Knebe, A., Libeskind, N. I., Knollmann, S. R., Yepes, G., Gottlöber, S., Hoffman, Y., 2010, Monthly Notices of the Royal Astronomical Society
, 405, 2 , 1119 Published: June 2010
We use two simulations performed within the Constrained Local UniversE Simulation (CLUES) project to study both the shape and radial alignment of (the dark matter component of) subhaloes; one of the simulations is a dark matter only model while the other run includes all the relevant gas physics and star formation recipes. We find that the involvement of gas physics does not have a statistically significant effect on either property - at least not for the most massive subhaloes considered in this study. However, we observe in both simulations including and excluding gas dynamics a (pronounced) evolution of the dark matter shapes of subhaloes as well as of the radial alignment signal since infall time. Further, this evolution is different when positioned in the central and outer regions of the host halo today; while subhaloes tend to become more aspherical in the central 50 per cent of their host's virial radius, the radial alignment weakens in the central regime while strengthening in the outer parts. We confirm that this is due to tidal torquing and the fact that subhaloes at pericentre move too fast for the alignment signal to respond.
The local universe is the best known part of our universe. Within the CLUES project (http://clues-project.org - Constrained Local UniversE Simulations) we perform numerical simulations of the evolution of the local universe. For these simulations we construct initial conditions based on observational data of the galaxy distribution in the local universe. Here we review the technique of these constrained simulations. In the second part we summarize our predictions of a possible Warm Dark Matter cosmology for the observed local distribution of galaxies and the local spectrum of mini-voids as well as a study of the satellite dynamics in a simulated Local Group.
Klimentowski, J., Łokas, E. L., Knebe, A., Gottlöber, S., Martinez-Vaquero, L. A., Yepes, G., Hoffman, Y., 2010, Monthly Notices of the Royal Astronomical Society
, 402, 3 , 1899 Published: March 2010
We use a simulation performed within the Constrained Local Universe Simulation (CLUES) project to study a realistic Local Group (LG)-like object. We employ this group as a numerical laboratory for studying the evolution of the population of its subhaloes from the point of view of the effects it may have on the origin of different types of dwarf galaxies. We focus on the processes of tidal stripping of the satellites, their interaction, merging and grouping before infall. The tidal stripping manifests itself in the transition between the phase of mass accretion and mass loss seen in most subhaloes, which occurs at the moment of infall on to the host halo, and the change of the shape of their mass function with redshift. Although the satellites often form groups, they are loosely bound within them and do not interact with each other. The infall of a large group could however explain the observed peculiar distribution of the LG satellites, but only if it occurred recently. Mergers between prospective subhaloes are significant only during an early stage of evolution, i.e. more than 7 Gyr ago, when they are still outside the host haloes. Such events could thus contribute to the formation of more distant early-type Milky Way companions. Once the subhaloes enter the host halo the mergers become very rare.
Libeskind, N. I., Yepes, G., Knebe, A., Gottlöber, S., Hoffman, Y., Knollmann, S. R., 2010, Monthly Notices of the Royal Astronomical Society
, 401, 3 , 1889 Published: January 2010
We examine the properties of satellites found in high-resolution simulations of the Local Group (LG). We use constrained simulations designed to reproduce the main dynamical features that characterize the local neighbourhood, i.e. within tens of Mpc around the LG. Specifically, an LG-like object is found located within the `correct' dynamical environment and consisting of three main objects which are associated with the Milky Way, M31 and M33. By running two simulations of this LG from identical initial conditions - one with and one without baryons modelled hydrodynamically - we can quantify the effect of gas physics on the z = 0 population of subhaloes in an environment similar to our own. We find that above a certain mass cut, Msub > 2 × 108h-1Msolar subhaloes in hydrodynamic simulations are more radially concentrated than those in simulations without gas. This is caused by the collapse of baryons into stars that typically sit in the central regions of subhaloes, making them denser. The increased central density of such a subhalo results in less mass loss due to tidal stripping than the same subhalo simulated with only dark matter. The increased mass in hydrodynamic subhaloes with respect to dark matter ones causes dynamical friction to be more effective, dragging the subhalo towards the centre of the host. This results in these subhaloes being effectively more radially concentrated than their dark matter counterparts.
Tikhonov, A. V., Gottlöber, S., Yepes, G., Hoffman, Y., 2009, Monthly Notices of the Royal Astronomical Society
, 399, 3 , 1611 Published: November 2009
Using high-resolution simulations within the cold dark matter (CDM) and warm dark matter (WDM) models, we study the evolution of small-scale structure in the local volume, a sphere of 8-Mpc radius around the Local Group. We compare the observed spectrum of minivoids in the local volume with the spectrum of minivoids determined from the simulations. We show that the ΛWDM model can easily explain both the observed spectrum of minivoids and the presence of low-mass galaxies observed in the local volume, provided that all haloes with circular velocities greater than 20 km s-1 host galaxies. On the contrary, within the ΛCDM model the distribution of the simulated minivoids reflects the observed one if haloes with maximal circular velocities larger than 35kms-1 host galaxies. This assumption is in contradiction with observations of galaxies with circular velocities as low as 20 km s-1 in our local Universe. A potential problem of the ΛWDM model could be the late formation of the haloes in which the gas can be efficiently photoevaporated. Thus, star formation is suppressed and low-mass haloes might not host any galaxy at all.
