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تسجيل مستخدم جديدHaloes at the ragged edge: The importance of the splashback radius
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We have explored the outskirts of dark matter haloes out to 2.5 times the virial radius using a large sample of halos drawn from Illustris, along with a set of zoom simulations (MUGS). Using these, we make a systematic exploration of the shape profile beyond R$_{vir}$. In the mean sphericity profile of Illustris halos we identify a dip close to the virial radius, which is robust across a broad range of masses and infall rates. The inner edge of this feature may be related to the virial radius and the outer edge with the splashback radius. Due to the high halo-to-halo variation this result is visible only on average. However, in four individual halos in the MUGS sample, a decrease in the sphericity and a subsequent recovery is evident close to the splashback radius. We find that this feature persists for several Gyr, growing with the halo. This feature appears at the interface between the spherical halo density distribution and the filamentary structure in the environment. The shape feature is strongest when there is a high rate of infall, implying that the effect is due to the mixing of accreting and virializing material. The filamentary velocity field becomes rapidly mixed in the halo region inside the virial radius, with the area between this and the splashback radius serving as the transition region. We also identify a long-lasting and smoothly evolving splashback region in the radial density gradient in many of the MUGS halos.
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The splashback radius, $R_{rm sp}$, is a physically motivated halo boundary that separates infalling and collapsed matter of haloes. We study $R_{rm sp}$ in the hydrodynamic and dark matter only IllustrisTNG simulations. The most commonly adopted sig
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ated at ~r_200m; the strength and location of this feature depends on the recent mass accretion rate, in good agreement with previous work. Interestingly, the stellar distribution (or intracluster light, ICL) also has a well-defined edge, which is directly related to the splashback radius of the halo. Thus, detecting the edge of the ICL can provide an independent measure of the physical boundary of the halo, and the recent mass accretion rate. We show that these caustics can also be seen in the projected density profiles, but care must be taken to account for the influence of substructures and other non-diffuse material, which can bias and/or weaken the signal of the steepest slope. This is particularly important for the stellar material, which has a higher fraction bound in subhaloes than the dark matter. Finally, we show that the `stellar splashback feature is located beyond current observational constraints on the ICL, but these large projected distances (>> 1 Mpc) and low surface brightnesses (mu >> 32 mag/arcsec^2) can be reached with upcoming observational facilities such as the Vera C. Rubin Observatory, the Nancy Grace Roman Space Telescope, and Euclid.
We present the direct detection of the splashback feature using the sample of massive galaxy clusters from the Local Cluster Substructure Survey (LoCuSS). This feature is clearly detected (above $5sigma$) in the stacked luminosity density profile obt
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We critically examine the methodology behind the claimed observational detection of halo assembly bias using optically selected galaxy clusters by Miyatake et al. (2016) and More et al. (2016). We mimic the optical cluster detection algorithm and app
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