188 research outputs found
The ARAUCARIA project: Grid-Based Quantitative Spectroscopic Study of Massive Blue Stars in NGC55
The quantitative study of the physical properties and chemical abundances of
large samples of massive blue stars at different metallicities is a powerful
tool to understand the nature and evolution of these objects. Their analysis
beyond the Milky Way is challenging, nonetheless it is doable and the best way
to investigate their behavior in different environments. Fulfilling this task
in an objective way requires the implementation of automatic analysis
techniques that can perform the analyses systematically, minimizing at the same
time any possible bias.
As part of the ARAUCARIA project we carry out the first quantitative
spectroscopic analysis of a sample of 12 B-type supergiants in the galaxy NGC55
at 1.94 Mpc away. By applying the methodology developed in this work, we derive
their stellar parameters, chemical abundances and provide a characterization of
the present-day metallicity of their host galaxy.
Based on the characteristics of the stellar atmosphere/line formation code
FASTWIND, we designed and created a grid of models for the analysis of massive
blue supergiant stars. Along with this new grid, we implemented a spectral
analysis algorithm. Both tools were specially developed to perform fully
consistent quantitative spectroscopic analyses of low spectral resolution of
B-type supergiants in a fast and objective way.
We present the main characteristics of our FASTWIND model grid and perform a
number of tests to investigate the reliability of our methodology. The
automatic tool is applied afterward to a sample of 12 B-type supergiant stars
in NGC55, deriving the stellar parameters and abundances. The results indicate
that our stars are part of a young population evolving towards a red supergiant
phase. The derived chemical composition hints to an average metallicity similar
to the one of the Large Magellanic Cloud, with no indication of a spatial trend
across the galaxy.Comment: 19 pages, 12 figures and 9 tables. Accpeted for publication in A&
El hiperparasitismo dificulta el control biológico de Aphis spiraecola en clementinos
Aphis spiraecola Patch. (Hemiptera: Aphididae) es actualmente una plaga
clave en clementinos. A pesar de que este pulgón tiene un rico complejo de enemigos
naturales perteneciente a diversos órdenes de insectos, no se ha identificado
ningún parasitoide capaz de regular sus poblaciones ni disminuir sus
daños. Trabajos recientes desarrollados en nuestro grupo de investigación han
arrojado luz sobre algunas de las razones que explican la baja eficacia de los
parasitoides en el control de A. spiraecola y que resumimos a continuación. Por
una parte, tan solo se encuentra un parasitoide primario, Binodoxys angelicae
Haliday (Hymenoptera: Braconidae), el cual presenta una tasa de parasitismo
muy baja sobre A. spiraecola. Por otra parte, existe un abundante y diverso
complejo de hiperparasitoides que influye negativamente sobre las poblaciones
de B. angelicae. La presencia de este complejo de hiperparasitoides en la regulación
natural de las poblaciones de A. spiraecola es una de las principales causas
que explica la baja eficacia de los parasitoides. Por lo tanto, a partir de estos
resultados, recomendaríamos que los futuros programas de control biológico de
A. spiraecola en clementinos se centraran en el uso de depredadores en lugar
de parasitoidesEsta investigación fue financiada por
Ministerio de Ciencia e Innovación
(AGL2011-30538-C03) y la Conselleria
d'Agricultura, Pesca i Alimentació
de la Generalitat Valenciana
The Araucaria Project: the Local Group Galaxy WLM--Distance and metallicity from quantitative spectroscopy of blue Supergiants
The quantitative analysis of low resolution spectra of A and B supergiants is
used to determine a distance modulus of 24.99 +/- 0.10 mag (995 +/- 46 Kpc) to
the Local Group galaxy WLM. The analysis yields stellar effective temperatures
and gravities, which provide a distance through the Flux weighted
Gravity--Luminosity Relationship (FGLR). Our distance is 0.07 mag larger than
the most recent results based on Cepheids and the tip of the RGB. This
difference is within the 1-sigma overlap of the typical uncertainties quoted in
these photometric investigations. In addition, non-LTE spectral synthesis of
the rich metal line spectra (mostly iron, chromium and titanium) of the A
supergiants is carried out, which allows the determination of stellar
metallicities. An average metallicity of -0.87 +/- 0.06 dex with respect to
solar metallicity is found.Comment: 46 pages, 14 figures (2 low resolution color figures). Accepted for
publication by Ap
The ARAUCARIA Project: VLT-FORS spectroscopy of blue supergiants in NGC 3109 - Classifications, first abundances and kinematics
We have obtained multi-object spectroscopy of luminous blue supergiants in
NGC 3109, a galaxy at the periphery of the Local Group at ~1.3 Mpc. We present
a detailed catalog including finding charts, V and I magnitudes, spectral
classifications, and stellar radial velocities. The radial velocities are seen
to trace the rotation curves obtained from studies of the HI gas. From
quantitative analysis of eight B-type supergiants we find a mean oxygen
abundance of 12+log(O/H) = 7.76 +/-0.07 (1-sigma systematic uncertainty), with
a median result of 7.8. Given its distance, we highlight NGC 3109 as the ideal
example of a low metallicity, dark-matter dominated, dwarf galaxy for
observations with the next generation of ground-based extremely large
telescopes (ELTs).Comment: 42 pages, 19 figures (most reduced in size). Accepted for publication
in ApJ. A copy with full res. & embedded figures is at
http://www.roe.ac.uk/~cje/ngc3109.ps.g
An Analysis of STIS HST UV Spectra of M33 early B Supergiants
We present terminal velocities of M33 B-supergiants, obtained from STIS HST
spectra as part of our programme to investigate the Wind Momentum -- Luminosity
Relationship (WLR) in the Local Group. Terminal velocities are derived from
their NV, CIV, and SiIV resonance lines in UV spectra. Comparing with IUE
spectra of Galactic B-supergiants we found evidence of low metallicity in three
of our objects. %%The terminal velocities are found to be consistent with the
%%values found for Galactic stars, except for B-133. For this The terminal
velocities are consistent with the corresponding values of Galactic stars,
except for B-133. For this star we find a very large vterm and a red SiIV
component deeper than the blue one, that might be an indication of binarity.
The average ratio between terminal and turbulent wind velocities is 0.25, well
above the value found for Galactic stars.Comment: 9 pages, 6 figure
On the alpha-element gradients of the Galactic thin disk using Cepheids
We present new homogeneous measurements of Na, Al and three alpha-elements
(Mg, Si, Ca) for 75 Galactic Cepheids. The abundances are based on high
spectral resolution (R ~ 38,000) and high signal-to-noise ratio (S/N ~ 50-300)
spectra collected with UVES at ESO VLT. The current measurements were
complemented with Cepheid abundances either provided by our group (75) or
available in the literature, for a total of 439 Galactic Cepheids. Special
attention was given in providing a homogeneous abundance scale for these five
elements plus iron (Genovali et al. 2013, 2014). In addition, accurate
Galactocentric distances (RG) based on near-infrared photometry are also
available for all the Cepheids in the sample (Genovali et al. 2014). They cover
a large fraction of the Galactic thin disk (4.1 <= RG <= 18.4 kpc). We found
that the above five elements display well defined linear radial gradients and
modest standard deviations over the entire range of RG. Moreover, the
[element/Fe] abundance ratios are constant across the entire thin disk; only
the Ca radial distribution shows marginal evidence of a positive slope. These
results indicate that the chemical enrichment history of iron and of the quoted
five elements has been quite similar across the four quadrants of the Galactic
thin disk. The [element/Fe] ratios are also constant over the entire period
range. This empirical evidence indicates that the chemical enrichment of
Galactic Cepheids has also been very homogenous during the range in age that
they cover (~10-300 Myr). Once again, [Ca/Fe] vs. log(P) shows a (negative)
gradient, being underabundant among youngest Cepheids. Finally, we also found
that Cepheid abundances agree quite well with similar abundances for thin and
thick disk dwarf stars and they follow the typical Mg-Al and Na-O correlations.Comment: 25 pages, 11 figures, 5 table
On the performance of SQL scalable systems on Kubernetes: a comparative study
The popularization of Hadoop as the the-facto standard platform for data analytics in the context of Big Data applications
has led to the upsurge of SQL-on-Hadoop systems, which provide scalable query execution engines allowing the use of
SQL queries on data stored in HDFS. In this context, Kubernetes appears as the leading choice to simplify the deployment
and scaling of containerized applications; however, there is a lack of studies about the performance of SQL-on-Hadoop
systems deployed on Kubernetes, and this is the gap we intend to fill in this paper. We present an experimental study
involving four representative SQL scalable platforms: Apache Drill, Apache Hive, Apache Spark SQL and Trino. Concretely, we analyze the performance of these systems when they are deployed on a Hadoop cluster with Kubernetes by
using the TPC-H benchmark. The results of our study can help practitioners and users about what they can expect in terms
of performance if they plan to use the advantages of Kubernetes to deploy applications using the analyzed SQL scalable
platforms.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Funding for open access charge: Universidad de Málaga / CBUA. This work has been partially funded by the Spanish Ministry of Science and Innovation via Grant PID2020-112540RB-C41 (AEI/FEDER, UE), Andalusian PAIDI program with grant P18-RT-2799, and by project ”Evolución y desarrollo de la plataforma DOP de Big Data” (702C2000044) under Andalusian “Programa de Apoyo a la I+D+i Empresarial”
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