We investigate the properties of satellite galaxies in cosmological N-body/SPH simulations of galaxy formation in Milky Way-sized haloes. Because of their shallow potential wells, satellite galaxies are very sensitive to heating processes which affect their gas content. Their properties can therefore be used to constrain the nature of feedback processes that regulate galaxy formation. In our simulations, we assume that all the energy produced by supernovae is used as kinetic energy to drive galactic winds. Several of our simulations produce bright, disc-dominated galaxies. We find that wind models in which the wind speed, v_w, is proportional to local velocity dispersion of dark matter, sigma, (and thus the wind mass-loading, eta_w \propto sigma^{-2}) have episodic star formation histories, reproduce the observed satellite luminosity function reasonably well (down to M_v=-7) and match the luminosity-metallicity relation observed in the Local Group satellites. By contrast, models that assume a constant wind speed overproduce faint satellites and predict an incorrect luminosity-metallicity relation. Our simulations therefore suggest that the feedback processes that operate on the scale of satellite galaxies should generate galactic outflows whose intensity varies inversely with the depth of the potential.
The hierarchical galaxy formation scenario in the Cold Dark Matter cosmogony with a non-vanishing cosmological constant and geometrically flat space has been very successful in explaining the large-scale distribution of galaxies. However, there have been claims that the scenario predicts too many satellite galaxies associated with massive galaxies compared to observations, called the missing satellite galaxy problem. Isolated groups of galaxies hosted by passively evolving massive early-type galaxies are ideal laboratories for finding the missing physics in the current theory. Here we report f…
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…
We investigate whether the satellite luminosity function (LF) of primary galaxies identified in the Sloan Digital Sky Survey (SDSS) depends on whether the host galaxy is in a filament or not. Isolated primary galaxies are identified in the SDSS spectroscopic sample while potential satellites (that are up to 4 magnitudes fainter than their hosts) are searched for in the much deeper photometric sample. Filaments are constructed from the galaxy distribution by the "Bisous" process. Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments. We examine…
Satellites are not randomly distributed around their central galaxies but show polar and planar structures. In this paper, we investigate the axis-asymmetry or lopsidedness of satellite galaxy distributions around isolated galaxies in a hydrodynamic cosmological simulation. We find a statistically significant lopsided signal by studying the angular distribution of the satellite galaxies' projected positions around isolated central galaxies in a two-dimensional plane. The signal is dependent on galaxy mass, color and large-scale environment. Satellites that inhabit low-mass blue hosts, or locat…
It has been shown, both in simulations and observationally, that the tidal field of a large galaxy can torque its satellites such that the major axis of satellite galaxies points towards their hosts. This so-called `shape alignment' has been observed in isolated Milky Way-like galaxies but not in `Local Group'-like pairs. In this study, we investigate the shape alignment of satellite galaxies in galaxy pairs similar to the Local Group identified in the Sloan Digital Sky Survey Data Release 13 (SDSS DR13). By stacking tens of thousands of satellite galaxies around primary galaxy pairs, we find …
We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS and SDSS around isolated central galaxies (ICGs) and paired galaxies from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to $M_V\sim-10$, and for central primary galaxies as small as $8.5<\log_{10}M_\ast/M_\odot<9.2$ and $9.2<\log_{10}M_\ast/M_\odot<9.9$, implying there are on average 3--8 satellites with $M_V<-10$ around LMC-mass ICGs. The bright end cutoff …
Collisionless simulations of the CDM cosmology predict a plethora of dark matter substructures in the halos of Milky Way sized galaxies, yet the number of known luminous satellites galaxies is very much smaller, a discrepancy that has become known as the `missing satellite problem'. The most massive substructures have been shown to be plausibly the hosts of the brightest satellites, but it remains unclear which processes prevent star formation in the many other, purely dark substructures. We use high-resolution hydrodynamic simulations of the formation of Milky Way sized galaxies in order to t…
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 study the projected radial distribution of satellite galaxies around more than 28,000 Luminous Red Galaxies (LRGs) at 0.28<z<0.40 and trace the gravitational potential of LRG groups in the range 15<r/kpc<700. We show that at large radii the satellite number density profile is well fitted by a projected NFW profile with r_s~270 kpc and that at small radii this model underestimates the number of satellite galaxies. Utilizing the previously measured stellar light distribution of LRGs from deep imaging stacks we demonstrate that this small scale excess is consistent with a non-negligible baryon…
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 satellite galaxies of the Milky Way (MW) define a vast polar structure (VPOS), a thin plane perpendicular to the MW disc. Proper motion (PM) measurements are now available for all of the 11 brightest, `classical' satellites and allow an updated analysis of the alignment of their orbital poles with this spatial structure. The coherent orbital alignment of 7 to 9 out of 11 satellites demonstrates that the VPOS is a rotationally stabilized structure and not only a pressure-supported, flattened ellipsoid. This allows us to empirically and model independently predict the PMs of almost all satel…
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…
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 study the spatial distribution of satellite galaxies around isolated primaries using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy catalogues. We select isolated primaries from the spectroscopic sample and search for potential satellites in the much deeper photometric sample. For specific luminosity primaries we obtain robust statistical results by stacking as many as ~50, 000 galaxy systems. We find no evidence for any anistropy in the satellite galaxy distribution relative to the major axes of the primaries. We derive accurate projected number density profiles o…
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…
Satellite galaxies of the Milky Way and of the Andromeda galaxy have been found to preferentially align in significantly flattened planes of satellite galaxies, and available velocity measurements are indicative of a preference of satellites in those structures to co-orbit. There is increasing evidence that such kinematically correlated satellite planes are also present around more distant hosts. Detailed comparisons show that similarly anisotropic phase-space distributions of sub-halos are exceedingly rare in cosmological simulations based on the $Λ$CDM paradigm. Analogs to the observed syste…
In the context of the current $Λ$CDM cosmological model small dark matter haloes are abundant and satellites of dwarf galaxies are expected to be predominantly dark. Since low mass galaxies have smaller baryon fractions interactions with these satellites may leave particularly dramatic imprints. We uncover the influence of the most massive of these dark satellites on disky dwarf galaxies and the possible dynamical and morphological transformations that result from these interactions. We use a suite of carefully set-up, controlled simulations of isolated dwarf galaxies. The primary dwarf galaxi…
We report the detection of two dwarf galaxies in a projected distance of ~50 kpc from NGC 7331 and suspect the physical nature of dwarfs of this spiral galaxy.
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 …
In the Local Group, nearly all of the dwarf galaxies (M_star < 10^9 M_sun) that are satellites within 300 kpc (the virial radius) of the Milky Way (MW) and Andromeda (M31) have quiescent star formation and little-to-no cold gas. This contrasts strongly with comparatively isolated dwarf galaxies, which are almost all actively star-forming and gas-rich. This near dichotomy implies a rapid transformation of satellite dwarf galaxies after falling into the halos of the MW or M31. We combine the observed quiescent fractions for satellites of the MW and M31 with the infall times of satellites from th…
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…
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 investigate the angular and kinematic distributions of satellite galaxies around a large sample of bright isolated primaries in the spectroscopic and photometric catalogues of the Sloan Digital Sky Survey (SDSS). We detect significant anisotropy in the spatial distribution of satellites. To test whether this anisotropy could be related to the rotating disks of satellites recently found by Ibata et al. in a sample of SDSS galaxies, we repeat and extend their analysis. Ibata et al. found an excess of satellites on opposite sides of their primaries having anticorrelated radial velocities. We f…
In order to find the possible progenitors of Milky Way globular clusters, we perform orbit integrations to track the orbits of 170 Galactic globular clusters and the eleven classical Milky Way satellite galaxies backwards in time for 11 Gyr in a Milky-Way-plus-satellites potential including the response of the MW to the infall of the Large Magellanic Cloud and the effect of dynamical friction on the satellites. To evaluate possible past associations, we devise a globular-cluster--satellite binding criterion based on the satellite's tidal radius and escape velocity and we test it on globular cl…
We show that a significant correlation (up to 5sigma) emerges between the bulge index, defined to be larger for larger bulge/disk ratio, in spiral galaxies with similar luminosities in the Galaxy Zoo 2 of SDSS and the number of tidal-dwarf galaxies in the catalogue by Kaviraj et al. (2012). In the standard cold or warm dark-matter cosmological models the number of satellite galaxies correlates with the circular velocity of the dark matter host halo. In generalized-gravity models without cold or warm dark matter such a correlation does not exist, because host galaxies cannot capture in-falling …
The high-resolution, SPH galaxies of the McMaster Unbiased Galaxy Survey (MUGS) are used to examine the satellite systems of sixteen model host galaxies. Each galaxy has a different mass, angular momentum and merger history that yield a rich set of satellite luminosity functions. With new observations of distant satellite systems, we can compare these luminosity functions to satellite systems beyond the Local Group. We find that the luminosity functions of our simulations compare well to observations when the luminosity functions are scaled according to host mass. We use the recently-found rel…
We present direct observational evidence for star formation quenching in galaxy groups in the redshift range 0<z<2.5. We utilize a large sample of nearly 6000 groups, selected by fixed cumulative number density from three photometric catalogs, to follow the evolving quiescent fractions of central and satellite galaxies over roughly 11 Gyr. At z~0, central galaxies in our sample range in stellar mass from Milky Way/M31 analogs (M=6.5x10^10 M\solar) to nearby massive ellipticals (M=1.5x10^11 M\solar). Satellite galaxies in the same groups reach masses as low as twice that of the Large Magellanic…
The Milky Way and Andromeda galaxy are each surrounded by a thin plane of satellite galaxies that may be corotating. Cosmological simulations predict that most satellite galaxy systems are close to isotropic with random motions, so those two well-studied systems are often interpreted as rare statistical outliers. We test this assumption using the kinematics of satellite galaxies around the Centaurus A galaxy. Our statistical analysis reveals evidence for corotation in a narrow plane: of the 16 Centaurus A's satellites with kinematic data, 14 follow a coherent velocity pattern aligned with the …
We study the kinematics of galaxies within massive clusters, as a probe of the physics of star-formation quenching within clusters. Using N-body simulations, we argue that satellite kinematics provide information about galaxy infall that is complementary to the (instantaneous) spatial distribution of satellites. Comparing the simulation results with measurements of real cluster galaxies, we find evidence that the kinematics of red (quiescent) satellite galaxies are consistent with earlier infall times than that of blue (star-forming) satellites.
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 study the spatial distribution of faint satellites of intermediate redshift (0.1<z<0.8), early-type galaxies, selected from the GOODS fields. We combine high resolution HST images and state-of-the-art host subtraction techniques to detect satellites of unprecedented faintness and proximity to intermediate redshift host galaxies (up to 5.5 magnitudes fainter and as close as 0."5/2.5 kpc to the host centers). We model the spatial distribution of objects near the hosts as a combination of an isotropic, homogenous background/foreground population and a satellite population with a power law radi…
Using the spectroscopic catalogue of the Sloan Digital Survey Data Release 10, we have explored the abundance of satellites around a sample of 254 massive (10^11< M_star < 2 x 10^11 M_sun) local (z < 0.025) galaxies. We have divided our sample into four morphological groups (E, S0, Sa, Sb/c). We find that the number of satellites with M_star > 10^9 M_sun and R < 300 kpc depends drastically on the morphology of the central galaxy. The average number of satellites per galaxy host (N_Sat/N_Host) down to a mass ratio of 1:100 is 4.5 +/- 0.3 for E hosts, 2.6 +/- 0.2 for S0, 1.5 +/- 0.1 for Sa and 1…
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…
Local Group satellite galaxies show a wide diversity of star formation histories (SFHs) whose origin is yet to be fully understood. Using hydrodynamical simulations from the Constrained Local UniversE project, we study the SFHs of satellites of Milky Way-like galaxies in a cosmological context: while in the majority of the cases the accretion onto their host galaxy causes the satellites to lose their gas, with a subsequent suppression in SF, in about 25$\%$ of our sample we observe a clear enhancement of SF after infall. Peaks in SF clearly correlate with the satellite pericentric passage arou…
One of the strongest predictions of the LambdaCDM cosmological model is the presence of dark satellites orbiting all types of galaxies. We focus here on the dynamical effects of such satellites on disky dwarf galaxies, and demonstrate that these encounters can be dramatic. Although mergers with M_sat > M_d are not very common, because of the lower baryonic content they occur much more frequently on the dwarf scale than for L_*-galaxies. As an example, we present a numerical simulation of a 20% (virial) mass ratio merger between a dark satellite and a disky dwarf (akin to the Fornax dwarf galax…
Our Milky Way galaxy is host to a number of companions. These companions are gravitationally bound to the Milky Way and are stellar systems in their own right. They include a population of some 30 dwarf satellite galaxies (DSGs) and about 150 globular clusters (GCs). Here we discuss the relationship between GCs and DSGs using an interactive 3D model of the Milky Way.
We aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in the Catalogue of Isolated Galaxies (CIG), as well as the effects of the Large Scale Structure (LSS) using the SDSS-DR9. To recover the physically bound galaxies we focus on the satellites which are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbours. The tidal strengths affecting the primary galaxy are estimated to quantify the effects of the local and LSS environments. We…
The Andromeda galaxy is observed to have a system of two large dwarf ellipticals and ~13 smaller satellite galaxies that are currently co-rotating in a thin plane, in addition to 2 counter-rotating satellite galaxies. We explored the consistency of those observations with a scenario where the majority of the co-rotating satellite galaxies originated from a subhalo group, where NGC 205 was the host and the satellite galaxies occupied dark matter sub-subhalos. We ran N-body simulations of a close encounter between NGC 205 and M31. In the simulations, NGC 205 was surrounded by massless particles …
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…
We study the correlation of orbital poles of the 11 classical satellite galaxies of the Milky Way, comparing results from previous proper motions with the independent data by Gaia DR2. Previous results on the degree of correlation and its significance are confirmed by the new data. A majority of the satellites co-orbit along the Vast Polar Structure, the plane (or disk) of satellite galaxies defined by their positions. The orbital planes of eight satellites align to $<20^\circ$ with a common direction, seven even orbit in the same sense. Most also share similar specific angular momenta, though…
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…
Imprints of tidal interactions on the stellar distribution of satellite galaxies: implications for dark matter deficient galaxies
Institute for Astronomy, School of Physics, Zhejiang University（浙江大学物理学院天体物理研究所）；Center for Cosmology and Computational Astrophysics, Zhejiang University（浙江大学宇宙学与计算天体物理中心）；Department of Astronomy, Yale University（耶鲁大学天文学系）
Using a large SDSS galaxy group catalogue, we study how the stellar ages and metallicities of central and satellite galaxies depend on stellar mass and halo mass. We find that satellites are older and metal-richer than centrals of the same stellar mass. In addition, the slopes of the age-stellar mass and metallicity-stellar mass relations are found to become shallower in denser environments. This is due to the fact that the average age and metallicity of low mass satellite galaxies increase with the mass of the halo in which they reside. A comparison with the semi-analytical model of Wang et a…
We explore how the star formation and metal enrichment histories of present-day galaxies have been affected by environment combining stellar population parameter estimates and group environment characterization for SDSS DR7. We compare stellar ages, stellar metallicities and element abundance ratios [alpha/Fe] of satellite and central galaxies, as a function of their stellar and host group halo mass, controlling for the current star formation rate and for the infall epoch. We confirm that below log(Mstar/Msun)=10.5 satellites are older and metal-richer than equally-massive central galaxies. On…
The alignment between satellite and central galaxies serves as a proxy for addressing the issue of galaxy formation and evolution and has been investigated abundantly in observations and theoretical works. Most scenarios indicate that the satellites preferentially locate along the major axis of their central galaxy. Recent work shows that the strength of alignment signals depends on large-scale environment in observations. We use the publicly-released data from EAGLE to figure out whether the same effect can be found in the hydrodynamic simulation. We found much stronger environmental dependen…
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…
Driven by increasingly complete observational knowledge of systems of satellite galaxies, mutual spatial alignments and relations in velocities among satellites belonging to a common host have become a productive field of research. Numerous studies have investigated different types of such phase-space correlations, and were met with varying degrees of attention by the community. The Planes of Satellite Galaxies issue is maybe the best-known example, with a rich field of research literature and an ongoing, controversial debate on how much of a challenge it poses to the LCDM model of cosmology. …
Satellites constitute an important fraction of the overall galaxy population and are believed to form in dark matter subhalos. Here we use the cosmological hydrodynamic simulation TNG100 to investigate how the formation histories of subhalos affect the properties and evolution of their host galaxies. We use a scaled formation time ($a_{\rm nf}$) to characterize the mass assembly histories of the subhalos before they are accreted by massive host halos. We find that satellite galaxies in young subhalos (low $a_{\rm nf}$) are less massive and more gas rich, and have stronger star formation and a …
We present results from a resolved stellar population search for dwarf satellite galaxies of six nearby (D $<5$ Mpc), sub-Milky-Way mass hosts using deep ($m\sim27$ mag) optical imaging from the Large Binocular Telescope. We perform image simulations to quantify our detection efficiency for dwarfs over a large range in luminosity and size, and develop a fast catalog-based emulator that includes a treatment of unresolved photometric blending. We discover no new dwarf satellites, but we recover two previously known dwarfs (DDO 113 and LV J1228+4358) with $M_{\text{V}}<-12$ that lie in our survey…
While many tensions between Local Group (LG) satellite galaxies and LCDM cosmology have been alleviated through recent cosmological simulations, the spatial distribution of satellites remains an important test of physical models and physical versus numerical disruption in simulations. Using the FIRE-2 cosmological zoom-in baryonic simulations, we examine the radial distributions of satellites with Mstar > 10^5 Msun around 8 isolated Milky Way- (MW) mass host galaxies and 4 hosts in LG-like pairs. We demonstrate that these simulations resolve the survival and physical destruction of satellites …
Observations of the Galactic Center (GC) have accumulated a multitude of "forensic" evidence indicating that several million years ago the center of the Milky Way galaxy was teaming with starforming and accretion-powered activity -- this paints a rather different picture from the GC as we understand it today. We examine a possibility that this epoch of activity could have been triggered by the infall of a satellite galaxy into the Milky Way which began at the redshift of 10 and ended few million years ago with a merger of the Galactic supermassive black hole with an intermediate mass black hol…
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 …
We investigate the spatial distribution of the satellites of isolated host galaxies in the TNG100 simulation. In agreement with a previous, similar analysis of the Illustris-1 simulation, the satellites are typically poor tracers of the mean host mass density. Unlike the Illustris-1 satellites, here the spatial distribution of the complete satellite sample is well-fitted by an NFW profile; however, the concentration is a factor of ~2 lower than that of the mean host mass density. The spatial distribution of the brightest 50% and faintest 50% of the satellites are also well-fitted by NFW profil…
The accretion of minor satellites is currently proposed as the most likely mechanism to explain the significant size evolution of the massive galaxies during the last ~10 Gyr. In this paper we investigate the rest-frame colors and the average stellar ages of satellites found around massive galaxies (Mstar 10^11Msun) since z~2. We find that the satellites have bluer colors than their central galaxies. When exploring the stellar ages of the galaxies, we find that the satellites have similar ages to the massive galaxies that host them at high redshifts, while at lower redshifts they are, on avera…
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…
We present a wide field survey of satellite galaxies in M106 (NGC 4258) covering a $1.7\degr \times 2\degr$ field around M106 using Canada-France-Hawaii Telescope/MegaCam. We find 16 satellite galaxy candidates of M106. Eight of these galaxies are found to be dwarf galaxies that are much smaller and fainter than the remaining galaxies. Four of these galaxies are new findings. Surface brightness profiles of 15 out of 16 satellite galaxies can be represented well by an exponential disk profile with varying scale length. We derive the surface number density distribution of these satellite galaxie…
The accretion of satellites onto central galaxies along vast cosmic filaments is an apparent outcome of the anisotropic collapse of structure in our Universe. Numerical work (based on gravitational dynamics of N-body simulations) indicates that satellites are beamed towards hosts along preferred directions imprinted by the velocity shear field. Here we use the Sloan Digital Sky Survey to observationally test this claim. We construct 3D filaments and sheets and examine the relative position of satellite galaxies. A statistically significant alignment between satellite galaxy position and filame…
