6,941 research outputs found
B\"acklund transformations in 2D dilaton gravity
We give a B\"acklund transformation connecting a generic 2D dilaton gravity
theory to a generally covariant free field theory. This transformation provides
an explicit canonical transformation relating both theories.Comment: LaTeX file, 7 page
Advanced optimal extraction for the Spitzer/IRS
We present new advances in the spectral extraction of point-like sources
adapted to the Infrared Spectrograph onboard the Spitzer Space Telescope. For
the first time, we created a super-sampled point spread function of the
low-resolution modules. We describe how to use the point spread function to
perform optimal extraction of a single source and of multiple sources within
the slit. We also examine the case of the optimal extraction of one or several
sources with a complex background. The new algorithms are gathered in a plugin
called Adopt which is part of the SMART data analysis software.Comment: Accepted for publication in PAS
PAH Strength and the Interstellar Radiation Field around the Massive Young Cluster NGC3603
We present spatial distribution of polycyclic aromatic hydrocarbons and
ionized gas within the Galactic giant HII region NGC3603. Using the IRS
instrument on board the Spitzer Space Telescope, we study in particular the PAH
emission features at ~5.7, 6.2, 7.7, 8.6, and 11.3um, and the [ArII] 6.99um,
[NeII] 12.81um, [ArIII] 8.99um, and [SIV] 10.51um forbidden emission lines. The
observations probe both ionized regions and photodissociation regions. Silicate
emission is detected close to the central cluster while silicate absorption is
seen further away. We find no significant variation of the PAH ionization
fraction across the whole region. The emission of very small grains lies closer
to the central stellar cluster than emission of PAHs. The PAH/VSG ratio
anticorrelates with the hardness of the interstellar radiation field suggesting
a destruction mechanism of the molecules within the ionized gas, as shown for
low-metallicity galaxies by Madden et al. (2006).Comment: Accepted for publication in ApJ. Corrected typo
Range analysis for storage problems of periodic-stochastic processes
November 1972.Bibliography: pages 75-76
Real-time Monocular Object SLAM
We present a real-time object-based SLAM system that leverages the largest
object database to date. Our approach comprises two main components: 1) a
monocular SLAM algorithm that exploits object rigidity constraints to improve
the map and find its real scale, and 2) a novel object recognition algorithm
based on bags of binary words, which provides live detections with a database
of 500 3D objects. The two components work together and benefit each other: the
SLAM algorithm accumulates information from the observations of the objects,
anchors object features to especial map landmarks and sets constrains on the
optimization. At the same time, objects partially or fully located within the
map are used as a prior to guide the recognition algorithm, achieving higher
recall. We evaluate our proposal on five real environments showing improvements
on the accuracy of the map and efficiency with respect to other
state-of-the-art techniques
Chemical composition and mixing in giant HII regions: NGC3603, 30Doradus, and N66
We investigate the chemical abundances of NGC3603 in the Milky Way, of
30Doradus in the Large Magellanic Cloud, and of N66 in the Small Magellanic
Cloud. Mid-infrared observations with the Infrared Spectrograph onboard the
Spitzer Space Telescope allow us to probe the properties of distinct physical
regions within each object: the central ionizing cluster, the surrounding
ionized gas, photodissociation regions, and buried stellar clusters. We detect
[SIII], [SIV], [ArIII], [NeII], [NeIII], [FeII], and [FeIII] lines and derive
the ionic abundances. Based on the ionic abundance ratio (NeIII/H)/(SIII/H), we
find that the gas observed in the MIR is characterized by a higher degree of
ionization than the gas observed in the optical spectra. We compute the
elemental abundances of Ne, S, Ar, and Fe. We find that the alpha-elements Ne,
S, and Ar scale with each other. Our determinations agree well with the
abundances derived from the optical. The Ne/S ratio is higher than the solar
value in the three giant HII regions and points toward a moderate depletion of
sulfur on dust grains. We find that the neon and sulfur abundances display a
remarkably small dispersion (0.11dex in 15 positions in 30Doradus), suggesting
a relatively homogeneous ISM, even though small-scale mixing cannot be ruled
out.Comment: Accepted for submission to ApJ. The present version replaces the
submitted one. Changes: new title, new figure, the text was modified in the
discussio
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