477 research outputs found
High-Velocity Molecular Gas in the Galactic Center Radio Lobe
We point out a possible association of high-velocity molecular gas with the
Galactic Center Radio Lobe (GCL). A molecular spur in the eastern GCL ridge is
receding at \Vlsr \sim +100 \kms, and the western spur approaching at \Vlsr
\sim -150 \kms, suggesting a high-velocity rotation of the GCL. We study the
kinematics of the GCL based on these molecular line data.Comment: To appear in ApJ. Letters, Plain TeX, Figures on reques
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
Bipolar-Hyper-Shell Galactic Center Statrburst Model: Further Evidence from ROSAT Data and New Radio and X-ray Simulations
Using the all-sky ROSAT soft X-ray and 408-MHz radio continuum data, we show
that the North Polar Spur and its western and southern counter-spurs draw a
giant dumbbell-shape necked at the galactic plane. We interpret these features
as due to a shock front originating from a starburst 15 million years ago with
a total energy of the order of ergs or type II
supernovae. We simulate all-sky distributions of radio continuum and soft X-ray
intensities based on the bipolar-hyper-shell galactic center starburst model.
The simulations can well reproduce the radio NPS and related spurs, as well as
radio spurs in the tangential directions of spiral arms. Simulated X-ray maps
in 0.25, 0.75 and 1.5 keV bands reproduce the ROSAT X-ray NPS, its western and
southern counter-spurs, and the absorption layer along the galactic plane. We
propose to use the ROSAT all-sky maps to probe the physics of gas in the
halo-intergalactic interface, and to directly date and measure the energy of a
recent Galactic Center starburst.Comment: To appear in ApJ, Latex MS in ApJ macro, 8 figures in jpg (original
quality ps figs available on request
Structural analysis of hollow blades: Torsional stress analysis of hollow fan blades for aircraft jet engines
A torsional stress analysis of hollow fans blades by the finite element method is presented. The fans are considered to be double circular arc blades, hollowed 30 percent, and twisted by a component of the centrifugal force by the rated revolution. The effects of blade hollowing on strength and rigidity are discussed. The effects of reinforcing webs, placed in the hollowed section in varying numbers and locations, on torsional rigidity and the convergence of stresses, are reported. A forecast of the 30 percent hollowing against torsional loadings is discussed
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
Near-Solar-Circle Method for Determination of the Galactic Constants
We propose a method to determine the galactic constants R_0 (distance to the
Galactic Center) and V_0 (rotation velocity of the Sun) from measurements of
distances, radial velocities and proper motions of objects near the solar
circle. This is a modification of the solar-circle method to a more practical
observational method. We apply the method to determine R_0 using data from the
literature with known distances and radial velocities, and obtain R_0 = 7.54
+/- 0.77 kpc.Comment: 5 pages, 4 figures, accepted for PASJ (Vol. 63 No. 5
The Virgo High-Resolution CO Survey. II. Rotation Curves and Dynamical Mass Distributions
Based on a high-resolution CO survey of Virgo spirals with the Nobeyama
Millimeter-wave Array, we determined the dynamical centers using velocity
fields, and derived position-velocity diagrams (PVDs) along the major axes of
the galaxies across their dynamical centers. We applied a new iteration method
to derive rotation curves (RCs), which reproduce the observed PVDs. The
obtained high-accuracy RCs generally show steep rise in the central 100 to 200
pc regions, followed by flat rotation in the disk. We applied a deconvolution
method to calculate the surface-mass density (SMD) using the RCs based on two
extreme assumptions that the mass distribution is either spherical or thin-disk
shaped. Both assumptions give nearly identical results, agreeing with each
other within a factor of two at any radii. The SMD distributions revealed
central massive cores with peak SMD of 10^4 - 10^5 Msun pc^-2 and total mass
within 200 pc radius of the order of about 10^9 Msun Correlation analysis among
the derived parameters show that the central CO-line intensity is positively
correlated with the central SMD, which suggests that the deeper is the
gravitational potential, the higher is the molecular gas concentration in the
nuclei regardless morphological types.Comment: PASJ 2003 in press, Latex 12 pages, 6 figures (Bigger gif/ps figures
available at http://www.ioa.s.u-tokyo.ac.jp/radio/virgo2
Iteration Method to Derive Exact Rotation Curves from Position-Velocity Diagrams of Spiral Galaxies
We present an iteration method to derive exact rotation curves (RC) of spiral
galaxies from observed position-velocity diagrams (PVD), which comprises the
following procedure. An initial rotation curve, RC0, is adopted from an
observed PV diagram (PV0), obtained by any simple method such as the
peak-intensity method. Using this rotation curve and an observed radial
distribution of intensity (emissivity), we construct a simulated PV diagram
(PV1). The difference between a rotation curve obtained from this PV1 and the
original RC (e.g., difference between peak-intensity velocities) is used to
correct the initial RC to obtain a corrected rotation curve, RC1. This RC1 is
used to calculated another PVD (PV2) using the observed intensity distribution,
and to obtain the second iterated RC (RC2). This iteration is repeated until
PV converges to PV0, so that the differences between PV and PV0 becomes
minimum. Finally RC is adopted as the most reliable rotation curve. We apply
this method to some observed PVDs of nearby galaxies, and show that the
iteration successfully converges to give reliable rotation curves. We show that
the method is powerful to detect central massive objects.Comment: To appear in ApJ.Letters, 5 pages Latex with 4 figure
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