Dense gas in normal and active galaxies

Dense molecular medium plays essential roles in galaxies. As demonstrated by the tight and linear correlation between HCN(1–0) and FIR luminosities among star-forming galaxies, from very nearby to high-z ones, the observation of a dense molecular component is indispensable to understand the star formation laws in galaxies. In order to obtain a general picture of the global distributions of dense molecular medium in normal star-forming galaxies, we have conducted an extragalactic CO(3–2) imaging survey of nearby spiral galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). From the survey (ADIoS; ASTE Dense gas Imaging of Star-forming galaxies), CO(3–2) images of M 83 and NGC 986 are presented. Emphasis is placed on the correlation between the CO(3–2)/CO(1–0) ratio and the star formation efficiency in galaxies. In the central regions of some active galaxies, on the other hand, we often find enhanced or overluminous HCN(1–0) emission. The HCN(1–0)/CO(1–0) and HCN(1–0)/HCO⁺(1–0) intensities are often enhanced up to ∼0.2–0.3 and ∼2–3, respectively. Such elevated ratios have never been observed in the nuclear starburst regions. One possible explanation for these high HCN(1–0)/CO(1–0) and HCN(1–0)/HCO⁺(1–0) ratios is X-ray induced chemistry in X-ray dominated regions (XDRs), i.e., the overabundance of the HCN molecule in the X-ray irradiated dense molecular tori. If this view is true, the known tight correlation between HCN(1–0) and the star-formation rate breaks in the vicinity of active nuclei. Although the interpretation of these ratios is still an open question, these ratios have a great potential for a new diagnostic tool for the energy sources of dusty galaxies in the ALMA era because these molecular lines are free from dust extinction.     

Displacement distribution along minor fault traces

The variation of displacement along fifteen traces of minor normal faults was measured in the multilayered Quaternary sediments of Kyushu, Japan. In the diagrams of distance along a fault trace (L) vs displacement (D) two distinct types of faults, a cone-shaped L-D pattern (C-type) and mesa-shaped one (M-type), were detected. Because the L-D pattern is subject to slip-parallel strain in the wall rocks, a D-constant pattern is ascribed to the competent (rigid) material and a D-variable pattern is found in the incompetent material. Therefore, C-type faults are characteristic of homogeneous incompetent materials, whereas M-types are representative of faults that cut through a rigid unit. However, the steep slopes in the flanking sections of M-type patterns indicate that the faulting of a rigid unit should terminate in a strain absorber of incompetent materials. The concept of lithologic control in the L-D pattern is important for the better understanding of faulting processes as well as the localization of faults.     

Seasonal changes in camera-based indices from an open canopy black spruce forest in Alaska,and comparison with indices from a closed canopy evergreen coniferous forest in Japan

Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests.     

The temperature dependence of the crystal structure of berlinite, a quartz-type form of AlPO4

The temperature dependence of atomic positions, mean-square displacements and probability density functions in a synthetic specimen of berlinite was analyzed using X-ray single crystal data measured at fourteen values of temperature. The characteristic features and the temperature dependence of the structure of berlinite were found to be quite similar to those of quartz, in detail. With increasing temperature, the equilibrium position of an atom, if expressed in fractional coordinates, appears to move steadily toward its β-position along a straight line, and finally attain the β-phase positions after abrupt displacements in a narrow temperature range around 583?°C. The temperature dependence of the displacements of atoms from the corresponding high-symmetry β-positions, in α-berlinite, is well fitted with a classical Landau type expression of first-order phase transitions. The highly anisotropic mean square displacements, 〈u ²〉, of O atoms increase with increasing temperature, especially in a narrow range just below the α–β transition, in the directions nearly perpendicular to the librating Al-O-P bonds, attaining a local maximum of 0.115–0.117 Ų just above the transition point. With varying temperature, the principal axes for the O atoms change their directions smoothly toward those of the high temperature phase, while the axis with the largest 〈u ²〉 of the Al or P thermal ellipsoid remains in 〈100〉. These diffraction results are interpreted in terms of displacive structure transition involving both the ordered α- and β-forms. The Al–O and P–O bond distances are nearly constant around 1.73 and 1.53 Å, respectively, through the experimental range of temperature.