar

Carl Tryggers Postdoctoral Fellow at Lund Observatory Department of Astronomy and Theoretical Physics Lund University

In Collaboration with: Melvyn B. Davies & Ross P. Church

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Galactic Nuclei: Nuclear Star Clusters and Massive Black Holes

  • Nuclear star clusters (NSCs) are extremely dense

( ) and massive star clusters ( ) occupying the nucleus of most galaxies.

  • Most frequent in galaxies with stellar masses in the range
  • Many cases where NSCs and massive black holes

(SMBH) are found to co-exist:

  • Milky Way NSC Mass:

SMBH Mass:

  • M31 NSC Mass:

SMBH Mass:

  • Masses of both SMBHs and NSCs follow a tight relation

with the masses of their host galaxies

  • Build-up of NSCs and the growth of massive black holes are

closely related

∼ 106 − 107 M⊙ pc−3 ∼ 106 − 109 M⊙ ∼ 108 − 1010 M⊙ ∼ 106 − 1010 M⊙

2.5 × 107 M⊙ 4 × 106 M⊙ ∼ 5 × 107 M⊙ ∼ 1.6 × 108 M⊙

Neumayer et al. 2020

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

M33: No Supermassive Black Hole

  • M33 contains a NSC but no SMBH!
  • NSC Mass:

(Kormendy et al. 2010, McConnachie 2012)

  • Upper limit on central black hole mass:

2 × 106 M⊙ 1500 M⊙

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Key Question: What came first?

Chicken or egg? Which comes first, a Supermassive Black Hole (SMBH) or a Nuclear Stellar Cluster (NSC)?

  • M33 contains a NSC but no SMBH!
  • NSC Mass:

(Kormendy et al. 2010, McConnachie 2012)

  • Upper limit on central black hole mass:

2 × 106 M⊙ 1500 M⊙

Can a SMBH form AFTER NSC?

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

What we did: Central ideas

  • Make nuclear stellar cluster by merging globular clusters
  • Antonini et al. 2012; Mastrobuono-Battisti et al. 2014
  • No pre-existing SMBH
  • Talk by Alessandra Mastrobuono-Battisti
  • Some of those globular clusters contain intermediate mass black holes (IMBHs)
  • What happens to the IMBHs?
  • Can we keep them?
  • How much must they grow to form SMBHs?

(Guillard, Emsellem & Renaud 2016)

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

What we did: Making NSC from Merging Globular Clusters

  • Carried out direct N-body simulations of 3 merging

globular clusters using NBODY6++GPU (Wang et al. 2015)

  • 3 merging cluster containing containing 50000, 30000

and 15000 stars

  • Containing up to 3 IMBH in different configurations

28.8 Myr 360 Myr

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Flowchart for Possible Outcomes

  • Infalling globular clusters bring (in total):

No IMBH One IMBH Two IMBHs Three IMBHs Many IMBHs

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Flowchart for Possible Outcomes

  • Infalling globular clusters bring (in total):

No SMBH Seed One SMBH Seed Many SMBH Seeds?

Go on to grow by tidal disruption of stars and gas accretion (i.e. wet growth with gas inflow)

No IMBH One IMBH Two IMBHs Three IMBHs Many IMBHs

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Flowchart for Possible Outcomes

  • Infalling globular clusters bring (in total):

No SMBH Seed One SMBH Seed Many SMBH Seeds?

Go on to grow by tidal disruption of stars and gas accretion (i.e. wet growth with gas inflow)

No IMBH One IMBH Two IMBHs Three IMBHs Many IMBHs

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

The 2 IMBH Case

  • Both IMBHs segregate to the center of the merged cluster and form a binary IMBH
  • IMBH binary hardens as it interacts with surrounding stars
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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

IMBH Binary Merger due to Gravitational Wave Radiation

  • Eccentricity of binary IMBH increases as the binary hardens → gravitational wave

radiation can efficiently merge the binary

  • Retention of merged BH depends on magnitude of gravitational recoil kick

Wiseman 1992 Morawski et al. 2018

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

1+1 = 1 1+1 = 0

Flowchart for Possible Outcomes

  • Infalling globular clusters bring (in total):

Go on to grow by tidal disruption of stars and gas accretion (i.e. wet growth with gas inflow)

No SMBH Seed One SMBH Seed Many SMBH Seeds? No IMBH One IMBH Two IMBHs Three IMBHs Many IMBHs Meet and merge First grows, then meet and merge

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

3 IMBH Case: Diverse Outcomes

  • 2 most massive IMBHs form a binary
  • Less massive IMBH gets scattered away due to

binary - single interaction

  • 2 + 1 = 2
  • If IMBH binary is sufficiently hard at interaction

time then all 3 IMBH can be ejected

  • 2 + 1 = 0
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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

1+1 = 1 1+1 = 0

Flowchart for Possible Outcomes

  • Infalling globular clusters bring (in total):

No SMBH Seed One SMBH Seed Many SMBH Seeds? No IMBH One IMBH Two IMBHs Three IMBHs Many IMBHs Meet and merge First grows, then meet and merge

Go on to grow by tidal disruption of stars and gas accretion (i.e. wet growth with gas inflow)

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Populating Galaxies with NSC and IMBH

  • Sample

galaxies from a double-Schechter galaxy stellar mass function (Baldry et al. 2012)

  • Find corresponding NSC Mass
  • Sample initial globular clusters masses from a

log-normal distribution (Schaerer & Charbonnel 2011) until we can reproduce NSC Mass

  • Assign probability for a globular cluster to bring an IMBH
  • Estimate mass of IMBH brought in by globular cluster
  • Depends on initial on globular cluster mass
  • Based on results on results from Monte Carlo simulations of dense clusters (Askar

et al. 2017, Morawski et al. 2018 and Arca Sedda et al. 2019) 1.5 × 105

Neumayer et al. 2020

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Nuclear Star Clusters and Massive Black Holes

Data from Neumayer et al. 2020

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

SMBH Seed Population Synthesis

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

SMBH Seed Population Synthesis

No Seed

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

SMBH Seed Population Synthesis

No Seed One Seed

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

SMBH Seed Population Synthesis

No Seed One Seed Many seeds but

  • ne remains
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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Conclusions

  • 1. Merging globular clusters can form nuclear stellar clusters
  • 2. IMBHs carried by globulars can seed SMBH
  • 3. Gravitational wave recoil kicks and few-body dynamics can eject the seed
  • Many pathways but all lead to one or zero SMBHs
  • Number, order, timing of IMBH injection matters
  • Mass ratio of IMBHs is also important
  • 4. Gas infall is needed to grow seeds and avoid ejection
  • 5. Dry merger of a few massive globular clusters could account for the mass of

nuclear stellar cluster in galaxies like M33 ( )

  • More than 50% probability of not having a SMBH seed for M33 NSC Mass

2 × 106M⊙

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Nuclear Star Clusters Properties

Neumayer et al. 2020

  • Mass
  • Correlates with host galaxy mass
  • 10 to 100x more massive than globular clusters
  • Densities
  • Effective radius less than 10 pc
  • Ellipticity values between 0 to 0.6
  • Correlates with NSC Mass

∼ 105 − 109 M⊙ ∼ 106 − 107 M⊙ pc−3

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Formation and Growth of NSCs and Massive Black Holes

  • NSC Formation: Merging Clusters vs In-Situ Formation
  • SMBH Formation:
  • Direct formation e to form a massive BH seed
  • Formation of an intermediate mass BH seed
  • Dense clusters and/or massive stars

∼ 106 M⊙ ∼ 102 − 105 M⊙

Smith, Bromm & Loeb 2017

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

Growth of IMBH in Globular Clusters

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Why BHs Matter in Globular Clusters - Abbas Askar

SMBH formation in galactic nuclei: the role of IMBHs - Abbas Askar Compact Objects For All, Lund, Sweden 10th February, 2020

IMBH Formation Channels

Credit Melvyn B. Davies