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We describe a NOVel form of Adaptive softening (NOVA) for collisionless N-body simulations, implemented in the RAMSES adaptive mesh refinement code. In RAMSES - that we refer to as a 'standard N-body method' - cells are only split if they containmore than eight particles (amass refinement criterion). Here, we introduce an additional criterion that the particle distribution within each cell be suff
Several scenarios have been proposed to explain the presence of multiple stellar populations in globular clusters. Many of them invoke multiple generations of stars to explain the observed chemical abundance anomalies, but it has also been suggested that self-enrichment could occur via accretion of ejecta from massive stars on to the circumstellar disc of low-mass pre-main sequence stars. These sc
Gravitational instabilities play an important role in galaxy evolution and in shaping the interstellar medium (ISM). The ISM is observed to be highly turbulent, meaning that observables like the gas surface density and velocity dispersion depend on the size of the region over which they are measured. In this work, we investigate, using simulations of Milky Way-like disc galaxies with a resolution
Radiation feedback is typically implemented using subgrid recipes in hydrodynamical simulations of galaxies. Very little work has so far been performed using radiation-hydrodynamics (RHD), and there is no consensus on the importance of radiation feedback in galaxy evolution. We present RHD simulations of isolated galaxy discs of different masses with a resolution of 18 pc. Besides accounting for s
The strong time-dependence of the dynamics of galactic bars yields a complex and rapidly evolving distribution of dense gas and star forming regions. Although bars mainly host regions void of any star formation activity, their extremities can gather the physical conditions for the formation of molecular complexes and mini-starbursts. Using a sub-parsec resolution hydrodynamical simulation of a Mil
Gravitational instabilities play a primary role in shaping the clumpy structure and powering the star formation activity of gas-rich high-redshift galaxies. Here, we analyse the stability of such systems, focusing on the size and mass ranges of unstable regions in the disc. Our analysis takes into account the mass-size and linewidth-size scaling relations observed in molecular gas, originally disc
Under conservative assumptions about the Galaxy, the derived velocity of the Smith Cloud indicates that it will have undergone at least one passage of the Galactic disc. Using hydrodynamicsimulations, we examine the present-day structure of the Smith Cloud and find that a dark matter supported cloud is able to reproduce the observed present-day neutral hydrogen mass, column density distribution an
We introduce the Assembling Galaxies Of Resolved Anatomy (AGORA) project, a comprehensive numerical study of well-resolved galaxies within the ΛCDM cosmology. Cosmological hydrodynamic simulations with force resolutions of 100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth, star formation history, morphological transformation, and the cycle of ba
Observations of turbulent velocity dispersions in the H i component of galactic discs show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry out several high-resolution adaptive mesh simulations of gaseous discs embedded within dark matter haloes to explore the roles of cooling, star formation, feed
Galaxy formation models and simulations rely on various feedback mechanisms to reproduce the observed baryonic scaling relations and galaxy morphologies. Although dwarf galaxy and giant elliptical properties can be explained using feedback from supernova and active galactic nuclei, Milky Way-sized galaxies still represent a challenge to current theories of galaxy formation. In this paper, we explo
We present results from high-resolution hydrodynamic simulations of isolated Small Magellanic Cloud (SMC)- and Milky-Way-sized galaxies that include a model for feedback from galactic cosmic rays (CRs). We find that CRs are naturally able to drive winds with mass loading factors of up to ∼10 in dwarf systems. The scaling of the mass loading factor with circular velocity between the two simulated s
We study the formation of disc galaxies in a fully cosmological framework using adaptive mesh refinement simulations. We perform an extensive parameter study of the main subgrid processes that control how gas is converted into stars and the coupled effect of supernovae feedback. We argue that previous attempts to form disc galaxies have been unsuccessful because of the universal adoption of strong
Standard formulations of smoothed particle hydrodynamics (SPH) are unable to resolve mixing at fluid boundaries. We use an error and stability analysis of the generalized SPH equations of motion to prove that this is due to two distinct problems. The first is a leading order error in the momentum equation. This should decrease with an increasing neighbour number, but does not because numerical ins
Dark matter direct detection experiments need to know the local phase space density of dark matter fdm(r,v,t) in order to derive dark matter particle properties. To date, calculations for fdm(r,v,t) have been based on simulations that model the dark matter alone. Here we include the influence of the baryonic matter. We find that a star/gas disc at high redshift (z∼1) causes merging satellites to b
A precise determination of the local dark matter density and an accurate control over the corresponding uncertainties are of paramount importance for dark matter (DM) searches. Using very recent high-resolution numerical simulations of a Milky Way like object, we study the systematic uncertainties that affect the determination of the local dark matter density based on dynamical measurements in the
We explore the gravitational instability of clumpy and turbulent gas discs, taking into account the Larson-type scaling laws observed in giant molecular clouds (GMCs) and H i, as well as more general scaling relations. This degree of freedom is of special interest in view of the coming high-z interstellar medium surveys and is thus potentially important for understanding the dynamical effects of t
The effects of particle discreteness in N-body ACDM simulations are still an intensively debated issue. In this paper we explore such effects, taking into account the scatter caused by the randomness of the initial conditions and focusing on the statistical properties of the cosmological density field. For this purpose, we run large sets of ACDM simulations and analyze them using a wide variety of
In a Λ cold dark matter (ΛCDM) cosmology, the Milky Way accretes satellites into the stellar disc. We use cosmological simulations to assess the frequency of near disc plane and higher inclination accretion events, and collisionless simulations of satellite mergers to quantify the final state of the accreted material and the effect on the thin disc. On average, a Milky Way-sized galaxy has three s
Predicting the flux of dark matter particles through the Earth is vital for current and future direct dark matter detection experiments. To date, such predictions have been based on simulations that model the dark matter alone. Here we make the first attempt to include the influence of the baryonic matter. We show that the presence of a stellar/gas disc at high redshift (z ∼ 1) causes merging sate
We have carried out a comparison study of hydrodynamical codes by investigating their performance in modelling interacting multiphase fluids. The two commonly used techniques of grid and smoothed particle hydrodynamics (SPH) show striking differences in their ability to model processes that are fundamentally important across many areas of astrophysics. Whilst Eulerian grid based methods are able t
