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 galaxy stellar mass function while the relation for satellite galaxies is constrained against recent measurements of the galaxy two-point correlation function (2PCF). At z ~ 0 the satellites, on average, have ~10% larger stellar masses at fixed peak subhalo mass compared to central galaxies of the same halo mass. This is required in order to reproduce the observed stellar mass-dependent 2PCF and satellite fractions. At low masses our model slightly under-predicts the correlation function at ~1 Mpc scales. At z ~ 1 the satellite and central galaxy M*-Mh relations are consistent within the errors, and the model provides an excellent fit to the clustering data. At present, the errors on the clustering data at z ~ 2 are too large to constrain the satellite model. A simple model in which satellite and central galaxies share the same M*-Mh relation is able to reproduce the extant z ~ 2 clustering data. We speculate that the striking similarity between the satellite and central galaxy M*-Mh relations since z ~ 2 arises because the central galaxy relation evolves very weakly with time and because the stellar mass of the typical satellite galaxy has not changed significantly since it was accreted. [Abridged]
The orbital properties of infalling satellite halos set the initial conditions which control the subsequent evolution of subhalos and the galaxies that they host, with implications for mass stripping, star formation quenching, and merging. Using a high-resolution, cosmological N-body simulation, I examine the orbital parameters of satellite halos as they merge with larger host halos, focusing primarily on orbital circularity and pericenter. I explore in detail how these orbital parameters depend on mass and redshift. Satellite orbits become more radial and plunge deeper into their host halo at…
The spatial distribution of the satellite populations of the Milky Way and Andromeda are puzzling in that they are nearly perpendicular to the disks of their central galaxies. To understand the origin of such configurations we study the alignment of the central galaxy, satellite system and dark matter halo in the largest of the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) simulation. We find that centrals and their satellite systems tend to be well aligned with their haloes, with a median misalignment angle of $33^{\circ}$ in both cases. While the centrals are better ali…
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…
The inference of the Milky Way halo mass requires modelling the phase space structure of dynamical tracers, with different tracers following different models and having different levels of sensitivity to the halo mass. For steady-state models, phase correlations among tracer particles lead to an irreducible stochastic bias. This bias is small for satellite galaxies and dark matter particles, but as large as a factor of 2 for halo stars. This is consistent with the picture that satellite galaxies closely trace the underlying phase space distribution of dark matter particles, while halo stars ar…
We present a semi-analytic model of satellite galaxies, SatGen, which can generate large samples of satellite populations for a host halo of desired mass, redshift, and assembly history. The model combines dark-matter halo merger trees, empirical relations for the galaxy-halo connection, and analytic prescriptions for tidal effects, dynamical friction, and ram pressure stripping. SatGen emulates cosmological zoom-in hydro-simulations in certain aspects. Satellites can reside in cored or cuspy DM subhaloes, depending on the halo response to baryonic physics that can be formulated from hydro-sim…
In the Local Group (LG), almost all satellite dwarf galaxies that are within the virial radius of the Milky Way (MW) and Andromeda (M31) exhibit strong environmental influence. The orbital histories of these satellites provide the key to understanding the role of the MW/M31 halo, lower-mass groups, and cosmic reionization on the evolution of dwarf galaxies. We examine the virial-infall histories of satellites with M_star = 10^{3-9} M_sun using the ELVIS suite of cosmological zoom-in dissipationless simulations of 48 MW/M31-like halos. Satellites at z = 0 fell into the MW/M31 halos typically 5 …
The Milky Way, the Andromeda galaxy, and Centaurus A host flattened distributions of satellite galaxies which exhibits coherent velocity trends indicative of rotation. Comparably extreme satellite structures are very rare in cosmological LCDM simulations, giving rise to the `satellite plane problem'. As a possible explanation it has been suggested that earlier-forming, higher concentration host halos contain more flattened and kinematically coherent satellite planes. We have tested for such a proposed correlation between the satellite plane and host halo properties in the ELVIS suite of simula…
The concordance $Λ$CDM cosmology predicts tens of satellite galaxies distributed in the inner region ($<40\ \lkpc$) of the Milky Way (MW), yet at most $12$ were discovered at present day, including 3 discovered very recently by Dark Energy Survey (DES) and 5 from other surveys (e.g. PanSTARRS, MagLiteS). We use $5$ ultra-high resolution simulations of MW sized dark matter haloes from the $\aqua$ project, combined with $\galf$ semi-analytical galaxy formation model, to investigate properties of the model satellite galaxy population inside $40\ \lkpc$ of MW sized haloes. On average, in each halo…
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…
The dwarf satellite galaxies of the Milky Way Crater II and Antlia II have uncommonly low dynamical mass densities, due to their large size and low velocity dispersion. Previous work have failed to identify formation scenarios within the $Λ$CDM framework and have invoked cored dark matter haloes, processed by tides. I show that the tidal evolution of $Λ$CDM NFW haloes is richer than previously recognised: tidal heating causes the innermost regions of haloes that fall short of the mass-concentration relation to expand significantly, resulting in the formation of giant, kinematically cold satell…
We investigate the quenching properties of central and satellite galaxies, utilizing the halo masses and central-satellite identifications from the SDSS galaxy group catalog of Yang et al. We find that the quenched fractions of centrals and satellites of similar stellar masses have similar dependence on host halo mass. The similarity of the two populations is also found in terms of specific star formation rate and 4000 Å break. The quenched fractions of centrals and satellites of similar masses show similar dependencies on bulge-to-total light ratio, central velocity dispersion and halo-centri…
We show that the mass of a dark matter halo can be inferred from the dynamical status of its satellite galaxies. Using 9 dark-matter simulations of halos like the Milky Way (MW), we find that the present-day substructures in each halo follow a characteristic distribution in the phase space of orbital binding energy and angular momentum, and that this distribution is similar from halo to halo but has an intrinsic dependence on the halo formation history. We construct this distribution directly from the simulations for a specific halo and extend the result to halos of similar formation history b…
Within the Cold Dark Matter scenario the hierarchical merging paradigm is the natural result to form massive galactic halos by the minor mergers of sub-halos and, by this, inherently their stellar halo. Although this must be also invoked for the Milky Way, the context of chemical and kinematic coherence of halo stars and dwarf spheroidal galaxies is yet unsolved a focus of present-day research. To examine this issue we model the chemo-dynamical evolution of the system of satellites selected from the cosmological Via Lactea II simulations to be similar for the Milky Way environment but at an ea…
We investigate the growth histories of dark matter halos associated with dwarf satellites in Local Group galaxies and the resultant evolution of the baryonic component. Our model is based on the recently proposed property that the mean surface density of a dark halo inside a radius at maximum circular velocity V_max is universal over a large range of V_max. Following that this surface density of 20 Msun/pc^2 well explains dwarf satellites in the Milky Way and Andromeda, we find that the evolution of the dark halo in this common surface-density scale is characterized by the rapid increase of th…
(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…
Motivated by previous findings that the magnitude gap between certain satellite galaxy and the central galaxy can be used to improve the estimation of halo mass, we carry out a systematic study of the information content of different member galaxies in the modelling of the host halo mass using a machine learning approach. We employ data from the hydrodynamical simulation IllustrisTNG and train a Random Forest (RF) algorithm to predict a halo mass from the stellar masses of its member galaxies. Exhaustive feature selection is adopted to disentangle the importances of different galaxy members. W…
Spatial segregation as the origin of anisotropic satellite quenching in haloes and beyond
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；College of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Universidad Autónoma de Madrid（马德里自治大学）；Centro de Investigación Avanzada en Física Fundamental (CIAFF), Universidad Autónoma de Madrid（马德里自治大学基础物理前沿研究中心）；Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理研究所）；Department of Physics and Astronomy, University of the Western Cape（西开普大学物理与天文学系）
Motivated by a recently found interesting property of the dark halo surface density within a radius, $r_{\rm max}$, giving the maximum circular velocity, $V_{\rm max}$, we investigate it for dark halos of the Milky Way's and Andromeda's dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos associated with Milky Way-sized dark halos and find that the values of their surface densities, $Σ_{V_{\rm max}}$, are in good agreement with those for the observed dwarf spheroidal satellites even without employing any fitting procedures. This implies that this sur…
We construct simple triaxial generalisations of Navarro-Frenk-White haloes. The models have elementary gravitational potentials, together with a density that is cusped like 1/r at small radii and falls off like 1/r^3 at large radii. The ellipticity varies with radius in a manner that can be tailored to the user's specification. The closed periodic orbits in the planes perpendicular to the short and long axes of the model are well-described by epicyclic theory, and can be used as building blocks for long-lived discs. As an application, we carry out the simulations of thin discs of satellites in…
We study the incidence of group and filamentary dwarf galaxy accretion into Milky Way (MW) mass haloes using two types of hydrodynamical simulations: EAGLE, which resolves a large cosmological volume, and the AURIGA suite, which are very high resolution zoom-in simulations of individual MW-sized haloes. The present-day 11 most massive satellites are predominantly (75%) accreted in single events, 14% in pairs and 6% in triplets, with higher group multiplicities being unlikely. Group accretion becomes more common for fainter satellites, with 60% of the top 50 satellites accreted singly, 12% in p…
Anisotropy of Satellite Galaxies-I: Contrasting Correlations with Central Galaxy, Host Halo, and Large-Scale Filament Structures
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；College of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Universidad Autónoma de Madrid（马德里自治大学）；Centro de Investigación Avanzada en Física Fundamental (CIAFF), Universidad Autónoma de Madrid（马德里自治大学基础物理前沿研究中心）；Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理研究所）；Department of Physics and Astronomy, University of the Western Cape（西开普大学物理与天文学系）；Observatoire Astronomique de Strasbourg, UMR 7550, CNRS, Université de Strasbourg（斯特拉斯堡天文台）
The population of Milky Way (MW) satellites contains the faintest known galaxies and thus provides essential insight into galaxy formation and dark matter microphysics. Here we combine a model of the galaxy--halo connection with newly derived observational selection functions based on searches for satellites in photometric surveys over nearly the entire high Galactic latitude sky. In particular, we use cosmological zoom-in simulations of MW-like halos that include realistic Large Magellanic Cloud (LMC) analogs to fit the position-dependent MW satellite luminosity function. We report decisive e…
We demonstrate how the total luminosity in satellite galaxies is a powerful probe of dark matter halos around central galaxies. The method cross-correlates central galaxies in spectroscopic galaxy samples with fainter galaxies detected in photometric surveys. After background subtraction, the excess galaxies around the central galaxies represent faint satellite galaxies within the dark matter halo. Using abundance matching models, we show that the the total galaxy luminosity, L_sat, scales linearly with host halo mass, making L_sat an excellent proxy for M_h. L_sat is also sensitive to the for…
It has been suggested that the central stellar velocity dispersion of galaxies can trace dark matter halo mass directly. We test this hypothesis using a complete spectroscopic sample of isolated galaxies surrounded by faint satellite galaxies from the Sloan Digital Sky Survey Data Release 12. We apply a friends-of-friends algorithm with projected linking length $ΔD < 100$ kpc and radial velocity linking length $ΔV < 1000$ km s$^{-1}$ to construct our sample. Our sample includes 2807 isolated galaxies with 3417 satellite galaxies at $0.01 < z < 0.14$. We divide the sample into two groups based …
We present distributions of orbital parameters of infalling satellites of $Λ$CDM haloes in the mass range $10^{12}-10^{14}$M$_\odot$, which represent the initial conditions for the subsequent evolution of substructures within the host halo. We use merger trees constructed in a high resolution cosmological N-body simulation to trace satellite haloes, and identify the time of infall. We find signficant trends in the distribution of orbital parameters with both the host halo mass and the ratio of satellite-to-host halo masses. For all host halo masses, satellites whose infall mass is a larger fra…
Halo models and halo occupation distributions (HODs) are important tools to model the galaxy and matter distribution. We present and assess a new method for constraining the parameters of HODs using the gravitational lensing shear around galaxy pairs, galaxy-galaxy-galaxy-lensing (G3L). In contrast to galaxy-galaxy-lensing, G3L is sensitive to correlations between the per-halo numbers of galaxies from different populations. We use G3L to probe these correlations and test the default hypothesis that they are negligible. We derive a halo model for G3L and validate it with realistic mock data fro…
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…
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…
We present an observational study of the stellar mass function of satellite galaxies around central galaxies at 0.2<z<1.2. Using statistical background subtraction of contaminating sources we derive satellite stellar mass distributions in four bins of central galaxy mass in three redshift ranges. Our results show that the stellar mass function of satellite galaxies increases with central galaxy mass, and that the distribution of satellite masses at fixed central mass is at most weakly dependent on redshift. We conclude that the average mass distribution of galaxies in groups is remarkably univ…
Ultrafaint dwarf galaxies ($M_\star\lesssim10^{5-6}\,{\rm M}_\odot$) are relics of an early phase of galaxy formation. They contain some of the oldest and most metal-poor stars in the Universe which likely formed before the epoch of hydrogen reionisation. These galaxies are so faint that they can only be detected as satellites of the Milky Way. They are so small that they are just barely resolved in current cosmological hydrodynamics simulations. Here we combine very high resolution cosmological $N$-body simulations with a semi-analytic model of galaxy formation to study the demographics and s…
We investigate the formation of the satellite galaxy population of a Milky Way-mass halo in a very highly resolved magneto-hydrodynamic cosmological zoom-in simulation (baryonic mass resolution $m_b =$ 800 $\rm M_{\odot}$). We show that the properties of the central star-forming galaxy, such as the radial stellar surface density profile and star formation history, are: i) robust to stochastic variations associated with the so-called ``Butterfly Effect''; and ii) well converged over 3.5 orders of magnitude in mass resolution. We find that there are approximately five times as many satellite gal…
We investigate the radial distribution of galaxies within their host dark matter halos by modeling their small-scale clustering, as measured in the Sloan Digital Sky Survey. Specifically, we model the Jiang et al. (2011) measurements of the galaxy two-point correlation function down to very small projected separations (10 < r < 400 kpc/h), in a wide range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -23). We use a halo occupation distribution (HOD) framework with free parameters that specify both the number and spatial distribution of galaxies within their host dark…
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…
Using galaxy group/cluster catalogs created from the Sloan Digital Sky Survey Data Release 7, we examine in detail the specific star formation rate (SSFR) distribution of satellite galaxies and its dependence on stellar mass, host halo mass, and halo-centric radius. All galaxies, regardless of central-satellite designation, exhibit a similar bimodal SSFR distribution, with a strong break at SSFR ~ 10^-11 yr^-1 and the same high SSFR peak; in no regime is there ever an excess of galaxies in the `green valley'. Satellite galaxies are simply more likely to lie on the quenched (`red sequence') sid…
In this work, we examine the different properties of galactic satellites in hydrodynamical and pure dark matter simulations. We use three pairs of simulations (collisional and collision-less) starting from identical initial conditions. We concentrate our analysis on pairs of satellites in the hydro and Nbody runs that form from the same Lagrangian region. We look at the radial positions, mass loss as a function of time and orbital parameters of these "twin" satellites. We confirm an overall higher radial density of satellites in the hydrodynamical runs, but find that trends in the mass loss an…
Galaxies that are several virial radii beyond groups/clusters show preferentially quiescent star formation rates. Using a galaxy group/cluster catalog from the Sloan Digital Sky Survey, together with a cosmological N-body simulation, we examine the origin of this environmental quenching beyond the virial radius. Accounting for the clustering of groups/clusters, we show that central galaxies show enhanced SFR quenching out to 2.5 virial radii beyond groups/clusters, and we demonstrate that this extended environmental enhancement can be explained simply by 'ejected' satellite galaxies that orbit…
We study the formation of planes of dwarf galaxies around Milky Way (MW)-mass haloes in the EAGLE galaxy formation simulation. We focus on satellite systems similar to the one in the MW: spatially thin or with a large fraction of members orbiting in the same plane. To characterise the latter, we introduce a robust method to identify the subsets of satellites that have the most co-planar orbits. Out of the 11 MW classical dwarf satellites, 8 have highly clustered orbital planes whose poles are contained within a $22^\circ$ opening angle centred around $(l,b)=(182^\circ,-2^\circ)$. This configur…
Rapid advance has been made recently in accurate distance measurements for nearby ($D < 11$ Mpc) galaxies based on the magnitude of the tip of red giant branch stars resolved with the Hubble Space Telescope. We use observational properties of galaxies presented in the last version of Updated Nearby Galaxy Catalog to derive a halo mass of luminous galaxies via orbital motion of their companions. Our sample contains 298 assumed satellites with known radial velocities around 25 Milky Way-like massive galaxies and 65 assumed satellites around 47 fainter dominant galaxies. The average total mass-to…
We present a Bayesian hierarchical inference formalism (Basilisk) to constrain the galaxy-halo connection using satellite kinematics. Unlike traditional methods, Basilisk does not resort to stacking the kinematics of satellite galaxies in bins of central luminosity, and does not make use of summary statistics, such as satellite velocity dispersion. Rather, Basilisk leaves the data in its raw form and computes the corresponding likelihood. In addition, Basilisk can be applied to flux-limited, rather than volume-limited samples, greatly enhancing the quantity and dynamic range of the data. And f…
We examine the effects of environment on the dynamical structure of satellite systems based on the Millennium--II Simulation. Satellite halos are defined as sub--halos within the virial radius of a host halo. The satellite sample is restricted to those sub--halos which showed a maximum circular velocity above 30 km/s at the time of accretion. Host halo masses range from 10^11 to 10^14 Msol/h. We compute the satellites' average accretion redshift, z_acc, velocity dispersion, sigma, and velocity anisotropy parameter, beta, utilising stacked satellite samples of equal mass hosts at similar backgr…
We infer the local stellar-to-halo/subhalo mass relations (MRs) for central and satellite galaxies separately. We constraint this relations by using several combinations of observational data, consisting of the total galaxy stellar mass function, its decomposition into centrals and satellites, and the projected two-point correlation functions measured in different stellar mass bins. The differences among the resulting MRs are within the model-fit uncertainties (which are very small, smaller than the intrinsic scatter between galaxy and halo mass), no matter what combination of data are used. W…
High resolution N-body simulations of galactic cold dark matter haloes indicate that we should expect to find a few satellite galaxies around the Milky Way whose haloes have a maximum circular velocity in excess of 40 kms. Yet, with the exception of the Magellanic Clouds and the Sagittarius dwarf, which likely reside in subhaloes with significantly larger velocities than this, the bright satellites of the Milky Way all appear to reside in subhaloes with maximum circular velocities below 40 kms. As recently highlighted by Boylan-Kolchin et al., this discrepancy implies that the majority of the …
Surprisingly little is known about the origin and evolution of the Milky Way's satellite galaxy companions. UV photoionisation, supernova feedback and interactions with the larger host halo are all thought to play a role in shaping the population of satellites that we observe today, but there is still no consensus as to which of these effects, if any, dominates. In this paper, we revisit the issue by re-simulating a Milky Way class dark matter (DM) halo with unprecedented resolution. Our set of cosmological hydrodynamic Adaptive Mesh Refinement (AMR) simulations, called the Nut suite, allows u…
Strong gravitational lensing by groups or clusters of galaxies provides a powerful technique to measure the dark matter properties of individual lens galaxies. We study in detail the mass distribution of the satellite lens galaxy in the group-scale lens SL2S J08544-0121 by modelling simultaneously the spatially extended surface brightness distribution of the source galaxy and the lens mass distribution using Markov chain Monte Carlo methods. In particular, we measure the dark matter halo size of the satellite lens galaxy to be 6.0^{+2.9}_{-2.0} kpc with a fiducial velocity dispersion of 127^{+…
We demonstrate the possibility of detecting tidal stripping of dark matter subhalos within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups, using various models with different distributions of mass between galaxy and group halos to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, …
We present results from N-body simulations of self-interacting dark matter (SIDM) subhalos, which could host ultra-faint dwarf spheroidal galaxies, inside a Milky-Way-like main halo. We find that high-concentration subhalos are driven to gravothermal core collapse, while low-concentration subhalos develop large (kpc-sized) low-density cores, with both effects depending sensitively on the satellite's orbit and the self-interaction cross section over mass $σ/m$. The overall effect for $σ/m \gtrsim 3 \ \rm cm^2/g$ is to increase the range of inner densities, potentially explaining the observed di…
We provide a set of numerical N-body simulations for studying the formation of the outer Milky Ways's stellar halo through accretion events. After simulating minor mergers of prograde and retrograde orbiting satellite halo with a Dark Matter main halo, we analyze the signal left by satellite stars in the rotation velocity distribution. The aim is to explore the orbital conditions where a retrograde signal in the outer part of the halo can be obtained, in order to give a possible explanation of the observed rotational properties of the Milky Way stellar halo. Our results show that, for satellit…
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 …
Observations have shown that the spatial distribution of satellite galaxies is not random, but aligned with the major axes of central galaxies. This alignment is dependent on galaxy properties, such that red satellites are more strongly aligned than blue satellites. Theoretical work done to interpret this phenomena has found that it is due to the non-spherical nature of dark matter halos. However, most studies over-predict the alignment signal under the assumption that the central galaxy shape follows the shape of the host halo. It is also not clear whether the color dependence of alignment is…
We study the kinematics of satellites around isolated galaxies selected from the Sloan Digital Sky Survey (SDSS) spectroscopic catalog. Using a model of the phase-space density previously measured for the halos of LCDM dark matter cosmological simulations, we determine the properties of the halo mass distribution and the orbital anisotropy of the satellites as a function of the colour-based morphological type and the stellar mass of the central host galaxy. We place constraints on the halo mass and the concentration parameter of dark matter and the satellite number density profiles. We obtain …
We select satellite galaxies from the galaxy group catalog constructed with the SDSS spectroscopic galaxies and measure the tangential shear around these galaxies with source catalog extracted from CFHT/MegaCam Stripe-82 Survey to constrain the mass of subhalos associated with them. The lensing signal is measured around satellites in groups with masses in the range [10^{13}, 5x10^{14}]h^{-1}M_{sun}, and is found to agree well with theoretical expectation. Fitting the data with a truncated NFW profile, we obtain an average subhalo mass of log M_{sub}= 11.68 \pm 0.67 for satellites whose project…
We combine the high-resolution Aquarius simulations with three-dimensional models of reionization based on the initial density field of the Aquarius parent simulation, Millennium-II, to study the impact of patchy reionization on the faint satellite population of Milky Way halos. Because the Aquarius suite consists of zoom-in simulations of halos in the Millennium-II volume, we follow the formation of substructure and the growth of reionization bubbles due to the larger environment simultaneously, and thereby determine the reionization redshifts of satellite candidates. We do this for four diff…
We calculate the orbital angular momentum of dark matter subhaloes in the Aquarius simulations of cold dark matter galactic haloes. We calculate the orientation of their angular momentum relative to that of the spin vector of their host halo and find a variety of different configurations. All six Aquarius haloes contain statistically significant populations of subhalo orbits that are aligned with the main halo spin. All haloes posses a population of subhaloes that rotates in the same direction as the main halo and three of them possess, in addition, a population that rotates in the opposite di…
We use the kinematics of satellite galaxies that orbit around the central galaxy in a dark matter halo to infer the scaling relations between halo mass and central galaxy properties. Using galaxies from the Sloan Digital Sky Survey, we investigate the halo mass-luminosity relation (MLR) and the halo mass-stellar mass relation (MSR) of central galaxies. In particular, we focus on the dependence of these scaling relations on the colour of the central galaxy. We find that red central galaxies on average occupy more massive haloes than blue central galaxies of the same luminosity. However, at fixe…
