Day 830

Tuesday.

Nature Letters
Evidence for dark matter in the inner Milky Way
Iocco, Pato, Bertone

The ubiquitous presence of dark matter in the Universe is today a central tenet in modern cosmology and astrophysics.  Throughout the universe, the evidence for DM is compelling in dwarfs, spiral galaxies, galaxy clusters as well as at cosmological scales.  However, it has been historically difficult to pin down the DM contribution to the total mass density in the MW, particularly in the innermost regions of the Galaxy and in the solar neighborhood.  Present an up-to-date compilation of MW rotation curve measurements, and compare it with state-of-the-art baryonic mass distribution models.  Show that current data strongly disfavor baryons as the sole contribution to the Galactic mass budge, even inside the solar circle.  Findings demonstrate the existence of DM in the inner Galaxy without making any assumptions about it distribution.  Anticipate that this result will compel new model-independent constraints on the DM local density and profile, thus reduction uncertainties on direct and indirect DM searches, and will help reveal the structure and evolution of the Galaxy.

1502.02046
The alignment of satellite galaxies and cosmic filaments: observations and simulations
Tempel, Guo, Kipper, Libeskind

The accretion of satellite onto central galaxies along vast cosmic filaments is an apparent outcome of the anisotropic collapse of structure in the Universe.  Numerical work (based on N-body sims) indicates that satellites are beamed towards hosts along preferred directions imprinted by the velocity shear field.  Use the SDSS to observationally test this claim.  Construct 3D filaments and sheets and examine the relative position of satellites galaxies.  A statistical significant alignment between satellite galaxy position and filament axis is confirmed.  Find a similar (but stronger) signal by examining satellites and filaments similarly identified in the Millennium simulation, semi-analytical galaxy catalogue.  Also examine the dependence of the alignment strength on galaxy properties such as color, magnitude and (relative) satellite magnitude, finding that the alignment is strongest for the reddest and brightest central and satellite galaxies.  Results confirm the theoretical picture and the old of the cosmic web in satellite accretion.  Furthermore, the results suggest that filaments identified on larger scales can be reflected in the positions of satellite galaxies that are quite close to their hosts.