1,019 research outputs found
MPWide: a light-weight library for efficient message passing over wide area networks
We present MPWide, a light weight communication library which allows
efficient message passing over a distributed network. MPWide has been designed
to connect application running on distributed (super)computing resources, and
to maximize the communication performance on wide area networks for those
without administrative privileges. It can be used to provide message-passing
between application, move files, and make very fast connections in
client-server environments. MPWide has already been applied to enable
distributed cosmological simulations across up to four supercomputers on two
continents, and to couple two different bloodflow simulations to form a
multiscale simulation.Comment: accepted by the Journal Of Open Research Software, 13 pages, 4
figures, 1 tabl
The formation and early evolution of embedded star clusters in spiral galaxies
The equipment was funded by BEIS capital funding via STFC capital grants ST/K000373/1 and ST/R002363/1 and STFC DiRAC Operations grant ST/K001014/1. DiRAC is part of the National E-Infrastructure. SR acknowledges funding from STFC Consolidated Grant ST/R000395/1. CLD acknowledges funding from the European Research Council for the Horizon 2020 ERC consolidator grant project ICYBOB, grant number 818940.We present Ekster, a new method for simulating star clusters from birth in a live galaxy simulation that combines the smoothed-particle hydrodynamics (SPH) method Phantom with the N-body method PeTar. With Ekster, it becomes possible to simulate individual stars in a simulation with only moderately high resolution for the gas, allowing us to study whole sections of a galaxy rather than be restricted to individual clouds. We use this method to simulate star and star cluster formation in spiral arms, investigating massive GMCs and spiral arm regions with lower mass clouds, from two galaxy models with different spiral potentials. After selecting these regions from pre-run galaxy simulations, we re-sample the particles to obtain a higher resolution. We then re-simulate these regions for 3 Myr to study where and how star clusters form. We analyse the early evolution of the embedded star clusters in these regions. We find that the massive GMC regions, which are more common with stronger spiral arms, form more massive clusters than the sections of spiral arms containing lower mass clouds. Clusters form both by accreting gas and by merging with other proto-clusters, the latter happening more frequently in the denser GMC regions.Publisher PDFPeer reviewe
Observational Bias and Young Massive Cluster Characterisation II. Can Gaia accurately observe young clusters and associations?
Observations of clusters suffer from issues such as completeness, projection
effects, resolving individual stars and extinction. As such, how accurate are
measurements and conclusions are likely to be? Here, we take cluster
simulations (Westerlund2- and Orion- type), synthetically observe them to
obtain luminosities, accounting for extinction and the inherent limits of Gaia,
then place them within the real Gaia DR3 catalogue. We then attempt to
rediscover the clusters at distances of between 500pc and 4300pc. We show the
spatial and kinematic criteria which are best able to pick out the simulated
clusters, maximising completeness and minimising contamination. We then compare
the properties of the 'observed' clusters with the original simulations. We
looked at the degree of clustering, the identification of clusters and
subclusters within the datasets, and whether the clusters are expanding or
contracting. Even with a high level of incompleteness (e.g. stellar
members identified), similar qualitative conclusions tend to be reached
compared to the original dataset, but most quantitative conclusions are likely
to be inaccurate. Accurate determination of the number, stellar membership and
kinematic properties of subclusters, are the most problematic to correctly
determine, particularly at larger distances due to the disappearance of cluster
substructure as the data become more incomplete, but also at smaller distances
where the misidentification of asterisms as true structure can be problematic.
Unsurprisingly, we tend to obtain better quantitative agreement of properties
for our more massive Westerlund2-type cluster. We also make optical style
images of the clusters over our range of distances.Comment: 19 pages, 10 figures, 6 tables. Accepted for publication in MNRA
Using Molecular Gas Observations to Guide Initial Conditions for Star Cluster Simulations
The earliest evolution of star clusters involves a phase of co-existence of
both newly-formed stars, and the gas from which they are forming. Observations
of the gas in such regions provide a wealth of data that can inform the
simulations which are needed to follow the evolution of such objects forward in
time. We present a method for transforming the observed gas properties into
initial conditions for simulations that include gas, stars, and ongoing star
formation. We demonstrate our technique using the Orion Nebula Cluster. Since
the observations cannot provide all the necessary information for our
simulations, we make choices for the missing data and assess the impact of
those choices. We find that the results are insensitive to the adopted choices
of the gas velocity in the plane of the sky. The properties of the surrounding
gas cloud (e.g. overall density and size), however, have an effect on the star
formation rate and pace of assembly of the resultant star cluster. We also
analyze the stellar properties of the cluster and find that the stars become
more tightly clustered and in a stronger radial distribution even as new stars
form in the filament.Comment: 11 pages, 12 figures, accepted for publication in MNRA
Felix:A Topology Based Framework for Visual Exploration of Cosmic Filaments
The large-scale structure of the universe is comprised of virialized blob-like clusters, linear filaments, sheet-like walls and huge near empty three-dimensional voids. Characterizing the large scale universe is essential to our understanding of the formation and evolution of galaxies. The density range of clusters, walls and voids are relatively well separated, when compared to filaments, which span a relatively larger range. The large scale filamentary network thus forms an intricate part of the cosmic web. In this paper, we describe Felix, a topology based framework for visual exploration of filaments in the cosmic web. The filamentary structure is represented by the ascending manifold geometry of the 2-saddles in the Morse-Smale complex of the density field. We generate a hierarchy of Morse-Smale complexes and query for filaments based on the density ranges at the end points of the filaments. The query is processed efficiently over the entire hierarchical Morse-Smale complex, allowing for interactive visualization. We apply Felix to computer simulations based on the heuristic Voronoi kinematic model and the standard LCDM cosmology, and demonstrate its usefulness through two case studies. First, we extract cosmic filaments within and across cluster like regions in Voronoi kinematic simulation datasets. We demonstrate that we produce similar results to existing structure finders. Second, we extract different classes of filaments based on their density characteristics from the LCDM simulation datasets. Filaments that form the spine of the cosmic web, which exist in high density regions in the current epoch, are isolated using Felix. Also, filaments present in void-like regions are isolated and visualized. These filamentary structures are often over shadowed by higher density range filaments and are not easily characterizable and extractable using other filament extraction methodologies
The early evolution of young massive clusters: The kinematic history of NGC6611 / M16
In the first few Myr the massive stars dynamically interact, produce runaways
and affect the initial binary population. Observing and interpreting the
dynamics of young massive clusters is key to our understanding of the star
formation process and predicting the outcome of stellar evolution. We have
studied NGC6611 in the Eagle Nebula (M16), a young massive cluster hosting 19 O
stars. We used Gaia EDR3 data to determine the membership, age, cluster
dynamics and the kinematics of the massive stars including runaways. The
membership analysis yields 137 members located at a mean distance of 1706
7 pc. The colour - absolute magnitude diagram reveals a blue and a red
population of pre-main-sequence stars, consistent with two distinct populations
of stars. In line with earlier studies, the youngest population has a mean
extinction = 3.6 0.1 mag and an age = 1.3 0.2 Myr, while the
older population of stars has a mean extinction = 2.0 0.1 mag and
an age = 7.5 0.4 Myr. The latter population is more spatially extended
than the younger generation of stars. We argue that most of the OB stars belong
to the younger population. We identify 8 runaways originating from the center
of NGC6611, consistent with the dynamical ejection scenario. We show that ~ 50%
of the O stars have velocities comparable to or greater than the escape
velocity. These O stars can be traced back to the center of NGC6611 with
kinematic ages ranging from 0 to 2 Myr. This suggests that dynamical
interactions played an important role in the early evolution of NGC6611, which
is surprising considering the low current stellar density. Comparing this to
simulations of young massive clusters, the required initial radius of 0.1-0.5
pc is not consistent with that of NGC6611. The O stars could have initially
formed in wide binaries and possibly harden through dynamical interactions.Comment: replaced with accepted version to A&A. 28 pages, 15 figure
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