We use three different cosmological dark matter simulations to study how the orientation of the angular momentum vector (AM) in dark matter haloes evolve with time. We find that haloes in this kind of simulations are constantly affected by a spurious change of mass, which translates into an artificial change in the orientation of the AM. After removing the haloes affected by artificial mass change, we found that the change in the orientation of the AM vector is correlated with time. The change in its angle and direction (i.e. the angle subtended by the AM vector in two consecutive timesteps) that affect the AM vector has a dependence on the change of mass that affects a halo, the time elapsed in which the change of mass occurs and the halo mass. We create a Monte-Carlo simulation that reproduces the change of angle and direction of the AM vector. We reproduce the angular separation of the AM vector since a look back time of 8.5 Gyrs to today ( $\rm α$) with an accuracy of approximately 0.05 in $\rm cos(α)$. We are releasing this Monte-Carlo simulation together with this publication. We also create a Monte Carlo simulation that reproduces the change of the AM modulus. We find that haloes in denser environments display the most dramatic evolution in their AM direction, as well as haloes with a lower specific AM modulus. These relations could be used to improve the way we follow the AM vector in low-resolution simulations.
We make use of publicly available results from N-body Millennium Simulation to create mock samples of lensed supernovae type Ia and core-collapse. Simulating galaxy-galaxy lensing we derive the rates of lensed supernovae and find than at redshifts higher that 0.5 about 0.06 per cent of supernovae will be lensed by a factor two or more. Future wide field surveys like Gaia or LSST should be able to detect lensed supernovae in their unbiased sky monitoring. Gaia (from 2013) will detect at least 2 cases whereas LSST (from 2018) will see more than 500 a year. Large number of future lensed supernova…
We construct merger trees of dark matter haloes and quantify their merger rates and mass growth rates using the joint dataset from the Millennium and Millennium-II simulations. The finer resolution of the Millennium-II Simulation has allowed us to extend our earlier analysis of halo merger statistics to an unprecedentedly wide range of descendant halo mass (10^10 < M0 < 10^15 Msun), progenitor mass ratio (10^-5 < xi < 1), and redshift (0 < z < 15). We update our earlier fitting form for the mean merger rate per halo as a function of M_0, xi, and z. The overall behavior of this quantity is unch…
We investigate from the fractal viewpoint the way in which the dark matter is grouped at z = 0 in the Millennium dark matter cosmological simulation. The determination of the cross to homogeneity in the Millennium Simulation data is described from the behaviour of the fractal dimension and the lacunarity. We use the sliding window technique to calculate the fractal mass-radius dimension, the pre-factor F and the lacunarity of this fractal relation. Besides, we determinate the multi-fractal dimension and the lacunarity spectrum, including their dependence with radial distance. This calculations…
We present a comprehensive analysis of the evolution of dark matter subhaloes in the cosmological Bolshoi simulation. We identify a complete set of 12 unique evolution channels by which subhaloes evolve in between simulation outputs, and study their relative importance and demographics. We show that instantaneous masses and maximum circular velocities of individual subhaloes are extremely noisy, despite the use of a sophisticated, phase-space-based halo finder. We also show that subhaloes experience frequent penetrating encounters with other subhaloes (on average about one per dynamical time),…
In this work I investigate the statistical properties of a huge catalog of closely interacting pairs of dark matter haloes, extracted from the Millennium Simulation database. Only haloes that reach a minimum mass greater than 8.6 \times 10^10 Msun/h (corresponding to 100 particles) are considered. Close pairs are selected if they come within a critical distance dcrit. I explore the effects of replacing dcrit = 1 Mpc/h with 200 kpc/h on the evolution of separations, lifetimes, total masses and mass ratios of these pairs.
For the last 30 years many observational and theoretical evidences have shown that galaxy clusters are not spherical objects, and that their shape is much better described by a triaxial geometry. With the advent of multi-wavelength data of increasing quality, triaxial investigations of galaxy clusters is gathering a growing interest from the community, especially in the time of "precision cosmology". In this work, we aim to provide the first statistically significant predictions in the unexplored mass range above 3x10^14 Mo/h, using haloes from two redshifts (z=0 and z=1) of the Millennium XXL…
In this paper we investigate the strong lensing statistics in galaxy clusters. We extract dark matter haloes from the Millennium-XXL simulation, compute their Einstein radius distribution, and find a very good agreement with Monte Carlo predictions produced with the MOKA code. The distribution of the Einstein radii is well described by a log-normal distribution, with a considerable fraction of the largest systems boosted by different projection effects. We discuss the importance of substructures and triaxiality in shaping the size of the critical lines for cluster size haloes. We then model an…
We use the large catalogues of haloes available for the Millennium Simulation to test whether recently merged haloes exhibit stronger large-scale clustering than other haloes of the same mass. This effect could help to understand the very strong clustering of quasars at high redshift. However, we find no statistically significant excess bias for recently merged haloes over the redshift range 2 < z < 5, with the most massive haloes showing an excess of at most ~5%. We also consider galaxies extracted from a semianalytic model built on the Millennium Simulation. At fixed stellar mass, we find an…
We present the online MultiDark Database -- a Virtual Observatory-oriented, relational database for hosting various cosmological simulations. The data is accessible via an SQL (Structured Query Language) query interface, which also allows users to directly pose scientific questions, as shown in a number of examples in this paper. Further examples for the usage of the database are given in its extensive online documentation (www.multidark.org). The database is based on the same technology as the Millennium Database, a fact that will greatly facilitate the usage of both suites of cosmological si…
The scientific exploitation of the Dark Energy Spectroscopic Instrument Bright Galaxy Survey (DESI BGS) data requires the construction of mocks with galaxy population properties closely mimicking those of the actual DESI BGS targets. We create a high fidelity mock galaxy catalogue, including information about galaxies and their host dark matter subhaloes. The mock catalogue uses subhalo abundance matching (SHAM) with scatter to populate the P-Millennium N-body simulation with galaxies at the median BGS redshift of ~ 0.2, using formation redshift information to assign (g-r) rest-frame colours. …
Ibata et al. (2013) recently reported the existence of a vast thin plane of dwarf galaxies (VTPD) orbiting around Andromeda. We investigate whether such a configuration can be reproduced within the standard cosmological framework and search for similar planes of co-rotating satellite galaxies around Andromeda-like host haloes in data from the Millennium II simulation combined with a semi-analytic galaxy formation model. We apply a baryonic mass cut of $2.8\times 10^4 \text{M}_{\text{sun}}$ for the satellite haloes and restrict the data to a PAndAS like field. If we include the so-called orphan…
We analyze the clustering properties of quasars simulated using a semianalytic model built on the Millennium Simulation, with the goal of testing scenarios in which black hole accretion and quasar activity are triggered by galaxy mergers. When we select quasars with luminosities in the range accessible by current observations, we find that predicted values for the redshift evolution of the quasar bias agree rather well with the available data and the clustering strength depends only weakly on luminosity. This is independent of the lightcurve model assumed, since bright quasars are black holes …
Previous studies indicate that assembly bias effects are stronger for lower mass dark matter haloes. Here we make use of high resolution re-simulations of rich clusters and their surroundings from the Phoenix Project and a large volume cosmological simulation, the Millennium-II run, to quantify assembly bias effects on dwarf-sized dark matter haloes. We find that, in the regions around massive clusters, dwarf-sized haloes ($[10^9,10^{11}]\ms$) form earlier ($Δz \sim 2$ in redshift) and possess larger $V_{\rm max}$ ($\sim20%$) than the field galaxies. We find that this environmental dependence …
We present a new algorithm which groups the subhaloes found in cosmological N- body simulations by structure finders such as SUBFIND into dark matter haloes whose formation histories are strictly hierarchical. One advantage of these `Dhaloes' over the commonly used friends-of-friends (FoF) haloes is that they retain their individual identity in cases when FoF haloes are artificially merged by tenuous bridges of particles or by an overlap of their outer diffuse haloes. Dhaloes are thus well-suited for modelling galaxy formation and their merger trees form the basis of the Durham semi-analytic g…
We present a detailed study of how dark matter haloes assemble their mass and grow their (central) potential well. We characterize these via their mass accretion histories (MAHs) and potential well growth histories (PWGHs), which we extract from the Bolshoi simulation and from semi-analytical merger trees supplemented with a method to compute the maximum circular velocity, Vmax, of progenitor haloes. The results of both methods are in excellent agreement, both in terms of the average and the scatter. We show that the MAH and PWGH are tightly correlated, and that growth of the central potential…
The massive substructures found in Abell 2744 by Jauzac et al. (2016) present a challenge to the cold dark matter paradigm due to their number and proximity to the cluster centre. We use one of the biggest N-body simulations, the Millennium XXL, to investigate the substructure in a large sample of massive dark matter haloes. A range of effects which influence the comparison with the observations is considered, extending the preliminary evaluation carried out by Jauzac et al. (2016). There are many tens of haloes in the simulation with a total mass comparable with or larger than that of Abell 2…
We use the extensive catalog of dark matter haloes from the Millennium simulation to investigate the statistics of the mass accretion histories (MAHs) and accretion rates of ~500,000 haloes from redshift z=0 to 6. We find only about 25% of the haloes to have MAHs that are well described by a 1-parameter exponential form. For the rest of the haloes, between 20% (Milky-Way mass) to 50% (cluster mass) experience late-time growth that is steeper than an exponential, whereas the remaining haloes show plateau-ed late-time growth that is shallower than an exponential. The haloes with slower late-time…
We present weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment. Using data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), we measure the weighted-average ratio of the aligned projected ellipticity components of galaxy matter haloes and their embedded galaxies, $f_\mathrm{h}$, split by galaxy type. We then compare our observations to measurements taken from the Millennium Simulation, assuming different models of galaxy-halo misalignment. Using the Millennium Simulation we verify that the statistical estimator used remove…
Dark matter haloes in Lambda CDM simulations grow by mergers with other haloes as well as accretion of "diffuse" non-halo material. We quantify the mass growth rates via these two processes, dM_mer/dt and dM_dif/dt, and their dependence on halo environment using the ~500,000 haloes in the Millennium simulation. Adopting a local mass density parameter as a measure of halo environment, we find the two rates show strong but opposite environmental dependence, with mergers playing an increasingly important role for halo growths in overdense regions and diffuse accretion dominating growth in voids. …
We introduce a new method for the identification of galaxy systems in redshift surveys based on the halo model. This method is a modified version of the K-means identification algorithm developed by Yang et al (2005). We have calibrated and tested our algorithms using mock catalogs generated using the Millennium simulations (Springel et al. 2005) and applied them to the NYU-DR7 galaxy catalog (based on the SDSS datasets). Using this local sample of groups and clusters of galaxies we have measured the effect of gravitational redshift produced by their host dark matter haloes. Our results shows …
We present a new statistical method to determine the relationship between the stellar masses of galaxies and the masses of their host dark matter haloes over the entire cosmic history from z~4 to the present. This multi-epoch abundance matching (MEAM) model self-consistently takes into account that satellite galaxies first become satellites at times earlier than they are observed. We employ a redshift-dependent parameterization of the stellar-to-halo mass relation to populate haloes and subhaloes in the Millennium simulations with galaxies, requiring that the observed stellar mass functions at…
We investigate the magnitude and internal alignment of the angular momentum of cold dark matter haloes in simulations with and without baryons. We analyse the cumulative angular momentum profiles of hundreds of thousands of haloes in the Millennium simulation and in a smaller, but higher resolution, simulation, in total spanning 5 orders of magnitude in mass. For haloes of a given mass, the median specific angular momentum increases as j(<r) proportional to r. The direction of the vector varies considerably with radius: the median angle between the inner (< 0.25 Rvir) and total (< Rvir) angula…
The mass aggregation and merger histories of present-day distinct haloes selected from the cosmological Millennium Simulations I and II are mapped into stellar mass aggregation and galaxy merger histories of central galaxies by using empirical stellar-to-halo and stellar-to-gas mass relations. The growth of bulges driven by the galaxy mergers/interactions is calculated using dynamical prescriptions. The predicted bulge demographics at redshift z~0 is consistent with observations (Zavala+2012). Here we present the evolution of the morphological mix (traced by the bulge-to-total mass ratio, B/T)…
We present cosmological hydrodynamical simulations of the formation of dwarf galaxies in a representative sample of haloes extracted from the Millennium-II Simulation. Our six haloes have a z = 0 mass of ~10^10 solar masses and show different mass assembly histories which are reflected in different star formation histories. We find final stellar masses in the range 5 x 10^7 - 10^8 solar masses, consistent with other published simulations of galaxy formation in similar mass haloes. Our final objects have structures and stellar populations consistent with dwarf elliptical and dwarf irregular gal…
We investigate the alignment of haloes with the filaments of the cosmic web using an unprecedently large sample of dark matter haloes taken from the P-Millennium $Λ$CDM cosmological N-body simulation. We use the state-of-the-art NEXUS morphological formalism which, due to its multiscale nature, simultaneously identifies structures at all scales. We find strong and highly significant alignments, with both the major axis of haloes and their peculiar velocity tending to orient along the filament. However, the spin - filament alignment displays a more complex trend changing from preferentially par…
Using the GAEA semi-analytic model, we analyse the connection between Damped Lyman-$α$ systems (DLAs) and HI in galaxies. Our state-of-the-art semi-analytic model is tuned to reproduce the local galaxy HI mass function, and that also reproduces other important galaxy properties, including the galaxy mass - gas metallicity relation. To produce catalogs of simulated DLAs we throw $10^5$ random lines of sight in a composite simulated volume: dark matter haloes with log$(\frac{M_{200}}{ M_{\odot}}) \geq 11.5$ are extracted from the Millennium Simulation, while for $9.2 \leq \log(\frac{M_{200}}{ M_…
We study the abundance of satellite galaxies as a function of primary stellar mass using the SDSS/DR7 spectroscopic catalogue. In contrast with previous studies, which focussed mainly on bright primaries, our central galaxies span a wide range of stellar mass, 10^7.5 < M_*^pri/M_sun < 10^11, from dwarfs to central cluster galaxies. Our analysis confirms that the average number of satellites around bright primaries, when expressed in terms of satellite-to-primary stellar mass ratio (m_*^sat/M_*^pri), is a strong function of M_*^pri. On the other hand, satellite abundance is largely independent …
We use the Millennium I and II cosmological simulations to revisit the impact of mergers in the growth of bulges in central galaxies in the LCDM scenario. We seed galaxies within the growing CDM haloes using semi-empirical relations to assign stellar and gaseous masses, and an analytic treatment to estimate the transfer of stellar mass to the bulge of the remnant after a galaxy merger. We find that this model roughly reproduces the observed correlation between the bulge-to-total (B/T) mass ratio and stellar mass in present-day central galaxies as well as their observed demographics, although l…
The combination of galaxy-galaxy lensing and galaxy clustering data has the potential to simultaneously constrain both the cosmological and galaxy formation models. In this paper we perform a comprehensive exploration of these signals and their covariances through a combination of analytic and numerical approaches. First, we derive analytic expressions for the projected galaxy correlation function and stacked tangential shear profile and their respective covariances, which include Gaussian and discreteness noise terms. Secondly, we measure these quantities from mock galaxy catalogues obtained …
We apply a recently developed scaling technique to the Millennium-XXL, one of the largest cosmological N-body simulations carried out to date 3x10^11 particles within a cube of volume ~70Gpc^3). This allows us to investigate the cosmological parameter dependence of the mass and evolution of haloes in the extreme high-mass tail of the z=6 distribution. We assume these objects to be likely hosts for the population of rare but ultraluminous high-redshift quasars discovered by the Sloan Digital Sky Survey. Haloes with a similar abundance to these quasars have a median mass of 9x10^12 Msun in the c…
(abridged) In this work, we investigate the nature of the host galaxies of long Gamma-Ray bursts (LGRBs) using a galaxy catalogue constructed from the Millennium Simulation. We developed an LGRB synthetic model based on the hypothesis that these events originate at the end of the life of massive stars following the collapsar model, with the possibility of including a constraint on the metallicity of the progenitor star. A complete observability pipeline was designed to calculate a probability estimation for a galaxy to be observationally identified as a host for LGRBs detected by present obser…
We explore the evolution of halo spins in the cosmic web using a very large sample of dark matter haloes in the $Λ$CDM Planck-Millennium N-body simulation. We use the NEXUS+ multiscale formalism to identify the hierarchy of filaments and sheets of the cosmic web at several redshifts. We find that at all times the magnitude of halo spins correlates with the web environment, being largest in filaments, and, for the first time, we show that it also correlates with filament thickness as well as the angle between spin-orientation and the spine of the host filament. For example, massive haloes in th…
Tidal gravitational forces can modify the shape of galaxies and clusters of galaxies, thus correlating their orientation with the surrounding matter density field. We study the dependence of this phenomenon, known as intrinsic alignment (IA), on the mass of the dark matter haloes that host these bright structures, analysing the Millennium and Millennium-XXL $N$-body simulations. We closely follow the observational approach, measuring the halo position-halo shape alignment and subsequently dividing out the dependence on halo bias. We derive a theoretical scaling of the IA amplitude with mass in…
[Abridged] The properties of observed galaxies and dark matter haloes in simulations depend on their environment. The term environment has been used to describe a wide variety of measures that may or may not correlate with each other. Popular measures of environment include the distance to the N'th nearest neighbour, the number density of objects within some distance, or the mass of the host dark matter halo. We use results from the Millennium simulation and a semi-analytic model for galaxy formation to quantify the relations between environment and halo mass. We show that the environmental pa…
We present a new exploratory framework to model galaxy formation and evolution in a hierarchical universe by using machine learning (ML). Our motivations are two-fold: (1) presenting a new, promising technique to study galaxy formation, and (2) quantitatively analyzing the extent of the influence of dark matter halo properties on galaxies in the backdrop of semi-analytical models (SAMs). We use the influential Millennium Simulation and the corresponding Munich SAM to train and test various sophisticated machine learning algorithms (k-Nearest Neighbors, decision trees, random forests and extrem…
We study the concentration of dark matter halos and its evolution in N-body simulations of the standard LCDM cosmology. The results presented in this paper are based on 4 large N-body simulations with about 10 billion particles each: the Millennium-I and II, Bolshoi, and MultiDark simulations. The MultiDark (or BigBolshoi) simulation is introduced in this paper. This suite of simulations with high mass resolution over a large volume allows us to compute with unprecedented accuracy the concentration over a large range of scales (about six orders of magnitude in mass), which constitutes the stat…
This paper describes a new publicly available codebase for modelling galaxy formation in a cosmological context, the "Semi-Analytic Galaxy Evolution" model, or SAGE for short. SAGE is a significant update to that used in Croton et al. (2006) and has been rebuilt to be modular and customisable. The model will run on any N-body simulation whose trees are organised in a supported format and contain a minimum set of basic halo properties. In this work we present the baryonic prescriptions implemented in SAGE to describe the formation and evolution of galaxies, and their calibration for three N-bod…
Fast Baryonic Field Painting for Sunyaev-Zel'dovich Analyses: Transfer Function vs. Hybrid Effective Field Theory
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Berkeley Center for Cosmological Physics（伯克利宇宙物理学中心）；Miller Institute for Basic Research in Science（米勒基础科学研究学院）；Institute for Computational Cosmology, Department of Physics, Durham University（达勒姆大学物理系计算宇宙学研究所）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理学研究所）；Excellence Cluster ORIGINS（ORIGINS卓越集群）
Cosmological simulations predict that galaxies are embedded into triaxial dark matter haloes, which appear approximately elliptical in projection. Weak gravitational lensing allows us to constrain these halo shapes and thereby test the nature of dark matter. Weak lensing has already provided robust detections of the signature of halo flattening at the mass scales of groups and clusters, whereas results for galaxies have been somewhat inconclusive. Here we combine data from five surveys (NGVSLenS, KiDS/KV450, CFHTLenS, CS82, and RCSLenS) in order to tighten observational constraints on galaxy-s…
Accumulating evidence suggests that galaxy interactions play an important role in shaping the properties of galaxies. For this reason, cosmological studies focused on the evolution of halo/subhalo pairs are vital. In this paper I describe a large catalogue of halo pairs extracted from the publicly available Millennium Simulation (Springel et. al. 2005). (Throughout this work I use the term `halo' to refer both to individual haloes in the field and subhaloes embedded in larger structures.) Pairs are selected according to whether or not they come within a given critical (comoving) distance dcrit…
(Abridged) We study the phase-space distribution of satellite galaxies associated with late-type galaxies in the GIMIC suite of simulations. GIMIC consists of re-simulations of 5 cosmologically representative regions from the Millennium simulation, which have higher resolution and incorporate baryonic physics. Whilst the disc of the galaxy is well aligned with the inner regions (r ~ 0.1r_200) of the dark matter halo, both in shape and angular momentum, there can be substantial misalignments at larger radii (r ~ r_200). Misalignments of > 45 deg are seen in ~ 30% of our sample. We find that the…
We introduce Copernicus Complexio (COCO), a high-resolution cosmological N-body simulation of structure formation in the $Λ{\rm CDM}{}$ model. COCO follows an approximately spherical region of radius $\sim 17.4h^{-1}\,{\rm Mpc}$ embedded in a much larger periodic cube that is followed at lower resolution. The high resolution volume has a particle mass of $1.135\times10^5h^{-1}{\rm M}_{\odot}$ (60 times higher than the Millennium-II simulation). COCO gives the dark matter halo mass function over eight orders of magnitude in halo mass; it forms $\sim 60$ haloes of galactic size, each resolved wi…
We investigate the influence of matter along the line of sight and in the strong lens vicinity on the properties of quad image configurations and on the measurements of the Hubble constant (H0). We use simulations of light propagation in a nonuniform universe model with the distribution of matter in space based on the data from Millennium Simulation. For a given strong lens and haloes in its environment we model the matter distribution along the line of sight many times, using different combinations of precomputed deflection maps representing subsequent layers of matter on the path of rays. We…
We study the evolution of the K-band luminosity function (LF) and the Halo Occupation Distribution (HOD) using Subaru observations of 15 X-ray clusters at z=0.8-1.5 and compare the results with mock clusters (0<z<1.3) extracted from the Millennium Simulation and populated with galaxies using the semi-analytic model (SAM) of Bower et al., matched in mass to our observed sample. We find that the characteristic luminosity K* defined by a Shechter LF is consistent with SAM predictions, which mimic well the evolution of K* in z>1 rich clusters. However, we cannot distinguish between this model and …
We investigate the evolution in the dark matter halo circular velocity function, measured at a fixed physical radius of 20 kpc (v_20), which is likely to be a good proxy for galaxy circular velocity, in the Millennium-II simulation. We find that the v_20 function evolves remarkably little since z ~ 4. We analyze the histories of the main progenitors of halos, and we find that the dark matter distribution within the central 20 kpc of massive halos has been in place since early times. This provides evidence for the inside-out growth of haloes. The constancy of the central circular velocity of ha…
The angular momentum of galactic discs in semi-analytic models of galaxy formation is usually updated in time as material is accreted to the disc by adopting a constant dimensionless spin parameter and little attention is paid to the effects of accretion with misaligned angular momenta. These effects are the subject of this paper, where we adopt a Monte-Carlo simulation for the changes in the direction of the angular momentum of a galaxy disc as it accretes matter based on accurate measurements from dark-matter haloes in the Millennium II simulation. In our semi-analytic model implementation, …
If dark matter is composed of neutralinos, one of the most exciting prospects for its detection lies in observations of the gamma-ray radiation created in pair annihilations between neutralinos, a process that may contribute significantly to the extragalactic gamma-ray background (EGB) radiation. We here use the high-resolution Millennium-II simulation of cosmic structure formation to produce the first full-sky maps of the expected radiation coming from extragalactic dark matter structures. Our map making procedure takes into account the total gamma-ray luminosity from all haloes and their sub…
Several recent studies have indicated that artificial subhalo disruption (the spontaneous, non-physical disintegration of a subhalo) remains prevalent in state-of-the-art dark matter-only cosmological simulations. In order to quantify the impact of disruption on the inferred subhalo demographics, we augment the semi-analytical SatGen dynamical subhalo evolution model with an improved treatment of tidal stripping that is calibrated using the DASH database of idealized high-resolution simulations of subhalo evolution, which are free from artificial disruption. We also develop a model of artifici…
We investigate the assembly of groups and clusters of galaxies using the Millennium dark matter simulation and the associated gas simulations and semi-analytic catalogues of galaxies. In particular, in order to find an observable quantity that could be used to identify early-formed groups, we study the development of the difference in magnitude between their brightest galaxies to assess the use of magnitude gaps as possible indicators. We select galaxy groups and clusters at redshift z=1 with dark matter halo mass M(R200) > 1E13/h Msun, and trace their properties until the present time (z=0). …
We show that, observationally, the projected local density distribution in high-z clusters is shifted towards higher values compared to clusters at lower redshift. To search for the origin of this evolution, we analyze a sample of haloes selected from the Millennium Simulation and populated using semi-analytic models, investigating the relation between observed projected density and physical 3D density, using densities computed from the 10 and 3 closest neighbours. Both observationally and in the simulations, we study the relation between number of cluster members and cluster mass, and number …
We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. We select the most massive dark matter halo at z=6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 10^5 Msun, and that seeding occurs around z~15 in dark matter haloes of mass 10^9-10^10 Msun, we find that it is possible to build up su…
