Evolution of intermediate-mass and stellar binary black ... - ArcaSedda_Prague_new.pdf-Arthur C....

MODEST 17 Under Prague's Starry Skies Charles University, Prague

September 18-22, 2017

Manuel Arca Sedda Astronomisches Rechen Institute

ZAH – Universität Heidelberg

Evolution of intermediate-mass and stellar binary black holes in galactic nuclei

The MEGaN project and beyond: a small project in numbers…

Manuel Arca Sedda, MODEST17, Prague, 22Sept. 2017

Two possibilities exist: either we are alone in the Universe or we are not. Both are

equally terrifying.

-Arthur C. Clarke-

- 200’000 core hours simulated - 5 published papers - 2 submitted (check it out on the ArXiv… ) - 6 in preparation - 10 in fieri … thanks also to the support by SFB881 (subproject Z2)

Star clusters impacting SMBHs in galactic nuclei … where ?


Normal galaxies

(and SMBH 105 − 107𝑀⊙)

• NC formation Arca Sedda + 2015 Mastrobuono-Battisti and Perets 2014 Antonini + 2012

• Role of a central SMBH

Arca Sedda + 2015 Arca Sedda & Capuzzo-Dolcetta 2016, 2017a

• Kinematic and morphology

Arca Sedda, Kocsis and Brandt 2017 Tsatsi + 2017

• Milky Way high-energy emission

Arca Sedda, Kocsis and Brandt 2017 Abbate + 2017 Fragione, Antonini and Gnedin 2017

Henize 2-10 model: • 11 Young Massive Clusters • mass spectrum: 𝑀 ∼ 0.2 − 2 ×

106𝑀⊙;

• age 5 Myr; • 𝑀𝑆𝑀𝐵𝐻 = 2.6 × 106M⊙

• Galactic nucleus up to ∼ 200 pc • three different sets: w/o SMBH • N=1048k particles

Extremely rapid

< 100 𝑀𝑦𝑟

After SMBH formation

Denser if SMBH absent

Subsequent SMBH formation

From roundy to disky shape

common scenario for

NCs and NDs



Normal galaxies

(and SMBH 105 − 107𝑀⊙)








Fornax-like dSph: • 5 GCs • mass spectrum: 𝑀 ∼ 0.03 − 3 × 105𝑀⊙;

• age 10 Gyr; • Fornax dSph up to ∼ 2 kpc • two Fornax models: 𝑟−𝑎; 𝑎 = 0.5 and 1 • N=1048k particles • MW gravitational field accounted for

steeper • GC disrupted! • Fornax slope

decreases

shallower • NC formation • rotation • central density

increases by a factor 10-100

Core/cusp problem

SMBH formation processes



Normal galaxies

(and SMBH 105 − 107𝑀⊙)








X and γ due to MSPs and CVs delivered to the galactic centre

DRY MERGER

IN SITU



Massive galaxies (𝑀𝑆𝑀𝐵𝐻 ≥ 108𝑀⊙)

• Quenching NC formation

Antonini 2013 Arca Sedda, Capuzzo-Dolcetta & Spera 2016 Arca Sedda & Capuzzo-Dolcetta 2017b

• Origin of nuclear disks (e.g. M31)

Tremaine 1995 Arca Sedda and Capuzzo-Dolcetta 2017b

• Increasing the tidal disruption rate

Arca Sedda & Capuzzo-Dolcetta 2017b Stone et al. 2017

• Increasing the EMRIs emission rate

Arca Sedda & Capuzzo-Dolcetta 2017c


Massive galaxies (𝑀𝑀𝐵𝐻𝐵 = 106 − 108𝑀⊙) Arca Sedda et al. in prep. Bortolas et al. in prep.

• Feedback on the SMBHB evolution

𝑀𝐵𝐻𝐵 = 107 − 108𝑀⊙

𝑞𝐵𝐻𝐵 = 1 𝑡𝐺𝑊𝑓𝑚𝑖𝑛 = 0.01𝑡𝐺𝑊0

𝑡𝐺𝑊𝑓 𝑖 = 𝜋 < 𝑡𝐺𝑊𝑓 𝑖 = 0

• Distribution of compact stellar BHs

• Quenching NC formation

𝑀𝑑𝑒𝑝 4𝑝𝑐 ≤ 0.1𝑀𝐺𝐶


Star clusters impacting SMBHs in galactic nuclei … the wonderful life of star clusters


mass segregation +

stellar evolution

IMBH formation

Stellar BHs evolution

coooomplex dynamics

Star clusters impacting SMBHs in galactic nuclei … when?

12 Gyr


T ≤ 1 Gyr

Cluster partly unsegregated

BHs and BHBs

inside the cluster

T ≥ 1 Gyr

Mass segregation

Possible IMBH

formation?

Portegies-Zwart & McMillan 2002 Giersz + 2015

Downing + 2009 Arca-Sedda 2016 Askar 2017 Banerjee 2017 Rastello, AS+ In prep

1 Gyr 5 Gyr


Direct N-body: MEGaN

• Galaxy 1011𝑀⊙

• SMBH 108𝑀⊙

• 42 GCs 0.2 − 2 × 106𝑀⊙

T ≤ 1 Gyr

4-body scattering: ARGdf ARGdf = ARCHAIN + 𝐹𝑔𝑎𝑙 + DF

ARCHAIN (Mikkola & Merritt 2008)

Star clusters impacting SMBHs in galactic nuclei … so?



2000 simulations

• 𝑀 = 1.8 × 106𝑀⊙ • 𝑀1 = 30 𝑀⊙ 𝑀2 = 20 𝑀⊙

• 𝑃 𝑎 𝑑𝑎 ∝ 𝑎−1 (Rodriguez + 2015)

• 𝑎𝑀 = 10−4𝑝𝑐 • 𝑎𝑚 = 100(𝑅𝑠1 + 𝑅𝑠2)

• 𝑃 𝑒 𝑑𝑒 ∝ 2𝑒𝑑𝑒 (Jeans 1919)

• 𝑟0 = 0.2 − 2 𝑝𝑐

𝑟0 𝑀

𝑀𝑆𝑀𝐵𝐻


Calculating the merger rate … ingredients:

• total number of events per cluster

f. BHB × f. of stars heavier than 𝑚∗ × f. of GCs (e>0.5) × f. of coal. <1 Gyr × n. of stars per cluster × n. of clusters

• Merger rate for galaxies above 1011𝑀⊙ within 𝑧 ≤ 0.3

(𝑁 clusters formed <𝑟) × (𝑁 events / df time-scale within 𝑟) × (n. density of galaxies M > 1011𝑀⊙ in 𝑧 < 0.3)


Star clusters impacting SMBHs in galactic nuclei … when?

12 Gyr


T ≤ 1 Gyr

Cluster partly unsegregated

BHs and BHBs

inside the cluster

T ≥ 1 Gyr

Mass segregation

Possible IMBH

formation?

Portegies-Zwart & McMillan 2002 Giersz + 2015

Downing + 2009 Arca-Sedda 2016 Askar 2017 Banerjee 2017 Rastello, AS+ In prep

1 Gyr 5 Gyr



Direct N-body 1M particles: MEGaN

• Galaxy 1011𝑀⊙

• SMBH 108𝑀⊙

• 42 GCs 0.2 − 2 × 106𝑀⊙

T > 1 Gyr

3-8 body scattering: ARGdf ARGdf = ARCHAIN + 𝐹𝑔𝑎𝑙 + DF ARCHAIN (Mikkola & Merritt 2008)



• Merger occurrence ∼ 50% • Weak dependence on the pericentre • Almost independent on inclination

2 IMBHs + 1 SMBHs 8 IMBHs + 1 SMBHs

Mass distribution of swallowed IMBHs

Merger time distribution

Conclusions Manuel Arca Sedda, MODEST17, Prague, 22Sept. 2017

𝑀𝑀𝐵𝐻𝐵 > 106𝑀⊙

• Binary shrinking • High-velocity stars

production • NC formation halted • Stars tidal disruption

𝑀𝑆𝑀𝐵𝐻 ≃ 105 − 107𝑀⊙

• NC formation • 𝑋 and 𝛾 ray emission

from CVs and MSPs

0

𝑀𝑆𝑀𝐵𝐻 > 108𝑀⊙

• enhance of TDEs rate • enhance of EMRIs emission rate

T>1Gyr

∼ 50% chance for IMBH-SMBH coalescence mediated by a 3° or multiple IMBHs

T<1Gyr ∼ 1% chance causing a stellar BHB merger



Calculating the merger rate for all galaxies 1010 − 1012𝑀⊙ (104 simulations) Arca Sedda, in prep.

-

But… many approximations (Cluster formation rate, 𝜂𝐵𝐻𝐵 …)

Direct N-body are needed but problem still too complex: Galaxy, Cluster, Stellar evolution, SMBH (Nbody6++GPU?)

(for GW140915 like sources)



IMBH and SBHs motion in the Milky Way centre Arca Sedda and Gualandris, in prep.

• 1𝑀 body for MW + 1GC + SMBH + IMBH • 12 simulations (𝑚∗ = 10 − 33𝑀⊙)

• 𝑒𝐺𝐶 = 0 − 0.7 − 1 • 𝑀𝐼𝑀𝐵𝐻 = 0 − 103 − 104𝑀⊙

• NC already formed (model M) or

not (model S)

• 𝑁𝑏ℎ𝑠 = 0 − 114

T > 1 Gyr 𝑒𝐺𝐶 = 0.5

Evolution of intermediate-mass and stellar binary black ... - ArcaSedda_Prague_new.pdf-Arthur C....

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