Depletion of CCS in a Candidate Warm-Carbon-Chain-Chemistry Source L483

We have carried out an observation of the CCS ($J_{N}$=2$_{1}-$1$_{0}$) line with the Very Large Array in its D-configuration toward a protostellar core L483 (IRAS~18140$-$0440). This is a candidate source of the newly found carbon-chain rich environment called "Warm-Carbon-Chain-Chemistry (WCCC)", according to the previous observations of carbon-chain molecules. The CCS distribution in L483 is found to consist of two clumps aligned in the northwest-southeast direction, well tracing the CCS ridge observed with the single-dish radio telescope. The most remarkable feature is that CCS is depleted at the core center. Such a CCS distribution with the central hole is consistent with those of previously observed prestellar and protostellar cores, but it is rather unexpected for L483. This is because the distribution of CS, which is usually similar to that of CCS, is centrally peaked. Our results imply that the CCS ($J_{N}$=2$_{1}-$1$_{0}$) 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

Spectrometer Using Superconductor Mixer Receiver (sumire) For Microwave Spectroscopy Of Molecules In Astronomical Interests

In radio astronomy, accurate rest frequencies of molecular transitions are indispensable for secure identification of molecular species and accurate analyses of Doppler shifts caused by motions of target sources. In observations, we have seriously realized the importance of the accurate rest frequencies of molecular transitions. For rare isotopic species lines and weak vibrational satellite lines, the situation is more serious. To overcome such a situation, an emission-type millimeter-wave spectrometer utilizing state-of-the-art radio-astronomical technologies is developed. The spectrometer is equipped with a 200 cm glass cylinder cell, a two sideband (2SB) Superconductor-Insulator-Superconductor (SIS) receiver in the 215-265 GHz band, and wide-band auto-correlation digital spectrometers. By using the four 2.5 GHz digital spectrometers, a total instantaneous bandwidth of the 2SB SIS receiver of 8 GHz can be covered with a frequency resolution of 88.5 kHz. This wide bandwidth allows us to measure relative intensities of lines which fall into the 8 GHz range. Spectroscopic measurements of HDO, CH$_3$CN, and CH$_3$OH are carried out in the 230 GHz band so as to examine frequency accuracy, stability, and sensitivity, as well as intensity calibration accuracy of our system. We confirm that the frequency accuracy for lines detected with a sufficient signal-to-noise ratio is better than 1 kHz, when the high-resolution spectrometer having a channel resolution of 17.7 kHz is used. Following this successive development of the spectrometer, we are measuring spectral lines of various isotopic species of molecules in astronomical interests

Survival of shrines from the 2011 Great Tsunami

A massive earthquake with a magnitude of 9.0 occurred on March 11, 2011, and a powerful tsunami devastated a large area along Japan???s eastern coastline. We investigated the tsunami damage using satellite images and aerial photographs, and visited damaged sites including 27 shrines near the coast in 2011 and 2012. It was found that all but two of these shrines survived the tsunami, even though the tsunami height differed from place to place. As a memorial to people who lost their lives in previous tsunamis, shrines were built on safe places where people can evacuate. Many of these shrines were undamaged because their elevation was higher than the tsunami height, and the lives of people who evacuated to the shrines were saved

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 $J$=3--2, HN$^{13}$C $J$=3--2, and N$_2$H$^+$ $J$=3--2 with the Atacama Large Millimeter/submillimeter Array (ALMA). The N$_2$H$^+$ 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 HN$^{13}$C emission is compact and mostly emanates from the hot core, whereas the DNC emission is extended around the hot core. Thus, the DNC and HN$^{13}$C emission traces warm regions near the protostar differently. The DNC emission is stronger than the HN$^{13}$C emission toward most parts of this clump. The DNC/HNC abundance ratio averaged within a $15^{\prime\prime} \times 15^{\prime\prime}$ 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 HN$^{13}$C $J$=1--0 ($\sim$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