Clusters of galaxies are excellent locations to probe the distribution baryons and dark matter (DM) over a wide range scales. We study sample seven massive, relaxed galaxy clusters with centrally-located brightest cluster (BCGs) at z=0.2-0.3. Using observational tools strong weak gravitational lensing, combined resolved stellar kinematics within BCG, we measure total radial density profile, comprising both baryonic matter, scales ~3-3000 kpc. Lensing-derived mass profiles typically agree...

We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, Gemini for a sample of 36 secure strong gravitational lens systems 17 candidates identified as part the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in redshift range zd = 0.2–0.8, while lensed sources zs 1–3.5. combine these data with photometric lensing measurements presented companion paper III lenses from Sloan Lens Advanced Camera Surveys Lènses Structure Dynamics...

It is argued that galaxies like ours sustain their star formation by transferring gas from an extensive corona to the star-forming disc. The transfer effected galactic fountain – cool clouds are shot up plane kiloparsec heights above plane. Kelvin–Helmholtz instability strips these clouds. If pressure and metallicity of high enough, stripped causes a similar mass coronal condense in cloud's wake. Hydrodynamical simulations cloud–corona interaction presented. These confirm existence critical...

We use recently published measurements of the kinematics, surface brightness and stellar mass-to-light ratio globular cluster NGC 2419 to examine possibility that this Galactic halo satellite is embedded in a low-mass dark matter halo. promising target for such study, since its extreme Galactocentric distance large mass would have greatly facilitated retention matter. A Markov chain Monte Carlo approach used investigate composite dynamical models containing component. find it unlikely...

Early-type galaxies (ETGs) are observed to be more compact at z>2 than in the local Universe. Remarkably, much of this size evolution appears take place a short (1.8 Gyr) time span between z=2.2 and z=1.3, which poses serious challenge hierarchical galaxy formation models where mergers occurring on similar timescale main mechanism for growth. We compute merger-driven redshift stellar mass Mstar\propto(1+z)^aM, half-mass radius Re\propto(1+z)^aR velocity-dispersion sigma0\propto(1+z)^asigma...

Dwarf Irregular galaxies (dIrrs) are the smallest stellar systems with extended HI discs. The study of kinematics such discs is a powerful tool to estimate total matter distribution at these very small scales. In this work, we 17 extracted from `Local Irregulars That Trace Luminosity Extremes, Nearby Galaxy Survey' (LITTLE THINGS). Our approach differs significantly previous studies in that directly fit 3D models (two spatial dimensions plus one spectral dimension) using software...

We investigate the cosmic evolution of internal structure massive early-type galaxies over half age universe. perform a joint lensing and stellar dynamics analysis sample 81 strong lenses from Strong Lensing Legacy Survey Sloan ACS Lens combine results with hierarchical Bayesian inference method to measure distribution dark matter mass initial function (IMF) across population galaxies. selection effects are taken into account. find that projected within inner 5 kpc increases for increasing...

We explore the effects of dissipationless merging on fundamental plane elliptical galaxies using an N-body code based a new, high-performance numerical scheme. investigate two extreme cases galaxy growth by equal-mass and accretion small stellar systems; in subset simulations we also consider presence dark matter haloes around galaxies. Curiously, found that is preserved major merging, while scenario its edge-on thickness only marginally reproduced, with substantial thickening case low...

The characteristic size of early-type galaxies (ETGs) given stellar mass is observed to increase significantly with cosmic time, from redshift z>2 the present. A popular explanation for this evolution that ETGs grow through dissipationless ("dry") mergers, thus becoming less compact. Combining N-body simulations up-to-date scaling relations local ETGs, we show such an problematic, because dry mergers do not decrease galaxy stellar-mass surface-density enough explain evolution, and also...

We examine the proposal that HI "high-velocity" clouds (HVCs) surrounding Milky Way and other disc galaxies form by condensation of hot galactic corona via thermal instability. Under assumption is well represented a non-rotating, stratified atmosphere, we find for this formation mechanism to work must have an almost perfectly flat entropy profile. In all cases growth perturbations suppressed combination buoyancy conduction. Even if profile were nearly flat, cold with sizes smaller than 10...

In galaxies like the Milky Way, cold (~ 10^4 K) gas ejected from disc by stellar activity (the so-called galactic-fountain gas) is expected to interact with virial-temperature 10^6 of corona. The associated transfer momentum between and hot has important consequences for dynamics both phases. We quantify effects such an interaction using hydrodynamical simulations clouds travelling through a medium at different relative velocities. Our main finding that there velocity threshold corona, about...

Simulations of the clustering cold dark matter yield haloes that have central density cusps, but observations totally dark-matter-dominated dwarf spheroidal galaxies imply they do not cuspy profiles. We use analytic calculations and numerical modelling to argue whenever stars form, cusps are likely be erased. Gas accumulates in potential well an initially halo settles into a disc. Eventually surface gas exceeds threshold for fragmentation self-gravitating clouds. The clouds massive enough...

We present the analysis of a kinematic data set stars in globular cluster NGC 2419, taken with Keck/DEIMOS. Combined reanalysis deep HST and Subaru imaging data, which provide an accurate luminosity profile cluster, we investigate validity large dynamical models system, are checked for stability via N-body simulations. find that isotropic either Newtonian or Modified Dynamics (MOND) ruled out extremely high confidence. However, simple Michie model gravity anisotropic velocity dispersion...

We present the analysis of a large sample early-type galaxies (ETGs) at 0<z<3 aimed tracing cosmic evolution their size and compare it with model pure dissipationless (dry) merging in LambdaCDM framework. The effective radius R_e depends on stellar mass M as R_e(M) \propto M}^{alpha} alpha ~ 0.5 all redshifts. redshift mass- or SDSS-normalized can be reproduced (1+z)^beta beta -1, most massive ETGs possibly showing fastest evolutionary rate (beta -1.4). This slows down significantly to -0.6...

We exploit the first Gaia data release to study properties of Galactic stellar halo as traced by RR Lyrae. demonstrate that it is possible select a pure sample Lyrae using only photometric information available in Gaia+2MASS catalogue. The final contains about 21 600 covering an unprecedented fraction ( ∼ 60 per cent) volume inner (R < 28 kpc). morphology analysing distribution with parametric and non-parametric techniques. Taking advantage uniform all-sky coverage, we test models more...

We present an approach to the design of distribution functions that depend on phase-space coordinates through action integrals. The makes it easy construct a dynamical model given stellar component. illustrate by deriving self-consistently generate several popular systems, including Hernquist, Jaffe, and Navarro, Frenk White models. focus non-rotating spherical but extension flattened rotating systems is trivial. Our are easily added each other previously published for discs create...

It is widely known that the gas in galaxy discs highly turbulent, but there much debate on which mechanism can energetically maintain this turbulence. Among possible candidates, supernova (SN) explosions are likely primary drivers doubts remain whether they be sufficient regions of moderate star formation activity, particular outer parts discs. Thus, a number alternative mechanisms have been proposed. In paper, we measure SN efficiency η , namely fraction total energy needed to sustain...

We have tested a previous analytical estimate of the dynamical friction time-scale in modified Newtonian dynamics (MOND) with fully non-linear N-body simulations. The simulations confirm that is significantly shorter MOND than equivalent systems, i.e. systems same phase-space distribution baryons and additional dark matter. An apparent conflict between this result long time-scales determined for bars to slow mergers be completed explained. confirmation short dynamical-friction underlines...

Dissipationless (gas-free or "dry") mergers have been suggested to play a major role in the formation and evolution of early-type galaxies, particularly growing their mass size without altering stellar populations. We perform new test dry merger hypothesis by comparing N-body simulations realistic systems empirical constraints provided recent studies lens galaxies. find that minor mergers: i) preserve nearly isothermal structure galaxies within observed scatter; ii) do not change more than...

We carry out a systematic investigation of the total mass density profile massive (Mstar>2e11 Msun) early-type galaxies and its dependence on galactic properties host halo with aid variety lensing/dynamical data large mock galaxy catalogs. The latter are produced via semi-empirical models that, by design, based just few basic input assumptions. Galaxies, measured stellar masses, effective radii S\'{e}rsic indices, assigned, abundance matching relations, dark matter halos characterized...

We present new dynamical models of dwarf spheroidal galaxies (dSphs) in which both the stellar component and dark halo are described by analytic distribution functions that depend on action integrals. In their most general form, these can represent axisymmetric possibly rotating systems. Here, as a first application, we model Fornax dSph, limiting ourselves, for simplicity, to non-rotating, spherical case. The compared with state-of-the-art spectroscopic photometric observations Fornax,...

We present new photometry of the dwarf irregular galaxy DDO 68, one most metal-poor and least massive dwarfs, located in Lynx-Cancer Void. The images were acquired with Large Binocular Telescope g r passbands, show unequivocally that 68 has previously unknown stellar streams related to accretion at two smaller companions: a flea fleas biting it, put it Jonathan Swift's words. Our data provide direct observational evidence multiple merging occurring very low galactic mass scales. results an...

Several open questions on galaxy formation and evolution have their roots in the lack of a universal star law, that could univocally link gas properties, e.g. its density, to rate (SFR) density. In recent paper, we used sample nearby disc galaxies infer volumetric (VSF) tight correlation between SFR volume densities derived under assumption hydrostatic equilibrium for disc. However, due dearth information about vertical distribution these galaxies, not find unique slope VSF but two...