6,286 research outputs found
Management of incidentally detected heart murmurs in dogs and cats
A dog or a cat has an incidentally detected heart murmur if the murmur is an unexpected discovery during a veterinary consultation that was not initially focused on the cardiovascular system. This document presents approaches for managing dogs and cats that have incidentally-detected heart murmurs, with an emphasis on murmur characteristics, signalment profiling, and multifactorial decision-making to choose an optimal course for a given patient
A Possible Massive Asteroid Belt Around zeta Lep
We have used the Keck I telescope to image at 11.7 microns and 17.9 microns
the dust emission around zeta Lep, a main sequence A-type star at 21.5 pc from
the Sun with an infrared excess. The excess is at most marginally resolved at
17.9 microns. The dust distance from the star is probably less than or equal to
6 AU, although some dust may extend to 9 AU. The mass of observed dust is
\~10^22 g. Since the lifetime of dust particles is about 10,000 years because
of the Poytning-Robertson effect, we robustly estimate at least 4 10^26 g must
reside in parent bodies which may be asteroids if the system is in a steady
state and has an age of ~300 Myr. This mass is approximately 200 times that
contained within the main asteroid belt in our solar system.Comment: 12 pages, 3 figures, ApJL in pres
Phases of the 2D Hubbard model at low doping
We show that the planar spiral phase of the 2D Hubbard model at low doping,
x, is unstable towards a noncoplanar spin configuration. The novel equilibrium
state we found at low doping is incommensurate with the inverse pitch of the
spiral varying as x^(1/2), but nevertheless has a dominant peak in the
susceptibility at (\pi,\pi). Relevance to the NMR and neutron scattering
experiments in La_2-xSr_xCuO_4 is disccussed.Comment: 12 pages, emtex v.3.
The properties of the Malin 1 galaxy giant disk: A panchromatic view from the NGVS and GUViCS surveys
Low surface brightness galaxies (LSBGs) represent a significant percentage of
local galaxies but their formation and evolution remain elusive. They may hold
crucial information for our understanding of many key issues (i.e., census of
baryonic and dark matter, star formation in the low density regime, mass
function). The most massive examples - the so called giant LSBGs - can be as
massive as the Milky Way, but with this mass being distributed in a much larger
disk. Malin 1 is an iconic giant LSBG, perhaps the largest disk galaxy known.
We attempt to bring new insights on its structure and evolution on the basis of
new images covering a wide range in wavelength. We have computed surface
brightness profiles (and average surface brightnesses in 16 regions of
interest), in six photometric bands (FUV, NUV, u, g, i, z). We compared these
data to various models, testing a variety of assumptions concerning the
formation and evolution of Malin 1. We find that the surface brightness and
color profiles can be reproduced by a long and quiet star-formation history due
to the low surface density; no significant event, such as a collision, is
necessary. Such quiet star formation across the giant disk is obtained in a
disk model calibrated for the Milky Way, but with an angular momentum
approximately 20 times larger. Signs of small variations of the star-formation
history are indicated by the diversity of ages found when different regions
within the galaxy are intercompared.For the first time, panchromatic images of
Malin 1 are used to constrain the stellar populations and the history of this
iconic example among giant LSBGs. Based on our model, the extreme disk of Malin
1 is found to have a long history of relatively low star formation (about 2
Msun/yr). Our model allows us to make predictions on its stellar mass and
metallicity.Comment: Accepted in Astronomy and Astrophysic
The outer halo globular cluster system of M31 - II. Kinematics
We present a detailed kinematic analysis of the outer halo globular cluster
(GC) system of M31. Our basis for this is a set of new spectroscopic
observations for 78 clusters lying at projected distances between Rproj ~20-140
kpc from the M31 centre. These are largely drawn from the recent PAndAS
globular cluster catalogue; 63 of our targets have no previous velocity data.
Via a Bayesian maximum likelihood analysis we find that GCs with Rproj > 30 kpc
exhibit coherent rotation around the minor optical axis of M31, in the same
direction as more centrally- located GCs, but with a smaller amplitude of
86+/-17 km s-1. There is also evidence that the velocity dispersion of the
outer halo GC system decreases as a function of projected distance from the M31
centre, and that this relation can be well described by a power law of index ~
-0.5. The velocity dispersion profile of the outer halo GCs is quite similar to
that of the halo stars, at least out to the radius up to which there is
available information on the stellar kinematics. We detect and discuss various
velocity correlations amongst subgroups of GCs that lie on stellar debris
streams in the M31 halo. Many of these subgroups are dynamically cold,
exhibiting internal velocity dispersions consistent with zero. Simple Monte
Carlo experiments imply that such configurations are unlikely to form by
chance, adding weight to the notion that a significant fraction of the outer
halo GCs in M31 have been accreted alongside their parent dwarf galaxies. We
also estimate the M31 mass within 200 kpc via the Tracer Mass Estimator,
finding (1.2 - 1.6) +/- 0.2 10^{12}M_sun. This quantity is subject to
additional systematic effects due to various limitations of the data, and
assumptions built in into the TME. Finally, we discuss our results in the
context of formation scenarios for the M31 halo.Comment: 24 pages, 12 figures, 7 tables; Accepted for publication in MNRA
A Photometric Technique to Search for Be Stars in Open Clusters
We describe a technique to identify Be stars in open clusters using Stromgren
b, y, and narrow-band Halpha photometry. We first identify the B-type stars of
the cluster using a theoretical isochrone fit to the (b-y, y) color-magnitude
diagram. The strongest Be stars are easily identified in a (b-y, y-Halpha)
color-color diagram, but those with weaker Halpha emission (classified as
possible Be star detections) may be confused with evolved or foreground stars.
Here we present such photometry plus Halpha spectroscopy of members of the
cluster NGC 3766 to demonstrate the accuracy of our technique. Statistical
results on the relative numbers of Be and B-type stars in additional clusters
will be presented in a future paper.Comment: 15 pages, 6 figures, 1 table. Accepted by Ap
A Parameter Study of Classical Be Star Disk Models Constrained by Optical Interferometry
We have computed theoretical models of circumstellar disks for the classical
Be stars Dra, Psc, and Cyg. Models were constructed
using a non-LTE radiative transfer code developed by \citet{sig07} which
incorporates a number of improvements over previous treatments of the disk
thermal structure, including a realistic chemical composition. Our models are
constrained by direct comparison with long baseline optical interferometric
observations of the H emitting regions and by contemporaneous H
line profiles. Detailed comparisons of our predictions with H
interferometry and spectroscopy place very tight constraints on the density
distributions for these circumstellar disks.Comment: 10 figures,28 pages, accepted by Ap
HistFitter software framework for statistical data analysis
We present a software framework for statistical data analysis, called
HistFitter, that has been used extensively by the ATLAS Collaboration to
analyze big datasets originating from proton-proton collisions at the Large
Hadron Collider at CERN. Since 2012 HistFitter has been the standard
statistical tool in searches for supersymmetric particles performed by ATLAS.
HistFitter is a programmable and flexible framework to build, book-keep, fit,
interpret and present results of data models of nearly arbitrary complexity.
Starting from an object-oriented configuration, defined by users, the framework
builds probability density functions that are automatically fitted to data and
interpreted with statistical tests. A key innovation of HistFitter is its
design, which is rooted in core analysis strategies of particle physics. The
concepts of control, signal and validation regions are woven into its very
fabric. These are progressively treated with statistically rigorous built-in
methods. Being capable of working with multiple data models at once, HistFitter
introduces an additional level of abstraction that allows for easy bookkeeping,
manipulation and testing of large collections of signal hypotheses. Finally,
HistFitter provides a collection of tools to present results with
publication-quality style through a simple command-line interface.Comment: 35 pages (excluding appendix) and 10 figures. Code publicly available
at: http://cern.ch/histfitte
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