scholarly journals Dynamics of stellar black holes in young star clusters with different metallicities – I. Implications for X-ray binaries

2013 ◽  
Vol 429 (3) ◽  
pp. 2298-2314 ◽  
Author(s):  
M. Mapelli ◽  
L. Zampieri ◽  
E. Ripamonti ◽  
A. Bressan
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Young Star ◽  
X Ray ◽  
Young Star Clusters ◽  
X Ray Binaries

scholarly journals Intermediate-mass black holes from stellar mergers in young star clusters

2021 ◽  
Vol 507 (4) ◽  
pp. 5132-5143
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Mario Pasquato ◽  
Sara Rastello ◽  
Alessandro Ballone ◽  
...  
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Mass Range ◽  
Young Star ◽  
Intermediate Mass ◽  
Stellar Collisions ◽  
Low Metallicity ◽  
Young Star Clusters ◽  
Stellar Mergers ◽  
Intermediate Mass Black Holes

ABSTRACT Intermediate-mass black holes (IMBHs) in the mass range $10^2\!-\!10^5\, \mathrm{M_{\odot }}$ bridge the gap between stellar black holes (BHs) and supermassive BHs. Here, we investigate the possibility that IMBHs form in young star clusters via runaway collisions and BH mergers. We analyse 104 simulations of dense young star clusters, featuring up-to-date stellar wind models and prescriptions for core collapse and (pulsational) pair instability. In our simulations, only nine IMBHs out of 218 form via binary BH mergers, with a mass ∼100–140 M⊙. This channel is strongly suppressed by the low escape velocity of our star clusters. In contrast, IMBHs with masses up to ∼438 M⊙ efficiently form via runaway stellar collisions, especially at low metallicity. Up to ∼0.2 per cent of all the simulated BHs are IMBHs, depending on progenitor’s metallicity. The runaway formation channel is strongly suppressed in metal-rich (Z = 0.02) star clusters, because of stellar winds. IMBHs are extremely efficient in pairing with other BHs: ∼70 per cent of them are members of a binary BH at the end of the simulations. However, we do not find any IMBH–BH merger. More massive star clusters are more efficient in forming IMBHs: ∼8 per cent (∼1 per cent) of the simulated clusters with initial mass 104–3 × 104 M⊙ (103–5 × 103 M⊙) host at least one IMBH.

scholarly journals Binary black holes in young star clusters: the impact of metallicity

2020 ◽  
Vol 498 (1) ◽  
pp. 495-506 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Nicola Giacobbo ◽  
Mario Spera ◽  
Yann Bouffanais ◽  
...  
Keyword(s):  
Black Holes ◽  
Initial Density ◽  
Star Clusters ◽  
Young Star ◽  
Binary Black Holes ◽  
Binary Evolution ◽  
Merger Rate ◽  
The Masses ◽  
The Impact ◽  
Young Star Clusters

ABSTRACT Young star clusters are the most common birthplace of massive stars and are dynamically active environments. Here, we study the formation of black holes (BHs) and binary black holes (BBHs) in young star clusters, by means of 6000 N-body simulations coupled with binary population synthesis. We probe three different stellar metallicities (Z = 0.02, 0.002, and 0.0002) and two initial-density regimes (density at the half-mass radius ρh ≥ 3.4 × 104 and ≥1.5 × 102 M⊙ pc−3 in dense and loose star clusters, respectively). Metal-poor clusters tend to form more massive BHs than metal-rich ones. We find ∼6, ∼2, and <1 per cent of BHs with mass mBH > 60 M⊙ at Z = 0.0002, 0.002, and 0.02, respectively. In metal-poor clusters, we form intermediate-mass BHs with mass up to ∼320 M⊙. BBH mergers born via dynamical exchanges (exchanged BBHs) can be more massive than BBH mergers formed from binary evolution: the former (latter) reach total mass up to ∼140 M⊙ (∼80 M⊙). The most massive BBH merger in our simulations has primary mass ∼88 M⊙, inside the pair-instability mass gap, and a mass ratio of ∼0.5. Only BBHs born in young star clusters from metal-poor progenitors can match the masses of GW 170729, the most massive event in first and second observing run (O1 and O2), and those of GW 190412, the first unequal-mass merger. We estimate a local BBH merger rate density ∼110 and ∼55 Gpc−3 yr−1, if we assume that all stars form in loose and dense star clusters, respectively.

scholarly journals Binary black holes in the pair instability mass gap

2020 ◽  
Vol 497 (1) ◽  
pp. 1043-1049 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Yann Bouffanais ◽  
Nicola Giacobbo ◽  
Filippo Santoliquido ◽  
...  
Keyword(s):  
Black Holes ◽  
Formation Rate ◽  
Star Clusters ◽  
Design Sensitivity ◽  
Young Star ◽  
Binary Black Holes ◽  
Single Star ◽  
Mass Gap ◽  
Young Star Clusters ◽  
Stellar Mergers

ABSTRACT Pair instability (PI) and pulsational PI prevent the formation of black holes (BHs) with mass ≳60 M⊙ from single star evolution. Here, we investigate the possibility that BHs with mass in the PI gap form via stellar mergers and multiple stellar mergers, facilitated by dynamical encounters in young star clusters. We analyse 104 simulations, run with the direct N-body code nbody6++gpu coupled with the population synthesis code mobse. We find that up to ∼6 per cent of all simulated BHs have mass in the PI gap, depending on progenitor’s metallicity. This formation channel is strongly suppressed in metal-rich (Z = 0.02) star clusters because of stellar winds. BHs with mass in the PI gap are initially single BHs but can efficiently acquire companions through dynamical exchanges. We find that ∼21 per cent, 10 per cent, and 0.5 per cent of all binary BHs have at least one component in the PI mass gap at metallicity Z = 0.0002, 0.002, and 0.02, respectively. Based on the evolution of the cosmic star formation rate and metallicity, and under the assumption that all stars form in young star clusters, we predict that ∼5 per cent of all binary BH mergers detectable by advanced LIGO and Virgo at their design sensitivity have at least one component in the PI mass gap.

scholarly journals Intermediate-mass Black Holes from High Massive-star Binary Fractions in Young Star Clusters

2021 ◽  
Vol 908 (2) ◽  
pp. L29 ◽  
Author(s):  
Elena González ◽  
Kyle Kremer ◽  
Sourav Chatterjee ◽  
Giacomo Fragione ◽  
Carl L. Rodriguez ◽  
...  
Keyword(s):  
Black Holes ◽  
Massive Star ◽  
Star Clusters ◽  
Young Star ◽  
Intermediate Mass ◽  
Star Binary ◽  
Young Star Clusters ◽  
Intermediate Mass Black Holes

scholarly journals Metallicity and X-ray luminosity variations in NGC 922

2020 ◽  
Vol 500 (1) ◽  
pp. 962-975
Author(s):  
K Kouroumpatzakis ◽  
A Zezas ◽  
A Wolter ◽  
A Fruscione ◽  
K Anastasopoulou ◽  
...  
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Massive Stars ◽  
Star Clusters ◽  
Young Star ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Main Driver ◽  
Young Star Clusters

ABSTRACT We present a systematic study of the metallicity variations within the collisional ring galaxy NGC 922 based on long-slit optical spectroscopic observations. We find a metallicity difference between star-forming regions in the bulge and the ring, with metallicities ranging from almost solar to significantly sub-solar ($\rm {[12+\log (O/H)]\sim 8.2}$). We detect $\rm{He\,{\small I}}$ emission in all the studied regions of the bulge and the ring, indicating ionization from massive stars associated with recent (<10 Myr) star formation, in agreement with the presence of very young star clusters. We find an anticorrelation between the X-ray luminosity and metallicity of the sub-galactic regions of NGC 922. The different regions have similar stellar population ages, leaving metallicity as the main driver of the anticorrelation. The dependence of the X-ray emission of the different regions in NGC 922 on metallicity is in agreement with similar studies of the integrated X-ray output of galaxies and predictions from X-ray binary population models.

scholarly journals Constraining the Fraction of Binary Black Holes Formed in Isolation and Young Star Clusters with Gravitational-wave Data

2019 ◽  
Vol 886 (1) ◽  
pp. 25 ◽  
Author(s):  
Yann Bouffanais ◽  
Michela Mapelli ◽  
Davide Gerosa ◽  
Ugo N. Di Carlo ◽  
Nicola Giacobbo ◽  
...  
Keyword(s):  
Black Holes ◽  
Gravitational Wave ◽  
Star Clusters ◽  
Young Star ◽  
Binary Black Holes ◽  
Wave Data ◽  
Young Star Clusters

scholarly journals Merging black holes in young star clusters

2019 ◽  
Vol 487 (2) ◽  
pp. 2947-2960 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Nicola Giacobbo ◽  
Michela Mapelli ◽  
Mario Pasquato ◽  
Mario Spera ◽  
...  
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Young Star ◽  
Young Star Clusters

scholarly journals Formation of massive black holes through runaway collisions in dense young star clusters

Nature ◽  
2004 ◽  
Vol 428 (6984) ◽  
pp. 724-726 ◽  
Author(s):  
Simon F. Portegies Zwart ◽  
Holger Baumgardt ◽  
Piet Hut ◽  
Junichiro Makino ◽  
Stephen L. W. McMillan
Keyword(s):  
Black Holes ◽  
Star Clusters ◽  
Young Star ◽  
Massive Black Holes ◽  
Young Star Clusters
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