366 research outputs found
Estudio comparativo de la incidencia de la Directiva Seveso por ámbitos territoriales. El caso particular de la región de Andalucía
Desde la entrada en vigor de la primera Directiva Seveso en Europa, el concepto de prevención de accidentes graves por sustancias peligrosas ha evolucionado de forma diferente dependiendo de la transposición particular de cada Estado Miembro a su propio ordenamiento jurídico. Adicionalmente, cada región con competencias en materia de seguridad industrial o protección civil ha contribuido, aún más, a la dispersión normativa existente lo que no favorece una regulación de forma universal o estándar. Uno de los aspectos normativos merecedor de una profunda actualización ante la próxima puesta en vigor de la nueva Directiva Seveso III, es aquel que incide sobre las zonas de influencia donde existen establecimientos industriales afectados por la Directiva. En el presente trabajo se va a realizar una evolución histórica de la afectación por ámbito geográfico en la década 2002-2012. El análisis territorial comienza con la distribución geográfica de laafectación en la Unión Europea. De manera similar, se vadescendiendo geográficamente hasta estudiar el estadoespañol y, finalmente, alcanzará a la región de Andalucíadonde, se profundizará aún más, hasta alcanzar el nivelterritorial de provincias y, municipios. Del análisis se deducenunas primeras conclusiones particulares relativas tanto a las concentraciones de establecimientos Seveso y de los sectores industriales más significativos cubiertos por dicha normativa
A photoionization model of the spatial distribution of the optical and mid-IR properties in NGC595
We present a set of photoionization models that reproduce simultaneously the
observed optical and mid-infrared spatial distribution of the HII region NGC595
in the disk of M33 using the code CLOUDY. Both optical (PMAS-Integral Field
Spectroscopy) and mid-infrared (8 mi and 24 mi bands from Spitzer) data provide
enough spatial resolution to model in a novel approach the inner structure of
the HII region. We define a set of elliptical annular regions around the
central ionizing cluster with an uniformity in their observed properties and
consider each annulus as an independent thin shell structure. For the first
time our models fit the relative surface brightness profiles in both the
optical (Halpha, [OII], [OIII]) and the mid-infrared emissions (8 mi and 24
mi), under the assumption of a uniform metallicity (12+log(O/H) = 8.45; Esteban
et al. 2009) and an age for the stellar cluster of 4.5 Myr (Malumuth et al.
1996). Our models also reproduce the observed uniformity of the R23 parameter
and the increase of the [OII]/[OIII] ratio due to the decrease of the
ionization parameter. The variation of the Halpha profile is explained in terms
of the differences of the occupied volume (the product of filling factor and
total volume of the shell) in a matter-bounded geometry, which also allows to
reproduce the observed pattern of the extinction. The 8 mi/24 mi ratio is low
(ranging between 0.04 and 0.4) because it is dominated by the surviving of
small dust grains in the HII region, while the PAHs emit more weakly because
they cannot be formed in these thin HII gas shells. The ratio is also well
fitted in our models by assuming a dust-to-gas ratio in each annulus compatible
with the integrated estimate for the whole HII region after the 70 mi, and 160
mi Spitzer observations.Comment: Accepted for publication in MNRAS, 9 pages, 17 figure
On emission-line spectra obtained from evolutionary synthesis models I. Dispersion in the ionising flux and Lowest Luminosity Limits
(abriged) Stellar clusters with the same general physical properties (e.g.,
total mass, age, and star-formation mode) may have very different stellar mass
spectra due to the incomplete sampling of the underlying mass function; such
differences are especially relevant in the high-mass tail due to the smaller
absolute number of massive stars. The dispersion in the number of massive stars
also produces a dispersion in the properties of the corresponding ionising
spectra. In this paper, we lay the bases for the future analysis of this effect
by evaluating the dispersion in the ionising fluxes of synthetic spectra. As an
important consequence, we found that the intensities of synthetic fluxes at
different ionisation edges are strongly correlated, a fact suggesting that no
additional dispersion will result from the inclusion of sampling effects in the
analysis of diagnostic diagrams; this is true for HII regions on all scales.
Additionally, we find convincing suggestions that the He II lines are strongly
affected by sampling, and so cannot be used to constrain the evolutionary
status of stellar clusters. We also establish the range of applicability of
synthesis models set by the Lowest Luminosity Limit for the ionising flux, that
is the lowest limit in cluster mass for which synthesis models can be applied
to predict ionising spectra. This limit marks the boundary between the
situations in which the ionising flux is better modeled with a single star as
opposed to a star cluster; this boundary depends on the metallicity and age,
ranging from 10^3 to more than 10^6 Mo. As a consequence, synthesis models
should not be used to try to account for the properties of clusters with
smaller masses.Comment: Replaced with accepted versio
Extremely Metal-Poor Galaxies: The HI Content
Extremely metal-poor (XMP) galaxies are chemically, and possibly dynamically,
primordial objects in the local Universe. Our objective is to characterize the
HI content of the XMP galaxies as a class, using as a reference the list of 140
known local XMPs compiled by Morales-Luis et al. (2011). We have observed 29
XMPs, which had not been observed before at 21 cm, using the Effelsberg radio
telescope. This information was complemented with HI data published in
literature for a further 53 XMPs. In addition, optical data from the literature
provided morphologies, stellar masses, star-formation rates and metallicities.
Effelsberg HI integrated flux densities are between 1 and 15 Jy km/s, while
line widths are between 20 and 120 km/s. HI integrated flux densities and line
widths from literature are in the range 0.1 - 200 Jy km/s and 15 - 150 km/s,
respectively. Of the 10 new Effelsberg detections, two sources show an
asymmetric double-horn profile, while the remaining sources show either
asymmetric (7 sources) or symmetric (1 source) single-peak 21 cm line profiles.
An asymmetry in the HI line profile is systematically accompanied by an
asymmetry in the optical morphology. Typically, the g-band stellar
mass-to-light ratios are ~0.1, whereas the HI gas mass-to-light ratios may be
up to 2 orders of magnitude larger. Moreover, HI gas-to-stellar mass ratios
fall typically between 10 and 20, denoting that XMPs are extremely gas-rich. We
find an anti-correlation between the HI gas mass-to-light ratio and the
luminosity, whereby fainter XMPs are more gas-rich than brighter XMPs,
suggesting that brighter sources have converted a larger fraction of their HI
gas into stars. The dynamical masses inferred from the HI line widths imply
that the stellar mass does not exceed 5% of the dynamical mass, while the
\ion{H}{i} mass constitutes between 20 and 60% of the dynamical mass.
(abridged)Comment: 30 pages, accepted for A&
On faint companions in the close environment of star-forming dwarf galaxies. Possible external star formation triggers ?
We have searched for companion galaxies in the close environment of 98
star-forming dwarf galaxies (SFDGs) from field and low density environments,
using the NASA Extragalactic Database. Most of the companions are dwarf
galaxies which due to observational selection effects were previously
disregarded in environmental studies of SFDGs. A subsample at low redshift,
cz<2000 km/s, was chosen to partially eliminate the observational bias against
distant dwarf companions. We find companion candidates for approximately 30% of
the objects within a projected linear separation s_p<100 kpc and a redshift
difference (Delta cz)<500 km/s. The limited completeness of the available data
sets, together with the non-negligible frequency of HI clouds in the vicinity
of SFDGs indicated by recent radio surveys, suggest that a considerably larger
fraction of these galaxies may be accompanied by low-mass systems. This casts
doubt on the hypothesis that the majority of them can be considered truly
isolated. The velocity differences between companion candidates and sample
SFDGs amount typically to (Delta cz)<250 km/s, and show a rising distribution
towards lower (Delta cz). This is similarly found for dwarf satellites of
spiral galaxies, suggesting a physical association between the companion
candidates and the sample SFDGs. SFDGs with a close companion do not show
significant differences in their Hbeta equivalent widths and B-V colours as
compared to isolated ones. However, the available data do not allow us to rule
out that interactions with close dwarf companions can influence the star
formation activity in SFDGs.Comment: 9 pages, 5 figures, to appear in A&A; also available at
http://www.uni-sw.gwdg.de/~knoeske/PUB_LIST/sfdg_comps.ps.g
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