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On the population of primordial star clusters in the presence of UV background radiation

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posted on 2023-06-07, 14:46 authored by Michael A MacIntyre, Fernando Santoro, Peter Thomas
We use the algorithm of Cole et al. to generate merger trees for the first star clusters in a ? cold dark matter (?CDM) cosmology under an isotropic ultraviolet background radiation field, parametrized by J21. We have investigated the problem in two ways: a global radiation background and local radiative feedback surrounding the first star clusters. Cooling in the first haloes at high redshift is dominated by molecular hydrogen, H2– we call these Generation 1 objects. At lower redshift and higher virial temperature, Tvir? 104 K, electron cooling dominates – we call these Generation 2. Radiation fields act to photodissociate H2, but also generate free electrons that can help to catalyze its production. At modest radiation levels, J21/(1 +z)3~ 10-12–10-7, the nett effect is to enhance the formation of Generation 1 star clusters. At higher fluxes, the heating from photoionization dominates and halts their production. With a realistic build-up of flux over time, the period of enhanced H2 cooling is so fleeting as to be barely discernable and the nett effect is to move primordial star cluster formation towards Generation 2 objects at lower redshift. A similar effect is seen with local feedback. Provided that enough photons are produced to maintain ionization of their host halo, they will suppress the cooling in Generation 1 haloes and boost the numbers of primordial star clusters in Generation 2 haloes. Significant suppression of Generation 1 haloes occurs for specific photon fluxes in excess of about 1043 ph s-1 M-1?.

History

Publication status

  • Published

File Version

  • Published version

Journal

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

Publisher

Oxford University Press

Issue

3

Volume

368

Page range

1301-1310

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2008-10-01

First Open Access (FOA) Date

2016-03-22

First Compliant Deposit (FCD) Date

2016-08-17

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