246 research outputs found
Analysis of the circumstellar environment of the B[e] star HD 45677 (FS CMa)
We studied the circumstellar environment of the B[e] star HD 45677 through
the analysis of the emission lines from ionized metals. We used the statistical
approach of the self absorption curve method (SAC) to derive physical
parameters of the line emitting region. The Fe II and Cr II double-peaked
emission line structure is explained by the presence of a thin absorption
component red shifted by ~3 km/s. This absorption component can be interpreted
geometricaly as being due to infalling material perpendicularly to the disk
seen nearly pole-on, as indicated by the emission line structure. The Cr II and
Fe II emission lines have a complex structure with two (narrow and broad)
components, of 45 and 180 km/s FWHM for the permitted lines and 25 and 100 km/s
FWHM for the forbidden ones, respectively. We argue that the narrow components
are principaly emitted by an optically thin disk seen nearly pole-on, in a
region whose minimum radius is estimated to be 4 10^12 cm, while the broad ones
are formed in a disk-linked wind.Comment: 14 pages, submitted to Astronomy and Astrophysic
Inférer les capacités de dispersion et de migration : de l'échelle locale à l'échelle globale -
Dans le contexte actuel de changements climatiques, il est important de pouvoir connaître au mieux les capacités de migration et de déplacement des espèces. Jusqu'à présent, on utilisait des approches empiriques pour évaluer cette dynamique. Aujourd'hui, la science devient plus prédictive, utilisant des approches basées sur des modèles intégrateurs, comme celui présenté ici, le noyau de dispersion, qui décrit la répartition spatiale des graines dispersées à partir d'une source
The Stellar Composition of the Star Formation Region CMa R1 -- III. A new outburst of the Be star component in Z CMa
We report on a recent event in which, after more than a decade of slowly
fading, the visual brightness of the massive young binary Z CMa suddenly
started to rise by about 1 magnitude in December 1999, followed by a rapid
decline to its previous brightness over the next six months. This behaviour is
similar to that exhibited by this system around its eruption in February 1987.
A comparison of the intrinsic luminosities of the system with recent
evolutionary calculations shows that Z CMa may consist of a 16 M_sun B0 IIIe
primary star and a ~ 3 M_sun FUOr secondary with a common age of ~ 3 x 10^5 yr.
We also compare new high-resolution spectra obtained in Jan. and Feb. 2000,
during the recent rise in brightness, with archive data from 1991 and 1996. The
spectra are rich in emission lines, which originate from the envelope of the
early B-type primary star. The strength of these emission lines increased
strongly with the brightness of Z CMa. We interpret the collected spectral data
in terms of an accretion disc with atmosphere around the Herbig B0e component
of Z CMa, which has expanded during the outbursts of 1987 and 2000. A high
resolution profile of the 6300 A [O I] emission line, obtained by us in March
2002 shows an increase in flux and a prominent blue shoulder to the feature
extending to ~ -700 km/s, which was much fainter in the pre-outburst spectra.
We propose that this change in profile is a result of a strong change in the
collimation of a jet, as a result of the outburst at the start of this century.Comment: 22 pages, 12 figures, accepted for publication in MNRA
Looking for local adaptation:Convergent microevolution in aleppo pine (pinus halepensis)
Finding outlier loci underlying local adaptation is challenging and is best approached by suitable sampling design and rigorous method selection. In this study, we aimed to detect outlier loci (single nucleotide polymorphisms, SNPs) at the local scale by using Aleppo pine (Pinus halepensis), a drought resistant conifer that has colonized many habitats in the Mediterranean Basin, as the model species. We used a nested sampling approach that considered replicated altitudinal gradients for three contrasting sites. We genotyped samples at 294 SNPs located in genomic regions selected to maximize outlier detection. We then applied three different statistical methodologies-Two Bayesian outlier methods and one latent factor principal component method-To identify outlier loci. No SNP was an outlier for all three methods, while eight SNPs were detected by at least two methods and 17 were detected only by one method. From the intersection of outlier SNPs, only one presented an allelic frequency pattern associated with the elevational gradient across the three sites. In a context of multiple populations under similar selective pressures, our results underline the need for careful examination of outliers detected in genomic scans before considering them as candidates for convergent adaptation
A Spitzer Space Telescope far-infrared spectral atlas of compact sources in the Magellanic Clouds. I. The Large Magellanic Cloud
[abridged] We present 52-93 micron spectra obtained with Spitzer in the
MIPS-SED mode, of a representative sample of luminous compact far-IR sources in
the LMC. These include carbon stars, OH/IR AGB stars, post-AGB objects and PNe,
RCrB-type star HV2671, OH/IR red supergiants WOHG064 and IRAS05280-6910, B[e]
stars IRAS04530-6916, R66 and R126, Wolf-Rayet star Brey3a, Luminous Blue
Variable R71, supernova remnant N49, a large number of young stellar objects,
compact HII regions and molecular cores, and a background galaxy (z~0.175). We
use the spectra to constrain the presence and temperature of cold dust and the
excitation conditions and shocks within the neutral and ionized gas, in the
circumstellar environments and interfaces with the surrounding ISM. Evolved
stars, including LBV R71, lack cold dust except in some cases where we argue
that this is swept-up ISM. This leads to an estimate of the duration of the
prolific dust-producing phase ("superwind") of several thousand years for both
RSGs and massive AGB stars, with a similar fractional mass loss experienced
despite the different masses. We tentatively detect line emission from neutral
oxygen in the extreme RSG WOHG064, with implications for the wind driving. In
N49, the shock between the supernova ejecta and ISM is revealed by its strong
[OI] 63-micron emission and possibly water vapour; we estimate that 0.2 Msun of
ISM dust was swept up. Some of the compact HII regions display pronounced
[OIII] 88-micron emission. The efficiency of photo-electric heating in the
interfaces of ionized gas and molecular clouds is estimated at 0.1-0.3%. We
confirm earlier indications of a low nitrogen content in the LMC. Evidence for
solid state emission features is found in both young and evolved object; some
of the YSOs are found to contain crystalline water ice.Comment: Accepted for publication in The Astronomical Journal. This paper
accompanies the Summer 2009 SAGE-Spec release of 48 MIPS-SED spectra, but
uses improved spectrum extraction. (Fig. 2 reduced resolution because of
arXiv limit.
Drought-Adaptation Potential in Fagus sylvatica: Linking Moisture Availability with Genetic Diversity and Dendrochronology
<div><h3>Background</h3><p>Microevolution is essential for species persistence especially under anticipated climate change scenarios. Species distribution projection models suggested that the dominant tree species of lowland forests in Switzerland, European beech (<em>Fagus sylvatica</em> L.), might disappear from most areas due to expected longer dry periods. However, if genotypes at the moisture boundary of the species climatic envelope are adapted to lower moisture availability, they can serve as seed source for the continuation of beech forests under changing climates.</p> <h3>Methodology/Principal Findings</h3><p>With an AFLP genome scan approach, we studied neutral and potentially adaptive genetic variation in <em>Fagus sylvatica</em> in three regions containing a dry and a mesic site each (<em>n</em><sub>ind.</sub> = 241, <em>n</em><sub>markers</sub> = 517). We linked this dataset with dendrochronological growth measures and local moisture availabilities based on precipitation and soil characteristics. Genetic diversity decreased slightly at dry sites. Overall genetic differentiation was low (<em>F</em><sub>st</sub> = 0.028) and Bayesian cluster analysis grouped all populations together suggesting high (historical) gene flow. The Bayesian outlier analyses indicated 13 markers with three markers differing between all dry and mesic sites and the others between the contrasting sites within individual regions. A total of 41 markers, including seven outlier loci, changed their frequency with local moisture availability. Tree height and median basal growth increments were reduced at dry sites, but marker presence/absence was not related to dendrochronological characteristics.</p> <h3>Conclusion and Their Significance</h3><p>The outlier alleles and the makers with changing frequencies in relation to moisture availability indicate microevolutionary processes occurring within short geographic distances. The general genetic similarity among sites suggests that ‘preadaptive’ genes can easily spread across the landscape. Yet, due to the long live span of trees, fostering saplings originating from dry sites and grown within mesic sites might increase resistance of beech forests during the anticipated longer dry periods.</p> </div
Pollen and seed flow patterns of Carapa guianensis Aublet. (Meliaceae) in two types of Amazonian forest
Paternity analysis of pollen-mediated gene flow for Fraxinus excelsior L. in a chronically fragmented landscape
Paternity analysis based on microsatellite marker genotyping was used to infer contemporary genetic connectivity by pollen of three population remnants of the wind-pollinated, wind-dispersed tree Fraxinus excelsior, in a deforested Scottish landscape. By deterministically accounting for genotyping error and comparing a range of assignment methods, individual-based paternity assignments were used to derive population-level estimates of gene flow. Pollen immigration into a 300ha landscape represents between 43% and 68% of effective pollination, mostly depending on assignment method. Individual male reproductive success is unequal, with 31 of 48 trees fertilising one seed or more, but only three trees fertilising more than ten seeds. Spatial analysis suggests a fat-tailed pollen dispersal curve with 85% of detected pollination occurring within 100m, and 15% spreading between 300m and 1900m from the source. Identification of immigrating pollen sourced from two neighbouring remnants indicates further effective dispersal at 2900m. Pollen exchange among remnants is driven by population size rather than geographic distance, with larger remnants acting predominantly as pollen donors, and smaller remnants as pollen recipients. Enhanced wind dispersal of pollen in a barren landscape ensures that the seed produced within the catchment includes genetic material from a wide geographic area. However, gene flow estimates based on analysis of non-dispersed seeds were shown to underestimate realised gene immigration into the remnants by a factor of two suggesting that predictive landscape conservation requires integrated estimates of post-recruitment gene flow occurring via both pollen and seed
Spatial and temporal population genetic variation and structure of Nothotsuga longibracteata (Pinaceae), a relic conifer species endemic to subtropical China
El laberinto de la autonomía indígena en el Ecuador: las circunscripciones territoriales indígenas en la Amazonía Central, 2010-2012
¿Cuáles son los avatares y desencuentros presentes en el proceso de constitución de las
Circunscripciones Territoriales Indígenas (CTIs) en relación a la vigencia del derecho a la
autodeterminación y autogestión territorial de las nacionalidades indígenas en el Ecuador? Para
responder a dicha interrogante, el artículo considera el reconocimiento al derecho a la
autonomía y autodeterminación de las nacionalidades y pueblos indígenas en Ecuador.
Posteriormente, analiza el alcance de los procedimientos establecidos tanto en la Constitución
Política como en el Código Orgánico de Ordenamiento Territorial y Descentralización
(COOTAD), y su alcance potencial en generar un nuevo tipo de institucionalidad y una nueva
organización territorial en el marco de la definición del Estado plurinacional Ecuatoriano. Esta
contribución analiza además el proceso derivado de una hoja de ruta acordada entre el Estado y
las nacionalidades amazónicas en el periodo comprendido entre 2010 y 2012, y analiza las
diferentes acciones desplegadas desde entonces, enfatizando en los avances y contradicciones,
tanto a lo interno del movimiento indígena como en su relación con otras instancias estatales
centrales y locales. Se examinan los desencuentros y tensiones a lo interno del aparato Estatal y
los sectores mestizos, que no se plantean ningún reparo al momento de obstaculizar los avances
del proceso. El artículo analiza el desafío de crear las CTIs en el territorio de los Kichwa de las
provincias de Napo y Orellana y en los territorios Kichwa y Achuar en la provincia de Pastaza,
en la Amazonía central. Finalmente, el texto puntualiza críticamente algunas de las perspectivas
y dilemas que dicho proceso plantea al futuro de la relación Estado-nacionalidades indígenas y
al proceso de construcción del Estado plurinacional e intercultural en Ecuador
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