14,752 research outputs found
Optical Surface Photometry of a Sample of Disk Galaxies. II Structural Components
This work presents the structural decomposition of a sample of 11 disk
galaxies, which span a range of different morphological types. The U, B, V, R,
and I photometric information given in Paper I (color and color-index images
and luminosity, ellipticity, and position-angle profiles) has been used to
decide what types of components form the galaxies before carrying out the
decomposition. We find and model such components as bulges, disks, bars, lenses
and rings.Comment: 14 figures. Accepted for publication in A&
Enacting Productive Dialogue: Addressing the Challenge that Non-Human Cognition Poses to Collaborations Between Enactivism and Heideggerian Phenomenology
This chapter uses one particular proposal for interdisciplinary collaboration – in this case, between early Heideggerian phenomenology and enactivist cognitive science – as an example of how such partnerships may confront and negotiate tensions between the perspectives they bring together. The discussion begins by summarising some of the intersections that render Heideggerian and enactivist thought promising interlocutors for each other. It then moves on to explore how Heideggerian enactivism could respond to the challenge of reconciling the significant differences in the ways that each discourse seeks to apply the structures it claims to uncover
Machine learning techniques to select Be star candidates. An application in the OGLE-IV Gaia south ecliptic pole field
Statistical pattern recognition methods have provided competitive solutions
for variable star classification at a relatively low computational cost. In
order to perform supervised classification, a set of features is proposed and
used to train an automatic classification system. Quantities related to the
magnitude density of the light curves and their Fourier coefficients have been
chosen as features in previous studies. However, some of these features are not
robust to the presence of outliers and the calculation of Fourier coefficients
is computationally expensive for large data sets. We propose and evaluate the
performance of a new robust set of features using supervised classifiers in
order to look for new Be star candidates in the OGLE-IV Gaia south ecliptic
pole field. We calculated the proposed set of features on six types of variable
stars and on a set of Be star candidates reported in the literature. We
evaluated the performance of these features using classification trees and
random forests along with K-nearest neighbours, support vector machines, and
gradient boosted trees methods. We tuned the classifiers with a 10-fold
cross-validation and grid search. We validated the performance of the best
classifier on a set of OGLE-IV light curves and applied this to find new Be
star candidates. The random forest classifier outperformed the others. By using
the random forest classifier and colour criteria we found 50 Be star candidates
in the direction of the Gaia south ecliptic pole field, four of which have
infrared colours consistent with Herbig Ae/Be stars. Supervised methods are
very useful in order to obtain preliminary samples of variable stars extracted
from large databases. As usual, the stars classified as Be stars candidates
must be checked for the colours and spectroscopic characteristics expected for
them
Emission Line Galaxies and Active Galactic Nuclei in WINGS clusters
We present the analysis of the emission line galaxies members of 46 low
redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy
cluster Survey, Fasano et al. 2006). Emission line galaxies were identified
following criteria that are meant to minimize biases against non-star forming
galaxies and classified employing diagnostic diagrams. We have examined the
emission line properties and frequencies of star forming galaxies, transition
objects and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified
galaxies with emission lines, and quiescent galaxies with no detectable line
emission. A deficit of emission line galaxies in the cluster environment is
indicated by both a lower frequency with respect to control samples, and by a
systematically lower Balmer emission line equivalent width and luminosity (up
to one order of magnitude in equivalent width with respect to control samples
for transition objects) that implies a lower amount of ionised gas per unit
mass and a lower star formation rate if the source is classified as Hii region.
A sizable population of transition objects and of low-luminosity LINERs
(approx. 10 - 20% of all emission line galaxies) is detected among WINGS
cluster galaxies. With respect to Hii sources they are a factor of approx. 1.5
more frequent than (or at least as frequent as) in control samples. Transition
objects and LINERs in cluster are most affected in terms of line equivalent
width by the environment and appear predominantly consistent with "retired"
galaxies. Shock heating can be a possible gas excitation mechanism able to
account for observed line ratios. Specific to the cluster environment, we
suggest interaction between atomic and molecular gas and the intracluster
medium as a possible physical cause of line-emitting shocks.Comment: Astronomy and Astrophysics, accepte
Disentangling the role of management practices on ecosystem services delivery in Mediterranean silvopastoral systems: Synergies and trade-offs through expert-based assessment
Silvopastoral systems (SPS) emerge with a renewal interest in the Mediterranean for their promotion of multifunctionality through a variety of ecosystem services (ES). However, the understanding of how combined forestry and pastoral practices affect the ES delivery as well as the synergies and trade-off dynamics amongst them is still very limited. We applied the structured expert consultation Delphi method to assess the medium-term effect of relevant silvopastoral management practices (SMP) on the delivery of provision, regulation and maintenance and cultural ES in Mediterranean mid-mountain SPS in Spain. The deliberation process entailed two rounds and the Delphi panel was finally formed by 69 experts covering a broad spectrum of background and expertise. Results show that some practices, such as silvicultural treatments (e.g., thinning or coppice selection), play a multifunctional role contributing to ES delivery in bundles while some trade-offs are also identified between SMP, such as free animal grazing, and the provision of some ES. Synergies are also found between ES, such as livestock production and recreational hunting and between timber production and carbon sequestration, whereas possible trade-offs were particularly relevant between wildfire prevention and carbon sequestration. These findings can support decision-making processes towards sustainable and multifunctional silvopastoral management in the northern Mediterranean basin
Two research avenues for future mate-choice copying studies: a comment on Davies et al
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