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Star-forming filaments in warm dark matter models.

Gao, L. and Theuns, T. and Springel, V. (2015) 'Star-forming filaments in warm dark matter models.', Monthly notices of the Royal Astronomical Society., 450 (1). pp. 45-52.


We performed a hydrodynamical cosmological simulation of the formation of a Milky Way-like galaxy in a warm dark matter (WDM) cosmology. Smooth and dense filaments, several comoving mega parsec long, form generically above z ∼ 2 in this model. Atomic line cooling allows gas in the centres of these filaments to cool to the base of the cooling function, resulting in a very striking pattern of extended Lyman-limit systems (LLSs). Observations of the correlation function of LLSs might hence provide useful limits on the nature of the dark matter. We argue that the self-shielding of filaments may lead to a thermal instability resulting in star formation. We implement a sub-grid model for this, and find that filaments rather than haloes dominate star formation until z ∼ 6, although this depends on how stars form in WDM. Reionization decreases the gas density in filaments, and the more usual star formation in haloes dominates below z ∼ 6, although star formation in filaments continues until z = 2. 15 per cent of the stars of the z = 0 galaxy formed in filaments. At higher redshift, these stars give galaxies a stringy appearance, which, if observed, might be a strong indication that the dark matter is warm.

Item Type:Article
Keywords:Galaxies: formation, Intergalactic medium, Dark matter.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:24 March 2015
Date deposited:18 February 2016
Date of first online publication:June 2015
Date first made open access:No date available

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