Age, metallicity and star formation history of spheroidal galaxies in cluster at z~1.2

We present the analysis, based on spectra collected at the Large Binocular Telescope, of the stellar populations in seven spheroidal galaxies in the cluster XLSSJ0223 at $z$$\sim$1.22. The aim is to constrain the epoch of their formation and their star formation history. Using absorption line strenghts and full spectral fitting, we derive for the stellar populations of the seven spheroids a median age =2.4$\pm$0.6 Gyr, corresponding to a median formation redshift $\sim2.6_{-0.5}^{+0.7}$ (lookback time = 11$_{-1.0}^{+0.6}$ Gyr). We find a significant scatter in age, showing that massive spheroids, at least in our targeted cluster, are not coeval. The median metallicity is [Z/H]=0.09$\pm$0.16, as for early-types in clusters at 0$<z$<0.9. This lack of evolution of [Z/H] over the range 0$<$$z$$<$1.3, corresponding to the last 9 billions years, suggests that no significant additional star formation and chemical enrichment are required for cluster spheroids to reach the present-day population. We do not detect significant correlation between age and velocity dispersion$\sigma_e$, or dynamical mass M$_{dyn}$, or effective stellar mass density$\Sigma_e$. On the contrary, the metallicity [Z/H] of the seven spheroids is correlated to their dynamical mass M$_{dyn}$, according to a relation similar to the one for local spheroids. [Z/H] is also anticorrelated to stellar mass density$\Sigma_e$because of the anticorrelation between M$_{dyn}$and$\Sigma_e$. Therefore, the basic trends observed in the local universe were already established at$z\sim1.3$, i.e. more massive spheroids are more metal rich, have lower stellar mass density and tend to be older than lower-mass galaxies.Comment: 16 pages, 6 figures, 6 tables, published on MNRA

A framework to evaluate the effects of organizational resilience on service quality

Disruptions and unexpected turbulences characterize the contemporary service industry and pose greater criticalities to organizations that have concerns about both their survival and their business sustainability. The answer to this challenge is to design an organizational system aimed at enhancing so-called organizational resilience. The aim of this work is to present and test an assessment methodology based on a framework that links key static and dynamic characteristics of firms as resilient systems and relates these characteristics with service quality preservation after disruptions. The framework adopts a set of indicators, namely resilience dimensions, to comprehend the real effects of resilience characteristics with service quality dimensions. Through the analysis of a real case, we provided evidence of how the model can be applied in a backward perspective to understand fault modes of specific events. Results show how inadequacies in terms of resilience characteristics determine losses of service quality, and also how the model can be used as a predictive tool to determine in which area companies should intervene in order to improve resilience and service quality

The nature and value of knowledge

Purpose: This paper aims to explain and discuss the complex nature and value of knowledge as an exploitable resource for business. Design/methodology/approach: The authors propose a conceptual explanation of knowledge based on three pillars: the plurality of its nature, understood to be conservative, multipliable and generative, its contextual value and the duality of carrier incorporating business knowledge, objects or processes. After conceptualizing the nature of knowledge, the authors offer a metaphor based on the classic transformation from \u201cpotential\u201d to \u201ckinetic\u201d energy in an inclined plane assuming that the conservative nature of knowledge makes it act as energy. Findings: The metaphor uses the concept of potential and kinetic energy: if energy is only potential, it has a potential value not yet effective, whereas if the potential energy (knowledge) becomes kinetic energy (products and/or services), it generates business value. In addition, business value is a function of the speed acquired and caused by the angle of inclined plan, namely, the company\u2019s business model. Knowledge is the source of the value and can be maintained and regenerated only through continuous investments. Several years later the value extraction reaches a null value of the company (potential energy) which will cease to act (kinetic energy) for triggering both the value generated and the value extracted. Originality/value: The paper proposes an initial attempt to explain the meaning of the transformation of knowledge using a metaphor derived from physics. The metaphor of the energy of knowledge clearly depicts the managerial dilemma of balancing a company\u2019s resources for both the generating and extracting value. Similarly, future study should try to associate other knowledge peculiarities to physical phenomena

The Luminosity Function of high-redshift QSOs - A combined analysis of GOODS and SDSS

Aims: In this work the luminosity function of QSOs is measured in the redshift range 3.5<z<5.2 for the absolute magnitude interval -21<M_{145}<-28. The determination of the faint end of the luminosity function at these redshifts provides important constraints on models of joint evolution of galaxies and AGNs. Methods: We have defined suitable criteria to select faint QSOs in the GOODS fields, checking in detail their effectiveness and completeness. Spectroscopic follow-up of the resulting QSO candidates has been carried out. The confirmed sample of faint QSOs is compared with a brighter one derived from the SDSS. We have used a Monte-Carlo technique to estimate the properties of the luminosity function, checking various parameterizations for its shape and evolution. Results: Models based on Pure Density Evolution show better agreement with observation than models based on Pure Luminosity Evolution. However a different break magnitude with respect to z~2.1 is required at 3.5<z<5.2. Models with a steeper faint end score a higher probability. We do not find any evidence for a flattening of the bright end at redshift z>3.5. Conclusions: The estimated space density evolution of QSOs indicates a suppression of the formation and/or feeding of Supermassive Black Holes at these redshifts. The QSO contribution to the UV background is insufficient to ionize the IGM at 3.5<z<5.2.Comment: 17 pages, 13 ps figures, A&A accepted. Updated to journal versio

The impact of implementation process on the perception of enterprise resource planning success

Purpose \u2013 The purpose of this paper is to investigate the impact of the implementation process on the ERP\u2019s success in the post-adoption stage, measured as system\u2019s acceptance, reliability and utility perceived by users, inside the organizations. Design/methodology/approach \u2013 The authors adopted a multiple case study research design. The data collected, provided by IT managers and 120 key-users from four companies, has been used to investigate the impact of the Enterprise Resource Planning (ERP) implementation phases on selected constructs of the Task-Technology Fit (TTF) and Technology Acceptance Model (TAM). The empirical evidences highlight a direct relation between the effectiveness of the implementation phases and the ERP\u2019s success. Findings \u2013 The research results emphasize the importance of the quality of the software, but especially the importance of the implementation phases\u2019 management, which require technical and managerial ability of the team made up of people from the system integrator and the company\u2019s key-users. Evidences suggest that the higher will be the organizational diffusion of an ERP implemented during a successful implementation project, the higher will be the perception of ERP success in the post-adoption stage. Moreover, the users\u2019 perception of ERP quality will be maintained over time. Research limitations/implications \u2013 The research has some limits due to its exploratory nature and to the chosen research approach, so the results may lack generalizability; consequently future research will concern with enlargement of the sample that will allow a better generalization of the results. Practical implications \u2013 This exploratory study suggest that companies\u2019 managers should be aware that a correct methodology of implementation, strongly influenced by the team, impacts on the technology consistency and therefore, on the ERP system success. So an appropriate choice is to invest more in the creation and development of internal and external project team than in the ERP\u2019s brand. Originality/value \u2013 This paper fulfils an identified need to clarify the explicit relationship between the quality of implementation phases and the subsequent ERP success in the post-adoption stage measured in terms of users\u2019 perception of information system qualit

A textbook example of ram-pressure stripping in the Hydra A/A780 cluster

In the current epoch, one of the main mechanisms driving the growth of galaxy clusters is the continuous accretion of group-scale halos. In this process, the ram pressure applied by the hot intracluster medium on the gas content of the infalling group is responsible for stripping the gas from its dark-matter halo, which gradually leads to the virialization of the infalling gas in the potential well of the main cluster. Using deep wide-field observations of the poor cluster Hydra A/A780 with XMM-Newton and Suzaku, we report the discovery of an infalling galaxy group 1.1 Mpc south of the cluster core. The presence of a substructure is confirmed by a dynamical study of the galaxies in this region. A wake of stripped gas is trailing behind the group over a projected scale of 760 kpc. The temperature of the gas along the wake is constant at kT ~ 1.3 keV, which is about a factor of two less than the temperature of the surrounding plasma. We observe a cold front pointing westwards compared to the peak of the group, which indicates that the group is currently not moving in the direction of the main cluster, but is moving along an almost circular orbit. The overall morphology of the group bears remarkable similarities with high-resolution numerical simulations of such structures, which greatly strengthens our understanding of the ram-pressure stripping process

Confirming EIS Clusters. Optical and Infrared Imaging

Clusters of galaxies are important targets in observationally cosmology, as they can be used both to study the evolution of the galaxies themselves and to constrain cosmological parameters. Here we report on the first results of a major effort to build up a sample of distant galaxy clusters to form the basis for further studies within those fields. We search for simultaneous overdensities in color and space to obtain supporting evidence for the reality of the clusters. We find a confirmation rate for EIS clusters of 66%, suggesting that a total of about 80 clusters with z>=0.6 are within reach using the EIS cluster candidates.Comment: 4 pages, 2 figures, to appear in the proceedings of the IGRAP International Conference 1999 on 'Clustering at high Redshift

Water resource management through systemic approach: The case of Lake Bracciano

Today natural water resources are becoming scarce, both due to global climate change but also due to irresponsible behaviour of human beings. Lakes are among the most delicate aquatic systems due to their limited size. The objective of this paper is to propose a System Dynamics model, employed in a real case study regarding the city of Rome and one of its water reserves, the Bracciano Lake, for the evaluation of different strategies and policies to reduce environmental impacts, considering different climatic and context scenarios. The results indicate that, as the system is currently exposed to a high risk of ecological disaster, the situation might worsen, and the disaster effectively happen. Simulation models may help agencies and administrations to explore policies and find solutions to address this fundamental problem, that may become even worst over the next years, given the potential severe consequences deriving from the current global warming trends

ESO Imaging Survey VII. Distant Cluster Candidates over 12 square degrees

In this paper the list of candidate clusters identified from the I-band data of the ESO Imaging Survey (EIS) is completed using the images obtained over a total area of about 12 square degrees. Together with the data reported earlier the total I-band coverage of EIS is 17 square degrees, which has yielded a sample of 252 cluster candidates in the redshift range 0.2 \lsim z \lsim 1.3. This is the largest optically-selected sample currently available in the Southern Hemisphere. It is also well distributed in the sky thus providing targets for a variety of VLT programs nearly year round.Comment: 5 pages, 3 figures, submitted to Astronomy & Astrophysic

Discovery of a faint, star-forming, multiply lensed, Lyman-alpha blob

We report the discovery of a multiply lensed Lyman-$\alpha$ blob (LAB) behind the galaxy cluster AS1063 using the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The background source is at $z=$ 3.117 and is intrinsically faint compared to almost all previously reported LABs. We used our highly precise strong lensing model to reconstruct the source properties, and we find an intrinsic luminosity of $L_{\rm Ly\alpha}$=$1.9\times10^{42}$ erg s$^{-1}$, extending to 33 kpc. We find that the LAB is associated with a group of galaxies, and possibly a protocluster, in agreement with previous studies that find LABs in overdensities. In addition to Lyman-$\alpha$ (Ly$\alpha$) emission, we find \ion{C}{IV}, \ion{He}{II}, and \ion{O}{III}] ultraviolet (UV) emission lines arising from the centre of the nebula. We used the compactness of these lines in combination with the line ratios to conclude that the \Lya nebula is likely powered by embedded star formation. Resonant scattering of the \Lya photons then produces the extended shape of the emission. Thanks to the combined power of MUSE and strong gravitational lensing, we are now able to probe the circumgalatic medium of sub-$L_{*}$ galaxies at $z\approx 3$.Comment: 7 pages, 7 figures; moderate changes to match the accepted A&A versoi