ABSTRACT
We explore the boundary of dark matter haloes through their bias and velocity profiles. Using cosmological N-body simulations, we show that the bias profile exhibits a ubiquitous trough that ...can be interpreted as created by halo accretion that depletes material around the boundary. The inner edge of the active depletion region is marked by the location of the maximum mass inflow rate that separates a growing halo from the draining environment. This inner depletion radius can also be interpreted as the radius enclosing a highly complete population of splashback orbits, and matches the optimal exclusion radius in a halo model of the large-scale structure. The minimum of the bias trough defines a characteristic depletion radius, which is located within the infall region bounded by the inner depletion radius and the turnaround radius, while approaching the turnaround radius in low-mass haloes that have stopped mass accretion. The characteristic depletion radius depends the most on halo mass and environment. It is approximately 2.5 times the virial radius and encloses an average density of ∼40 times the background density of the universe, independent on halo mass but dependent on other halo properties. The inner depletion radius is smaller by 10–20 per cent and encloses an average density of ∼63 times the background density. These radii open a new window for studying the properties of haloes.
N-body simulations suggest that the substructures that survive inside dark matter haloes follow universal distributions in mass and radial number density. We demonstrate that a simple analytical ...model can explain these subhalo distributions as resulting from tidal stripping which increasingly reduces the mass of subhaloes with decreasing halocentric distance. As a starting point, the spatial distribution of subhaloes of any given infall mass is shown to be largely indistinguishable from the overall mass distribution of the host halo. Using a physically motivated statistical description of the amount of mass stripped from individual subhaloes, the model fully describes the joint distribution of subhaloes in final mass, infall mass and radius. As a result, it can be used to predict several derived distributions involving combinations of these quantities including, but not limited to, the universal subhalo mass function, the subhalo spatial distribution, the gravitational lensing profile, the dark matter annihilation radiation profile and boost factor. This model clarifies a common confusion when comparing the spatial distributions of galaxies and subhaloes, the so-called anti-bias, as a simple selection effect. We provide a python code subgen for populating haloes with subhaloes at http://icc.dur.ac.uk/data/.
We present a new model to describe the galaxy-dark matter connection across cosmic time, which unlike the popular subhalo abundance-matching technique is self-consistent in that it takes account of ...the facts that (1) subhalos are accreted at different times and (2) the properties of satellite galaxies may evolve after accretion. Using observations of galaxy stellar mass functions (SMFs) out to z ~ 4, the conditional SMF at z ~ 0.1 obtained from Sloan Digital Sky Survey galaxy group catalogs, and the two-point correlation function (2PCF) of galaxies at z ~ 0.1 as a function of stellar mass, we constrain the relation between galaxies and dark matter halos over the entire cosmic history from z ~ 4 to the present. This relation is then used to predict the median assembly histories of different stellar mass components within dark matter halos (central galaxies, satellite galaxies, and halo stars). We also make predictions for the 2PCFs of high-z galaxies as function of stellar mass. Our main findings are the following: (1) Our model reasonably fits all data within the observational uncertainties, indicating that the LAMBDACDM concordance cosmology is consistent with a wide variety of data regarding the galaxy population across cosmic time. (2) At low-z, the stellar mass of central galaxies increases with halo mass as M super(0.3) and M super(> ~4.0) at the massive and low-mass ends, respectively. The ratio Mlow *,c/M reveals a maximum of ~0.03 at a halo mass M ~ 10 super(11.8) h super(-1) M sub(middot in circle), much lower than the universal baryon fraction (~0.17). At higher redshifts the maximum in Mlow *,c/M remains close to ~0.03, but shifts to higher halo mass. (3) The inferred timescale for the disruption of satellite galaxies is about the same as the dynamical friction timescale of their subhalos. (4) The stellar mass assembly history of central galaxies is completely decoupled from the assembly history of its host halo; the ratio Mlow *,c/M initially increases rapidly with time until the halo mass reaches ~10 super(12) h super(-1) M sub(middot in circle), at which point Mlow *,c/M ~ 0.03. Once M > ~10 super(12) h super(-1) M sub(middot in circle), there is little growth in Mlow *,c, causing the ratio Mlow *,c/M to decline. In Milky Way (MW)-sized halos more than half of the central stellar mass is assembled at z <, ~ 0.5. (5) In low-mass halos, the accretion of satellite galaxies contributes little to the formation of their central galaxies, indicating that most of their stars must have formed in situ. In massive halos more than half of the stellar mass of the central galaxy has to be formed in situ, and the accretion of satellites can only become significant at z <, ~ 2. (6) The total mass in halo stars is more than twice that of the central galaxy in massive halos, but less than 10% of Mlow *,c in MW-sized halos. (7) The 2PCFs of galaxies on small scales hold important information regarding the evolution of satellite galaxies, which at high-z is predicted to be much steeper than at low-z, especially for more massive galaxies. We discuss various implications of our findings regarding the formation and evolution of galaxies in a LambdaCDM cosmology.
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•A bibliometric analysis of groundwater vulnerability (GV) research was conducted.•Nine aspects of the literature database were visualized.•Current research frontiers, future ...challenges and suggestions were identified.•Sustainable development goals (SDGs) were interlinked with GV.
Groundwater is the main source of drinking and irrigation on earth because of its large quantity and worldly distribution, albeit unequally. However, it is presently being threatened by over-consumption and contamination. Groundwater vulnerability (GV) is to assess the aquifer sustainability under a contaminant load for an area, which plays a significant part in sustainable groundwater management in practice. In the last several decades, the studies of GV have increased exponentially over the entire globe, and there is currently no statistical review in GV by using bibliometric analysis with the increasing publications. In this review, a global bibliometric analysis was conducted to analyze and visualize the current status and determine future challenges of GV research by considering a total of 949 articles based on Web of Science core collection database. Nine different aspects, including trend, related disciplines, journals, author productivity, countries or regions, institutions, citations, keywords and practical implementation were visualized and analyzed by CiteSpace 5.8 R3, Microsoft’s Excel and Tableau. By in-depth analysis, this review clearly showed the major contribution members and the evolutionary process of GV, as well as identified four research frontiers (model development, modification and optimization, climate change impacts, human activity impacts and sustainable groundwater management) and four future challenges (unequal research development, insufficient cooperation, response to climate change and human activities, and SDGs in groundwater management). Finally, the corresponding suggestions for overcoming the challenges were proposed to achieve sustainable groundwater management.
The mass of the dark matter halo of the Milky Way can be estimated by fitting analytical models to the phase-space distribution of dynamical tracers. We test this approach using realistic mock ...stellar haloes constructed from the Aquarius N-body simulations of dark matter haloes in the Λ cold dark matter cosmology. We extend the standard treatment to include a Navarro–Frenk–White potential and use a maximum likelihood method to recover the parameters describing the simulated haloes from the positions and velocities of their mock halo stars. We find that the estimate of halo mass is highly correlated with the estimate of halo concentration. The best-fitting halo masses within the virial radius, R
200, are biased, ranging from a 40 per cent underestimate to a 5 per cent overestimate in the best case (when the tangential velocities of the tracers are included). There are several sources of bias. Deviations from dynamical equilibrium can potentially cause significant bias; deviations from spherical symmetry are relatively less important. Fits to stars at different galactocentric radii can give different mass estimates. By contrast, the model gives good constraints on the mass within the half-mass radius of tracers even when restricted to tracers within 60 kpc. The recovered velocity anisotropies of tracers, β, are biased systematically, but this does not affect other parameters if tangential velocity data are used as constraints.
Fiber collision is a persistent problem faced by modern spectroscopic galaxy surveys. In this work, we propose a new method to correct for this undesired effect, focusing on the clustering from the ...fiber-collision scale up to . We assume that the fiber-collided galaxies are in association with their nearest three angular neighbors. Compared with the conventional nearest-neighbor method, we have properly accounted for the foreground (background) galaxies that are associated with the foreground (background) cosmic webs relative to the nearest neighbor. We have tested the new method with mock catalogs of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). The test demonstrates that our new method can recover the projected two-point correlation functions at an accuracy better than 1% on small (below the fiber-collision scale) to intermediate (i.e., ) scales, where the fiber collision takes effect and the SDSS main sample can probe. The new method also gives a better recovery of the redshift-space correlation functions almost on all scales that we are interested in.
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