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1.
CS(J=1–0), C34S(J=1–0), and CH3OH(10–00A and E) emission lines in the core region of molecular cloud associated with NGC 7538 have been surveyed at angular resolution of 33. Distribution of CS column density shows two prominent peaks. Both blue and red wings in CS line are most prominent at 30 northwest of IRS 11.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.This work was carried out under the common use observation program at the Nobeyama Radio Observatory (NRO). NRO, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open to outside users.  相似文献   

2.
Methanol 72–81 A + is mapped for the first time in Orion KL. Analysing the observed data and solving the statistical equilibrium and radiative transfer equations, it is concluded that line series ofJ 2–(J+1)1 A + (J=7,8,9) is in quasi-thermal emission rather than the masers in Orion KL. The maser spots of methanolJ 2–J 1 E (J=6,7) and 80–71 A + are distributed in the northeast part of the contour plot of 72–81 A +. The physical conditions of the regions of maser seriesJ 0–(J–1)1 A + (J=7,8,9) are discussed. Also from the calculation results another maser seriesJ 1–(J–1)2 A – (J=10,11,12) that might coexist with maser seriesJ 2–J 1 E, is found. The sizes of the 2-dimension Gaussian fit plots of methanol 72–81 A + and HCOOCH3 10(0,10)–9(0,9)A are almost the same, and the main parts overlap each other.  相似文献   

3.
Interstellar H2O and OH masers associated with massive star-forming regions can be classified into three morphological types: isolated H2O masers; isolated OH masers; and spatially overlapping OH/H2O maser groups. In a large sample of star-forming regions the total number of maser groups of each type is approximately equal. In order to account for these statistics we propose a pumping scheme based on a broadband radiative pump which produces inverted populations of both OH and H2O masers by a process involving predissociation and dissociation of H2O. This scheme overcomes some drawbacks of earlier radiative pumping models, and may account for the association of OH and H2O masers in massive star forming regions.  相似文献   

4.
A new pumping mechanism – methanol masers without population inversion is presented in this paper. It can be used to explain the formation of a series of J 0 → J -1 E methanol masers, while the 21 → 30 A + methanol masers are regarded as a driving coherent micrwave field. In the new mechanism, the intensities of J 0 - J -1 E methanol masers are increased with the decreasing transition frequencies (or with rotational number J, approximately). These results agree with Slysh et al. (1995) and Slysh et al. (1999) J ≤ 5 observations for G3345.01+1.79 and W48, in which both J 0 → J -1 E and 21 → 30 A + methanol masers are detected coincidentally. Other astronomical conditions, such as magnetic field, 21 → 30 A + coherent radition, incoherent pumping rate by thermal radition and so on are also discussed. The new mechanism can operate as a complement to other ordinary maser pumping mechanisms for some class II methonal maser sources. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

5.
By use of the data for VLBI observation of SiO masrs, and MERLIN observation of H2O and OH masers of VX Sgr, we found that the SiO, H2O, OH 1665/7, OH 1612 masers occur on a few separated shells, and the order of magnitude of the radii of their corresponding shells is 1014, 1015, 1016 cm, respectively. The field of the expanding velocity of the shells is obtained. It is important to note ice-layer covers on the surface of dust and grain for outlayer envelopes.  相似文献   

6.
We have observed C2H2 and HCN rovibrational transitions near 13µm in absorption against GL2591. We also have observed rotational transitions at 0.6-3 mm of CS, HCN, H2CO, and HCO+. Analysis of the rotational lines, which arise in the extended cloud around the source, shows that no single density model can explain all the data. Models with density and temperature gradients do much better; in particular models withn(r) r –1.5 can reproduce the observed pattern of emission line strengths. The abundances show significant depletion compared to models of gas-phase chemistry. The rovibrational data were analyzed in comparison to the absorption line analysis of CO by Mitchellet al. (1989). Our data are consistent with the C2H2 and HCN absorption arising in the same warm (200 K) and hot (1010 K) components seen in CO, but we see little evidence for the cold (38 K) component seen in CO. The rovibrational lines from higher states (J 21) indicate that the hot HCN deviates from LTE, leading to a density of about 3 × 107 cm–3. Comparison of the two data sets shows that the rovibrational absorption of HCN, rather than arising in the extended envelope, must come from a region with a small angular extent. A model in which early-time gas phase abundances are preserved on grain mantles and released at high temperature can explain the data.  相似文献   

7.
The evolution of the different chemical species are followed in a model of contracting interstellar cloud. The central density increases from n = 10 cm–3 diffuse initial cloud model to a dense cloud with central density number of n >- 105 cm–3 after a time of 1.2 × 107 yr. A network of 622 reactions has been involved. The chemistry of the cloud is integrated simultaneously with the hydrodynamic equations of contraction.The results predict that the different molecular species increase in abundance as the contraction proceeds. The species which enhance significantly are CO, HCO, CS and NO. The fractional abundances of many of the other molecular species increase distinctly with contraction, e.g. CH, C2H, CN, SO2, CO2, H2O, C2, NH3, HCN, SO, OCS and SN. The transformation of the initial diffuse cloud model with small abundances of molecular species to a dense molecular cloud with enhancement of the different molecular species is confirmed. The results predict good agreements of our results with both the observations and other theoretical studies.  相似文献   

8.
The masers of E-type methanol in orion KL and SGR B2   总被引：2，自引：0，他引：2  
Using a simplified model the statistical equilibrium and radiative transfer equations of E-type-CH3OH are solved for Orion KL and SgrB2. According to our calculation results and the observation data taken by Matsakiset al. (1980) and Morimotoet al. (1985a, b), the physical conditions of both sources are estimated. In theJ 2-J 1 E methanol maser region of Orion KL, the density, kinetic temperature, dust temperature, and the fractional abundance are 0.8–2×106 cm–3, 150, 30–90 K, 0.8–8×10–6. In the 4–1-30 E and 5–1-40 E methanol maser region of Sgr B2 the correspondance physical conditions above are 104 cm3, 45, 23 K, and 7×10–7, respectively.  相似文献   

9.
The M17SW molecular cloud core has been mapped at high resolution in the C17OJ = 3 2 transition and in 450, 600, 800, 1100 and 1300µm continuum emission, using the JCMT. The clumpy nature of the cloud core is clearly revealed and the northern condensation has been resolved into 3 main clumps, each of which lies close to an H2O maser, suggesting that they may contain young embedded stellar objects.  相似文献   

10.
We present MERLIN observations of OH and H2O masers in the circumstellar envelope of S Per. The results are consistent with a model of a thick shell of H2O masers in a region which is still accelerating.  相似文献   

11.
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12.
New J=1-0 HCO+ and J=2-1 C18O observations of HH24–26 reveal striking differences between these and previous maps of higher-J transitions of HCO+ and CS. The high-J HCO+ and CS emission traces the densest portions of the cloud, while C18O traces the more tenuous envelope. This is also evident in the velocity structure. HCO+ and C18O appear to be depleted from the gas phase by amounts which vary with position.  相似文献   

13.
With the 13.7 m millimeter wave telescope of Purple Mountain Observatory at Qinghai Station, the simultaneous mapping observations at the 12CO(J=1-0), 13CO(J=1-0) and C18O(J=1-0) lines were performed towards the 24 Galactic high-mass star-forming cores, which are associated with water masers and have available Spitzer's infrared data. The average mapping range was 8′ × 8′. The C18O line emission was detected in all the cores, in which 11 cores were observed to the half maximum of their C18O integrated intensities and the rather extended (5′ − 8′) C18O maps were obtained, while the others were failed to make such a large scale mapping because of the low SNR or the intrinsically extended morphology of the cores. On the 11 completely mapped dense cores, we analyzed their characteristics and made the statistics and comparisons on the integrated intensity ratios between 12CO and 13CO (R12/13), 13CO and C18O(R13/18), as well as 12CO and C18O(R12/18). We concluded that as a tracer of dense gas, C18O is absolutely optically thin and can be used to detect the detailed structures of the cores, and that in general the 3 ratios increase gradually from the core center to the periphery. We found that the integrated intensity ratio R12/13 ranges from 2 to 6; R13/18 fluctuates between 4 and 20, but in central regions it is concentrated in the range 6–12 with a small fluctuation; and R12/18 occupies a wider range 13–90, but it is concentrated between 13 and 50 in the denser regions of the cores.  相似文献   

14.
Abstract— Toluene extracts from two (CSn)x photopolymers were examined with high‐performance liquid chromatography (HPLC), matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, particle‐induced x‐ray emission (PIXE), and 12C(d,p)13C nuclear microprobing. the extracts contained elemental s and at least from 17 to 20 distinct cmsn compounds with m/z less than ～500 amu. Whereas H2S is the dominant S‐bearing compound of the normal jovian atmosphere, elemental S, CS, and CS2 were observed at Shoemaker‐Levy 9 cometary impact sites and at altitudes of the transiently disturbed jovian atmosphere where photodissociation and photopolymerization occur. It is uncertain whether the CS2 molecular densities were sufficiently large for both to occur, but photopolymerization could have occurred during larger impacts of Jupiter's history. Because the known stable CmSn compounds are yellow, orange and deep red, they could contribute significantly to the colors of the jovian clouds.  相似文献   

15.
The solar and galactic cosmic rays interact directly with lunar surface materials, and the dominant nature of interactions is essentially the complete absorption of corpuscles. These corpuscles damage the lattice structure, and induce a complex set of reactions in the materials producing various species. The cosmic ray damage of the lattice would not produce an amorphous layer, similar to that produced by the solar wind, because the solar wind erosion rate is faster than the cosmic ray-induced amorphous layer formation rate. The species formation rate considered in this paper are those produced by protons, the dominant component of cosmic rays. Protons produce H, H2, OH, H2O, and hydrogenated species of carbon, nitrogen, sulfur, etc. These species, while migrating in the material, encounter oncoming cosmic ray corpuscles, and undergo a complex set of reactions. Although a variety of species are produced by protons, the dominant contributor to the atmosphere is H2. The H2 flux (molecules cm–2 sec–1) is about 1.5 × 105 as compared to the H flux of 8.4 × 101 and the H2O flux of 4.6 × 10–2. These fluxes are about 10–3 smaller than the fluxes of the same species produced by the solar wind protons. Thus the contributions of the cosmic ray-induced species to the atmosphere is very small compared to the solar wind-induced species. Although simulated experiments showed high concentractions of OH and H2O in the terrestrial materials of lunar type, these species concentrations in the lunar materials under the lunar environment is much smaller than those observed in the simulated experiments.  相似文献   

16.
Total internal partition sums are determined from 65 to 3010 K for 13C18O2, 13C18O17O, 12CH3D, 13CH3D, H12C12CD, 13C12CH6, 12CH379Br, 12CH381Br, 12CF4, H12C12C12C12CH, H12C12C12C14N, H12C12C13C14N, H12C13C12C14N, H13C12C12C14N, H12C12C12C15N, D12C12C12C14N, 14N12C12C14N, 15N12C12C15N, 12C32S, 12C33S, 12C34S, 13C32S, H2, HD, 32S16O, 32S18O, 34S16O, 12C3H4, 12CH3, 12C32S2, 32S12C34S, 13C32S2, and 32S12C33S. These calculations complete the partition sum data needed for additional isotopologues in HITRAN2008 and also extend the partition sums to molecules of astrophysical interest. These data, at 25 K steps, are incorporated into a FORTRAN code (TIPS_2011.for) that can be used to rapidly generate the data at any temperature in the range 70-3000 K.  相似文献   

17.
A unified picture of the photodissociation of theC 2 H radical has been developed using the results from the latest experimental and theoretical work. This picture shows that a variety of electronic states ofC 2 are formed during the photodissociation of theC 2 H radical even if photoexcitation accesses only one excited state. This is because the excited states have many avoided corssings and near intersections where two electronic states come very close to one another. At these avoided crossings and near intersections, the excited radical can hop from one electronic state to another and access new final electronic states of theC 2 radical. The complexity of the excited state surfaces also explains the bimodal rotational distributions that are observed in all of the electronic states studied. The excited states that dissociate through a direct path are limited by dynamics to produceC 2 fragments with a modest amount of rotational energy, whereas those that dissociate by a more complex path have a greater chance to access all of phase space and produce fragments with higher rotational excitation. Finally, the theoretical transition moments and potential energy curves have been used to provide a better estimate of the photochemical lifetimes in comets of the different excited states of theC 2 H radical. The photochemically active states are the 22+, 22II, 32II, and 32+, with photodissociation rate constants of 1.0×10–6, 4.0×10–6, 0.7×10–6, and 1.3×10–6s–1, respectively. These rate constants lead to a total photochemical lifetime of 1.4×105 s.  相似文献   

18.
W. Landgraf 《Solar physics》1992,142(2):403-406
From astrometric observations of minor planet (1566) Icarus from 1949 to 1987 were made solutions for improved orbital elements of Icarus and the quadrupole moment of the Sun. The formal result was J2 = -0.6±5.8 &d 10–6. From this we can conclude that J 2 is very probably less than 2 · 10–-5.  相似文献   

19.
To explain the intensity fluctuations observed from bursts of W3(OH) and Cep A H2O masers in the period of 50–60 days, we propose a new idea that energy of the maser pump is injected in the maser region with pulse form not only once but several times, and that it is supplied by the radiation diffusing through the gas cloud, in spite of the pump mechanism being radiation pump or collision pump. With our model the fits are obviously better than what many authors obtained in previous literature.  相似文献   

20.
The collisional pumping of H216O and H218O masers in hot dense gas-dust clouds has been simulated numerically. New data on the rate coefficients for collisional transitions from Faure et al. (2007) were used in the calculations. The possibility of detecting H218O emission in 22.2-GHz H216O maser sources is investigated. The medium is shown to become optically thick in the H218O lines for which an inverted level population is observed at H2O column densities of ∼1019–1020 cm−2. A simultaneous observation of H218O emission and H216O maser emission in the same source will allow the physical conditions in the gas-dust cloud to be refined.  相似文献   

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