Spectral data for doubly excited states of helium with non-zero total angular momentum

A spectral approach is used to evaluate energies and widths for a wide range of singlet and triplet resonance states of helium. Data for total angular momentum $L=1,...,4$ is presented for resonances up to below the 5th single ionization threshold. In addition the expectation value of $\cos(\theta_{12})$ is given for the calculated resonances.Comment: 35 pages, 16 tables, to be published in Atomic Data and Nuclear Data Table

Properties of Active Galaxies Deduced from H I Observations

We completed a new survey for H I emission for a large, well-defined sample of 154 nearby (z < 0.1) galaxies with type 1 AGNs. We make use of the extensive database presented in a companion paper to perform a comprehensive appraisal of the cold gas content in active galaxies and to seek new strategies to investigate the global properties of the host galaxies and their relationship to their central black holes (BHs). We show that the BH mass obeys a strong, roughly linear relation with the host galaxy's dynamical mass. BH mass follows a looser, though still highly significant, correlation with the maximum rotation velocity of the galaxy, as expected from the known scaling between rotation velocity and central velocity dispersion. Neither of these H I-based correlations is as tight as the more familiar relations between BH mass and bulge luminosity or velocity dispersion, but they offer the advantage of being insensitive to the glare of the nucleus and therefore are promising new tools for probing the host galaxies of both nearby and distant AGNs. We present evidence for substantial ongoing BH growth in the most actively accreting AGNs. In these nearby systems, BH growth appears to be delayed with respect to the assembly of the host galaxy but otherwise has left no detectable perturbation to its mass-to-light ratio or its global gas content. The host galaxies of type 1 AGNs, including those luminous enough to qualify as quasars, are generally gas-rich systems, possessing a cold interstellar medium reservoir at least as abundant as that in inactive galaxies of the same morphological type. This calls into question current implementations of AGN feedback in models of galaxy formation that predict strong cold gas depletion in unobscured AGNs. (Abridged)Comment: To appear in ApJ; 14 page

Thermal analysis of continuous and patterned multilayer films in the presence of a nanoscale hot spot

Thermal responses of multilayer films play essential roles in state-of-the-art electronic systems, such as photo/micro-electronic devices, data storage systems, and silicon-on-insulator transistors. In this paper, we focus on the thermal aspects of multilayer films in the presence of a nanoscale hot spot induced by near field laser heating. The problem is set up in the scenario of heat assisted magnetic recording (HAMR), the next-generation technology to overcome the data storage density limit imposed by superparamagnetism. We characterized thermal responses of both continuous and patterned multilayer media films using transient thermal modeling. We observed that material configurations, in particular, the thermal barriers at the material layer interfaces crucially impact the temperature field hence play a key role in determining the hot spot geometry, transient response and power consumption. With a representative generic media model, we further explored the possibility of optimizing thermal performances by designing layers of heat sink and thermal barrier. The modeling approach demonstrates an effective way to characterize thermal behaviors of micro and nano-scale electronic devices with multilayer thin film structures. The insights into the thermal transport scheme will be critical for design and operations of such electronic devices

Infrared Studies of Molecular Shocks in the Supernova Remnant HB21: I. Thermal Admixture of Shocked H_2 Gas in the North

We present near- and mid-infrared observations on the shock-cloud interaction region in the northern part of the supernova remnant HB21, performed with the InfraRed Camera (IRC) aboard AKARI satellite and the Wide InfraRed Camera (WIRC) at the Palomar 5 m telescope. The IRC 7 um (S7), 11 um (S11), and 15 um (L15) band images and the WIRC H2 v = 1 -> 0 S(1) 2.12 um image show similar shock-cloud interaction features. We chose three representative regions, and analyzed their IRC emissions through comparison with H2 line emissions of several shock models. The IRC colors are well explained by the thermal admixture model of H2 gas--whose infinitesimal H2 column density has a power-law relation with the temperature T, dN ~ T^-b dT--with n(H2) ~ 10^3 cm^-3, b ~ 3, and N(H2 ;T > 100K) ~ 3x10^20 cm^-2. The derived b value may be understood by a bow shock picture, whose shape is cycloidal (cuspy) rather than paraboloidal. However, this picture raises another issue that the bow shocks must reside within ~0.01 pc size-scale, smaller than the theoretically expected. Instead, we conjectured a shocked clumpy interstellar medium picture, which may avoid the sizescale issue while explaining the similar model parameters. The observed H2 v = 1 -> 0 S(1) intensities are a factor of ~17 - 33 greater than the prediction from the power-law admixture model. This excess may be attributed to either an extra component of hot H2 gas or to the effects of collisions with hydrogen atoms, omitted in our power-law admixture model, both of which would increase the population in the v = 1 level of H2.Comment: 14 pages, 9 figures, ApJ accepted, higher resolution @ http://astro.snu.ac.kr/~jhshinn/ms.pd

Gas diffusion through columnar laboratory sea ice: implications for mixed-layer ventilation of CO₂ in the seasonal ice zone

Gas diffusion through the porous microstructure of sea ice represents a pathway for ocean–atmosphere exchange and for transport of biogenic gases produced within sea ice. We report on the experimental determination of the bulk gas diffusion coefficients, D, for oxygen (O2) and sulphur hexafluoride (SF6) through columnar sea ice under constant ice thickness conditions for ice surface temperatures between -4 and -12 °C. Profiles of SF6 through the ice indicate decreasing gas concentration from the ice/water interface to the ice/air interface, with evidence for solubility partitioning between gas-filled and liquid-filled pore spaces. On average, DSF6 inline image was 1.3 × 10-4 cm2 s-1 (±40%) and DO2 was 3.9 × 10-5 cm2 s-1 (±41%). The preferential partitioning of SF6 to the gas phase, which is the dominant diffusion pathway produced the greater rate of SF6 diffusion. Comparing these estimates of D with an existing estimate of the air–sea gas transfer through leads indicates that ventilation of the mixed layer by diffusion through sea ice may be negligible, compared to air–sea gas exchange through fractures in the ice pack, even when the fraction of open water is less than 1%

Addition Spectra of Chaotic Quantum Dots: Interplay between Interactions and Geometry

We investigate the influence of interactions and geometry on ground states of clean chaotic quantum dots using the self-consistent Hartree-Fock method. We find two distinct regimes of interaction strength: While capacitive energy fluctuations $\delta \chi$ follow approximately a random matrix prediction for weak interactions, there is a crossover to a regime where $\delta \chi$ is strongly enhanced and scales roughly with interaction strength. This enhancement is related to the rearrangement of charges into ordered states near the dot edge. This effect is non-universal depending on dot shape and size. It may provide additional insight into recent experiments on statistics of Coulomb blockade peak spacings.Comment: 4 pages, final version to appear in Phys. Rev. Let

Prevalence of Tidal Interactions among Local Seyfert Galaxies: The Control Experiment

We test whether there is a relation between the observed tidal interactions and Seyfert activity by imaging in HI twenty inactive galaxies at the same spatial resolution and detection threshold as the Seyfert sample. This control sample of inactive galaxies were closely matched in Hubble type, range in size and inclination, and have roughly comparable galaxy optical luminosity to the Seyfert galaxies. We find that only ~15% of the galaxies in our control sample are disturbed in HI, whereas the remaining ~85% show no disturbances whatsoever in HI. Even at a spatial resolution of ~10 kpc, none of the latter galaxies show appreciable HI disturbances reminiscent of tidal features. In a companion paper (Kuo et al. 2008), we report results from the first systematic imaging survey of Seyfert galaxies in atomic hydrogen (HI) gas. We find that only ~28% of the eighteen Seyfert galaxies in that sample are visibly disturbed in optical starlight. By contrast, ~94% of the same Seyfert galaxies are disturbed spatially and usually also kinematically in HI gas on galactic scales of >~20 kpc. In at least ~67% and up to perhaps ~94% of cases, the observed disturbances can be traced to tidal interactions with neighboring galaxies detected also in HI. The dramatic contrast between the observed prevalence of HI disturbances in the Seyfert and control samples implicates tidal interactions in initiating events that lead to luminous Seyfert activity in a large fraction of local disk galaxies.Comment: 38 pages, 27 figures, Accepted for publication in ApJ. Changes from previous version: The title of the previous version of this paper appeared in Astroph was incorrect. It has been replaced with the correct on

Microscopic description of nuclei in the middle of the pf-shell by a shell model calculation with G-matrix interaction

Energy levels and electromagnetic properties of with $N=28\sim 30$ nuclides are studied in terms of a large-scale shell model calculation, which contains no newly adjusted parameters. The Kuo-Brown $G$-matrix interaction is shown to reproduce energy levels of 205 low-lying states of these nuclei. We evaluate effective charges by incorporating the core-polarization effects caused by the coupling to GQR's. We then compute E2 moments and transition probabilities. The M1 moments and transition rates are calculated by quoting the effective $g$-factors of Towner, which are obtained by taking into account the meson-exchange and the core-polarization mechanisms. By this microscopic calculation most of the E2 properties and the magnetic moments are reproduced. Although there are agreements and disagreements in the M1 transition rates, the general tendency is reproduced. The $(e,e')$ and $(p,p')$ excitation from the ground state to some low-lying $2^+$ states is also discussed.Comment: 63 pages (LaTeX, to be published in Nucl. Phys. A

A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies

We have completed an optical spectroscopic survey of the nuclear regions (r < 200 pc) of a large sample of nearby galaxies. Although the main objectives of the survey are to search for low-luminosity active galactic nuclei and to quantify their luminosity function, the database can be used for a variety of other purposes. This paper presents measurements of the spectroscopic parameters for the 418 emission-line nuclei, along with a compilation of the global properties of all 486 galaxies in the survey. Stellar absorption generally poses a serious obstacle to obtaining accurate measurement of emission lines in nearby galactic nuclei. We describe a procedure for removing the starlight from the observed spectra in an efficient and objective manner. The main parameters of the emission lines (intensity ratios, fluxes, profile widths, equivalent widths) are measured and tabulated, as are several stellar absorption-line and continuum indices useful for studying the stellar population. Using standard nebular diagnostics, we determine the probable ionization mechanisms of the emission-line objects. The resulting spectral classifications provide extensive information on the demographics of emission-line nuclei in the local universe. This new catalog contains over 200 objects showing spectroscopic evidence for recent star formation and an equally large number of active galactic nuclei, including 46 which show broad H-alpha emission. These samples will serve as the basis of future studies of nuclear activity in nearby galaxies.Comment: To appear in the Astrophysical Journal Supplements. LaTex, 31 pages, plus an additional 23 figures and 5 tables. AASTex macro aaspp4.st