Journal Article

Subhaloes in scale-free cosmologies

Pascal J. Elahi, Robert J. Thacker, Lawrence M. Widrow and Evan Scannapieco

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 4, pages 1950-1962
Published in print June 2009 | ISSN: 0035-8711
Published online May 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14707.x
Subhaloes in scale-free cosmologies

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We explore the dependence of the subhalo mass function on the spectral index n of the linear matter power spectrum using scale-free Einstein-de Sitter simulations with n=−1 and −2.5. We carefully consider finite volume effects that may call into question previous simulations of n < −2 power spectra. Subhaloes are found using a 6D friends-of-friends algorithm in all haloes originating from high-σ peaks. For n=−1, we find that the cumulative subhalo mass function is independent of the parameters used in the subhalo finding algorithm and is consistent with the subhalo mass function found in Λ cold dark matter (ΛCDM) simulations. In particular, the subhalo mass function is well fit by a power-law with an index of α=−0.9, that is the mass function has roughly equal mass in subhaloes per logarithmic interval in subhalo mass. Conversely, for n=−2.5, the algorithm parameters affect the subhalo mass function since subhaloes are more triaxial with less well-defined boundaries. We find that the index α is generally larger with α≳−0.75. We infer that although the subhalo mass function appears to be independent of n so long as n≳−2, it begins to flatten as n→−3. Thus, the common practice of using α≈−1.0 may greatly overestimate the number of subhaloes at the smallest scales in the CDM hierarchy.

Keywords: methods: N-body simulations; methods: numerical; galaxies: haloes; dark matter

Journal Article.  8745 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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