http://arxiv.org/abs/1712.00094
We study the dependence of surface mass density profiles, which can be directly measured by weak gravitational lensing, on the orientation of haloes with respect to the line-of-sight direction, using a suite of $N$-body simulations. We find that, when major axes of haloes are aligned with the line-of-sight direction, surface mass density profiles have higher amplitudes than those averaged over all halo orientations, over all scales from $0.1$ to $100\, \mathrm{Mpc}/h$ we studied. While the orientation dependence at small scales is ascribed to the halo triaxiality, our results indicate even stronger orientation dependence in the so-called two-halo regime, up to $100\,\mathrm{Mpc}/h$. The orientation dependence for the two-halo term is well approximated by a constant shift of the amplitude and therefore a shift in the halo bias parameter value. The halo bias from the two-halo term can be overestimated or underestimated by up to $\sim 30 \%$ depending on the viewing angle, which translates into the bias in estimated halo masses by up to a factor of two from halo bias measurements. The orientation dependence at large scales originates from the anisotropic halo-matter correlation function, which has an elliptical shape with the axis ratio of $\sim 0.55$ up to $100\,\mathrm{Mpc}/h$. We discuss potential impacts of halo orientation bias on other observables such as optically selected cluster samples and a clustering analysis of large-scale structure tracers such as quasars.
K. Osato, T. Nishimichi, M. Oguri, et. al.
Mon, 4 Dec 17
46/72
Comments: 14 pages, 10 figures, submitted to MNRAS