Search

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 ($\sim14$ Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, $r\sim200$ pc) and a starburst ring (SB ring, $r\sim1.3$ kpc). These high-resolution maps ($\sim0.5$", $\sim35$ pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in each sub-region, followed by non-LTE analysis conducted using the radiative transfer code RADEX to fit observations and constrain gas temperature, CS column density and hydrogen density. Finally, the chemical code UCLCHEM is used to reconstruct the gas, allowing an insight into its origin and chemical history. The density of hydrogen in the CND is found to be $\geq10^5$ cm$^{-2}$, although exact values vary, reaching $10^6$ cm$^{-2}$ at the AGN. The conditions in the two arms of the SB ring appear similar to one another, though the density found ($\sim10^4$ cm$^{-2}$) is lower than in the CND. The temperature in the CND increases from east to west, and is also overall greater than found in the SB ring. These modelling methods indicate the requirement for multi-phase gas components in order to fit the observed emission over the galaxy. A larger number of high resolution transitions across the SLED may allow for further constraining of the conditions, particularly in the SB ring., 32 pages, 19 figures, 6 tables, accepted for publication in MNRAS

Recent developments in (sub-)millimeter facilities have drastically changed the amount of information obtained from extragalactic spectral scans. In this paper, we present a feature extraction technique using principal component analysis (PCA) applied to arcsecond-resolution (1.0-2.0 arcsec = 72-144 pc) spectral scan datasets for the nearby type-2 Seyfert galaxy, NGC 1068, using Band 3 of the Atacama Large Millimeter/submillimeter Array. We apply PCA to 16 well-detected molecular line intensity maps convolved to a common 150 pc resolution. In addition, we include the [SIII]/[SII] line ratio and [CI] $^3P_1$-$^3P_0$ maps in the literature, both of whose distributions show remarkable resemblance with that of a kpc-scale biconical outflow from the central AGN. We identify two prominent features: (1) central concentration at the circumnuclear disk (CND) and (2) two peaks across the center that coincide with the biconical outflow peaks. The concentrated molecular lines in the CND are mostly high-dipole molecules (e.g., H$^{13}$CN, HC$_3$N, and HCN). Line emissions from molecules known to be enhanced in irradiated interstellar medium, CN, C$_2$H, and HNC, show similar concentrations and extended components along the bicone, suggesting that molecule dissociation is a dominant chemical effect of the cold molecular outflow of this galaxy. Although further investigation should be made, this scenario is consistent with the faintness or absence of the emission lines from CO isotopologues, CH$_3$OH, and N$_2$H$^+$, in the outflow, which are easily destroyed by dissociating photons and electrons., 15 pages, 6 figures, 2 tables, accepted for publication in ApJ

Molecules in diffuse and translucent clouds experience cooling as a result of radiation and less excitation from collisions. However, rotation around a molecular axis of acetonitrile, CH3CN, cannot be cooled by radiation, causing rotational populations to concentrate at the J = K levels. We aim to search for absorption lines of CH3CN having J = K level concentrations in diffuse and translucent clouds. The JK = 43–33 transition at 73.6 GHz was investigated toward Sgr B2(M) in the Galactic Centre region and other sources, using the Nobeyama 45-m telescope. Based on the absorption lines detected toward Sgr B2(M), a radiation temperature of 2.8 ± 0.5 K, kinetic temperature of 88 ± 29 K and column density of (1.35 ± 0.14) × 1014 cm−2 were derived for this molecule, revealing extremely concentrated J = K levels due to the lower excitation temperature and higher kinetic temperature. The absorption lines occurred at a velocity of 64 km s−1. The results confirm that CH3CN with J = K level concentrations exists in the envelope of Sgr B2(M).

An unbiased spectral line survey toward a solar-type Class 0/I protostar, IRAS04368+2557, in L1527 has been carried out in the 3 mm band with the Nobeyama 45 m telescope. L1527 is known as a warm carbon-chain chemistry (WCCC) source, which harbors abundant unsaturated organic species such as C$_n$H ($n = 3,\ 4,\ 5,\ldots$) in a warm and dense region near the protostar. The observation covers the frequency range from 80 to 116 GHz. A supplementary observation has also been conducted in the 70 GHz band to observe fundamental transitions of deuterated species. In total, 69 molecular species are identified, among which 27 species are carbon-chain species and their isomers, including their minor isotopologues. This spectral line survey provides us with a good template of the chemical composition of the WCCC source., published online in PASJ

We present observational data of a molecular line survey toward the nearby galaxies NGC 1068, NGC 253, and IC 342 at the wavelengths of 3 mm ($\sim$85--116 GHz) obtained with the Nobeyama 45 m radio telescope. In IC 342 the line survey with high spectral resolution at the 3 mm region was reported for the first time. NGC 1068 is a nearby gas-rich galaxy with X-rays from an active galactic nucleus (AGN), and NGC 253 and IC 342 are nearby gas-rich galaxies with prototypical starbursts. These galaxies are useful to study the impacts of X-rays and ultraviolet radiation on molecular abundances. The survey was carried out with the resulting rms noise level of a few mK ($T\rm{_A^*}$). As a result we could obtain almost complete data of these galaxies at the 3 mm region: We detected 19--23 molecular species depending on the galaxies including several new detections (e.g., cyclic-C$_3$H$_2$ in IC 342). We found that the intensities of HCN, CN, and HC$_3$N relative to $^{13}$CO are significantly strong in NGC 1068 compared to those in NGC 253 and IC 342. On the other hand, CH$_3$CCH was not detected in NGC 1068. We obtained these results with the narrow beam (15$''$.2--19$''$.1) of the 45 m telescope among the single-dish telescopes, and in particular selectively observed the molecular gas close to the circumnuclear disk (CND) in NGC 1068. Our line intensities in NGC 1068 were compared to those obtained with the IRAM 30 m radio telescope already reported. As a result, the intensity ratio of each line was found to have information on the spatial distribution. Our observations obtained the line intensities and stringent constraints on the upper limit for the three galaxies with such narrow beam, and consequently, the data will be a basis for further observations with high spatial resolution., Comment: 30 pages, 13 figures, accepted for publication in PASJ

We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map $^{12}$CO($J$ = 1-0), $^{12}$CO($J$ = 2-1), $^{12}$CO($J$ = 3-2), $^{13}$CO($J$ = 2-1), and [CI]($^3P_1$-$^3P_0$) emission lines around the type 1 active galactic nucleus (AGN) of NGC 7469 ($z = 0.0164$) at $\sim 100$ pc resolutions. The CO lines are bright both in the circumnuclear disk (central $\sim 300$ pc) and the surrounding starburst (SB) ring ($\sim 1$ kpc diameter), with two bright peaks on either side of the AGN. By contrast, the [CI]($^3P_1$-$^3P_0$) line is strongly peaked on the AGN. Consequently, the brightness temperature ratio of [CI]($^3P_1$-$^3P_0$) to $^{13}$CO(2-1) is $\sim 20$ at the AGN, as compared to $\sim 2$ in the SB ring. Our local thermodynamic equilibrium (LTE) and non-LTE models indicate that the enhanced line ratios (or CI enhancement) are due to an elevated C$^0$/CO abundance ratio ($\sim 3-10$) and temperature ($\sim 100-500$ K) around the AGN as compared to the SB ring (abundance ratio $\sim 1$, temperature $\lesssim 100$ K), which accords with the picture of the X-ray-dominated Region (XDR). Based on dynamical modelings, we also provide CO(1-0)-to- and [CI]($^3P_1$-$^3P_0$)-to-molecular mass conversion factors at the central $\sim 100$ pc of this AGN as $\alpha_{\rm CO} = 4.1$ and $\alpha_{\rm CI} = 4.4~M_\odot$ (K km s$^{-1}$ pc$^2$)$^{-1}$, respectively. Our results suggest that the CI enhancement is potentially a good marker of AGNs that could be used in a new submillimeter diagnostic method toward dusty environments., Comment: 25 pages, 12 figures, 8 tables. Accepted for publication in ApJ. Minor updates in a replacement

It is important to investigate the relationships between the power sources and the chemical compositions of galaxies for understanding the scenario of galaxy evolution. We carried out an unbiased molecular line survey towards AGN host galaxy NGC1068, and prototypical starburst galaxies, NGC 253 and IC 342, with the Nobeyama 45-m telescope in the 3-mm band. The advantage of this line survey is that the obtained spectra have the highest angular resolution ever obtained with single-dish telescopes. In particular, the beam size of this telescope is ~15"--19", which is able to spatially separate the nuclear molecular emission from that of the starburst ring (d~30") in NGC 1068. We successfully detected approximately 23 molecular species in each galaxy, and calculated rotation temperatures and column densities. We estimate the molecular fractional abundances with respect to 13CO and CS molecules and compare them among three galaxies in order to investigate the chemical signatures of an AGN environment. As a result, we found clear trends on the abundances of molecules surrounding the AGN on 1 kpc scale. HCN, H13CN, CN, 13CN, and HC3N are more abundant, and CH3CCH is deficient in NGC 1068 compared with the starburst galaxies. High abundances of HCN, H13CN, and HC3N suggest that the circumnuclear disk in NGC 1068 is in a high-temperature environment. The reason for the non-detection of CH3CCH is likely to be dissociation by high energy radiation or less sublimation of a precursor of CH3CCH from grains., 36 pages, 11 figures, Accepted for publication in PASJ

We report the detection of two CH$_3$OH lines (J$_K$ = 2$_K$-1$_K$ and 3$_K$-2$_K$) between the progenitor's disks ("Overlap") of the mid-stage merging galaxy VV 114 obtained using the Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 and Band 4. The detected CH$_3$OH emission show an extended filamentary structure (~ 3 kpc) across the progenitor's disks with relatively large velocity width (FWZI ~ 150 km/s). The emission is only significant in the "overlap" and not detected in the two merging nuclei. Assuming optically-thin emission and local thermodynamic equilibrium (LTE), we found the CH$_3$OH column density relative to H$_2$ ($X_{\rm CH_3OH}$) peaks at the "Overlap" (~ 8 $\times$ 10$^{-9}$), which is almost an order of magnitude larger than that at the eastern nucleus. We suggest that kpc-scale shocks driven by galaxy-galaxy collision may play an important role to enhance the CH$_3$OH abundance at the "Overlap". This scenario is consistent with that shock-induced large velocity dispersion components of ionized gas have been detected in optical wavelength at the same region. Conversely, low $X_{\rm CH_3OH}$ at the nuclear regions might be attributed to the strong photodissociation by nuclear starbursts and/or putative active galactic nucleus (AGN), or inefficient production of CH$_3$OH on dust grains due to initial high temperature conditions (i.e., desorption of the precursor molecule, CO, into gas-phase before forming CH$_3$OH on dust grains). These ALMA observations demonstrate that CH$_3$OH is a unique tool to address kpc-scale shock-induced gas dynamics and star formation in merging galaxies., 8 pages, 4 figures, 3 tables, accepted for publication in ApJ

We have observed the J = 2–1 rotational emission line of PN toward the low-mass star forming region L 1157 with the Nobeyama 45 m telescope. The PN line has been detected toward the two shocked regions (B1 and B2) caused by the interaction between the blue lobe of the outflow from the protostar IRAS 20386+6751 and the ambient gas, whereas it has not been detected toward the protostar position. The fractional abundances of PN relative to H2 are evaluated to be (2–6) � 10 � 10 and (3–7) � 10 � 10 toward B1 and B2, respectively. Detection of PN in the B1 and B2 positions indicates that the formation of PN can be triggered by shocks. It seems most likely that PN is formed in the gas phase from PH3 evaporated from grain mantles, as suggested by the existing chemical model.

We have conducted a sensitive 3 mm observation toward the shocked region, Lynds 1157 B1, which is an interaction spot between a molecular outflow and its ambient gas. We have successfully detected the CH3CHO, HCOOCH3, and HCOOH lines, as well as the CH2DOH line. The abundances of these molecules relative to CH3OH are found to be lower than those in the low-mass star-forming core, IRAS 16293� 2422. Since these molecules are thought to evaporate from grain mantles, the observational results mean that complex molecules are less abundant in grain mantles residing in the ambient cloud surrounding a prestellar/protostellar core. Instead, efficient formation of the complex organic species and deuterated species should take place in a prestellar/protostellar core. The present result verifies the importance of an unbiased line survey of this source.

We present high-resolution observations (0".2-1".5) of multiple dense gas tracers, HCN and HCO$^+$ ($J$ = 1-0, 3-2, and 4-3), HNC ($J$ = 1-0), and CS ($J$ = 7-6) lines, toward the nearby luminous infrared galaxy VV 114 with the Atacama Large Millimeter/submillimeter Array. All lines are robustly detected at the central gaseous filamentary structure including the eastern nucleus and the Overlap region, the collision interface of the progenitors. We found that there is no correlation between star formation efficiency and dense gas fraction, indicating that the amount of dense gas does not simply control star formation in VV 114. We predict the presence of more turbulent and diffuse molecular gas clouds around the Overlap region compared to those at the nuclear region assuming a turbulence-regulated star formation model. The intracloud turbulence at the Overlap region might be excited by galaxy-merger-induced shocks, which also explains the enhancement of gas-phase CH$_3$OH abundance previously found there. We also present spatially resolved spectral line energy distributions of HCN and HCO$^+$ for the first time, and derive excitation parameters by assuming optically-thin and local thermodynamic equilibrium (LTE) conditions. The LTE model revealed that warmer, HCO$^+$-poorer molecular gas medium is dominated around the eastern nucleus, harboring an AGN. The HCN abundance is remarkably flat ($\sim$3.5 $\times$ 10$^{-9}$) independently of the various environments within the filament of VV 114 (i.e., AGN, star formation, and shock)., 23 pages, 21 figures (downconverted), 5 tables, accepted for publication in ApJ

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.

We report Very Large Array CnB- and A-configuration observations of the 22 GHz H2O maser line toward the starburst galaxy NGC 253. We detect a broad, highly blueshifted (VLSR = 120.5 km s-1) H2O line coincident with the continuum source TH4, which is believed to be a supernova remnant. The H2O maser emission arises from an area whose size is smaller than 0.9 pc. A weaker feature at VLSR = 60.0 km s-1 is also seen at the same position. We also detect the extended 1.3 cm continuum along the galactic disk of NGC 253, as well as the two central continuum sources TH2 and TH4.

We present 0.8-mm band molecular images and spectra obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) toward one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068. Distributions of CO isotopic species ($^{13}$CO and C$^{18}$O) $\it{J}$ = 3--2, CN $\it{N}$ = 3--2 and CS $\it{J}$ = 7--6 are observed toward the circumnuclear disk (CND) and a part of the starburst ring with an angular resolution of $\sim$1.$^{\prime\prime}$3 $\times$ 1.$^{\prime\prime}$2. The physical properties of these molecules and shock-related molecules such as HNCO, CH$_{3}$CN, SO, and CH$_{3}$OH detected in the 3-mm band were estimated using rotation diagrams under the assumption of local thermodynamic equilibrium. The rotational temperatures of the CO isotopic species and the shock-related molecules in the CND are, respectively, 14--22 K and upper limits of 20--40 K. Although the column densities of the CO isotopic species in the CND are only from one-fifth to one-third of that in the starburst ring, those of the shock-related molecules are enhanced by a factor of 3--10 in the CND. We also discuss the chemistry of each species, and compare the fractional abundances in the CND and starburst ring with those of Galactic sources such as cold cores, hot cores, and shocked molecular clouds in order to study the overall characteristics. We find that the abundances of shock-related molecules are more similar to abundances in hot cores and/or shocked clouds than to cold cores. The CND hosts relatively complex molecules, which are often associated with shocked molecular clouds or hot cores. Because a high X-ray flux can dissociate these molecules, they must also reside in regions shielded from X-rays., 26 pages, 3 figures, Accepted for publication in PASJ

We observed ammonia (J,K)= (1,1), (2,2), (3,3), and (4,4) transitions at a wavelength of 1.3 cm toward a prototypical ultraluminous infrared galaxy, Arp 220, with the Nobeyama 45-m radio telescope. We detected extremely wide absorption lines at the (1,1) and (3,3) transitions. The maximum total velocity width was ∼ 1800kms−1. Such wide molecular absorption lines were detected for the first time in galaxies. The absorption lines are formed by ammonia only in front of the central compact continuum emission (∼ 1′′ = 370pc). The present results clearly indicate the existence of extremely high-velocity motion in the central compact region of Arp 220. A possible origin of such motion is rapidly rotating gas, suggesting the existence of an active galactic nucleus, or outflowing or inflowing gas.

Several transitions of the cyclopropenylidene (cyclic-C3H2) molecule have been observed in the 83–218GHz region toward NGC 253 and M 82. Assuming local thermodynamic equilibrium, the rotational temperatures were determined to be 10.8 ± 2. 4K and 11.5 ± 3.0 K for NGC 253 and M 82, respectively, where the errors indicate three standard deviations (3 σ). The column densities of cyclic-C3H2 were determined to be N(NGC 253) = (2.7 ±1.1) ×10 13 cm −2 and N(M 82)=(1.9±0.9)×10 13 cm −2 . Large velocity gradient calculations were applied to estimate kinetic temperatures of around 60K for NGC 253 and M 82. Considering the present result and recent observations of NH3 in both galaxies, molecular production mechanisms are discussed.

We report the results of the presently lowest frequency spectral line survey of the asymptotic giant branch carbon star IRC +10°216. The entire Arecibo C band (4-6 GHz) was observed with a noise level of ~0.3 mJy (1 σ). We report the detection of HC5N (J = 2-1), which is the lowest frequency transition of the HC5N molecule found in the envelope of IRC +10°216. The HC5N J = 2 column density derived from our observations confirms the presence of two temperature components in the molecular envelope of IRC +10°216. The HC5N J = 2-1 transition traces the cold molecular component characterized by an excitation temperature of ~13.8 K. We derive upper limits for several transitions of molecules that had previously been detected in IRC +10°216 at higher frequencies. We also report the frequency ranges in the Arecibo C band that were affected by radio frequency interference.

Developed a W-band (75-110 GHz) waveguide photomixer with a uni-traveling carrier photodiode, which can be driven by two 1.5-/spl mu/m lasers. It generates an output power of 2.2/spl plusmn/0.2 mW at 100 GHz with a laser power of less than 100 mW, and its relative power variation is as small as 3 dB across the entire frequency range of the W-band. A 100-GHz superconductor-insulator-superconductor receiver driven by this photomixer shows the same noise temperature around 26 K as that driven by a conventional Gunn oscillator.

Very high-resolution ( ∼ 30 kHz) and very precise (±2 kHz) saturation dip and crossover dip measurements are reported for HCN. Nine consecutive rotational transitions of the vibrational ground state were recorded, covering the rotational spectrum up to the J = 11 ← 10 transition at 975 GHz. Commencing the saturation dip measurements with the J = 3 ← 2 transition located at 265 886.4 MHz, all rotational transitions were measured up to J = 11 ← 10 (ΔF = 1), positioned at a center frequency of 974 487.2 MHz. It has become possible to resolve the hyperfine structure of every rotational transition to varying degrees. Transitions obeying the selection rules ΔJ = 1, ΔF = 0 are have been resolved, those obeying the selection rules J = 1, F = 1 are only resolved for transitions lower than the J = 6 ← 5 transition. These new experimental saturation dip data, together with the molecular beam maser emission data of the J = 1 → 0 and J = 2 → 1 transitions reported by De Lucia and Gordy, (Phys. Rev. 187, 58 (1969)), and the recent terahertz measurements performed in this laboratory up to J = 22-21 at 1.946 THz (Maiwald et al., J. Mol. Spectrosc. 202, 166 (2000)), were subjected to a least squares analysis which yielded a highly precise set of molecular constants for the ground state of HCN: B = 44 315.974 970 (156) MHz, D = 0.087 216 35 (169) MHz, H = 0.086 96 (242) Hz; eQq = -4.709 03 (162) MHz, eQqJ = 0.244 (88) Hz, CN = 10.09 (38) kHz, CNJ = -0.0143 (86) mHz. Two constants, the hydrogen spin-rotation, CH = -4.35 (5) kHz, and the spin-spin interaction between the proton and nitrogen nucleus, SNH = 0.154 (3) kHz, can not be determined from the saturation dip measurements and have been taken from Ebenstein and Muenter, J. Chem. Phys. 80, 3989 (1984). There also a value for the ground state permanent electric dipole moment (in Debye’s) is given, which we quote for completeness: 〈μ〉000 = 2.985 188 (3) D. We also report the discovery of the J = 3 → 2 and J = 4 → 3 ground state rotational transitions of HCN in the dark, cold molecular cloud TMC1 by using the KOSMA 3m-Submillimeter Telescope located in the central Swiss Alps. For the J = 3 → 2 transition the hyperfine splitting has partly been resolved. The intensities of the hyperfine components are anomalous, and they are not in thermodynamic equilibrium.

The ammonia $(J,K) = (1,1)$ , $(2,2)$ , $(3,3)$ , and $(4,4)$ transitions in the 23.7–24.1 GHz region were searched for in nearby galaxies, NGC 253 and M 82, to study the relation between the molecular abundances and physical conditions. The $(1,1)$ , $(2,2)$ , and $(3,3)$ emission lines were clearly detected in NGC 253, but no lines were found in M 82. In NGC 253 the shapes of the three emission lines were different from one another. The rotational temperatures obtained in NGC 253 were $\lesssim 17 \hbox{-} 50 \,{\rm K}$ , depending on the velocity components. There are two main results: (1) The ortho-to-para abundance ratio was obtained in NGC 253 and found to be different depending on the velocity components. The ratio was about 1 for the velocity component where the $(2,2)$ line is detected. On the other hand, the ratio was more than 6 for another velocity component where the $(2,2)$ line is barely detected. This high ratio corresponds to an equilibration temperature of less than 8 K between ortho and para. (2) The abundance of ${\rm NH}_3$ in NGC 253 was found to be about an order of magnitude larger than the upper limit in M 82. This result is an additional evidence for the different molecular abundances which were already reported between NGC 253 and M 82. In addition, the molecular abundances including ${\rm NH}_3$ in nearby galaxies with rich molecular gas were compared, and we found that the molecular abundance in M 82 is systematically peculiar concerning the formation mechanisms of molecules. We discussed factors which cause such a peculiarity in M 82.

Surprisingly large column densities of H3+ have been detected using infrared absorption spectroscopy in seven diffuse cloud sightlines (Cygnus OB2 12, Cygnus OB2 5, HD 183143, HD 20041, WR 104, WR 118, and WR 121), demonstrating that H3+ is ubiquitous in the diffuse interstellar medium. Using the standard model of diffuse cloud chemistry, our H3+ column densities imply unreasonably long path lengths (~1 kpc) and low densities (~3 cm^-3). Complimentary millimeter-wave, infrared, and visible observations of related species suggest that the chemical model is incorrect and that the number density of H3+ must be increased by one to two orders of magnitude. Possible solutions include a reduced electron fraction, an enhanced rate of H2 ionization, and/or a smaller value of the H3+ dissociative recombination rate constant than implied by laboratory experiments.

We present $1''.4$ (98 pc) resolution ALMA observations of $^{13}$CO($J$=1-0), C$^{18}$O($J$=1-0), CS($J$=2-1) and CH$_3$OH($J_K$=$2_K$-$1_K$) molecular lines in the central $1'$ (4.2 kpc) region of NGC 1068 to study the physical and chemical properties of giant molecular clouds (GMCs) and to test whether these GMC-scale properties are linked to the larger-scale galactic environment. Using the derived $^{13}$CO cube, we have identified 187 high-significance ($> 8\sigma$) GMCs by employing the CLUMPFIND algorithm. The molecular gas masses of GMCs $M_{\rm ^{13}CO}$, derived from the $^{13}$CO data, range from $1.8 \times 10^4 ~ M_\odot$ to $4.2 \times 10^7 ~M_\odot$. A mass function of GMCs in NGC 1068 has been obtained for the first time at $\sim$100 pc resolution. We find the slope of the mass function $\gamma = -1.25 \pm 0.07$ for a mass range of $M_{\rm ^{13}CO} \geq 10^5M_\odot$. This is shallower than the GMCs in the disk regions of the Milky Way, M51 and NGC 300. Further, we find that the high mass cut-off of the GMC mass function occurs at $M_{\rm ^{13}CO} \sim 6 \times 10^7 M_\odot$, which is an order of magnitude larger than that in the nuclear bar region of M51, indicating that the more massive clouds dominate the mass budget in NGC 1068. The observed C$^{18}$O)/$^{13}$CO intensity ratios are found to be fairly uniform (0.27 $\pm$ 0.05) among the identified GMCs. In contrast, the CH$_3$OH/$^{13}$CO ratios exhibit striking spatial variation across the disk, with the smallest values around the bar-end ($, Comment: 35 pages, 13 figures, in press at Publ. Astron. Soc. Japan

We report the development of the software-based polarization spectrometer‘ PolariS ’and early results from commissioning on the Nobeyama 45-m radio telescope. PolariS aims to detect the Zeeman effect of CCS line to measure ~ 100 μG magnetic fields in star-forming molecular cores. The PolariS consists of the K5/VSSP32 digitizer and a Linux-based PC with a GPU to process full-Stokes spectroscopy of 2 x 131072 ch for bandwidth of 4 or 8 MHz. We have verified performance of PolariS and succeeded to take full-stokes spectra of SiO masers. Since the code is open at GitHub everybody can utilize it.

We present the results of sulfur monoxide, SO line emission observations of G0.253+0.016 with the Atacama Large Millimeter/submillimeter Array (ALMA) at an angular resolution of 1.7 arcsec. The dense and massive molecular cloud of G0.253+0.016 is highly sub-structured, yet shows no obvious signs of cluster formation. We found three outstanding features of the cloud from the SO emission, namely, shell structure of radius 1.3 pc, large velocity gradients of 20 km/s/pc with the cloud, and cores with large velocity dispersions (30-40 km/s) around the shell structure. We suggest that these large-velocity dispersion cores will form high-mass stars in the future. In attempt to explore the formation scenario of the dense cloud, we compared our results with numerical simulations, thus, we propose that G0.253+0.016 may have formed due to a cloud-cloud collision process., Comment: 16 pages, 5 figures, accepted for publication in the Astronomical Journal

The Serpens South infrared dark cloud consists of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS ($J_N=4_3-3_2$), HC$_3$N ($J=5-4$), N$_2$H$^+$ ($J=1-0$), and SiO ($J=2-1, v=0$) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament in the protocluster clump. We emphasize that Serpens South is the first cluster-forming region where extremely-strong CCS emission is detected. The CCS-to-N$_2$H$^+$ abundance ratio is estimated to be about 0.5 toward the protocluster clump, whereas it is about 3 in the other parts of the main filament. We identify six dense ridges with different $V_{\rm LSR}$. These ridges appear to converge toward the protocluster clump, suggesting that the collisions of these ridges may have triggered cluster formation. The collisions presumably happened within a few $\times \ 10^5$ yr because CCS is abundant only in such a short time. The short lifetime agrees with the fact that the number fraction of Class I objects, whose typical lifetime is $0.4 \times \ 10^5$ yr, is extremely high as about 70 percent in the protocluster clump. In the northern part, two ridges appear to have partially collided, forming a V-shape clump. In addition, we detected strong bipolar SiO emission that is due to the molecular outflow blowing out of the protostellar clump, as well as extended weak SiO emission that may originate from the filament collisions., Comment: Accepted by ApJL, 13 pages, 4 figures, higher resolution figures available via http://th.nao.ac.jp/MEMBER/nakamrfm/sflegacy/paper/nakamura2014.pdf

Accepted: 2001-03-09, 資料番号: SA1002174000

Using the Green Bank 100 m telescope and the Nobeyama 45 m telescope, we have observed the rotational emission lines of the three 13C isotopic species of HC3N in the 3 and 7 mm bands toward the low-mass star-forming region L1527 in order to explore their anomalous 12C/13C ratios. The column densities of the 13C isotopic species are derived from the intensities of the J = 5-4 lines observed at high signal-to-noise ratios. The abundance ratios are determined to be 1.00:1.01 +- 0.02:1.35 +- 0.03:86.4 +- 1.6 for [H13CCCN]:[HC13CCN]:[HCC13CN]:[HCCCN], where the errors represent one standard deviation. The ratios are very similar to those reported for the starless cloud, Taurus Molecular Cloud-1 Cyanopolyyne Peak (TMC-1 CP). These ratios cannot be explained by thermal equilibrium, but likely reflect the production pathways of this molecule. We have shown the equality of the abundances of H13CCCN and HC13CCN at a high-confidence level, which supports the production pathways of HC3N via C2H2 and C2H2+. The average 12C/13C ratio for HC3N is 77 +- 4, which may be only slightly higher than the elemental 12C/13C ratio. Dilution of the 13C isotope in HC3N is not as significant as that in CCH or c-C3H2. We have also simultaneously observed the DCCCN and HCCC15N lines and derived the isotope ratios: [DCCCN]/[HCCCN] = 0.0370 +- 0.0007 and [HCCCN]/[HCCC15N] = 338 +- 12., Comment: 3 figures, 4 tables, 20 pages

The ammonia (J,K) = (1,1), (2,2), (3,3), and (4,4) transitions at 23.7 -- 24.1 GHz region were searched for in a nearby galaxy Maffei 2 to study relation between molecular abundances and physical conditions in galaxies. The (1,1), (2,2), and (3,3) emission lines were clearly detected. The rotational temperatures and ortho-to-para abundance ratios obtained are about 30 K and about 2.6, respectively. The abundance of NH3 relative to H2 in Maffei 2 was found to be the largest among galaxies where NH3 is already detected, and the abundance in Maffei 2 is more than an order of magnitude larger than the already reported upper limit in M82. Hence, we further confirmed the systematically peculiar molecular abundance in the aspect of formation mechanisms of molecules already reported in M82., Comment: 6 pages, 2 fugures

We report the first detection of rotational transitions of methyl formate (HCOOCH3) in the first torsionally excited state (vt = 1). Recent progress on the assignment of laboratory spectra of methyl formate made it possible for us to assign about 20 unidentified lines in Orion KL from previous line surveys below 200 GHz to the first torsionally excited methyl formate. The rotational temperature and column density obtained in the first torsionally excited state were 44 ± 10 K and (8.6 ± 3.2) × 1014 cm-2, respectively. They were compared with those in the ground state.

We have studied the abundances of the (13)C isotopic species of C3S and C4H in the cold molecular cloud, Taurus Molecular Cloud-1 (Cyanopolyyne Peak), by radioastronomical observations of their rotational emission lines. The CCCS/(13)CCCS and CCCS/C(13)CCS ratios are determined to be206 and 48 ± 15, respectively. The CC(13)CS line is identified with the aid of laboratory microwave spectroscopy, and the range of the CCCS/CC(13)CS ratio is found to be from 30 to 206. The abundances of at least two (13)C isotopic species of C3S are thus found to be different. Similarly, it is found that the abundances of the four (13)C isotopic species of C4H are not equivalent. The CCCCH/(13)CCCCH, CCCCH/C(13)CCCH, CCCCH/CC(13)CCH, and CCCCH/CCC(13)CH ratios are evaluated to be 141 ± 44, 97 ± 27, 82 ± 15, and 118 ± 23, respectively. Here the errors denote 3 times the standard deviation. These results will constrain the formation pathways of C3S and C4H, if the nonequivalence is caused during the formation processes of these molecules. The exchange reactions after the formation of these two molecules may also contribute to the nonequivalence. In addition, we have confirmed that the (12)C/(13)C ratio of some species are significantly higher than the interstellar elemental (12)C/(13)C ratio of 60-70. The observations of the (13)C isotopic species provide us with rich information on chemical processes in cold interstellar clouds.

The vibration–rotation absorption spectra of the C 3 S molecule were studied using a tunable infrared diode laser spectrometer. The ν 1 fundamental and ν 1 + ν 5 − ν 5 hot bands were measured between 2046 and 2067 cm −1 . The C 3 S molecule was produced by a glow discharge in a flowing mixture of CS 2 , C 2 H 2 , and He. The analysis of the measured spectral lines yielded the band origins, the rotational and centrifugal distortion constants in the upper vibrational states, and the l -type doubling constant for the ν 1 + ν 5 state. The band origins were determined to be 2058.21875(47) and 2053.03769(45) cm −1 for the ν 1 fundamental and ν 1 + ν 5 − ν 5 bands, respectively. The values in the parentheses correspond to three standard deviations.