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We have mapped three star-forming regions (G265.14+1.45, G269.16?1.14, G291.27?0.71) in the CS(3–2) and C34S(2–1) lines using the 15 m SEST telescope (Chile), and analyzed the relative positions of methanol and H2O masers, IRAS sources, and emission maxima in the CS lines. In most cases, the maser positions are close to those of the IRAS sources. We compared the radial velocities of the maser sources and high-density CS cores, and estimated the CS column densities assuming LTE. The sizes, densities, and masses of the dense core are estimated; the masses obtained in the LTE approximation agree with the virial masses. 相似文献
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A. I. Reshetnikov A. V. Zinchenko S. V. Yagovkina I. L. Karol V. E. Lagun N. N. Paramonova 《Russian Meteorology and Hydrology》2009,34(3):171-179
Methane emitted into the atmosphere from sources located in the Urengoi natural gas field is estimated from direct methane concentration measurements in the atmospheric boundary layer and modeling. The results of direct profile measurements in the summer-fall season of 2003 are generalized versus the data from the previous field studies and background monitoring of greenhouse gases in the northern polar region. The use of models for calculating the intensity of emission from sources located in the field area together with a set of methane concentration measurements at three altitudes allowed the authors to develop a method of verification of emission from a specific source, a deposit. The method estimates the emission both from part of the field area and from the whole field with an irregular distribution of the intensity of sources across the deposit area. 相似文献
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New expressions for ON and NS calibrations (we call them ON11 and NS11 calibrations) for the determination of oxygen and nitrogen abundances in HII regions are proposed. New criteria for the division of HII regions into three classes (hot, warm, and cold) are also proposed. ON11 and NS11 calibrations provide more accurate determination of oxygen and nitrogen abundances from integrated emission spectra, in comparison with ON and NS calibrations. Oxygen and nitrogen abundances are estimated for a sample of 57 470 SDSS galaxies using ON11 and NS11 calibrations. Strongline flux measurements for SDSS spectra of these galaxies are taken from the MPA/JHU catalog. A ??mass-metallicity?? diagram for several redshift ranges is constructed. It is found that the interstellar medium of galaxies with high masses log(M/M ??) > 11.3 was hardly enriched with either oxygen or nitrogen over the last 4 Gyrs (corresponding to the redshift interval z = 0?C0.4). This indicates that an active stage of star formation in massive galaxies was completed more than 4 Gyrs ago. For galaxies of lower masses, changes in oxygen and nitrogen abundances over the time period under consideration increase as galaxy mass decreases. 相似文献
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We have analyzed HCN(1-0) and CS(2-1) line profiles obtained with high signal-to-noise ratios toward distinct positions in three selected objects in order to search for small-scale structure in molecular cloud cores associated with regions of high-mass star formation. In some cases, ripples were detected in the line profiles, which could be due to the presence of a large number of unresolved small clumps in the telescope beam. The number of clumps for regions with linear scales of ～0.2–0.5 pc is determined using an analytical model and detailed calculations for a clumpy cloud model; this number varies in the range: ～2 × 104–3 × 105, depending on the source. The clump densities range from ～3 × 105–106 cm?3, and the sizes and volume filling factors of the clumps are ～(1–3) × 10?3 pc and ～0.03–0.12. The clumps are surrounded by inter-clump gas with densities not lower than ～(2–7) × 104 cm?3. The internal thermal energy of the gas in the model clumps is much higher than their gravitational energy. Their mean lifetimes can depend on the inter-clump collisional rates, and vary in the range ～104–105 yr. These structures are probably connected with density fluctuations due to turbulence in high-mass star-forming regions. 相似文献
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L. E. Pirogov V. M. Shul’ga I. I. Zinchenko P. M. Zemlyanukha A. N. Patoka M. Tomasson 《Astronomy Reports》2016,60(10):904-923
Five regions of massive-star formation have been observed in various molecular lines in the frequency range～85?89 GHz. The studied regions comprise dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including the kinetic temperatures (～20?40 K), the sizes of the emitting regions (～0.1?0.6 pc), and the virial masses (～40?500 M⊙). The column densities and abundances of various molecules are calculated assuming Local Thermodynamical Equilibrium(LTE). The core in 99.982+4.17, which is associated with the weakest IRAS source, is characterized by reduced molecular abundances. The molecular line widths decrease with increasing distance from the core centers (b). For b ? 0.1 pc, the dependences ΔV (b) are close to power laws (∝b?p), where p varies from ~0.2 to ~0.5, depending on the object. In four cores, the asymmetries of the optically thick HCN(1–0) and HCO+(1–0) lines indicates systematicmotions along the line of sight: collapse in two cores and expansion in two others. Approximate estimates of the accretion rates in the collapsing cores indicate that the forming stars have masses exceeding the solar mass. 相似文献
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A. V. Zinchenko N. N. Paramonova V. I. Privalov A. I. Reshetnikov V. S. Titov 《Russian Meteorology and Hydrology》2008,33(1):34-42
Data on atmospheric methane concentrations, measured at different levels (20, 30, and 60 m) with a time step of 20 min at an observation point at a distance of 50 km from the Urengoi field, are presented. The NOAA HYSPLIT model was used to identify technogenic emissions, and method of nocturnal accumulation was used to evaluate emissions from wetlands. It is demonstrated that observed short-term increases in methane concentration can be caused by salvo gas emissions during technological operations in the gas field. Mean methane flux density is estimated for the wetland adjoining the observation point. 相似文献
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L. S. Pilyugin I. A. Zinchenko T. X. Thuan 《Kinematics and Physics of Celestial Bodies》2010,26(5):215-232
A sample of 93 emission-line high luminosity galaxies from the Sloan Digital Sky Survey (SDSS) has been investigated. Line
intensities have been measured in 116 SDSS spectra. Oxygen abundance has been determined in the studied galaxies. Since the
auroral line of twice ionized oxygen [O III] λ 436.3 nm cannot be detected in the spectra of the sample, the intensity ratio
of nebular to auroral lines needed to determine the electron temperature is calculated using the ff-relation. The oxygen abundances obtained in SDSS high luminosity galaxies are 0.2–0.5 dex lower than the maximum attainable
value. This is caused by the fact that the sample includes only the gas-rich galaxies in which intense bursts of star formation
occur. The equivalent number of O7 V stars which are responsible for excitation of luminescent H II regions in the studied
sample is two or three orders of magnitude more than the number of stars which cause the luminescence of the brightest H II
regions in nearby galaxies, and it exceeds by one order of magnitude the number of stars which cause gas in SBS 0335-052 E
to glow. 相似文献
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The parameters of molecular clouds formed via the Parker instability with dominant radiative losses are estimated. In this scenario, the cloud parameters (such as their mean densities and masses) should depend on galactocentric radius. This dependence is determined mainly by radial variations of the gas metallicity and the flux of heating radiation in the Galaxy. Due to the development of the interchange mode of the Parker instability, the angular momentum of the clouds will not necessarily be parallel to the galactic rotation axis. 相似文献
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Considered is a source of solid particles (dust) that are visually observed in the layers of an ice core sampled by a joint Russian-Swiss expedition in 2001 in a saddle of Mount Belukha of the Altai mountain massif (the Katun Range, Altai Republic). Based on analysis of the archival data and a synoptic situation in the Central Asian region, it was found that the most likely source of solid aerosol particles in a glacier layer dated by 1985 is the uplift and transport of the surface soil layer by a whirlwind, observed on August 7, 1985, in the settlement of Dolino, Rubtsov region, Altai Territory. 相似文献