Séminaire / Seminar GReCO |
| « Universality of galactic surface densities within dark halo cores » |
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B. Famaey |
| The universality of the mean dark matter surface density within one dark halo core radius is known to hold for galaxies spanning a luminosity range of 14 magnitudes and the whole Hubble sequence. We show that a similar relation exists for the baryonic matter, namely that the mean baryonic surface density is also universal within the halo core radius. This means that the gravitational acceleration generated by the baryonic component in galaxies is always the same at this radius. While the total baryonic-to-dark matter ratio is not universal in galaxies, our result, together with the universality of the dark matter surface density, implies that the baryonic-to-dark matter ratio is universal inside the halo core radius. We show that our finding can be interpreted as a close correlation between the enclosed surface densities of - and thus the gravitational accelerations generated by - baryonic and dark matter in galaxies. This argues in favor of a key role played by the interactions between baryonic and dark matter in the process of galaxy formation and evolution, or even in favor of modified gravity. |
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jeudi 3 décembre 2009 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |