2,302 research outputs found
The bimodal spiral galaxy surface brightness distribution
We have assessed the significance of Tully and Verheijen's (1997) bimodal
Ursa Major Cluster spiral galaxy near-infrared surface brightness distribution,
focussing on whether this bimodality is simply an artifact of small number
statistics. A Kolmogorov-Smirnov style of significance test shows that the
total distribution is fairly represented by a single-peaked distribution, but
that their isolated galaxy subsample (with no significant neighbours within a
projected distance of around 80 kpc) is bimodal at the 96 per cent level. We
have also investigated the assumptions underlying the isolated galaxy surface
brightness distribution, finding that the (often large) inclination corrections
used in the construction of this distribution reduce the significance of the
bimodality. We conclude that the Ursa Major Cluster dataset is insufficient to
establish the presence of a bimodal near-infrared surface brightness
distribution: an independent sample of around 100 isolated, low inclination
galaxies is required to establish bimodality at the 99 per cent level.Comment: 5 pages LaTeX; 2 embedded figures; re-submitted to MNRAS after
replying to referee's comment
A High-Resolution Rotation Curve of NGC 6822: A Test-case for Cold Dark Matter
We present high resolution rotation curves of the local group dwarf irregular
galaxy NGC 6822 obtained with the Australia Telescope Compact Array. Our best
curves have an angular resolution of 8'' or 20 pc and contain some 250
independent points. The stellar and gas components of NGC 6822 cannot explain
the shape of the curve, except for the very inner regions, and NGC 6822 is
consequently very dark matter dominated. There is no evidence for the presence
of a steep density cusp down to scales of ~20 pc, contrary to the predictions
of Cold Dark Matter.Comment: Accepted for publication in MNRA
Two-body hadronic charmed meson decays
We study in this work the two-body hadronic charmed meson decays, including
both the PP and VP modes. The latest experimental data are first analyzed in
the diagrammatic approach. The magnitudes and strong phases of the flavor
amplitudes are extracted from the Cabibbo-favored (CF) decay modes using
minimization. The best-fitted values are then used to predict the
branching fractions of the singly-Cabibbo-suppressed (SCS) and
doubly-Cabibbo-suppressed decay modes in the flavor SU(3) symmetry limit. We
observe significant SU(3) breaking effects in some of SCS channels. In the case
of VP modes, we point out that the and amplitudes cannot be
completely determined based on currently available data. We conjecture that the
quoted experimental results for both and are overestimated. We compare the sizes of color-allowed and
color-suppressed tree amplitudes extracted from the diagrammatical approach
with the effective parameters and defined in the factorization
approach. The ratio is more or less universal among the , and modes. This feature allows
us to discriminate between different solutions of topological amplitudes. For
the long-standing puzzle about the ratio , we argue that, in addition to the SU(3)
breaking effect in the spectator amplitudes, the long-distance resonant
contribution through the nearby resonance can naturally explain why
decays more copiously to than through the
-exchange topology.Comment: 32 pages, 5 figures. An alternative method for error bar extraction
is used; last columns of Tables~I to VI, and all entries in Tables~VII, VIII
and X are modified. To appear in PRD
The First CO Map of a Low Surface Brightness Galaxy
Using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO)
we have obtained the first CO map of a low surface brightness (LSB) galaxy. The
studied galaxy, UGC 01922, was chosen for these observations because both of
its previous CO detection with the IRAM 30m telescope and its classification as
a Malin 1 `cousin' - an LSB galaxy with M_HI > 10^10 Msol. The OVRO map
detected approximately 65% of the CO(1-0) flux found earlier with the single
dish measurements, giving a detected gas mass equivalent to M_H2 = 1.1X10^9
Msol. The integrated gas peak lies at the center of the galaxy and coincides
with both the optical and 1.4 GHz continuum emission peaks. The molecular gas
extends well beyond the OVRO beam size (~4'' or 3 kpc), covering ~25% of the
optical bulge. In all, perhaps the most remarkable aspect of this map is its
unexceptional appearance. Given that it took over ten years to successfully
detect molecular gas in any low surface brightness system, it is surprising
that the appearance and distribution of UGC 01922's CO is similar to what would
be expected for a high surface brightness galaxy in the same morphological
class.Comment: 5 pages, including 3 figures and 3 tables. also available online at
http://www.gb.nrao.edu/~koneil. Accepted by ApJ
Coordinating criminal justice: a Qualitative Comparative Analysis of inter-organisational information sharing of four EU Member States
Qualitative-comparative analysis of four cases of inter-organisational information sharing in
criminal justice chains demonstrates the causal asymmetry between successful and
unsuccessful inter-organisational information sharing. While unsuccessful information sharing
requires poor project management, successful information sharing also requires compatible
technologies which are implemented either by means of a small-scale, bottom-up approach to
standardization or a top-down, centralised architecture. By triggering the radical restructuring
of information-sharing workflows, good project management and compatible technologies set
in motion underlying mechanisms that generate successful inter-organisational information
sharing. Implications are discussed by highlighting the role of coordination by technological
feedback in a context of increasing digitization
Digitizing criminal justice: A Qualitative Comparative Analysis of supply-chain integration across four EU Member States
Drawing on Qualitative Comparative Analysis (QCA) techniques, we formally analyse four cases of supply-chain integration within the European Union (EU). Our findings demonstrate the causal asymmetry between successful and unsuccessful digitization of inter-organizational information flows. While unsuccessful digitization requires poor project management skills, successful digitization is much more demanding because it also requires compatible technologies which are implemented either by means of a small-scale, bottom-up approach to standardization or a single, centralised architecture developed in a top-down fashion. Theoretical and practical implications are discussed by highlighting the key role of coordination by feedback in a context of increasing digitization of criminal justice systems
Further Discoveries of 12CO in Low Surface Brightness Galaxies
Using the IRAM 30m telescope we have obtained seven new, deep CO J(1-0) and
J(2-1) observations of low surface brightness (LSB) galaxies. Five of the
galaxies have no CO detected to extremely low limits (0.1-0.4 K km/s at
J(1-0)), while two of the galaxies, UGC 01922 and UGC 12289, have clear
detections in both line transitions. When these observations are combined with
all previous CO observations taken of LSB systems, we compile a total of 34
observations, in which only 3 galaxies have had detections of their molecular
gas. Comparing the LSB galaxies with and without CO detections to a sample of
high surface brightness (HSB) galaxies with CO observations indicates that it
is primarily the low density of baryonic matter within LSB galaxies which is
causing their low CO fluxes. Finally, we note that one of the massive LSB
galaxies studied in this project, UGC 06968 (a Malin-1 `cousin'), has upper
limits placed on both M_H2 and M_H2/M_HI which are 10-20 times lower than the
lowest values found for any galaxy (LSB or HSB) with similar global properties.
This may be due to an extremely low temperature and metallicity within UGC
06968, or simply due to the CO distribution within the galaxy being too diffuse
to be detected by the IRAM beam.Comment: 18 pages, 8 figures, 4 tables. Accepted by Ap
Electromagnetic superconductivity of vacuum induced by strong magnetic field: numerical evidence in lattice gauge theory
Using numerical simulations of quenched SU(2) gauge theory we demonstrate
that an external magnetic field leads to spontaneous generation of quark
condensates with quantum numbers of electrically charged rho mesons if the
strength of the magnetic field exceeds the critical value eBc = 0.927(77) GeV^2
or Bc =(1.56 \pm 0.13) 10^{16} Tesla. The condensation of the charged rho
mesons in strong magnetic field is a key feature of the magnetic-field-induced
electromagnetic superconductivity of the vacuum.Comment: 14 pages, 5 figures, 2 tables, elsarticle style; continuum limit is
analyzed, best fit parameters are presented in Table 2, published versio
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