Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-08-06
Astronomy and Astrophysics
Astrophysics
9 pages, proceedings of IAU Symposium 244, Dark Galaxies & Lost Baryons
Scientific paper
10.1017/S1743921307013798
Deep optical/near-IR surface photometry of galaxies outside the Local Group have revealed faint and very red halos around objects as diverse as disk galaxies and starbursting dwarf galaxies. The colours of these structures are too extreme to be reconciled with stellar populations similar to those seen in the stellar halos of the Milky Way or M31, and alternative explanations like dust reddening, high metallicities or nebular emission are also disfavoured. A stellar population obeying an extremely bottom-heavy initial mass function (IMF), is on the other hand consistent with all available data. Because of its high mass-to-light ratio, such a population would effectively behave as baryonic dark matter and could account for some of the baryons still missing in the low-redshift Universe. Here, we give an overview of current red halo detections, alternative explanations for the origin of the red colours and ongoing searches for red halos around types of galaxies for which this phenomenon has not yet been reported. A number of potential tests of the bottom-heavy IMF hypothesis are also discussed.
Bergvall Nils
Caldwell Brady
Flynn Chris
Micheva Genoveva
Ostlin Goeran
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