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Originally published in Science Express on 10 May 2007
Science 25 May 2007:
Vol. 316. no. 5828, pp. 1166 - 1169
DOI: 10.1126/science.1142114
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Reports

Missing Mass in Collisional Debris from Galaxies

Frédéric Bournaud,1* Pierre-Alain Duc,1 Elias Brinks,2 Médéric Boquien,1 Philippe Amram,3 Ute Lisenfeld,4,5 Bärbel S. Koribalski,6 Fabian Walter,7 Vassilis Charmandaris8,9,10

Recycled dwarf galaxies can form in the collisional debris of massive galaxies. Theoretical models predict that, contrary to classical galaxies, these recycled galaxies should be free of nonbaryonic dark matter. By analyzing the observed gas kinematics of such recycled galaxies with the help of a numerical model, we demonstrate that they do contain a massive dark component amounting to about twice the visible matter. Staying within the standard cosmological framework, this result most likely indicates the presence of large amounts of unseen, presumably cold, molecular gas. This additional mass should be present in the disks of their progenitor spiral galaxies, accounting for a substantial part of the so-called missing baryons.

1 Laboratoire Astrophysique des Interactions Multi-Echelles, Commissariat à l'Energie Atomique (CEA) Direction des Sciences de la Matière–CNRS–Université Paris Diderot, Laboratoire de recherches sur les lois fondamentales de l'Univers (Dapnia)/Service d'Astrophysique, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex, France.
2 Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK.
3 Observatoire Astronomique Marseille-Provence, Laboratoire d'Astrophysique de Marseille UMR 6110, 2 place Le Verrier, F-13248 Marseille Cedex 4, France.
4 Departamento Física Teórica y del Cosmos, Universidad de Granada, Spain.
5 Instituto de Astrofísica de Andalucía (CSIC), Post Office Box 3004, 18080 Granada, Spain.
6 Commonwealth Scientific and Industrial Research Organisation (CSIRD), Australia Telescope National Facility (ATNF), Post Office Box 76, Epping NSW 1710, Australia.
7 Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany.
8 Department of Physics, University of Crete, GR-71003 Heraklion, Greece.
9 Foundation for Research and Technology (IESL), Hellas, GR-71110, Heraklion, Greece.
10 Observatoire de Paris, F-75014, Paris, France.

* To whom correspondence should be addressed. E-mail: frederic.bournaud{at}cea.fr

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Science. ISSN 0036-8075 (print), 1095-9203 (online)