nIFTy Galaxy Cluster simulations VI: The dynamical imprint of substructure on gaseous cluster outskirts

Galaxy cluster outskirts mark the transition region from the mildly non-linear cosmic web to the highly non-linear, virialised, cluster interior. It is in this transition region that the intra-cluster medium (ICM) begins to influence the properties of accreting galaxies and groups, as ram pressure impacts a galaxy's cold gas content and subsequent star formation rate. Conversely, the thermodynamical properties of the ICM in this transition region should also feel the influence of accreting substructure (i.e. galaxies and groups), whose passage can drive shocks. In this paper, we use a suite of cosmological hydrodynamical zoom simulations of a single galaxy cluster, drawn from the nIFTy comparison project, to study how the dynamics of substructure accreted from the cosmic web influences the thermodynamical properties of the ICM in the cluster's outskirts. We demonstrate how features evident in radial profiles of the ICM (e.g. gas density and temperature) can be linked to strong shocks, transient and short-lived in nature, driven by the passage of substructure. The range of astrophysical codes and galaxy formation models in our comparison are broadly consistent in their predictions (e.g. agreeing when and where shocks occur, but differing in how strong shocks will be); this is as we would expect of a process driven by large-scale gravitational dynamics and strong, inefficiently radiating, shocks. This suggests that mapping such shock structures in the ICM in a cluster's outskirts (via e.g. radio synchrotron emission) could provide a complementary measure of its recent merger and accretion history

Early Life Socioeconomic Circumstance and Late Life Brain Hyperintensities : A Population Based Cohort Study

Funding: Image acquisition and image analysis for this study was funded by the Alzheimer's Research Trust (now Alzheimer's Research UK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Acknowledgments The authors would like to thank the participants of the Aberdeen 1936 Birth Cohort (ABC36), without whom this research would not have been possible.Peer reviewedPublisher PD

nIFTY galaxy cluster simulations - III. The similarity and diversity of galaxies and subhaloes

We examine subhaloes and galaxies residing in a simulated $\Lambda$ cold dark matter galaxy cluster ($M^{crit} _{200}$ = 1.1 × 10$^{15}$ $h^{−1}$ M$_\odot$) produced by hydrodynamical codes ranging from classic smooth particle hydrodynamics (SPH), newer SPH codes, adaptive and moving mesh codes. These codes use subgrid models to capture galaxy formation physics. We compare how well these codes reproduce the same subhaloes/galaxies in gravity-only, non-radiative hydrodynamics and $\textit{full feedback physics}$ runs by looking at the overall subhalo/galaxy distribution and on an individual object basis. We find that the subhalo population is reproduced to within $\lesssim$10 per cent for both dark matter only and non-radiative runs, with individual objects showing code-to-code scatter of $\lesssim$0.1 dex, although the gas in non-radiative simulations shows significant scatter. Including feedback physics significantly increases the diversity. Subhalo mass and $V_{max}$ distributions vary by ≈20 per cent. The galaxy populations also show striking code-to-code variations. Although the Tully–Fisher relation is similar in almost all codes, the number of galaxies with 10$^9$ $h^{−1}$ M$_\odot$ $\lesssim$ $M_∗$ $\lesssim$ 10$^{12}$ $h^{−1}$ M$_\odot$ can differ by a factor of 4. Individual galaxies show code-to-code scatter of ~0.5 dex in stellar mass. Moreover, systematic differences exist, with some codes producing galaxies 70 per cent smaller than others. The diversity partially arises from the inclusion/absence of active galactic nucleus feedback. Our results combined with our companion papers demonstrate that subgrid physics is not just subject to fine-tuning, but the complexity of building galaxies $\textit{in all environments}$ remains a challenge. We argue that even basic galaxy properties, such as stellar mass to halo mass, should be treated with errors bars of ~0.2–0.4 dex

Multi-photon attenuation-compensated light-sheet fluorescence microscopy

We thank the UK Engineering and Physical Sciences Research Council for funding (grants EP/P030017/1 and EP/R004854/1), the European Union’s Horizon 2020 Framework Programme (H2020) (675512, BE-OPTICAL), the Danish Council for Independent Research (DFF FTP grant 7017-00021), and the Otto Mønsted Foundation (grant 19-70-0109).Attenuation of optical fields owing to scattering and absorption limits the penetration depth for imaging. Whilst aberration correction may be used, this is difficult to implement over a large field-of-view in heterogeneous tissue. Attenuation-compensation allows tailoring of the maximum lobe of a propagation-invariant light field and promises an increase in depth penetration for imaging. Here we show this promising approach may be implemented in multi-photon (two-photon) light-sheet fluorescence microscopy and, furthermore, can be achieved in a facile manner utilizing a graded neutral density filter, circumventing the need for complex beam shaping apparatus. A “gold standard” system utilizing a spatial light modulator for beam shaping is used to benchmark our implementation. The approach will open up enhanced depth penetration in light-sheet imaging to a wide range of end users.Publisher PDFPeer reviewe

nIFTY galaxy cluster simulations - III. The similarity and diversity of galaxies and subhaloes

We examine subhaloes and galaxies residing in a simulated $\Lambda$ cold dark matter galaxy cluster ($M^{crit} _{200}$ = 1.1 × 10$^{15}$ $h^{−1}$ M$_\odot$) produced by hydrodynamical codes ranging from classic smooth particle hydrodynamics (SPH), newer SPH codes, adaptive and moving mesh codes. These codes use subgrid models to capture galaxy formation physics. We compare how well these codes reproduce the same subhaloes/galaxies in gravity-only, non-radiative hydrodynamics and $\textit{full feedback physics}$ runs by looking at the overall subhalo/galaxy distribution and on an individual object basis. We find that the subhalo population is reproduced to within $\lesssim$10 per cent for both dark matter only and non-radiative runs, with individual objects showing code-to-code scatter of $\lesssim$0.1 dex, although the gas in non-radiative simulations shows significant scatter. Including feedback physics significantly increases the diversity. Subhalo mass and $V_{max}$ distributions vary by ≈20 per cent. The galaxy populations also show striking code-to-code variations. Although the Tully–Fisher relation is similar in almost all codes, the number of galaxies with 10$^9$ $h^{−1}$ M$_\odot$ $\lesssim$ $M_∗$ $\lesssim$ 10$^{12}$ $h^{−1}$ M$_\odot$ can differ by a factor of 4. Individual galaxies show code-to-code scatter of ~0.5 dex in stellar mass. Moreover, systematic differences exist, with some codes producing galaxies 70 per cent smaller than others. The diversity partially arises from the inclusion/absence of active galactic nucleus feedback. Our results combined with our companion papers demonstrate that subgrid physics is not just subject to fine-tuning, but the complexity of building galaxies $\textit{in all environments}$ remains a challenge. We argue that even basic galaxy properties, such as stellar mass to halo mass, should be treated with errors bars of ~0.2–0.4 dex

nIFTy galaxy cluster simulations – V. Investigation of the cluster infall region

We examine the properties of the galaxies and dark matter haloes residing in the cluster infall region surrounding the simulated $\Lambda$ cold dark matter galaxy cluster studied by Elahi et al. at $z$ = 0. The 1.1 × 10$^{15}$ $h^{−1}$ M$_\odot$ galaxy cluster has been simulated with eight different hydrodynamical codes containing a variety of hydrodynamic solvers and sub-grid schemes. All models completed a dark-matter-only, non-radiative and full-physics run from the same initial conditions. The simulations contain dark matter and gas with mass resolution $m_\text{DM}$ = 9.01 × 10$^8$ $h^{−1}$ M$_\odot$ and $m_\text{gas}$ = 1.9 × 10$^8$ $h^{−1}$ M$_\odot$, respectively. We find that the synthetic cluster is surrounded by clear filamentary structures that contain ~60 per cent of haloes in the infall region with mass ~10$^{12.5}$–10$^{14}$ $h^{−1}$ M$_\odot$, including 2–3 group-sized haloes (>10$^{13}$ $h^{−1}$ M$_\odot$). However, we find that only ~10 per cent of objects in the infall region are sub-haloes residing in haloes, which may suggest that there is not much ongoing pre-processing occurring in the infall region at $z$ = 0. By examining the baryonic content contained within the haloes, we also show that the code-to-code scatter in stellar fraction across all halo masses is typically ~2 orders of magnitude between the two most extreme cases, and this is predominantly due to the differences in sub-grid schemes and calibration procedures that each model uses. Models that do not include active galactic nucleus feedback typically produce too high stellar fractions compared to observations by at least ~1 order of magnitude.The authors would like the acknowledge the Centre for High Performance Computing in Rosebank, Cape Town, for financial support and for hosting the ‘Comparison Cape Town’ workshop in 2016, July. The authors would further like to acknowledge the support of the International Centre for Radio Astronomy Research (ICRAR) node at the University of Western Australia (UWA) in hosting the precursor workshop ‘Perth Simulated Cluster Comparison’ in 2015, March; the financial support of the UWA Research Collaboration Award 2014 and 2015 schemes; the financial support of the ARC Centre of Excellence for All Sky Astrophysics (CAASTRO) CE110001020 and ARC Discovery Projects DP130100117 and DP140100198. We would also like to thank the Instituto de Fisica Teorica (IFT-UAM/CSIC in Madrid) for its support, via the Centro de Excelencia Severo Ochoa Program under Grant No. SEV- 2012-0249, during the three-week workshop ‘nIFTy Cosmology’ in 2014, where the foundation for the whole comparison project was established. JA acknowledges support from a post-graduate award from STFC. PJE is supported by the SSimPL programme and the Sydney Institute for Astronomy (SIfA) and Australian Research Council (ARC) grants DP130100117 and DP140100198. AK is supported by the Ministerio de Econom´ıa y Competitividad (MINECO) in Spain through grant AYA2012-31101 as well as the ConsoliderIngenio 2010 Programme of the Spanish Ministerio de Ciencia e Innovacion (MICINN) under grant MultiDark CSD2009-00064. ´ He also acknowledges support from the ARC grant DP140100198. He further thanks Noonday Underground for surface noise. STK acknowledges support from STFC through grant ST/L000768/1. CP acknowledges the support of the ARC through Future Fellowship FT130100041 and Discovery Project DP140100198. WC and CP acknowledge the support of ARC DP130100117. GY and FS acknowledge support from MINECO (Spain) through the grant AYA 2012-31101. GY thanks also the Red Espanola de Supercomputa- ˜ cion for granting the computing time in the Marenostrum Supercomputer at BSC, where all the MUSIC simulations have been performed. AMB is supported by the DFG Research Unit 1254 ‘Magnetisation of interstellar and intergalactic media’ and by the DFG Cluster of Excellence ‘Universe’. GM acknowledge support from the PRIN-MIUR 2012 Grant ‘The Evolution of Cosmic Baryons’ funded by the Italian Minister of University and Research, by the PRIN-INAF 2012 Grant ‘Multi-scale Simulations of Cosmic Structures’, by the INFN INDARK Grant and by the ‘Consorzio per la Fisica di Trieste’. IGM acknowledges support from an STFC Advanced Fellowship. EP acknowledges support by the ERC grant ‘The Emergence of Structure During the Epoch of Reionization’

The politicisation of evaluation: constructing and contesting EU policy performance

Although systematic policy evaluation has been conducted for decades and has been growing strongly within the European Union (EU) institutions and in the member states, it remains largely underexplored in political science literatures. Extant work in political science and public policy typically focuses on elements such as agenda setting, policy shaping, decision making, or implementation rather than evaluation. Although individual pieces of research on evaluation in the EU have started to emerge, most often regarding policy “effectiveness” (one criterion among many in evaluation), a more structured approach is currently missing. This special issue aims to address this gap in political science by focusing on four key focal points: evaluation institutions (including rules and cultures), evaluation actors and interests (including competencies, power, roles and tasks), evaluation design (including research methods and theories, and their impact on policy design and legislation), and finally, evaluation purpose and use (including the relationships between discourse and scientific evidence, political attitudes and strategic use). The special issue considers how each of these elements contributes to an evolving governance system in the EU, where evaluation is playing an increasingly important role in decision making