928 research outputs found
A Polar-Nulceus Dark Lane in the Barred Spiral M83: Three-Dimensional Accretion in the Nucleus
The central region of the barred spiral galaxy M83 reveals a polar-nucleus
dust lane, wh ich extends from the NE molecular bar and crosses the central
bulge. Its SW counterpart is not visible, being hidden behind the bulge. This
asymmetry, in spite of the galaxy's face-on orientation and the symmetric bar
struct ure in the CO-line emission, indicates that the dark lane is an
off-plane structure. Such a ``polar-nucleus'' structure can be formed by a
non-coplanar, three-dimensional acc retion in a warped disk.Comment: (to appear in AJ), 5 pages, plainTeX, U-Tokyo Astro. No.93-2
Pi N sigma-term and chiral-odd twist-3 distribution function e(x) of the nucleon in the chiral quark soliton model
The isosinglet combination of the chiral-odd twist-3 distribution function
of the nucleon has outstanding properties that its first moment
is proportional to the well-known sigma-term and that it contains a
-function singularity at . These two features are inseparably
connected in that the above sum rule would be violated, if there is no such a
singularity in . Very recently, we found that the physical
origin of this -function singularity can be traced back to the
long-range quark-quark correlation of scalar type, which signals the
spontaneous chiral symmetry breaking of the QCD vacuum. The main purpose of the
present paper is to give complete theoretical predictions for the chiral-odd
twist-3 distribution function of each flavor on the basis of the
chiral quark soliton model, without recourse to the derivative expansion type
approximation. These theoretical predictions are then compared with the
empirical information extracted from the CLAS data of the semi-inclusive DIS
processes by assuming the Collins mechanism only. A good agreement with the
CLAS data is indicative of a sizable violation of the sigma-term sum
rule, or equivalently, the existence of a -function singularity in
.Comment: 35 pages, 10 figure
Generalized form factors, generalized parton distributions and the spin contents of the nucleon
With a special intention of clarifying the underlying spin contents of the
nucleon, we investigate the generalized form factors of the nucleon, which are
defined as the -th -moments of the generalized parton distribution
functions, within the framework of the chiral quark soliton model. A particular
emphasis is put on the pion mass dependence of final predictions, which we
shall compare with the predictions of lattice QCD simulations carried out in
the so-called heavy pion region around . We find that some observables are very sensitive to the variation of
the pion mass. It will be argued that the negligible importance of the quark
orbital angular momentum indicated by the LHPC and QCDSF lattice collaborations
might be true in the unrealistic heavy pion world, but it is not necessarily
the case in our real world close to the chiral limit.Comment: Final version accepted for publication in Phys. Rev.
CO Observations of Luminous IR Galaxies at Intermediate Redshift
We present new measurement of CO() emission from 16 luminous
infrared galaxies (LIGs) at intermediate redshift (). These new data were selected by isolated and normal
morphology. The CO observations were performed using the NRO 45-m telescope.
Comparison of the CO and dust properties of the new result with those from
other CO measurements revealed characteristics of this sample: (1) It is the
deepest CO observations of IRAS galaxies at intermediate redshift without
strong interaction features. (2) It has typical properties of normal IRAS
galaxies in terms of star-formation efficiency, color-color diagrams and
galactic nuclear activity. (3) It has smaller gas-to-dust ratio than normal
IRAS galaxies. This can be explained by two-component dust model, and our
sample consists of most of warm dust.Comment: To appear in PASJ, text 9 pages, 5 tables, and 12 figure
The nonperturbative origin of delta-function singularity in the chirally-odd twist-3 distribution function e(x)
We analytically prove that the existence of the delta-function singularity in
the chirally-odd twist-3 distribution of the nucleon is inseparably
connected with the nonvanishing quark condensate as a signal of the spontaneous
chiral symmetry breaking of the QCD vacuum. This singularity in , which
would be observed as a sizable violation of the 1st moment sum rule, is then
interpreted as giving a very rare case that the nontrivial vacuum structure of
QCD manifests in an observable of a localized QCD excitation, i.e. the nucleon.Comment: 9 pages, 1 eps-figur
Distance Measurement of Galaxies to Redshift of 0.1 using the CO-Line Tully-Fisher Relation
We report on the first results of a long-term project to derive distances of
galaxies at cosmological distances by applying the CO-line width-luminosity
relation. We have obtained deep CO-line observations of galaxies at redshifts
up to 29,000 km/s using the Nobeyama 45-m mm-wave Telescope, and some
supplementary data were obtained by using the IRAM 30-m telescope. We have
detected the CO line emission for several galaxies, and used their CO line
widths to estimate the absolute luminosities using the line-width-luminosity
relation. In order to obtain photometric data and inclination correction, we
also performed optical imaging observations of the CO-detected galaxies using
the CFHT 3.6-m telescope at high resolution. The radio and optical data have
been combined to derive the distance moduli and distances of the galaxies, and
Hubble ratios were estimated for these galaxies. We propose that the CO line
width-luminosity relation can be a powerful method to derive distances of
galaxies to redfhift of z = 0.1 and to derive the Hubble ratio in a significant
volume of the universe.
Key words: Cosmology - Galaxies: general - Distance scale - CO lineComment: To appear in PASJ, Plain Tex, 3 figures (in 10 ps files
On the physics behind the form factor ratio
We point out that there exist two natural definitions of the nucleon
magnetization densities : the density introduced in Kelly's
phenomenological analysis and theoretically more standard one . We
can derive an explicit analytical relation between them, although Kelly's
density is more useful to disentangle the physical origin of the different
dependence of the Sachs electric and magnetic form factors of the
nucleon. We evaluate both of and as well as the
charge density of the proton within the framework of the chiral
quark soliton model, to find a noticeable qualitative difference between
and , which is just consistent with Kelly's result
obtained from the empirical information on the Sachs electric and magnetic form
factors of the proton.Comment: 12 pages, 5 figures. version to appear in J. Phys. G.: Nucl. Part.
Phy
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