Volume 614, June 2018
|Number of page(s)||9|
|Section||Cosmology (including clusters of galaxies)|
|Published online||06 June 2018|
Collisions in primordial star clusters
Formation pathway for intermediate mass black holes
Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción,
Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C,
2 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
3 Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
4 CIDMA, Departamento de Física, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
Accepted: 17 January 2018
Collisions were suggested to potentially play a role in the formation of massive stars in present day clusters, and have likely been relevant during the formation of massive stars and intermediate mass black holes within the first star clusters. In the early Universe, the first stellar clusters were particularly dense, as fragmentation typically only occurred at densities above 109 cm−3, and the radii of the protostars were enhanced as a result of larger accretion rates, suggesting a potentially more relevant role of stellar collisions. We present here a detailed parameter study to assess how the number of collisions and the mass growth of the most massive object depend on the properties of the cluster. We also characterize the time evolution with three effective parameters: the time when most collisions occur, the duration of the collisions period, and the normalization required to obtain the total number of collisions. We apply our results to typical Population III (Pop. III) clusters of about 1000 M⊙, finding that a moderate enhancement of the mass of the most massive star by a factor of a few can be expected. For more massive Pop. III clusters as expected in the first atomic cooling halos, we expect a more significant enhancement by a factor of 15–32. We therefore conclude that collisions in massive Pop. III clusters were likely relevant to form the first intermediate mass black holes.
Key words: stars: Population III / dark ages, reionization, first stars / quasars: supermassive black holes
© ESO 2018
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