Giuliano Taffoni

The morgana model for the rise of galaxies and active nuclei

We present the Model for the Rise of Galaxies and Active Nuclei (MORGANA), a new code for the formation and evolution of galaxies and active galactic nuclei (AGNs). Starting from the merger trees of dark matter (DM) haloes and a model for the evolution of substructure within the haloes, the complex physics of baryons is modelled with a set of state-of-the-art models that describe the mass, metal and energy flows between the various components (baryonic halo, bulge, disc) and phases (cold and hot gas, stars) of a galaxy. These flows are then numerically integrated to produce predictions for the evolution of galaxies. The processes of shock-heating and cooling, star formation, feedback, galactic winds and superwinds, accretion on to black holes and AGN feedback are described by new models. In particular, the evolution of the halo gas explicitly follows the thermal and kinetic energies of the hot and cold phases, while star formation and feedback follow the results of the multiphase model recently proposed by Monaco. The increased level of sophistication of these models allows to move from a phenomenological description of gas physics, based on simple scalings with the depth of the DM halo potential, towards a fully physically motivated one. We deem that this is fully justified by the level of maturity and rough convergence reached by the latest versions of numerical and semi-analytic models of galaxy formation. The comparison of the predictions of MORGANA with a basic set of galactic data reveals from the one hand an overall rough agreement, and from the other hand highlights a number of well- or less-known problems: (i) producing the cut-off of the luminosity function requires to force the quenching of the late cooling flows by AGN feedback, (ii) the normalization of the Tully‐Fisher relation of local spirals cannot be recovered unless the DM haloes are assumed to have a very low concentration, (iii) the mass function of H I gas is not easily fitted at small masses, unless a similarly low concentration is assumed, (iv) there is an excess of small elliptical galaxies at z = 0. These discrepancies, more than the points of agreement with data, give important clues on the missing ingredients of galaxy formation.

Workflow-Based Data Parallel Applications on the EGEE Production Grid Infrastructure

Setting up and deploying complex applications on a Grid infrastructure is still challenging and the programming models are rapidly evolving. Efficiently exploiting Grid parallelism is often not straight forward. In this paper, we report on the techniques used for deploying applications on the EGEE production Grid through four experiments coming from completely different scientific areas: nuclear fusion, astrophysics and medical imaging. These applications have in common the need for manipulating huge amounts of data and all are computationally intensive. All the cases studied show that the deployment of data intensive applications require the development of more or less elaborated application-level workload management systems on top of the gLite middleware to efficiently exploit the EGEE Grid resources. In particular, the adoption of high level workflow management systems eases the integration of large scale applications while exploiting Grid parallelism transparently. Different approaches for scientific workflow management are discussed. The MOTEUR workflow manager strategy to efficiently deal with complex data flows is more particularly detailed. Without requiring specific application development, it leads to very significant speed-ups.

Grid and Databases: BaSTI as a Practical Integration Example

Stellar Astrophysics and in particular stellar evolutionary computations are extremely important to face a wealth of astrophysical problems, but they are also extremely demanding in terms of computing power and data storage. The Bag of Stellar Tracks and Isochrones (BaSTI) database is a theoretical astrophysical catalogue that collects fundamental data sets involving stars formation and evolution. To create this database it is necessary to run a large number of stellar evolutionary computations. The Grid technology seems to be a promising answer to data storage and processing needs of the BaSTI catalogue. In the framework of the EGEE Grid infrastructure, we managed to run a number of experiments aimed at designing and defining an application specific environment for the stellar simulation software and its interaction with the BaSTI database. Our successful implementation demonstrates that the “gridification” of stellar evolution code is not only possible but also even extremely convenient in terms of data processing speed and data sharing, and it can be a valuable instrument to support Astrophysical research.

Interconnecting the Virtual Observatory with computational grid infrastructures

The term ‘grid’, in the Virtual Observatory (VO) context, has mainly been used to indicate a set of interoperable services, allowing transparent access to a set of geographically distributed and heterogeneous archives and catalogues, data exchange and analysis, etc. The design of the VO has been however mainly geared at allowing users to access registered services .

Creating Gateway Alliances Using WS-PGRADE/gUSE

The STARnet Gateway Federation is a unique example of a federated network of science gateways based on WS-PGRADE/gUSE technologies, and explicitly designed and tuned to the needs of the astronomical and astrophysical (A&A) community in Europe. The use of a federated gateway infrastructure allows scientists to explore new collaboration opportunities and advancing the scientific research activity within A&A. STARnet Gateways share a common authentication system, a distributed computing infrastructure, data archives, portlets, and workflow repositories. Building upon these technologies, a number of challenging applications from different A&A domains have been successfully prototyped and tested.

The Next Generation of Exascale-Class Systems: The ExaNeSt Project

The ExaNeSt project started on December 2015 and is funded by EU H2020 research framework (call H2020-FETHPC-2014, n. 671553) to study the adoption of low-cost, Linux-based power-efficient 64-bit ARM processors clusters for Exascale-class systems. The ExaNeSt consortium pools partners with industrial and academic research expertise in storage, interconnects and applications that share a vision of an Euro-pean Exascale-class supercomputer. Their goal is designing and implementing a physical rack prototype together with its cooling system, the storage non-volatile memory (NVM) architecture and a low-latency interconnect able to test different options for interconnection and storage. Furthermore, the consortium is to provide real HPC applications to validate the system. Herein we provide a status report of the project initial developments.

A Formal Approach to Support Interoperability in Scientific Meta-workflows

Scientific workflows orchestrate the execution of complex experiments frequently using distributed computing platforms. Meta-workflows represent an emerging type of such workflows which aim to reuse existing workflows from potentially different workflow systems to achieve more complex and experimentation minimizing workflow design and testing efforts. Workflow interoperability plays a profound role in achieving this objective. This paper is focused at fostering interoperability across meta-workflows that combine workflows of different workflow systems from diverse scientific domains. This is achieved by formalizing definitions of meta-workflow and its different types to standardize their data structures used to describe workflows to be published and shared via public repositories. The paper also includes thorough formalization of two workflow interoperability approaches based on this formal description: the coarse-grained and fine-grained workflow interoperability approach. The paper presents a case study from Astrophysics which successfully demonstrates the use of the concepts of meta-workflows and workflow interoperability within a scientific simulation platform.

Instruments in Grid: the Instrument Element

This work is focused on the interoperability aspects between the Grid and the scientific instrumentation. The IE (Instrument Element) makes possible the monitoring and the remote control of any kind of scientific instrumentation, although the test-bed of this first implementation is constituted of telescopes and related astronomical instrumentation. The first implementation of the IE deals with monitoring aspects; astronomers can remotely interface the telescope and related instrumentation and check the telemetric and scientific data when they are acquired. Future releases of the IE will include extensions, so that remote control capabilities will be also covered.

The Grid Data Source Engine Batch Query System

The interest in grid-databases integration has been steadily increasing in recent years and several projects provided different grid middleware components or tools trying to face this challenge. Among them the Grid Data Source Engine is offering native access to relational and non-relational data sources in a grid environment. In this paper we present its asynchronous query mechanism and we focus on the ability of this GSI/VOMS based middleware component to be integrated in workflow management systems.

Astrocook: a thousand recipes to cook a spectrum

Astrocook is a new Python package to analyze the spectra of quasi-stellar objects (QSOs) from the near-UV band to the near-infrared band. The project stems from the lessons learned in developing the data analysis software for the VLT ESPRESSO spectrograph. The idea is to leverage numerical libraries like SciPy, NumPy, and Lmfit and astronomical libraries like Astropy to produce a collection of high-level recipes capable of interpreting the features observed in QSO spectra (such as the emission continuum and the absorption systems) in an automated and validated way. The package provides great flexibility in designing the operational workflow, as well as a set of interactive tools to apply the recipes in a seamless way. The aim is to achieve the combination of accuracy, stability, and repeatability of the procedure that is required by several compelling science cases in the era of ”precision cosmology” (e.g. the measurement of a possible variability in the value of fundamental constants, and the direct measurement of the accelerated expansion of the Universe).