595 research outputs found
Multiple pattern classification by sparse subspace decomposition
A robust classification method is developed on the basis of sparse subspace
decomposition. This method tries to decompose a mixture of subspaces of
unlabeled data (queries) into class subspaces as few as possible. Each query is
classified into the class whose subspace significantly contributes to the
decomposed subspace. Multiple queries from different classes can be
simultaneously classified into their respective classes. A practical greedy
algorithm of the sparse subspace decomposition is designed for the
classification. The present method achieves high recognition rate and robust
performance exploiting joint sparsity.Comment: 8 pages, 3 figures, 2nd IEEE International Workshop on Subspace
Methods, Workshop Proceedings of ICCV 200
Depletion of CCS in a Candidate Warm-Carbon-Chain-Chemistry Source L483
We have carried out an observation of the CCS (=21) line
with the Very Large Array in its D-configuration toward a protostellar core
L483 (IRAS~181400440). This is a candidate source of the newly found
carbon-chain rich environment called "Warm-Carbon-Chain-Chemistry (WCCC)",
according to the previous observations of carbon-chain molecules. The CCS
distribution in L483 is found to consist of two clumps aligned in the
northwest-southeast direction, well tracing the CCS ridge observed with the
single-dish radio telescope. The most remarkable feature is that CCS is
depleted at the core center. Such a CCS distribution with the central hole is
consistent with those of previously observed prestellar and protostellar cores,
but it is rather unexpected for L483. This is because the distribution of CS,
which is usually similar to that of CCS, is centrally peaked. Our results imply
that the CCS (=21) line would selectively trace the outer
cold envelope in the chemically less evolved phase that is seriously resolved
out with the interferometric observation. Thus, it is most likely that the high
abundance of CCS in L483 relative to the other WCCC sources is not due to the
activity of the protostar, although it would be related to its younger chemical
evolutionary stage, or a short timescale of the prestellar phase.Comment: 10 pages, 3 figures, accepted for publication in ApJ Part
ALMA Observations of the IRDC Clump G34.43+00.24 MM3: DNC/HNC Ratio
We have observed the clump G34.43+00.24 MM3 associated with an infrared dark
cloud in DNC =3--2, HNC =3--2, and NH =3--2 with the
Atacama Large Millimeter/submillimeter Array (ALMA). The NH emission is
found to be relatively weak near the hot core and the outflows, and its
distribution is clearly anti-correlated with the CS emission. This result
indicates that a young outflow is interacting with cold ambient gas. The
HNC emission is compact and mostly emanates from the hot core, whereas
the DNC emission is extended around the hot core. Thus, the DNC and HNC
emission traces warm regions near the protostar differently. The DNC emission
is stronger than the HNC emission toward most parts of this clump. The
DNC/HNC abundance ratio averaged within a area around the phase center is higher than 0.06. This ratio
is much higher than the value obtained by the previous single-dish observations
of DNC and HNC =1--0 (0.003). It seems likely that the DNC and
HNC emission observed with the single-dish telescope traces lower density
envelopes, while that observed with ALMA traces higher density and highly
deuterated regions. We have compared the observational results with
chemical-model results in order to investigate the behavior of DNC and HNC in
the dense cores. Taking these results into account, we suggest that the low
DNC/HNC ratio in the high-mass sources obtained by the single-dish observations
are at least partly due to the low filling factor of the high density regions.Comment: accepted to Ap
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