CLUES Publications

Publications retrieved from NASA ADS and sorted by publication date in reverse order

More from CLUES library at ADS

High resolution simulations of the Local Group in the CLUES project
Martínez-Vaquero, L. A., Yepes, G., Gottloeber, S., Hoffman, Y., 2011, Highlights of Spanish Astrophysics VI , 259
Published: November 2011
doi:
Abstract:
Constrained simulations with different resolution, cosmological models and dark matter components were carried out within the CLUES project. They allowed us to study some important properties for both the Local Group (LG) and its environment. We have studied the evolution and structure of the main galactic haloes in the Local Group and their galaxies as well as the substructures in these haloes. We paid special attention to the missing satellite problem in the standard Cold Dark Matter scenario and studied whether the possible biases between dark and luminous components could alleviate or even solve this problem.
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Libeskind, N. I., Knebe, A., Hoffman, Y., Gottlöber, S., Yepes, G., 2011, Monthly Notices of the Royal Astronomical Society , 418, 1 , 336
Published: November 2011
doi:10.1111/j.1365-2966.2011.19487.x
Abstract:
The outer haloes of the Milky Way (MW) and Andromeda (M31) galaxies contain as much important information on their assembly and formation history as the properties of the discs resident in their centres. Whereas the structure of dark matter (DM) haloes has been studied for a long time, new observations of faint structures hiding in the depths of the stellar halo have opened up the question of how the stellar halo is related to the DM underlying it. In this paper, we have used the Constrained Local UniversE Simulation (CLUES) project to disentangle the stellar and DM components of three galaxies that resemble the MW, M31 and M33 using both DM-only simulations and DM + gas-dynamical ones. We find that stars accreted in substructures and then stripped follow a completely different radial distribution than the stripped DM: the stellar halo is much more centrally concentrated than DM. In order to understand how the same physical process - tidal stripping - can lead to different z= 0 radial profiles, we examined the potential at accretion of each stripped particle. We found that star particles sit at systematically higher potentials than DM, making them harder to strip. We then searched for a threshold in the potential of accreted particles φth, above which DM particles in a DM-only simulation behave as star particles in the gas-dynamical one. We found that in order to reproduce the radial distribution of star particles, one must choose DM particles whose potential at accretion is ≳16φsubhalo, where φsubhalo is the potential at a subhaloes edge at the time of accretion. A rule as simple as selecting particles according to their potential at accretion is able to reproduce the effect that the complicated physics of star formation has on the stellar distribution. This result is universal for the three haloes studied here and reproduces the stellar halo to an accuracy of within ∼2 per cent. Studies which make use of DM particles as a proxy for stars will undoubtedly miscalculate their proper radial distribution and structure unless particles are selected according to their potential at accretion. Furthermore, we have examined the time it takes to strip a given star or DM particle after accretion. We find that, owing to their higher binding energies, stars take longer to be stripped than DM. The stripped DM halo is thus considerably older than the stripped stellar halo.
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Forero-Romero, J. E., Hoffman, Y., Yepes, G., Gottlöber, S., Piontek, R., Klypin, A., Steinmetz, M., 2011, Monthly Notices of the Royal Astronomical Society , 417, 2 , 1434
Published: October 2011
doi:10.1111/j.1365-2966.2011.19358.x
Abstract:
We make detailed theoretical predictions for the assembly properties of the Local Group (LG) in the standard Λ cold dark matter cosmological model. We use three cosmological N-body dark matter simulations from the Constrained Local Universe Simulations project, which are designed to reproduce the main dynamical features of the matter distribution down to the scale of a few Mpc around the LG. Additionally, we use the results of an unconstrained simulation with a 60 times larger volume to calibrate the influence of cosmic variance. We characterize the mass aggregation history (MAH) for each halo by three characteristic times: the formation, assembly and last major merger times. A major merger is defined by a minimal mass ratio of 10: 1.

We find that the three LGs share a similar MAH with formation and last major merger epochs placed on average ≈10-12 Gyr ago. Between 12 and 17 per cent of the haloes in the mass range 5 × 1011 < Mh < 5 × 1012 h-1 M⊙ have a similar MAH. In a set of pairs of haloes within the same mass range, a fraction of 1-3 per cent share similar formation properties as both haloes in the simulated LG. An unsolved question posed by our results is the dynamical origin of the MAH of the LGs. The isolation criteria commonly used to define LG-like haloes in unconstrained simulations do not narrow down the halo population into a set with quiet MAHs, nor does a further constraint to reside in a low-density environment.

The quiet MAH of the LGs provides a favourable environment for the formation of disc galaxies like the Milky Way and M31. The timing for the beginning of the last major merger in the Milky Way dark matter halo matches with the gas-rich merger origin for the thick component in the galactic disc. Our results support the view that the specific large- and mid-scale environments around the LG play a critical role in shaping its MAH and hence its baryonic structure at present.

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Knebe, A., Libeskind, N. I., Doumler, T., Yepes, G., Gottlöber, S., Hoffman, Y., 2011, Monthly Notices of the Royal Astronomical Society , 417, 1 , L56
Published: October 2011
doi:10.1111/j.1745-3933.2011.01119.x
Abstract:
Using a dark matter only Constrained Local UniversE Simulation (CLUES) we examine the existence of subhaloes that change their affiliation from one of the two prominent hosts in the Local Group (i.e. the Milky Way and the Andromeda galaxy) to the other, and call these objects 'renegade subhaloes'. In light of recent claims that the two Magellanic Clouds (MCs) may have originated from another region (or even the outskirts) of the Local Group or that they have been spawned by a major merger in the past of the Andromeda galaxy, we investigate the nature of such events. However, we cannot confirm that renegade subhaloes enter as deep into the potential well of their present host nor that they share the most simplest properties with the MCs, namely mass and relative velocity. Our simulation rather suggests that these renegade subhaloes appear to be flying past one host before being pulled into the other. A merger is not required to trigger such an event, it is rather the distinct environment of our simulated Local Group facilitating such behaviour. Since just a small fraction of the full z= 0 subhalo population are renegades, our study indicates that it will be intrinsically difficult to distinguish them despite clear differences in their velocity, radial distribution, shape and spin parameter distributions.
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Di Cintio, A., Knebe, A., Libeskind, N. I., Yepes, G., Gottlöber, S., Hoffman, Y., 2011, Monthly Notices of the Royal Astronomical Society , 417, 1 , L74
Published: October 2011
doi:10.1111/j.1745-3933.2011.01123.x
Abstract:
Using Constrained Local UniversE Simulations (CLUES) of the formation of the Local Group in a cosmological context, we investigate the recently highlighted problem that the majority of the most massive dark subhaloes of the Milky Way (MW) are too dense to host any of its bright satellites. In particular, we examine the influence of baryonic processes and find that they leave a twofold effect on the relation between the peak of the rotation curve and its position (Vmax and Rmax). Satellites with a large baryon fraction experience adiabatic contraction, thus decreasing Rmax while leaving Vmax more or less unchanged. Subhaloes with smaller baryon fractions undergo a decrease in Vmax possibly due to outflows of material. Furthermore, the situation of finding subhaloes in simulations that lie outside the confidence interval for possible hosts of the bright MW dwarf spheroidals appears to be far more prominent in cosmologies with a high σ8 normalization and depends on the mass of the host. We conclude that the problem cannot be simply solved by including baryonic processes and hence demands further investigations.
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