On the geometry of Siegel-Jacobi domains

We study the holomorphic unitary representations of the Jacobi group based on Siegel-Jacobi domains. Explicit polynomial orthonormal bases of the Fock spaces based on the Siegel-Jacobi disk are obtained. The scalar holomorphic discrete series of the Jacobi group for the Siegel-Jacobi disk is constructed and polynomial orthonormal bases of the representation spaces are given.Comment: 15 pages, Latex, AMS fonts, paper presented at the the International Conference "Differential Geometry and Dynamical Systems", August 25-28, 2010, University Politehnica of Bucharest, Romani

The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics

We present observations of the distribution and kinematics of neutral and ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk of NGC 1144, but HI emission is detected over only 1/3 of this velocity range, in an area that corresponds to the NW half of the disk. In the nuclear region of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is observed. Faint, narrow HI absorption lines are also detected against radio sources in the SE part of the disk of NGC 1144, which includes regions of massive star formation and a Seyfert nucleus. The peculiar HI distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution which is concentrated in the SE disk. Although this may partly be the result of the destruction of HI clouds in the SE disk, there is circumstantial evidence that the entire HI emission spectrum of NGC 1144 is affected by a deep nuclear absorption line covering a range of 600 km/s, and is likely blueshifted with respect to the nucleus. In this picture, a high column-density HI stream is associated with the nuclear ionized gas velocity discontinuity, and the absorption effectively masks any HI emission that would be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures: arp118.fig1-16.ps; Accepted to Ap

IC 225: a dwarf elliptical galaxy with a peculiar blue core

We present the discovery of a peculiar blue core in the elliptical galaxy IC 225 by using images and spectrum from the Sloan Digital Sky Survey (SDSS). The outer parts of the surface brightness profiles of u-, g-, r-, i- and z-band SDSS images for IC 225 are well fitted with an exponential function. The fitting results show that IC 225 follows the same relations between the magnitude, scale length and central surface brightness for dwarf elliptical galaxies. Its absolute blue magnitude (M_B) is -17.14 mag, all of which suggest that IC 225 is a typical dwarf elliptical galaxy. The g-r color profile indicates a very blue core with a radius of 2 arcseconds, which is also clearly seen in the RGB image made of g-, r- and i-band SDSS images. The SDSS optical spectrum exhibits strong and very narrow nebular emission lines. The metal abundances derived by the standard methods, which are 12+log(O/H) = 8.98, log(N/O) = -0.77 and 12+log(S+/H+) = 6.76, turn out to be significantly higher than that predicted by the well-known luminosity-metallicity relation. After carefully inspecting the central region of IC 225, we find that there are two distinct nuclei, separated by 1.4 arcseconds, the off-nucleated one is even bluer than the nucleus of IC 225. The asymmetric line profiles of higher-order Balmer lines indicate that the emission lines are bluer shifted relative to the absorption lines, suggesting that the line emission arises from the off-center core, whose nature is a metal-rich Hii region. To the best of our knowledge, it is the first high-metallicity Hii region detected in a dwarf elliptical galaxy.Comment: 7 figures, accepted for publication in A

Anomalous Metal-Insulator Transition in Filled Skutterudite CeOs4_4Sb12_{12}

Anomalous metal-insulator transition observed in filled skutterudite CeOs$_4$Sb$_{12}$ is investigated by constructing the effective tight-binding model with the Coulomb repulsion between f electrons. By using the mean field approximation, magnetic susceptibilities are calculated and the phase diagram is obtained. When the band structure has a semimetallic character with small electron and hole pockets at $\Gamma$ and H points, a spin density wave transition with the ordering vector $\mathbf{Q}=(1,0,0)$ occurs due to the nesting property of the Fermi surfaces. Magnetic field enhances this phase in accord with the experiments.Comment: 4 pages, 4 figure

Electron correlation in FeSe superconductor studied by bulk-sensitive photoemission spectroscopy

We have investigated the electronic structures of recently discovered superconductor FeSe by soft-x-ray and hard-x-ray photoemission spectroscopy with high bulk sensitivity. The large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF), which is demonstrated to be a coherent quasi-particle peak. Compared with the results of the band structure calculation with local-density approximation, Fe 3d band narrowing and the energy shift of the band toward EF are found, suggesting an importance of the electron correlation effect in FeSe. The self energy correction provides the larger mass enhancement value (Z^-1=3.6) than in Fe-As superconductors and enables us to separate a incoherent part from the spectrum. These features are quite consistent with the results of recent dynamical mean-field calculations, in which the incoherent part is attributed to the lower Hubbard band.Comment: 8 pages, 5 figures, 1 talbl

Possible unconventional superconductivity in iron-based layered compound LaFePO: Study of heat capacity

Heat capacity measurements were performed on recently discovered iron based layered superconductors, non doped LaFePO and fluorine doped LaFePO. A relatively large electronic heat capacity coefficient and a small normalized heat capacity jump at Tc = 3.3 K were observed in LaFePO. LaFePO0.94F0.06 had a smaller electronic heat capacity coefficient and a larger normalized heat capacity jump at Tc = 5.8 K. These values indicate that these compounds have strong electron electron correlation and magnetic spin fluctuation, which are the signatures of unconventional superconductivity mediated by spin fluctuation.Comment: 15 Pages, 3 Figure

The Structure of Rapidly Rotating Late-Type Spiral Galaxies: I. Photometry, HI and Optical Kinematics

We present I-band photometry, long-slit optical spectroscopy, and new aperture synthesis HI observations for eight late-type spirals with rotation velocities in the range 243 km/s < V_{rot} < 308 km/s. The sample will be used to study the structure and angular momentum of disks at the high-mass end of the spiral galaxy population; here we discuss the basic properties of these ``fast rotators'', and derive hybrid optical/HI rotation curves for each. Despite the presence of HI warps and low-mass companions in many systems, their kinematics are regular and there is excellent agreement between optical and HI tracers near the optical radius r_{opt}. At high inclinations at which projection effects are negligible, the sample galaxies exhibit flat, featureless rotation curves out to their last measured points at 1.7r_{opt}--3.5 r_{opt}. The intermediate inclination systems are also consistent with a constant rotation amplitude for r > 0.5 r_{opt}. We therefore find no evidence for declining rotation curves at the high-mass end of the late-type spiral galaxy population. Combining our data with the compilation of spirals with reliable outer HI kinematics from the work of Casertano & van Gorkom, we find no convincing trends between logarithmic outer rotation curve slopes and rotation amplitudes or surface brightnesses for galaxies with V_{rot} > 220 km/s. Correlations between these slopes and morphological types or disk scale lengths are also marginal in this regime.Comment: v2: minor changes to match proofs. 23 pages, 15 figures, AJ in press. For version with high resolution figures, see http://www.physics.rutgers.edu/~spekkens/papers/fast1.pd