Site Map
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

How much dark matter is there inside early-type galaxies?

A. Nigoche-Netro, A. Ruelas-Mayorga, P. Lagos, G. Ramos-Larios, C. Kehrig, S. N. Kemp, A. D. Montero-Dorta, J. González-Cervantes

We study the luminous mass as a function of the dynamical mass inside the effective radius (re) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs – ranging from 19 000 to 98 000 objects – from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations (see Appendix A) of galaxy samples and compare them with real samples. The main results are (i) MC simulations show that the distribution of the dynamical versus luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. (ii) The amount of dark matter inside re is approximately 7 ± 22 per cent. (iii) This amount of dark matter is lower than the minimum estimate (10 per cent) found in the literature and four times lower than the average (30 per cent) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.

galaxies: distances and redshifts, galaxies: fundamental parameters, galaxies photometry, dark matter

Monthly Notices of the Royal Astronomical Society
Volume 446, Page 85
January 2015

>> PDF>> ADS>> DOI

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.

Proceed on CAUP's website|Go to IA website