3,073 research outputs found
Gaia-ESO Survey: Gas dynamics in the Carina nebula through optical emission lines
Aims. We present observations from the Gaia-ESO Survey in the lines of Hα, [N II], [S II], and He I of nebular emission in the central part of the Carina nebula. Methods. We investigate the properties of the two already known kinematic components (approaching and receding), which account for the bulk of emission. Moreover, we investigate the features of the much less known low-intensity high-velocity (absolute RV >50 km s) gas emission. Results. We show that gas giving rise to Hα and He I emission is dynamically well correlated with but not identical to gas seen through forbidden-line emission. Gas temperatures are derived from line-width ratios, and densities from [S II] doublet ratios. The spatial variation of N ionization is also studied, and found to differ between the approaching and receding components. The main result is that the bulk of the emission lines in the central part of Carina arise from several distinct shell-like expanding regions, the most evident found around η Car, the Trumpler 14 core, and the star WR25. These >shells> are non-spherical and show distortions probably caused by collisions with other shells or colder, higher-density gas. Some of them are also partially obscured by foreground dust lanes, while very little dust is found in their interior. Preferential directions, parallel to the dark dust lanes, are found in the shell geometries and physical properties, probably related to strong density gradients in the studied region. We also find evidence that the ionizing flux emerging from η Car and the surrounding Homunculus nebula varies with polar angle. The high-velocity components in the wings of Hα are found to arise from expanding dust reflecting the η Car spectrum. © ESO, 2016.This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541Peer Reviewe
Machine-Readable Privacy Certificates for Services
Privacy-aware processing of personal data on the web of services requires
managing a number of issues arising both from the technical and the legal
domain. Several approaches have been proposed to matching privacy requirements
(on the clients side) and privacy guarantees (on the service provider side).
Still, the assurance of effective data protection (when possible) relies on
substantial human effort and exposes organizations to significant
(non-)compliance risks. In this paper we put forward the idea that a privacy
certification scheme producing and managing machine-readable artifacts in the
form of privacy certificates can play an important role towards the solution of
this problem. Digital privacy certificates represent the reasons why a privacy
property holds for a service and describe the privacy measures supporting it.
Also, privacy certificates can be used to automatically select services whose
certificates match the client policies (privacy requirements).
Our proposal relies on an evolution of the conceptual model developed in the
Assert4Soa project and on a certificate format specifically tailored to
represent privacy properties. To validate our approach, we present a worked-out
instance showing how privacy property Retention-based unlinkability can be
certified for a banking financial service.Comment: 20 pages, 6 figure
The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M8)
We present a spectroscopic study of the dynamics of the ionized and neutral
gas throughout the Lagoon nebula (M8), using VLT/FLAMES data from the Gaia-ESO
Survey. We explore the connections between the nebular gas and the stellar
population of the associated star cluster NGC6530. We characterize through
spectral fitting emission lines of H-alpha, [N II] and [S II] doublets, [O
III], and absorption lines of sodium D doublet, using data from the
FLAMES/Giraffe and UVES spectrographs, on more than 1000 sightlines towards the
entire face of the Lagoon nebula. Gas temperatures are derived from line-width
comparisons, densities from the [S II] doublet ratio, and ionization parameter
from H-alpha/[N II] ratio. Although doubly-peaked emission profiles are rarely
found, line asymmetries often imply multiple velocity components along the line
of sight. This is especially true for the sodium absorption, and for the [O
III] lines. Spatial maps for density and ionization are derived, and compared
to other known properties of the nebula and of its massive stars 9 Sgr,
Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing
flux. The detailed velocity fields across the nebula show several expanding
shells, related to the cluster NGC6530, the O stars 9 Sgr and Herschel 36, and
the massive protostar M8East-IR. The origins of kinematical expansion and
ionization of the NGC6530 shell appear to be different. We are able to put
constrains on the line-of-sight (relative or absolute) distances between some
of these objects and the molecular cloud. The large obscuring band running
through the middle of the nebula is being compressed by both sides, which might
explain its enhanced density. We also find an unexplained large-scale velocity
gradient across the entire nebula. At larger distances, the transition from
ionized to neutral gas is studied using the sodium lines.Comment: 26 pages, 31 figures, accepted on Astronomy and Astrophysics journa
The Chandra survey of the COSMOS field II: source detection and photometry
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program,
that covers the central contiguous ~0.92 deg^2 of the COSMOS field. C-COSMOS is
the result of a complex tiling, with every position being observed in up to six
overlapping pointings (four overlapping pointings in most of the central ~0.45
deg^2 area with the best exposure, and two overlapping pointings in most of the
surrounding area, covering an additional ~0.47 deg^2). Therefore, the full
exploitation of the C-COSMOS data requires a dedicated and accurate analysis
focused on three main issues: 1) maximizing the sensitivity when the PSF
changes strongly among different observations of the same source (from ~1
arcsec up to ~10 arcsec half power radius); 2) resolving close pairs; and 3)
obtaining the best source localization and count rate. We present here our
treatment of four key analysis items: source detection, localization,
photometry, and survey sensitivity. Our final procedure consists of a two step
procedure: (1) a wavelet detection algorithm, to find source candidates, (2) a
maximum likelihood Point Spread Function fitting algorithm to evaluate the
source count rates and the probability that each source candidate is a
fluctuation of the background. We discuss the main characteristics of this
procedure, that was the result of detailed comparisons between different
detection algorithms and photometry tools, calibrated with extensive and
dedicated simulations.Comment: Accepted for publication in The Astrophysical Journal Supplement
Serie
Measuring and explaining the diversity of voices and viewpoints in the news
News media can be considered to fulfil their democratic role as a “marketplace of
ideas” only if they present a diverse content that gives space to a wider range of ideas
and viewpoints. But how can content diversity be assessed? And what determines
actor and viewpoint diversity in the first place? By employing measurements of actor
and viewpoint diversity at the article and newspaper level, this study provides a
complete overview on the content diversity of immigration news, and it investigates
factors that have an impact on content diversity of immigration newspaper articles in
Belgium, Germany, Italy and the United Kingdom (2013-2014). The results of a
multilevel analysis indicate that both the articles’ size and the elite character of a
newspaper play a key role in enhancing news’ multiperspectivalness. Also, the
findings show that these two measurements of content diversity are different yet
related to each other
Multimodality in Pervasive Environment
Future pervasive environments are expected to immerse users in a consistent
world of probes, sensors and actuators. Multimodal interfaces combined
with social computing interactions and high-performance networking can foster a
new generation of pervasive environments. However, much work is still needed to
harness the full potential of multimodal interaction. In this paper we discuss some
short-term research goals, including advanced techniques for joining and correlating
multiple data flows, each with its own approximations and uncertainty models.
Also, we discuss some longer term objectives, like providing users with a mental
model of their own multimodal "aura", enabling them to collaborate with the network
infrastructure toward inter-modal correlation of multimodal inputs, much in
the same way as the human brain extracts a single self-conscious experience from
multiple sensorial data flows
The Gaia-ESO Survey: Tracing interstellar extinction
Large spectroscopic surveys have enabled in the recent years the computation
of three-dimensional interstellar extinction maps thanks to accurate stellar
atmospheric parameters and line-of-sight distances. Such maps are complementary
to 3D maps extracted from photometry, allowing a more thorough study of the
dust properties. Our goal is to use the high-resolution spectroscopic survey
Gaia-ESO in order to obtain with a good distance resolution the interstellar
extinction and its dependency as a function of the environment and the
Galactocentric position. We use the stellar atmospheric parameters of more than
5000 stars, obtained from the Gaia-ESO survey second internal data release, and
combine them with optical (SDSS) and near-infrared (VISTA) photometry as well
as different sets of theoretical stellar isochrones, in order to calculate
line-of-sight extinction and distances. The extinction coefficients are then
compared with the literature to discuss their dependancy on the stellar
parameters and position in the Galaxy. Within the errors of our method, our
work does not show that there is any dependence of the interstellar extinction
coefficient on the atmospheric parameters of the stars. We do not find any
evidence of the variation of E(J-H)/E(J-K) with the angle from the Galactic
centre nor with Galactocentric distance. This suggests that we are dealing with
a uniform extinction law in the SDSS ugriz bands and the near-IR JHKs bands.
Therefore, extinction maps using mean colour-excesses and assuming a constant
extinction coefficient can be used without introducing any systematic errors.Comment: 13 pages, 14 figures, 1 Appendix accepted for publication in
Astronomy&Astrophysic
Aclimatização e crescimento de plântulas de mirtileiro 'Climax' micropropagadas em função do substrato e da cobertura plástica.
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