306 research outputs found
Near-Infrared Counterparts to Chandra X-ray Sources toward the Galactic Center. I. Statistics and a Catalog of Candidates
We present a catalog of 5184 candidate infrared counterparts to X-ray sources
detected towards the Galactic center. The X-ray sample contains 9017 point
sources detected in this region by the Chandra X-ray Observatory, including
data from a recent deep survey of the central 2 x 0.8 deg of the Galactic
plane. A total of 6760 of these sources have hard X-ray colors, and the
majority of them lie near the Galactic center, while most of the remaining 2257
soft X-ray sources lie in the foreground. We cross-correlated the X-ray source
positions with the 2MASS and SIRIUS near-infrared catalogs, which collectively
contain stars with a 10-sigma limiting flux of K_s<=15.6 mag. In order to
distinguish absorbed infrared sources near the Galactic center from those in
the foreground, we defined red and blue sources as those which have H-K_s>=0.9
and <=0.9 mag, respectively. We find that 5.8(1.5)% of the hard X-ray sources
have real infrared counterparts, of which 228(99) are red and 166(27) are blue.
The red counterparts are probably comprised of WR/O stars, HMXBs, and
symbiotics near the Galactic center. We also find that 39.4(1.0)% of the soft
X-ray sources have blue infrared counterparts; most of these are probably
coronally active dwarfs in the foreground. There is a noteworthy collection of
~20 red counterparts to hard X-ray sources near the Sagittarius-B H II region,
which are probably massive binaries that have formed within the last several
Myr. For each of the infrared matches to X-ray sources in our catalog we
derived the probability that the association is real, based on the results of
the cross-correlation analysis. The catalog will serve spectroscopic surveys to
identify infrared counterparts to X-ray sources near the Galactic center.Comment: Submitted to ApJ January 16, 2009; accepted July 21, 2009; 30 pages,
6 figure
Deep K_s-near-infrared Surface Photometry of 80 Dwarf Irregular Galaxies in the Local Volume
We present deep near-infrared (K_s) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ~5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies
The Structure of Screening in QED
The possibility of constructing charged particles in gauge theories has long
been the subject of debate. In the context of QED we have shown how to
construct operators which have a particle description. In this paper we further
support this programme by showing how the screening interactions arise between
these charges. Unexpectedly we see that there are two different gauge invariant
contributions with opposite signs. Their difference gives the expected result.Comment: 8 pages, LaTe
Recommended from our members
Codification, Technology Absorption, and the Globalization of the Industrial Revolution
This paper studies technology absorption worldwide in the late nineteenth century. We construct several novel datasets to test the idea that the codification of technical knowledge in the vernacular was necessary for countries to absorb the technologies of the Industrial Revolution. Using the rapid and unprecedented codification of technical knowledge in Meiji Japan as a natural experiment, we show that productivity growth in Japan was higher in industries that could potentially benefit from Western technical knowledge only after the Japanese government codified as much technical knowledge as what was available in Germany in 1870. We find no similar patterns in other parts of the world that did not codify knowledge. Our findings shed new light on the frictions associated with technology diffusion and offer a novel take on why Meiji Japan was unique among non-Western countries in successfully industrializing during the first wave of globalization.
JEL CLASSIFICATION: F14, F63, N15
KEYWORDS: Industrialization, Codification, Technology Adoption, Late Development, Productivity, Industrial Policy, Japa
Classical Exchange Algebra of the Superstring on S^5 with the AdS-time
A classical exchange algebra of the superstring on S^5 with the AdS-time is
shown on the light-like plane. To this end we use the geometrical method of
which consistency is guaranteed by the classical Yang-Baxter equation. The
Dirac method does not work, there being constraints which contain first-class
and second-class and one can disentangle with each other keeping the isometry
hardly.Comment: 12 pages, v2: argument on alternative representation of S^5 spherical
functions added, typos corrected, one reference added, matches journal
versio
Enhancement of dye regeneration kinetics in dichromophoric porphyrin-carbazole triphenylamine dyes influenced by more exposed radical cation orbitals
Reduction kinetics of oxidized dyes absorbed on semiconductor surfaces and immersed in redox active electrolytes has been mainly modeled based on the free energy difference between the oxidation potential of the dye and the redox potential of the electrolyte. Only a few mechanisms have been demonstrated to enhance the kinetics by other means. In this work, the rate constant of the reduction of oxidized porphyrin dye is enhanced by attaching non-conjugated carbazole triphenylamine moiety using iodine/triiodide and tris(2,2âČ-bispyridinium)cobalt II/III electrolytes. These results are obtained using transient absorption spectroscopy by selectively probing the regeneration kinetics at the porphyrin radical cation and the carbazole triphenylamine radical cation absorption wavelengths. The enhancement in the reduction kinetics is not attributed to changes in the driving force, but to the more exposed dye cation radical orbitals of the dichromophoric dye. The results are important for the development of high efficiency photo-electrochemical devices with minimalized energy loss at electron transfer interfaces
Magnetic translation groups in an n-dimensional torus
A charged particle in a uniform magnetic field in a two-dimensional torus has
a discrete noncommutative translation symmetry instead of a continuous
commutative translation symmetry. We study topology and symmetry of a particle
in a magnetic field in a torus of arbitrary dimensions. The magnetic
translation group (MTG) is defined as a group of translations that leave the
gauge field invariant. We show that the MTG on an n-dimensional torus is
isomorphic to a central extension of a cyclic group Z_{nu_1} x ... x
Z_{nu_{2l}} x T^m by U(1) with 2l+m=n. We construct and classify irreducible
unitary representations of the MTG on a three-torus and apply the
representation theory to three examples. We shortly describe a representation
theory for a general n-torus. The MTG on an n-torus can be regarded as a
generalization of the so-called noncommutative torus.Comment: 29 pages, LaTeX2e, title changed, re-organized, to be published in
Journal of Mathematical Physic
Topological Landau-Ginzburg theory with a rational potential and the dispersionless KP hierarchy
Based on the dispersionless KP (dKP) theory, we give a comprehensive study of
the topological Landau-Ginzburg (LG) theory characterized by a rational
potential. Writing the dKP hierarchy in a general form, we find that the
hierarchy naturally includes the dispersionless (continuous) limit of Toda
hierarchy and its generalizations having finite number of primaries. Several
flat solutions of the topological LG theory are obtained in this formulation,
and are identified with those discussed by Dubrovin. We explicitly construct
gravitational descendants for all the primary fields. Giving a residue formula
for the 3-point functions of the fields, we show that these 3-point functions
satisfy the topological recursion relation. The string equation is obtained as
the generalized hodograph solutions of the dKP hierarchy, which show that all
the gravitational effects to the constitutive equations (2-point functions) can
be renormalized into the coupling constants in the small phase space.Comment: 54 pages, Plain TeX. Figure could be obtained from Kodam
Herbig Ae/Be Stars in the Magellanic Bridge
We have found Herbig Ae/Be star candidates in the western region of the
Magellanic Bridge. Using the near infrared camera SIRIUS and the 1.4 m
telescope IRSF, we surveyed about 3.0 deg x 1.3 deg (24 deg < RA < 36 deg, -75
deg < Dec. < -73.7 deg) in the J, H, and Ks bands. On the basis of colors and
magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering
the contaminations by miscellaneous sources such as foreground stars and
early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (about
40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one
concentration of the candidates at the young star cluster NGC 796, strongly
suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic
Bridge. This is the first detection of PMS star candidates in the Magellanic
Bridge, and if they are genuine PMS stars, this could be direct evidence of
recent star formation. However, the estimate of the number of Herbig Ae/Be
stars depends on the fraction of classical Be stars, and thus a more precise
determination of the Be star fraction or observations to differentiate between
the Herbig Ae/Be stars and classical Be stars are required.Comment: 22 pages, 6 figures. Accepted for publication in Ap
Deep Ks -near-infrared surface photometry of 80 dwarf irregular galaxies in the local volume
We present deep near-infrared (K_s) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ~5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies
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