Wojciech A. Hellwing, Marius Cautun, Alexander Knebe, Steffen Knollmann, Roman Juszkiewicz
We investigate how long-range scalar interactions affect the properties of dark matter haloes and their large scale distribution. For doing so we employ the ReBEL model which implements an additional interaction between dark matter particles. On the phenomenological level this is equivalent to a modification of gravity. We analyse the differences between five ReBEL models and $\Lambda$CDM using a series of high resolution cosmological simulations. In the first part of our study we investigate how halo properties change in the presence of a fifth force. We report that the density profile of ReBEL haloes is well described by the NFW profile but with mean concentrations from 5% to a few times higher than the standard $\Lambda$CDM value. We also find a slight increase of the halo spin for haloes more massive than $5\times10^{11}\Msol$, reflecting a higher rotational support of the haloes due to scalar forces. In addition, the dark matter haloes in our models are more spherical than their counterparts in $\Lambda$CDM. The ReBEL haloes are also more virialised, with a large difference from $\Lambda$CDM for strong fifth forces and a much smaller change for weak scalar interactions. In the second part we analyse how the halo environment changes in the presence of the fifth force. We find that ReBEL predicts more mass and volume in filaments at the downside of walls and voids which become noticeably more empty. Even though voids have less mass, they have many more haloes in fifth force models than in $\Lambda$CDM. This is because more of the mass in voids is inside gravitationally bound structures. We report that the halo population in voids seems to be a particularly sensitive probe of modified gravity since the mass function of these objects is very sensitive to the presence of even a weak fifth force.
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http://arxiv.org/abs/1111.7257
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