Journal Article

Hierarchical formation of bulgeless galaxies – II. Redistribution of angular momentum via galactic fountains

C. B. Brook, G. Stinson, B. K. Gibson, R. Roškar, J. Wadsley and T. Quinn

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 419, issue 1, pages 771-779
Published in print January 2012 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2011.19740.x
Hierarchical formation of bulgeless galaxies – II. Redistribution of angular momentum via galactic fountains

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Within a fully cosmological hydrodynamical simulation, we form a galaxy which rotates at 140 km s−1, and it is characterized by two loose spiral arms and a bar, indicative of a Hubble-type SBc/d galaxy. We show that our simulated galaxy has no classical bulge, with a pure disc profile at z = 1, well after the major merging activity has ended. A long-lived bar subsequently forms, resulting in the formation of a secularly formed ‘pseudo-’bulge, with the final bulge-to-total light ratio of 0.21. We show that the majority of gas which loses angular momentum and falls to the central region of the galaxy during the merging epoch is blown back into the hot halo, with much of it returning later to form stars in the disc. We propose that this mechanism of redistribution of angular momentum via a galactic fountain, when coupled with the results from our previous study which showed why gas outflows are biased to have low angular momentum, can solve the angular momentum/bulgeless disc problem of the cold dark matter paradigm.

Keywords: galaxies: bulges; galaxies: evolution; galaxies: formation; galaxies: spiral

Journal Article.  6546 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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