Overture: An advanced object-oriented software system for moving overlapping grid computations

While the development of high-level, easy-to-use, software libraries for numerical computations has been successful in some areas (e.g. linear system solvers, ODE solvers, grid generation), this has been an elusive goal for developers of partial differential equation (PDE) solvers. The advent of new high level languages such as C++ has begun to make this an achievable goal. This report discusses an object- oriented environment that we are developing for solving problems on overlapping (Chimera) grids. The goal of this effort is to support flexible PDE solvers on adaptive, moving, overlapping grids that cover a domain and overlap where they meet. Solutions values at the overlap are determined by interpolation. The overlapping grid approach is particularly efficient for rapidly generating high- quality grids for moving geometries since as the component grids move, only the list of interpolation points changes, and the component grids do not have to be regenerated. We use structured component grids so that efficient, fast finite-difference algorithms can be used. Oliger-Berger-Corella type mesh refinement is used to efficiently resolve fine features of the flow

Overture: an object-oriented software system for solving partial differential equations in serial and parallel environments

The OVERTURE Framework is an object-oriented environment for solving PDEs on serial and parallel architectures. It is a collection of C++ libraries that enables the use of finite difference and finite volume methods at a level that hides the details of the associated data structures, as well as the details of the parallel implementation. It is based on the A++/P++ array class library and is designed for solving problems on a structured grid or a collection of structured grids. In particular, it can use curvilinear grids, adaptive mesh refinement and the composite overlapping grid method to represent problems with complex moving geometry

‘The Brick’ is not a brick: a comprehensive study of the structure and dynamics of the central molecular zone cloud G0.253+0.016

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.In this paper we provide a comprehensive description of the internal dynamics of G0.253+0.016 (a.k.a. ‘the Brick’); one of the most massive and dense molecular clouds in the Galaxy to lack signatures of widespread star formation. As a potential host to a future generation of high-mass stars, understanding largely quiescent molecular clouds like G0.253+0.016 is of critical importance. In this paper, we reanalyse Atacama Large Millimeter Array cycle 0 HNCO J = 4(0, 4) − 3(0, 3) data at 3 mm, using two new pieces of software that we make available to the community. First, SCOUSEPY, a Python implementation of the spectral line fitting algorithm SCOUSE. Secondly, ACORNS (Agglomerative Clustering for ORganising Nested Structures), a hierarchical n-dimensional clustering algorithm designed for use with discrete spectroscopic data. Together, these tools provide an unbiased measurement of the line-of-sight velocity dispersion in this cloud, σvlos,1D=4.4±2.1 km s−1, which is somewhat larger than predicted by velocity dispersion-size relations for the central molecular zone (CMZ). The dispersion of centroid velocities in the plane of the sky are comparable, yielding σvlos,1D/σvpos,1D∼1.2±0.3⁠. This isotropy may indicate that the line-of-sight extent of the cloud is approximately equivalent to that in the plane of the sky. Combining our kinematic decomposition with radiative transfer modelling, we conclude that G0.253+0.016 is not a single, coherent, and centrally condensed molecular cloud; ‘the Brick’ is not a brick. Instead, G0.253+0.016 is a dynamically complex and hierarchically structured molecular cloud whose morphology is consistent with the influence of the orbital dynamics and shear in the CMZ

Star formation in 'the Brick': ALMA reveals an active protocluster in the Galactic centre cloud G0.253+0.016

Interstellar matter and star formatio

Star clusters near and far; tracing star formation across cosmic time

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00690-x.Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e.\ detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.Peer reviewedFinal Accepted Versio

Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages