11,881 research outputs found
DENIS Observations of Multibeam Galaxies in the Zone of Avoidance
Roughly 25% of the optical extragalactic sky is obscured by the dust and
stars of our Milky Way. Dynamically important structures might still lie hidden
in this zone. Various surveys are presently being employed to uncover the
galaxy distribution in the Zone of Avoidance (ZOA) but all suffer from
(different) limitations and selection effects.
We illustrate the promise of using a multi-wavelength approach for
extragalactic large-scale studies behind the ZOA, i.e. a combination of three
surveys -- optical, systematic blind HI and near-infrared (NIR), which will
allow the mapping of the peculiar velocity field in the ZOA through the NIR
Tully-Fisher relation. In particular, we present here the results of
cross-identifying HI-detected galaxies with the DENIS NIR survey, and the use
of NIR colours to determine foreground extinctions.Comment: Accepted for publication in PASA. Proceedings of workshop "HI in the
Local Universe, II", held in Melbourne, Sept. 1998. 9 pages, LaTeX2e, 2
encapsulated PS figures, 3 JPEG figures, Full resolution figures 2, 3 and 4
and full resolution paper are at
ftp://ftp.iap.fr/pub/from_users/gam/PAPERS/HICONF
The Parkes HI Zone of Avoidance Survey
A blind HI survey of the extragalactic sky behind the southern Milky Way has
been conducted with the multibeam receiver on the 64-m Parkes radio telescope.
The survey covers the Galactic longitude range 212 < l < 36 and Galactic
latitudes |b| < 5, and yields 883 galaxies to a recessional velocity of 12,000
km/s. The survey covers the sky within the HIPASS area to greater sensitivity,
finding lower HI-mass galaxies at all distances, and probing more completely
the large-scale structures at and beyond the distance of the Great Attractor.
Fifty-one percent of the HI detections have an optical/NIR counterpart in the
literature. A further 27% have new counterparts found in existing, or newly
obtained, optical/NIR images. The counterpart rate drops in regions of high
foreground stellar crowding and extinction, and for low-HI mass objects. Only
8% of all counterparts have a previous optical redshift measurement. A notable
new galaxy is HIZOA J1353-58, a possible companion to the Circinus galaxy.
Merging this catalog with the similarly-conducted northern extension (Donley et
al. 2005), large-scale structures are delineated, including those within the
Puppis and Great Attractor regions, and the Local Void. Several
newly-identified structures are revealed here for the first time. Three new
galaxy concentrations (NW1, NW2 and NW3) are key in confirming the diagonal
crossing of the Great Attractor Wall between the Norma cluster and the CIZA
J1324.7-5736 cluster. Further contributors to the general mass overdensity in
that area are two new clusters (CW1 and CW2) in the nearer Centaurus Wall, one
of which forms part of the striking 180 deg (100/h Mpc) long filament that
dominates the southern sky at velocities of ~3000 km/s, and the suggestion of a
further Wall at the Great Attractor distance at slightly higher longitudes.Comment: Published in Astronomical Journal 9 February 2016 (accepted 26
September 2015); 42 pages, 7 tables, 18 figures, main figures data tables
only available in the on-line version of journa
Effective potential for Polyakov loops from a center symmetric effective theory in three dimensions
We present lattice simulations of a center symmetric dimensionally reduced
effective field theory for SU(2) Yang Mills which employ thermal Wilson lines
and three-dimensional magnetic fields as fundamental degrees of freedom. The
action is composed of a gauge invariant kinetic term, spatial gauge fields and
a potential for the Wilson line which includes a "fuzzy" bag term to generate
non-perturbative fluctuations. The effective potential for the Polyakov loop is
extracted from the simulations including all modes of the loop as well as for
cooled configuration where the hard modes have been averaged out. The former is
found to exhibit a non-analytic contribution while the latter can be described
by a mean-field like ansatz with quadratic and quartic terms, plus a
Vandermonde potential which depends upon the location within the phase diagram.Comment: 10 pages, 22 figures, v2: published version (minor clarifications,
update of reference list
Multiscale 3D Shape Analysis using Spherical Wavelets
©2005 Springer. The original publication is available at www.springerlink.com:
http://dx.doi.org/10.1007/11566489_57DOI: 10.1007/11566489_57Shape priors attempt to represent biological variations within a population. When variations are global, Principal Component Analysis (PCA) can be used to learn major modes of variation, even from a limited training set. However, when significant local variations exist, PCA typically cannot represent such variations from a small training set. To address this issue, we present a novel algorithm that learns shape variations from data at multiple scales and locations using spherical wavelets and spectral graph partitioning. Our results show that when the training set is small, our algorithm significantly improves the approximation of shapes in a testing set over PCA, which tends to oversmooth data
Metamagnetic phase transition of the antiferromagnetic Heisenberg icosahedron
The observation of hysteresis effects in single molecule magnets like
Mn-acetate has initiated ideas of future applications in storage
technology. The appearance of a hysteresis loop in such compounds is an outcome
of their magnetic anisotropy. In this Letter we report that magnetic hysteresis
occurs in a spin system without any anisotropy, specifically, where spins
mounted on the vertices of an icosahedron are coupled by antiferromagnetic
isotropic nearest-neighbor Heisenberg interaction giving rise to geometric
frustration. At T=0 this system undergoes a first order metamagnetic phase
transition at a critical field \Bcrit between two distinct families of ground
state configurations. The metastable phase of the system is characterized by a
temperature and field dependent survival probability distribution.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Matching small functions using centroid jitter and two beam position monitors
Matching to small beta functions is required to preserve emittance in plasma
accelerators. The plasma wake provides strong focusing fields, which typically
require beta functions on the mm-scale, comparable to those found in the final
focusing of a linear collider. Such beams can be time consuming to
experimentally produce and diagnose. We present a simple, fast, and noninvasive
method to measure Twiss parameters in a linac using two beam position monitors
only, relying on the similarity of the beam phase space and the jitter phase
space. By benchmarking against conventional quadrupole scans, the viability of
this technique was experimentally demonstrated at the FLASHForward
plasma-accelerator facility.Comment: 8 pages, 7 figure
Magnetic fields in single late-type giants in the Solar vicinity: How common is magnetic activity on the giant branches?
We present our first results on a new sample containing all single G,K and M
giants down to V = 4 mag in the Solar vicinity, suitable for
spectropolarimetric (Stokes V) observations with Narval at TBL, France. For
detection and measurement of the magnetic field (MF), the Least Squares
Deconvolution (LSD) method was applied (Donati et al. 1997) that in the present
case enables detection of large-scale MFs even weaker than the solar one (the
typical precision of our longitudinal MF measurements is 0.1-0.2 G). The
evolutionary status of the stars is determined on the basis of the evolutionary
models with rotation (Lagarde et al. 2012; Charbonnel et al., in prep.) and
fundamental parameters given by Massarotti et al. (1998). The stars appear to
be in the mass range 1-4 M_sun, situated at different evolutionary stages after
the Main Sequence (MS), up to the Asymptotic Giant Branch (AGB). The sample
contains 45 stars. Up to now, 29 stars are observed (that is about 64 % of the
sample), each observed at least twice. For 2 stars in the Hertzsprung gap, one
is definitely Zeeman detected. Only 5 G and K giants, situated mainly at the
base of the Red Giant Branch (RGB) and in the He-burning phase are detected.
Surprisingly, a lot of stars ascending towards the RGB tip and in early AGB
phase are detected (8 of 13 observed stars). For all Zeeman detected stars v
sin i is redetermined and appears in the interval 2-3 km/s, but few giants with
MF possess larger v sin i.Comment: 4 pages, 3 figures, Proceedings IAU Symposium No. 302, 201
Scaling approach to itinerant quantum critical points
Based on phase space arguments, we develop a simple approach to metallic
quantum critical points, designed to study the problem without integrating the
fermions out of the partition function. The method is applied to the
spin-fermion model of a T=0 ferromagnetic transition. Stability criteria for
the conduction and the spin fluids are derived by scaling at the tree level. We
conclude that anomalous exponents may be generated for the fermion self-energy
and the spin-spin correlation functions below , in spite of the spin fluid
being above its upper critical dimension.Comment: 3 pages, 2 figures; discussion of the phase space restriction
modified and, for illustrative purposes, restricted to the tree-level
analysis of the ferromagnetic transitio
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