We study the properties of building blocks (BBs, i.e. accreted satellites) and surviving satellites of present-day galaxies using the SAG semi-analytic model of galaxy formation in the context of a concordance Lambda Cold Dark Matter (LCDM) cosmology. We consider large numbers of DM halo merger trees spanning a wide range of masses (~1x10^10 - 2.14x10^15 Msun). We find higher metallicities for BBs with respect to surviving satellites, an effect produced by the same processes behind the build-up of the mass-metallicity relation. We prove that these metallicity differences arise from the higher peak height in the density fluctuation field occupied by BBs and central galaxies which have collapsed into a single object earlier than surviving satellites. BBs start to form stars earlier, during the peak of the merger activity in LCDM, and build-up half of their final stellar mass (measured at the moment of disruption) up to four times faster than surviving satellites. Surviving satellites keep increasing their stellar masses rather quiescently down to z~1. The difference between the metallicities of satellites, BBs and central galaxies depends on the host DM halo mass, in a way that can be used as a further test for the concordance cosmology.
Satellites within simulated massive clusters are significantly spatially correlated with each other, even when those satellites are not gravitationally bound to each other. This correlation is produced by satellites that entered their hosts relatively recently, and is undetectable for satellites that have resided in their hosts for multiple dynamical timescales. Therefore, a measurement of clustering statistics of cluster satellites may be used to determine the typical accretion redshifts of those satellites into their observed hosts. We argue that such measurements may be used to determine th…
We analyze the clustering of red and blue galaxies from four samples spanning a redshift range of 0.4<z<2.0 to test the various scenarios by which galaxies evolve onto the red sequence. The data are taken from the UKIDSS Ultra Deep Survey, DEEP2, and COMBO-17. The use of clustering allows us to determine what fraction of the red sequence is made up of central galaxies and satellite galaxies. At all redshifts, including z=0, the data are consistent with ~60% of satellite galaxies being red or quenched, implying that ~1/3 of the red sequence is comprised of satellite galaxies. More than three-fo…
We analyze the angular clustering of z~2.3 distant red galaxies (DRGs) measured by Quadri et al 2008. We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w(theta) at theta=10 arcsec, nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is ~44%, implying that the format…
We test different implementations of the halo occupation distribution (HOD) model to reconstruct the spatial distribution of galaxies as predicted by a publicly available semi-analytical model (SAM). We compare the measured two-point correlation functions of the HOD mock catalogues and the SAM samples to quantify the fidelity of the reconstruction. We use fixed number density galaxy samples selected according to stellar mass or star formation rate (SFR). We develop three different schemes to populate haloes with galaxies with increasing complexity, considering the scatter of the satellite HOD …
We measure the angular clustering of galaxies from the Sloan Digital Sky Survey Data Release 7 in order to probe the spatial distribution of satellite galaxies within their dark matter halos. Specifically, we measure the angular correlation function on very small scales (7-320") in a range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (the so-called plate overlap region). We choose to measure angular clustering in this reduced survey footprint in order to minimiz…
The clustering amplitude of galaxies depends on their intrinsic luminosity. We compare the properties of publicly available galaxy formation models with clustering measurements from the two-degree field galaxy redshift survey. The model predictions show the same qualitative behaviour as the data but fail to match the observations at the level of accuracy at which current measurements can be made. We demonstrate that this is due to the model producing too many satellite galaxies in massive haloes. We implement simple models to describe two new processes, satellite-satellite mergers and the tida…
The observed population of the Milky Way satellite galaxies offer a unique testing ground for galaxy formation theory on small-scales. Our novel approach was to investigate the clustering of the known Milky Way satellite galaxies and to quantify the amount of substructure within their distribution using a two-point correlation function statistic in each of three spaces: configuration space, line-of-sight velocity space, and four-dimensional phase-space. These results were compared to those for three sets of subhaloes in the Via Lactea II Cold Dark Matter simulation defined to represent the lum…
We present a physically motivated semi-analytic model to understand the clustering of high redshift LBGs. We show that the model parameters constrained by the observed luminosity function, can be used to predict large scale (θ> 80 arcsec) bias and angular correlation function of galaxies. These predictions are shown to reproduce the observations remarkably well. We then adopt these model parameters to calculate the halo occupation distribution (HOD) using the conditional mass function. The halo model using this HOD is shown to provide a reasonably good fit to the observed clustering of LBGs at…
Galaxy clustering sets strong constraints on the physics governing galaxy formation and evolution. However, most current models fail to reproduce the clustering of low-mass galaxies on small scales ($r<1Mpc/h$). In this paper we study the galaxy clusterings predicted from a few semi-analytical models. We firstly compare two Munich versions, Guo et al. (2011, Guo11) and De Lucia \& Blazoit (2007, DLB07). The Guo11 model well reproduces the galaxy stellar mass function, but over-predicts the clustering of low-mass galaxies on small scales. The DLB07 model provides a better fit to the clustering …
We combine the most precise small scale ($< 100\, \rm h^{-1}kpc$) quasar clustering constraintsto date with recent measurements at large scales ($> 1\, \rm h^{-1}Mpc$) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to better constrain the satellite fraction of quasars at $z\sim 1.5$ in the halo occupation formalism. We build our Halo Occupation Distribution (HOD) framework based on commonly used analytic forms for the one and two-halo terms with two free parameters: the minimum halo mass that hosts a central quasar and the fraction of satellite quasars that are within one ha…
The peculiar velocity field measured by redshift-space distortions (RSD) in galaxy surveys provides a unique probe of the growth of large-scale structure. However, systematic effects arise when including satellite galaxies in the clustering analysis. Since satellite galaxies tend to reside in massive halos with a greater halo bias, the inclusion boosts the clustering power. In addition, virial motions of the satellite galaxies cause a significant suppression of the clustering power due to nonlinear RSD effects. We develop a novel method to recover the redshift-space power spectrum of halos fro…
We investigate the luminosity and colour dependence of clustering of CMASS galaxies in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Tenth Data Release. The halo occupation distribution framework is adopted to model the projected two-point correlation function measurements on small and intermediate scales (from $0.02$ to $60\,h^{-1}{\rm {Mpc}}$) and to interpret the observed trends and infer the connection of galaxies to dark matter halos. We find that luminous red galaxies reside in massive halos of mass $M{\sim}10^{13}$--$10^{14}\,h^{-1}{\rm M_\odot}$ and more lumi…
We model the small-scale clustering of luminous red galaxies (LRGs; Masjedi et al. 2006) in the Sloan Digital Sky Survey (SDSS). Specifically, we use the halo occupation distribution (HOD) formalism to model the projected two-point correlation function of LRGs on scales well within the sizes of their host halos (0.016 Mpc/h < r < 0.42 Mpc/h). We start by varying P(N|M), the probability distribution that a dark matter halo of mass M contains N LRGs, and assuming that the radial distribution of satellite LRGs within halos traces the NFW dark matter density profile. We find that varying P(N|M) al…
We present a clustering comparison of 12 galaxy formation models (including Semi-Analytic Models (SAMs) and Halo Occupation Distribution (HOD) models) all run on halo catalogues and merger trees extracted from a single ΛCDM N-body simulation. We compare the results of the measurements of the mean halo occupation numbers, the radial distribution of galaxies in haloes and the 2-Point Correlation Functions (2PCF). We also study the implications of the different treatments of orphan (galaxies not assigned to any dark matter subhalo) and non-orphan galaxies in these measurements. Our main result is…
Realistic lightcone mocks are important in the clustering analyses of large galaxy surveys. For simulations where only the snapshots are available, it is common to create approximate lightcones by joining together the snapshots in spherical shells. We assess the two-point clustering measurements of central galaxies in approximate lightcones built from the Millennium-XXL simulation, which are constructed using different numbers of snapshots. The monopole and quadrupole of the real-space correlation function is strongly boosted on small scales below 1 Mpc/h, due to some galaxies being duplicated…
We examine recent high-precision measurements of small-scale quasar clustering (at $z\sim0.5-2$ on scales of $\sim25~\mathrm{kpc/h}$) from the SDSS in the context of the MassiveBlackII (MBII) cosmological hydrodynamic simulation and conditional luminosity function (CLF) modeling. At these high luminosities ($g < 20.85$ quasars), the MBII simulation volume ($100~\mathrm{cMpc}/h$ comoving boxsize) has only 3 quasar pairs at distances of $1-4$ Mpc. The black-hole masses for the pairs range between $M_{bh}\sim1-3\times 10^{9}~M_{\odot}/h$ and the quasar hosts are haloes of $M_h\sim1-3\times10^{14}…
Satellite galaxies in rich clusters are subject to numerous physical processes that can significantly influence their evolution. However, the typical L* satellite galaxy resides in much lower mass galaxy groups, where the processes capable of altering their evolution are generally weaker and have had less time to operate. To investigate the extent to which satellite and central galaxy evolution differs, we separately model the stellar mass - halo mass (M* -Mh) relation for these two populations over the redshift interval 0 < z < 1. This relation for central galaxies is constrained by the galax…
We develop a new method which measures the projected density distribution w_p(r_p)n of photometric galaxies surrounding a set of spectroscopically-identified galaxies, and simultaneously the projected correlation function w_p(r_p) between the two populations. In this method we are able to divide the photometric galaxies into subsamples in luminosity intervals when redshift information is unavailable, enabling us to measure w_p(r_p)n and w_p(r_p) as a function of not only the luminosity of the spectroscopic galaxy, but also that of the photometric galaxy. Extensive tests show that our method ca…
The number and distribution of dwarf satellite galaxies remain a critical test of cold dark matter-dominated structure formation on small scales. Until recently, observational information about galaxy formation on these scales has been limited mainly to the Local Group. We have searched for faint analogues of Local Group dwarfs around nearby bright galaxies, using a spatial clustering analysis of the photometric catalog of the Sloan Digital Sky Survey (SDSS) Data Release 8. Several other recent searches of SDSS have detected clustered satellite populations down to $Δm_r \equiv ({m}_{r,\, {\rm …
This is the second paper of a series that reports on our investigation of the clustering properties of AGNs in the ROSAT All-Sky Survey (RASS) through cross-correlation functions (CCFs) with Sloan Digital Sky Survey (SDSS) galaxies. In this paper, we apply the Halo Occupation Distribution (HOD) model to the CCFs between the RASS Broad-line AGNs with SDSS Luminous Red Galaxies (LRGs) in the redshift range 0.16<z<0.36 that was calculated in paper I. In our HOD modeling approach, we use the known HOD of LRGs and constrain the HOD of the AGNs by a model fit to the CCF. For the first time, we are a…
The Impact of Cosmic Variance and Satellites on JWST Clustering Measurements at Redshift around 6
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森天体物理中心）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）
We utilize $Λ$CDM halo occupation models of galaxy clustering to investigate the evolving stellar mass dependent clustering of galaxies in the PRIsm MUlti-object Survey (PRIMUS) and DEEP2 Redshift Survey over the past eight billion years of cosmic time, between $0.2<z<1.2$. These clustering measurements provide new constraints on the connections between dark matter halo properties and galaxy properties in the context of the evolving large-scale structure of the universe. Using both an analytic model and a set of mock galaxy catalogs, we find a strong correlation between central galaxy stellar …
We use data from the SDSS to investigate the evolution of the large-scale galaxy bias as a function of luminosity for red galaxies. We carefully consider correlation functions of galaxies selected from both photometric and spectroscopic data, and cross-correlations between them, to obtain multiple measurements of the large-scale bias. We find, for our most robust analyses, a strong increase in bias with luminosity for the most luminous galaxies, an intermediate regime where bias does not evolve strongly over a range of two magnitudes in galaxy luminosity, and no evidence for an upturn in bias …
We model the apparent clustering anisotropy of Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey using subhalos identified in cosmological $N$-body simulations. We first conduct a Markov-chain Monte Carlo analysis on the parameters characterizing subhalos hosting LRGs assuming a specific $Λ$CDM cosmology on which we run the simulations. We show that simple models with central and satellite subhalos can explain the observed multipole moments of the power spectrum up to hexadecapole on large scales ($k\lesssim0.3~h\mathrm{Mpc}^{-1}$). A satellite fraction of $20$ to $30$ per cent is f…
The effect of baryons on the positions and velocities of satellite galaxies in the MTNG simulation
Universidad de Sevilla（塞维利亚大学）；Donostia International Physics Center（多诺斯蒂亚国际物理中心）；IKERBASQUE, Basque Foundation for Science（伊卡巴斯基，巴斯克科学基金会）；Institute for Computational Cosmology, Department of Physics, Durham University（杜伦大学物理学院计算宇宙学研究所）；Kavli Institute for Cosmology Cambridge（剑桥卡弗里宇宙学研究所）；Institute of Astronomy（天文学研究所）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森尼天体物理中心）；Columbia Astrophysics Laboratory, Columbia University（哥伦比亚大学天体物理学实验室）；Max Planck Institute for Astrophysics（马克斯·普朗克天体物理学研究所）
We present a clustering analysis of near ultraviolet (NUV) - optical color selected luminosity bin samples of green valley galaxies. These galaxy samples are constructed by matching the Sloan Digital Sky Survey Data Release 7 with the latest Galaxy Evolution Explorer source catalog which provides NUV photometry. We present cross-correlation function measurements and determine the halo occupation distribution of these transitional galaxies using a new multiple tracer analysis technique. We extend the halo-occupation formalism to model the cross-correlation function between a galaxy sample of in…
In this work we investigate the link between galaxy velocity dispersion, mass and other properties (color, morphology) with the properties of dark matter halos by comparing the clustering of galaxies at both fixed mass and velocity dispersion. We use the Sloan Digital Sky Survey to define a volume limited sample of massive galaxies complete in both stellar mass (>6e10 Msun) and velocity dispersion (>75 km/s). Using this sample we show that at fixed velocity dispersion there is no dependence of the clustering amplitude on stellar or dynamical mass. Conversely when stellar or dynamical mass are …
We investigate the radial number density profile and the abundance distribution of faint satellites around central galaxies in the low redshift universe using the CFHT Legacy Survey. We consider three samples of central galaxies with magnitudes of M_r=-21, -22, and -23 selected from the Sloan Digital Sky Survey (SDSS) group catalog of Yang et al.. The satellite distribution around these central galaxies is obtained by cross-correlating these galaxies with the photometric catalogue of the CFHT Legacy Survey. The projected radial number density of the satellites obeys a power law form with the b…
The triggering mechanisms for Active Galactic Nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disk instabilities (DI). Using an advanced semi analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modeling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the center of halos …
We present new results on the relationship between central galaxies and dark matter haloes inferred from observations of satellite kinematics in the Sloan Digital Sky Survey (SDSS) DR7. We employ an updated analysis framework that includes detailed mock catalogues to model observational effects in SDSS. Our results constrain the colour-dependent conditional luminosity function (CLF) of dark matter haloes, as well as the radial profile of satellite galaxies. Confirming previous results, we find that red central galaxies live in more massive haloes than blue galaxies at fixed luminosity. Additio…
We construct halo occupation distribution (HOD) models of high redshift ($z \gtrsim 7.5$) galaxies with $M_{*}>10^8~M_{\odot}/h$ using the BlueTides hydrodynamic simulation suite, with a particular emphasis on modelling the small scale / 1-halo clustering ($0.01\lesssim r \lesssim 1~ h^{-1}\rm{Mpc}$). Similar to low redshift studies, we find that the central and satellite mean HODs ($\left<N_{\mathrm{cen}}\right>$ and $\left<N_{\mathrm{sat}}\right>$) can be modeled by a smoothed step function and a power law respectively. The number density of satellite galaxies is however significantly suppre…
We use the hydrodynamical galaxy formation simulations from the Illustris suite to study the origin and properties of galaxy velocity bias, i.e., the difference between the velocity distributions of galaxies and dark matter inside halos. We find that galaxy velocity bias is a decreasing function of the ratio of galaxy stellar mass to host halo mass. In general, central galaxies are not at rest with respect to dark matter halos or the core of halos, with a velocity dispersion above 0.04 times that of the dark matter. The central galaxy velocity bias is found to be mostly caused by the close int…
We introduce a new technique that uses galaxy clustering to constrain how satellite galaxies lose stellar mass and contribute to the diffuse "intrahalo light" (IHL). We implement two models that relate satellite galaxy stellar mass loss to the detailed knowledge of subhalo dark matter mass loss. Model 1 assumes that the fractional stellar mass loss of a galaxy is proportional to the fractional amount of dark matter mass loss of its subhalo. Model 2 accounts for a delay in the time that stellar mass is lost since the galaxy resides deep in the potential well of the subhalo which may experience …
We present an analysis of the clustering of galaxies as a function of their stellar mass at 1 < z < 2 using data from the NEWFIRM Medium Band Survey (NMBS). The precise photometric redshifts and stellar masses that the NMBS produces allows us to define a series of mass limited samples of galaxies more massive than 0.7, 1 and 3x10^10 Msun in redshift intervals centered on z = 1.1, 1.5 and 1.9 respectively. In each redshift interval we show that there exists a strong dependence of clustering strength on the stellar mass limit of the sample, with more massive galaxies showing a higher clustering …
We measure the angular clustering of 33 415 extremely red objects (EROs) in the Elais-N1 field covering 5.33 deg$^{2}$, which cover the redshift range $z=0.8$ to $2$. This sample was made by merging the UKIDSS Deep eXtragalactic Survey (DXS) with the optical Subaru and Pan-STARRS PS1 datasets. We confirm the existence of a clear break in the angular correlation function at $\sim 0.02^{\circ}$ corresponding to $1 h^{-1}$ Mpc at $z\sim1$. We find that redder or brighter EROs are more clustered than bluer or fainter ones. Halo Occupation Distribution (HOD) model fits imply that the average mass o…
We perform an analysis of the spatial clustering properties of HI selected galaxies from the HI Parkes All Sky Survey (HIPASS) using the formalism of the halo occupation distribution (HOD). The resulting parameter constraints show that the fraction of satellite galaxies (i.e. galaxies which are not the central member of their host dark matter halo) among HIPASS galaxies is <20%, and that satellite galaxies are therefore less common in HIPASS than in optically selected galaxy redshift surveys. Moreover the lack of fingers-of-god in the redshift space correlation function of HIPASS galaxies may …
We simultaneously constrain cosmology and galaxy bias using measurements of galaxy abundances, galaxy clustering and galaxy-galaxy lensing taken from the Sloan Digital Sky Survey. We use the conditional luminosity function (which describes the halo occupation statistics as function of galaxy luminosity) combined with the halo model (which describes the non-linear matter field in terms of its halo building blocks) to describe the galaxy-dark matter connection. We explicitly account for residual redshift space distortions in the projected galaxy-galaxy correlation functions, and marginalize over…
Recent studies emphasize that an empirical relation between the stellar mass of galaxies and the mass of their host dark matter subhaloes can predict the clustering of galaxies and its evolution with cosmic time. In this paper we study the assumptions made by this methodology using a semi-analytical model (SAM). To this end, we randomly swap between the locations of model galaxies within a narrow range of subhalo mass (M_infall). We find that shuffled samples of galaxies have different auto-correlation functions in comparison with the original model galaxies. This difference is significant eve…
We present new constraints on the relationship between galaxies and their host dark matter halos, measured from the location of the peak of the stellar-to-halo mass ratio (SHMR), up to the most massive galaxy clusters at redshift $z\sim0.8$ and over a volume of nearly 0.1~Gpc$^3$. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by $\sim60\,000$ secure spectroscopic redshifts, analysing galaxy clustering, galaxy-galaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distri…
Understanding the impact of halo properties beyond halo mass on the clustering of galaxies (namely galaxy assembly bias) remains a challenge for contemporary models of galaxy clustering. We explore the use of machine learning to predict the halo occupations and recover galaxy clustering and assembly bias in a semi-analytic galaxy formation model. For stellar-mass selected samples, we train a Random Forest algorithm on the number of central and satellite galaxies in each dark matter halo. With the predicted occupations, we create mock galaxy catalogues and measure the clustering and assembly bi…
We present a Halo Occupation Distribution (HOD) analysis of the luminosity- and colour-dependent galaxy clustering in the Sloan Digital Sky Survey. A novelty of our technique is that it uses a combination of clustering measurements in luminosity bins to perform a global likelihood analysis, simultaneously constraining the HOD parameters for a range of luminosity thresholds. We present simple, smooth fitting functions which accurately describe the resulting luminosity dependence of the best-fit HOD parameters. To minimise systematic halo modelling effects, we use theoretical halo 2-point correl…
We use the Halo Model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models -- one in which this luminosity function $p(L)$ is universal -- naturally produces a number of features associated with previous analyses based on the `central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the Lognormal distribution around this mean, and the tight relation between the central and satellite ma…
We present the clustering properties of low-$z$ $(z\leq1.4)$ galaxies selected by the Hyper Suprime-Cam Subaru Strategic Program Wide layer over $145$ deg$^{2}$. The wide-field and multi-wavelength observation yields $5,064,770$ galaxies at $0.3\leq z\leq1.4$ with photometric redshifts and physical properties. This enables the accurate measurement of angular correlation functions and subsequent halo occupation distribution (HOD) analysis allows the connection between baryonic properties and dark halo properties. The fraction of less-massive satellite galaxies at $z\lesssim1$ is found to be alm…
We study the dependence of angular two-point correlation functions on stellar mass ($M_{*}$) and specific star formation rate (sSFR) of $M_{*}>10^{10}M_{\odot}$ galaxies at $z\sim1$. The data from UKIDSS DXS and CFHTLS covering 8.2 deg$^{2}$ sample scales larger than 100 $h^{-1}$Mpc at $z\sim1$, allowing us to investigate the correlation between clustering, $M_{*}$, and star formation through halo modeling. Based on halo occupation distributions (HODs) of $M_{*}$ threshold samples, we derive HODs for $M_{*}$ binned galaxies, and then calculate the $M_{*}/M_{\rm halo}$ ratio. The ratio for cent…
We present a fully analytical halo model of colour-dependent clustering that incorporates the effects of galactic conformity in a halo occupation distribution (HOD) framework. The model, based on our previous numerical work, describes conformity through a correlation between the colour of a galaxy and the concentration of its parent halo, leading to a correlation between central and satellite galaxy colours at fixed halo mass. The strength of the correlation is set by a tunable `group quenching efficiency', and the model can separately describe group-level correlations between galaxy colour (1…
We present the measurements and modelling of the small-to-intermediate scale (0.1--25 Mpc/h) projected and three-dimensional (3D) redshift-space two-point correlation functions (2PCFs) of local galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7. We find a clear dependence of galaxy clustering on luminosity in both projected and redshift spaces, generally being stronger for more luminous samples. The measurements are successfully interpreted within the halo occupation distribution (HOD) framework with central and satellite velocity bias parameters to describe galaxy kinematics insid…
The kinematics of satellite galaxies moving in a dark matter halo are a direct probe of the underlying gravitational potential. Thus, the phase-space distributions of satellites represent a powerful tool to determine the galaxy-halo connection from observations. By stacking the signal of a large number of satellite galaxies this potential can be unlocked even for haloes hosting a few satellites on average. In this work, we test the impact of various modelling assumptions on constraints derived from analysing satellite phase-space distributions in the non-linear, 1-halo regime. We discuss their…
In hierarchical structure formation, dark matter halos that merge with larger halos can persist as subhalos. These subhalos are likely hosts of visible galaxies. While the dense halo environment rapidly strips subhalos of their dark mass, the compact luminous material can remain intact for some time, making the correspondence of galaxies with severely stripped subhalos unclear. Many galaxy evolution models assume that satellite galaxies eventually merge with their central galaxy, but this ignores the possibility of satellite tidal disruption. We use a high-resolution $N$-body simulation of cos…
The reflex motion and distortion of the Milky Way (MW) halo caused by the infall of a massive Large Magellanic Cloud (LMC) has been demonstrated to result in an excess of orbital poles of dark matter halo particles towards the LMC orbital pole. This was suggested to help explain the observed preference of MW satellite galaxies to co-orbit along the Vast Polar Structure (VPOS). We test this idea by correcting the positions and velocities of the MW satellites for the Galactocentric-distance-dependent shifts inferred from a LMC-infall simulation. While this should substantially reduce the observe…
We investigate the clustering of Lyman-break galaxies (LBGs) at $z\sim4$. Using the hierarchical galaxy formation model GALFORM, we predict, for the first time using a semi-analytical model with feedback from active galactic nuclei (AGN), the angular correlation function (ACF) of LBGs and find agreement within $3\,σ$ with new measurements of the ACF from surveys including the Hubble eXtreme Deep Field (XDF) and CANDELS field. Our simulations confirm the conclusion reached using independent models that although the predicted ACFs reproduce the trend of increased clustering with luminosity, the …
We investigate the spatial distribution of the satellites of bright, isolated host galaxies. In agreement with previous studies, we find that, on average, the satellites of red hosts are found preferentially close to their hosts' major axes, while the satellites of blue hosts are distributed isotropically. We compute the pairwise clustering of the satellites and find a strong tendency for pairs of satellites to be located on the same side of their host, resulting in lopsided distributions. The signal is most pronounced for the satellites of blue hosts, where the number of pairs on the same sid…
