Volume 585, January 2016
|Number of page(s)||12|
|Section||Cosmology (including clusters of galaxies)|
|Published online||09 December 2015|
The chemical evolution of self-gravitating primordial disks
Departamento de AstronomíaFacultad Ciencias Físicas y Matemáticas,
Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario,
2 Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
3 Sorbonne Universités, UPMC Univ Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
4 CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
5 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
6 Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, 277-8583 Kashiwa, Japan
7 Centre for Star and Planet Formation, Natural History Museum of Denmark, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
8 Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
Received: 19 April 2015
Accepted: 7 October 2015
Numerical simulations show the formation of self-gravitating primordial disks during the assembly of the first structures in the Universe, in particular, during the formation of Population III and supermassive stars. Their subsequent evolution is expected to be crucial in determining the mass scale of the first cosmological objects, which depends on the temperature of the gas and dominant cooling mechanism. Here, we derive a one-zone framework to explore the chemical evolution of these disks and show that viscous heating leads to the collisional dissociation of an initially molecular gas. The effect is relevant on scales of 10 AU (1000 AU) for a central mass of 10 M⊙ (104 M⊙) at an accretion rate of 10-1 M⊙ yr-1, and provides a substantial heat input to stabilize the disk. If the gas is initially atomic, it remains atomic during the further evolution and the effect of viscous heating is less significant. The additional thermal support is particularly relevant for the formation of very massive objects, such as the progenitors of the first supermassive black holes. The stabilizing impact of viscous heating thus alleviates the need for strong radiation background as a means of keeping the gas atomic.
Key words: cosmology: theory / dark ages, reionization, first stars / accretion, accretion disks / astrochemistry / stars: formation / stars: Population III
© ESO, 2015
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