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Centro de Astrofísica da Universidade do Porto

Constraints on the dark matter sound speed from galactic scales: The cases of the modified and extended Chaplygin gas

P. P. Avelino, V. M. C. Ferreira

We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dark matter to be cs<104c , where c is the speed of light in vacuum. Using the modified Chaplygin gas as a representative example of a class of unified dark energy models incorporating an effective dark matter component with a nonzero sound speed, we determine the most stringent constraint to date on the value of the constant contribution to the equation of state parameter in this class of models. Finally, we explain the reason why previous constraints using the cosmic microwave background and baryonic acoustic oscillations were not as competitive as the one presented in this paper and discuss the limitations of the recently proposed extended Chaplygin gas.

Dark matter, Dark energy, Galactic halos, Cosmology

Physical Review D
Volume 91, Page 083508
April 2015

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Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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