4,906 research outputs found
Near infrared observations of quasars with extended ionized envelopes
We have observed a sample of 15 and 8 quasars with redshifts between 0.11 and
0.87 (mean value 0.38) in the J and K' bands respectively. Eleven of the
quasars were previously known to be associated with extended emission line
regions. After deconvolution of the image, substraction of the PSF when
possible, and identification of companions with the help of HST archive images
when available, extensions are seen for at least eleven quasars. However,
average profiles are different from that of the PSF in only four objects, for
which a good fit is obtained with an law, suggesting that the
underlying galaxies are ellipticals. Redshifts were available in the literature
for surrounding objects in five quasar fields. For these objects, one to five
companion galaxies were found. One quasar even belongs to a richness class 1
cluster. Most other quasars in our sample have nearby galaxies in projection
which may also be companions. Environmental effects are therefore probably
important to account for the properties of these objects.Comment: Accepted for publication in A&A
Hexagonal Tilings: Tutte Uniqueness
We develop the necessary machinery in order to prove that hexagonal tilings
are uniquely determined by their Tutte polynomial, showing as an example how to
apply this technique to the toroidal hexagonal tiling.Comment: 12 figure
Integral field spectroscopy of the radio galaxy 3C 171
We have performed integral field spectroscopy of the radio galaxy 3C 171
(redshift z=0.238) with the TIGER instrument at the Canada France Hawaii
telescope in the Hbeta-[OIII]4959-5007 wavelength region. We present the
reconstructed Hbeta and [OIII] images and compare them to the HST and radio
maps. We discuss the variations of the [OIII]/Hbeta line ratio throughout the
nebulosity. We also analyze the velocity field in detail, in particular the
presence of several components. We find that the kinematics derived with
emission lines in the central region (inside 1 arcsec) are compatible with a
disk-like rotation of low amplitude (50 km/s). The continuum surface brightness
profile follows an r^{1/4} law, suggesting that the underlying galaxy is an
elliptical with an effective radius of 15 kpc.
We have fit two components in the region centered 2.7 arcsec to the West and
of extension 3 arcsec^2. We find that the blueshifted component is an extension
of the central part, whereas the second one is redshifted by 600 km/s. In both
components, line ratios and FWHM are compatible with the presence of shocks
induced by jet-cloud interactions.Comment: 8 pages, 15 figures. Accepted for publication in A&A Main Journal
(July, 3rd
Combination Strategies for Semantic Role Labeling
This paper introduces and analyzes a battery of inference models for the
problem of semantic role labeling: one based on constraint satisfaction, and
several strategies that model the inference as a meta-learning problem using
discriminative classifiers. These classifiers are developed with a rich set of
novel features that encode proposition and sentence-level information. To our
knowledge, this is the first work that: (a) performs a thorough analysis of
learning-based inference models for semantic role labeling, and (b) compares
several inference strategies in this context. We evaluate the proposed
inference strategies in the framework of the CoNLL-2005 shared task using only
automatically-generated syntactic information. The extensive experimental
evaluation and analysis indicates that all the proposed inference strategies
are successful -they all outperform the current best results reported in the
CoNLL-2005 evaluation exercise- but each of the proposed approaches has its
advantages and disadvantages. Several important traits of a state-of-the-art
SRL combination strategy emerge from this analysis: (i) individual models
should be combined at the granularity of candidate arguments rather than at the
granularity of complete solutions; (ii) the best combination strategy uses an
inference model based in learning; and (iii) the learning-based inference
benefits from max-margin classifiers and global feedback
Hexagonal Tilings and Locally C6 Graphs
We give a complete classification of hexagonal tilings and locally C6 graphs,
by showing that each of them has a natural embedding in the torus or in the
Klein bottle. We also show that locally grid graphs are minors of hexagonal
tilings (and by duality of locally C6 graphs) by contraction of a perfect
matching and deletion of the resulting parallel edges, in a form suitable for
the study of their Tutte uniqueness.Comment: 14 figure
Experimental prospects for indirect BSM searches in () processes at Higgs Factories
This contribution explores the ability to probe BSM physics by using the
experimental prospects for measuring the forward-backward asymmetry ()
in and
processes at the baseline energy points of ILC: 250 and 500 GeV. The studies
are based on the full simulation samples and reconstruction chains from the ILD
concept group. The BSM models studied are two different types of gauge-Higgs
unification (GHU) models that predict BSM Z resonances at the TeV
scale.Comment: EPS-HEP Proceeding
On the use of machine learning algorithms in the measurement of stellar magnetic fields
Regression methods based in Machine Learning Algorithms (MLA) have become an
important tool for data analysis in many different disciplines.
In this work, we use MLA in an astrophysical context; our goal is to measure
the mean longitudinal magnetic field in stars (H_ eff) from polarized spectra
of high resolution, through the inversion of the so-called multi-line profiles.
Using synthetic data, we tested the performance of our technique considering
different noise levels: In an ideal scenario of noise-free multi-line profiles,
the inversion results are excellent; however, the accuracy of the inversions
diminish considerably when noise is taken into account. In consequence, we
propose a data pre-process in order to reduce the noise impact, which consists
in a denoising profile process combined with an iterative inversion
methodology.
Applying this data pre-process, we have found a considerable improvement of
the inversions results, allowing to estimate the errors associated to the
measurements of stellar magnetic fields at different noise levels.
We have successfully applied our data analysis technique to two different
stars, attaining by first time the measurement of H_eff from multi-line
profiles beyond the condition of line autosimilarity assumed by other
techniques.Comment: Accepted for publication in A&
Experimental prospects for precision observables in with processes at the ILC operating at 250 and 500 GeV of center of mass
Future Higgs Factories will allow the precise study of with interactions at different energies, from the Z-pole
up to high energies never reached before. In this contribution, we will discuss
the experimental prospects for the measurement of differential observables in
and processes
at high energies, 250 and 500 GeV, using full simulation samples and the full
reconstruction chain from the ILD concept group. These processes call for
superb primary and secondary vertex measurements, a high tracking efficiency to
correctly measure the vertex charge and excellent hadron identification
capabilities using . This latter aspect will be discussed in detail
together with its implementation within the standard flavour tagging tools
developed for ILD (LCFI+). In addition, prospects associated with potential
improvements using cluster counting techniques instead of traditional
will be discussed.Comment: This work was carried out in the framework of the ILD concept group.
Talk presented at the International Workshop on Future Linear Colliders (LCWS
2023), 15-19 May 2023. C23-05-15.
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