2,733 research outputs found
Study of the Bipolar Nebula IRAS 19312+1950. I. Mapping Observations
IRAS 19312+1950 is an SiO maser source that exhibits a prominent bipolar
nebulosity. Mapping observations of this object were made in the CO J=1--0,
13CO J=1--0, C18O J=1--0, CS J=2--1, and HCN J=1--0 lines and in the 150 GHz
continuum band. Near-infrared imaging observations were also made in the J, H,
and K-bands. The line profiles of the 12CO and HCN spectra consist of a weak
broad component with a line width of about 50 km/s and a strong narrow
component of the width of about 3 km/s. The profiles of the 13CO, C18O, and CS
lines have only the narrow component. Both of the components have an intensity
peak at the IRAS position. The narrow component was clearly resolved with a
15'' telescope beam. The spectral energy distribution of this object exhibits a
doubly peaked profile between 1 and 25 micron. The 150 GHz continuum flux
density was found to be 0.07 Jy, which is consistent with the flux density
predicted by the expanding envelope model with a mass loss rate of ~10^{-4}
M_sun/y at a distance of 2.5 kpc. We argue that the broad component originates
from the expanding envelope of this object, and that the hot dust cloud, which
is the source of the narrow component, is also physically associated with this
object. Though the present observations do not preclude the possibility of a
young stellar object, we argue that it is less plausible. We conclude that IRAS
19312+1950 is an AGB/post-AGB star that is evolved from a massive progenitor.Comment: 13 pages, 6 figures (jpg), high resolution figures available as no598
in http://www.nro.nao.ac.jp/library/report/list.html. PASJ, 56 No. 1 in pres
A New High Resolution CO Map of the inner 2.'5 of M51 I. Streaming Motions and Spiral Structure
[Abridged] The Owens Valley mm-Array has been used to map the CO 1--0
emission in the inner 2'.5 of the grand design spiral galaxy M51 at 2''-3''
resolution. The molecular spiral arms are revealed with unprecedented clarity:
supermassive cloud complexes, Giant Molecular Associations, are for the first
time resolved both along and perpendicular to the arms. Major complexes occur
symmetrically opposite each other in the two major arms. Streaming motions can
be studied in detail along the major and minor axes of M51. The streaming
velocities are very large, 60-150 km/s. For the first time, sufficient
resolution to resolve the structure in the molecular streaming motions is
obtained. Our data support the presence of galactic shocks in the arms of M51.
In general, velocity gradients across arms are higher by a factor of 2-10 than
previously found. They vary in steepness along the spiral arms, becoming
particularly steep in between GMAs. The steep gradients cause conditions of
strong reverse shear in several regions in the arms, and thus the notion that
shear is generally reduced by streaming motions in spiral arms will have to be
modified. Of the three GMAs studied on the SW arm, only one shows reduced
shear. We find an expansion in the NE molecular arm at 25'' radius SE of the
center. This broadening occurs right after the end of the NE arm at the Inner
Lindblad Resonance. Bifurcations in the molecular spiral arm structure, at a
radius of 73'', may be evidence of a secondary compression of the gas caused by
the 4/1 ultraharmonic resonance. Inside the radius of the ILR, we detect narrow
(~ 5'') molecular spiral arms possibly related to the K-band arms found in the
same region. We find evidence of non-circular motions in the inner 20'' which
are consistent with gas on elliptical orbits in a bar.Comment: 29 pages, 15 figures, uses latex macros for ApJ; accepted for
publication in Ap
Variation of Molecular Cloud Properties across the Spiral Arm in M 51
We present the results of high-resolution 13CO(1-0) mapping observations with
the NRO 45m telescope of the area toward the southern bright arm region of M51,
including the galactic center. The obtained map shows the central depression of
the the circumnuclear ring and the spiral arm structure.The arm-to-interarm
ratio of the 13CO(1-0) integrated intensity is 2-4. We also have found a
feature different from that found in the 12CO results. The 12CO/13CO ratio
spatially varies, and shows high values (~20) for the interarm and the central
region, but low values(~10) for the arm. These indicate that there is a denser
gas in the spiral arm than in the interarm. The distribution of the 13CO shows
a better correspondence with that of the H\alpha emission than with the 12CO in
the disk region, except for the central region. We found that the 13CO emission
is located on the downstream side of the 12CO arm, namely there is an offset
between the 12CO and the 13CO as well as the H\alpha emission. This suggests
that there is a time delay between the accumulation of gas caused by the
density wave and dense gas formation, accordingly star formation. This time
delay is estimated to be ~10^7 yr based on the assumption of galactic rotation
derived by the rotation curve and the pattern speed of M51. It is similar to
the growth timescale of a gravitational instability in the spiral arm of M51,
suggesting that the gravitational instability plays an important role for dense
gas formation.Comment: 23 pages, 10 figures, PASJ Vol.54, No.2 (2002), in pres
Search for lepton flavor violation via the intense high-energy muon beam
A deep inerastic scattering process \mutau is discussed to study lepton
flavor violation between muons and tau leptons. In supersymmetric models, the
Higgs boson mediated diagrams could be important for this reaction. We find
that at a muon energy () higher than 50 GeV, the predicted cross
section significantly increases due to the contribution from sea -quarks.
The number of produced tau leptons can be at = 300
GeV from muons, whereas events are given at
GeV.Comment: Contribution to the 6th International Workshop on Neutrino Factories
& Superbeams(NuFact04), Jul. 26-Aug. 1, 2004, Osaka Univerisity, Osaka,
Japan, talk given by S.K., to appear in the Proceedings, 3 pages, 4 figure
Benchmarking adaptive indexing
Ideally, realizing the best physical design for the current and all subsequent
workloads would impact neither performance nor storage usage.
In reality, workloads and datasets can
change dramatically over time and index creation impacts the
performance of concurrent user and system activity.
We propose a framework that evaluates the key premise
of adaptive indexing --- a new indexing paradigm where index creation and re-organization
take place automatically and incrementally,
as a side-effect of query execution.
We focus on how the incremental costs and benefits of dynamic
reorganization are distributed across the workload's lifetime.
We believe measuring
the costs and utility of the stages of adaptation
are relevant metrics
for evaluating new query processing paradigms
and comparing them to traditional approaches
The mapping class group and the Meyer function for plane curves
For each d>=2, the mapping class group for plane curves of degree d will be
defined and it is proved that there exists uniquely the Meyer function on this
group. In the case of d=4, using our Meyer function, we can define the local
signature for 4-dimensional fiber spaces whose general fibers are
non-hyperelliptic compact Riemann surfaces of genus 3. Some computations of our
local signature will be given.Comment: 24 pages, typo adde
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