Shuro Takano

A survey of CCS, HC3N, HC5N, and NH3 toward dark cloud cores and their production chemistry

Survey observations of CCS (J N = 4 3 -3 2 , J N = 2 1 -1 0 ), HC 3 N (J = 5-4), HC 5 N (J = 9-8, J = 17-16), and NH 3 (J, K = 1, 1) were carried out toward 49 dark cloud cores to examine the existence of a systematic relation between the chemical evolution and the physical evolution of dark clouds. The J N = 3 3 -2 2 and J N = 3 4 -2 3 lines of CCS and the J = 4-3 line of C 3 S were also observed in several cores

Laboratory spectroscopy of MgNC : the first radioastronomical identification of Mg-bearing molecule

The linear MgNC radical was detected, for the first time, by laboratory microwave spectroscopy, and six unidentified lines in IRC +10216 reported by Guelin et al. (1986) were assigned to the transitions of this radical. The radical was produced in a free space absorption cell by a DC discharge in a mixture of magnesium vapor, argon, and cyanogen. Observed spectral lines in the 250-370 GHz region were analyzed by using the 2 Σ energy level expression, to give the rotational, centrifugal distortion and spin-rotation constants: B 0 = 5966.896(24) MHz, D 0 =0.004 2338(35) MHz, H 0 =0.308(16)×10 −7 MHz, and B 0 =15.219(13) MHz, with one standard deviation in parentheses

Mapping observations of sulfur-containing carbon-chain molecules in Taurus Molecular Cloud 1 (TMC-1)

High-resolution mapping observations were carried out toward Taurus Molecular Cloud 1 (TMC-1) with sulfur-containing carbon-chain molecules, CCS and C 3 S, and other molecules, CS, C 34 S, HCS + , HC 3 N, HC 5 N, C 4 H, and NH 3 , to investigate detailed molecular distribution and physical structure of the cold dark cloud.

Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC1097

We present the first 100 pc scale view of the dense molecular gas in the central ~ 1.3 kpc region of the type-1 Seyfert NGC 1097 traced by HCN (J=4-3) and HCO+ (J=4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we study the characteristics of the dense gas around this AGN and search for the mechanism of HCN enhancement. We find a high HCN (J=4-3) to HCO+ (J=4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (v2=1^{1f}, J=4-3) to HCN (J=4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J=4-3) to CS (J=7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined from similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J=4-3 and 1-0 data from ALMA, and J=3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 < [HCN]/[HCO+] < 20: non-LTE analysis) in the nucleus, and that the high-J lines (J=4-3 and 3-2) are emitted from dense (10^{4.5} < n_H2 [/cc] < 10^6), hot (70 < Tkin [K] < 550) regions. Finally we propose that the high temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than the pure gas phase PDR/XDR chemistry.

Detection of HNCCC in TMC-1

The HNCCC molecule, an isomer of cyanoacetylene HCCCN, has been identified in TMC-1 through the observations with the Nobeyama 45 m telescope, considering the observed spectral pattern, results of ab initio calculations, and laboratory microwave spectroscopy. The column density of HNCCC in TMC-1 has been determined to be 3.8(0.6)×10 11 cm −2 , which is 160-450 times smaller than that of HCCCN

Abundance anomaly of the 13C species of CCH

Aims. We have observed the N = 1−0 lines of CCH and its 13 C isotopic species toward a cold dark cloud, TMC-1 and a star-forming region, L1527, to investigate the 13 C abundances and formation pathways of CCH. Methods. The observations have been carried out with the IRAM 30 m telescope. Results. We have successfully detected the lines of 13 CCH and C 13 CH toward the both sources and found a significant intensity difference between the two 13 C isotopic species. The [C 13 CH]/[ 13 CCH] abundance ratios are 1.6 ± 0. 4( 3σ )a nd 1.6 ± 0. 1( 3σ )f or TMC-1 and L1527, respectively. The abundance difference between C 13 CH and 13 CCH means that the two carbon atoms of CCH are not equivalent in the formation pathway. On the other hand, the [CCH]/[C 13 CH] and [CCH]/[ 13 CCH] ratios are evaluated to be larger than 170 and 250 toward TMC-1, and to be larger than 80 and 135 toward L1527, respectively. Therefore, both of the 13 C species are significantly diluted in comparison with the interstellar 12 C/ 13 C ratio of 60. The dilution is discussed in terms of a behavior of 13 Ci n

Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims. Exploring the distribution of di erent molecular species allows us to understand the physical processes a ecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods. We carried out 3 mm ALMA observations that include seven di erent molecular species, namely HCN, HCO + , CCH, CS, HNCO, SiO, HC3N, and SO, as well as the 13 C isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc ( 30 00 ) of the galaxy at a resolution of 2.2 00 1:5 00 (150 pc 100 pc). Results. HCO + and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions. Di erences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO + and HCN/CS di erences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation e ects, where a high density gas component ( 10 6 cm 3 ) may be more prominent in SB galaxies. However, the most promising are the di erences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.

Production Pathways of CCS and CCCS Inferred from Their 13C Isotopic Species

The rotational spectral lines (JN = 32-21 and JN = 21-10) of 13CCS and C13CS have been observed toward a cold dark cloud, TMC-1. The strongest hyperfine component lines of 13CCS and C13CS (JN = 21-10, F = 5/2-3/2) have successfully been detected. The / abundance ratio is determined to be 4.2 ± 2.3 (3 σ). The / ratio is evaluated to be 230 ± 130 (3 σ), and hence, 13CCS is found to be significantly diluted. Such a difference between the 13CCS and C13CS abundances is also found in L1521E, which is a very young core with rich carbon-chain molecules. Therefore, the anomaly is not specific to TMC-1, but seems to be common for the CCS-rich clouds. Furthermore, we have also observed the J = 4-3 transition of 13CCCS and CCC34S in TMC-1 and L1521E and have found that the / ratio is larger than 8.4 (3 σ). This lower limit is considerably larger than the interstellar / ratio of 3, indicating that 13CCCS is diluted as in the case of 13CCS. These results give us strong constraints on the main pathways to produce CCS and CCCS.

Tetrad effect in lanthanide partitioning between calcium sulfate crystal and its saturated solution

Abstract The distribution of rare-earth elements (REEs) between anhydrite crystal of calcium sulfate and its saturated solution was investigated at different temperatures. The lanthanide tetrad effect was observed as the apparent distribution coefficients. Furthermore, from the dependence of the apparent distribution coefficients on the growth of the anhydrite crystal, it was found that the process of the REE incorporation into the anhydrite crystal could be divided into two stages, namely, nonselective incorporation followed by thermodynamically controlled differential incorporation. It can be presumed that the factor affecting the extent of the tetrad effect depends effectively on the relative intensity of the two processes of incorporation of REEs into the anhydrite. This result would throw light on understanding of tetrad effects observed in various natural environments.

Microwave spectra of the AlO (X 2Σ+) radical in the v= 1 and 2 states

Abstract The microwave spectra of the aluminum monoxide radical (X 2 Σ + ) for v = 1 and 2 have been observed by using a source-modulated spectrometer combined with a free-space absorption cell. The Al atom was generated by discharge in pure N 2 O or Ar with an aluminum hollow-cathode containing several pieces of alumina. Five rotational transitions in the region 180–380 GHz were measured. The fine and hyperfine structure patterns of a certain rotational transition showed that the spin-rotation coupling constant changes anomalously by vibrational excitation. The rotational constant, centrifugal distortion constant, spin-rotation coupling constant with its centrifugal distortion term, and hyperfine coupling constants for the Al nucleus were precisely determined for the v = 1 and 2 states.