arXiv subjects

N. Sato

Publications and source records attributed to N. Sato.

81 records · Page 5Linked to original sources

arXiv2011

The AMIGA sample of isolated galaxies IX. Molecular gas properties

Aims: We characterize the molecular gas content using CO emission of a redshift-limited subsample of isolated galaxies from the AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) project. Methods: We present the 12CO(1-0) data for 273 AMIGA galaxies. We constructed a redshift-limited sample containing galaxies with 1500\kms <v<5000\kms and excluded objects with morphological evidence of possible interaction. This sample ($n=173$) is the basis for our statistical analysis. It is dominated, both in absolute number and in detection rate, by galaxies of type T=3-5 (Sb-Sc). Most galaxies were observed with a single pointing towards their centers. Therefore, we performed an extrapolation to the total molecular gas mass expected in the entire disk based on the assumption of an exponential distribution. We then studied the relationships between \mhtwo\ and other galactic properties (\lb,\dopttwo,\lk, \lfir, and \mhi). Results: We find correlations between \mhtwo\ and \lb, \dopttwo, \lk, and \lfir. The tightest correlation of \mhtwo\ holds with \lfir\ and, for $T=3-5$, with \lk, and the poorest with \dopttwo. The correlations with \lfir and \lk are very close to linearity. The correlation with \lb is nonlinear so that \mhtwo/\lb\ increases with \lb. The molecular and the atomic gas masses of our sample show no strong correlation. We find a low mean value, log(\mhtwo/\mhi)=-0.7 (for $T=3-5$), and a strong decrease in this ratio with morphological type. The molecular gas column density and the surface density of the star formation rate (the Kennicutt-Schmidt law) show a tight correlation with a rough unity slope. We compare the relations of \mhtwo\ with \lb and \lk found for AMIGA galaxies to samples of interacting galaxies from the literature and find an indication for an enhancement of the molecular gas in interacting galaxies of up to 0.2-0.3 dex.

astro-ph.CO↗

arXiv2009

Decay Properties of $^{266}$Bh and $^{262}$Db Produced in the $^{248}$Cm + $^{23}$Na Reaction

Decay properties of an isotope $^{266}$Bh and its daughter nucleus $^{262}$Db produced by the $^{248}$Cm($^{23}$Na, 5\textit{n}) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. $^{266}$Bh was clearly identified from the correlation of the known nuclide, $^{262}$Db. The obtained decay properties of $^{266}$Bh and $^{262}$Db are consistent with those observed in the $^{278}$113 chain, which provided further confirmation of the discovery of $^{278}$113.

nucl-ex↗

arXiv2007

Nobeyama CO Atlas of Nearby Spiral Galaxies: Distribution of Molecular Gas in Barred and Non-barred Spiral Galaxies

The data from a CO(1 - 0) mapping survey of 40 nearby spiral galaxies performed with the Nobeyama 45-m telescope are presented. The criteria of the sample selection were (1) RC3 morphological type in the range Sa to Scd, (2) distance less than 25 Mpc, (3) inclination angle less than 79deg (RC3), (4) flux at 100 um higher than ~ 10 Jy, (5) spiral structure is not destroyed by interaction. The maps of CO cover most of the optical disk of the galaxies. We investigated the influence of bar on the distribution of molecular gas in spiral galaxies using these data. We confirmed that the degree of central concentration is higher in barred spirals than in non-barred spirals as shown by the previous works. Furthermore, we present an observational evidence that bars are efficient in driving molecular gas that lies within the bar length toward the center, while the role in bringing gas in from the outer parts of the disks is small. The transported gas accounts for about half of molecular gas within the central region in barred spiral galaxies. We found a correlation between the degree of central concentration and bar strength. Galaxies with stronger bars tend to have higher central concentration. The correlation implies that stronger bars accumulate molecular gas toward the center more efficiently. These results are consistent with long-lived bars.

astro-ph↗

arXiv2006

Pulse tube cryocooler with self-cancellation of cold stage vibration

We experimentally demonstrated a new method for reducing the vibration of the cold stage of a cryocooler. Comparing the RMS amplitude with the case of no phase shift of the driving gas pressure between the two pairs, the longitudinal vibration of the cold stage was reduced by 96.1% at 126 K by supplying gas pressure with 180 degrees of phase shift.

physics.ins-det↗

arXiv2004

Problems on invariants of knots and 3-manifolds

This is a list of open problems on invariants of knots and 3-manifolds with expositions of their history, background, significance, or importance. This list was made by editing open problems given in problem sessions in the workshop and seminars on `Invariants of Knots and 3-Manifolds' held at Kyoto in 2001.

math.GT↗

arXiv2004

Radio Observations of the Afterglow of GRB 030329

We present the results of the radio observations of the afterglow of GRB 030329 with the Nobeyama 45-m telescope. The observations were made at 23.5 GHz, 43 GHz, and 90 GHz. The light curves show steep decline after constant phase. The start time of the decline depends on frequency. Namely, the decline started earlier at higher frequency. The spectrum has a peak at mm wavelength range. The peak frequency and the peak flux decreased with time. These results are consistent with the expectation from fireball model.

astro-ph↗

arXiv2002

Three-dimensional reconstruction of the Fermi surface of LaB6

The 2-dimensional angular correlations of the positron annihilation radiation (2D-ACAR) on a single crystal of LaB6 was measured for three projections. The 2D-ACAR spectra were subjected to the Van Citter-Gerhard deconvolution alghorithm. From the experimental spectra we produced the 3D k-space density rho(k) via three different methods: i) we reconstructed the 3D electron-positron momentum density rho(p) via the Cormack method. rho(k) was then obtained by applying the 3D LCW transformation to rho(p). ii) The same steps of point i) were repeated adopting a modified Fourier-transform-based algorithm. iii) The 3d k-space occupancy rho(k) was obtained directly by parameterising the Fermi surface volume with prolate ellipsoids whose axes were determined by a least-square fit to the 2D LCW transformations applied to two high symmetry projections. The ellipsoids diameters along high symmetry directions of the cubic Brillouin zone (BZ), as a fraction of the BZ size, were 0.64 (dir. X-M) and 0.82 (dir. Gamma-X). The resulting Fermi volume, as a fraction of the BZ volume, was 0.55. These results agree within 1% with those obtained via the de Haas van Alphen experiments.

cond-mat.mtrl-sci↗

arXiv2002

Force measurements of a superconducting-film actuator for a cryogenic interferometric gravitational-wave detector

We measured forces applied by an actuator with a YBCO film at near 77 K for the Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. An actuator consisting of both a YBCO film of 1.6 micrometers thickness and 0.81 square centimeters area and a solenoid coil exerted a force of up to 0.2 mN on a test mass. The presented actuator system can be used to displace the mirror of LCGT for fringe lock of the interferometer.

gr-qc↗

arXiv1999

Lattice Chern-Simons Gravity via Ponzano-Regge Model

We propose a lattice version of Chern-Simons gravity and show that the partition function coincides with Ponzano-Regge model and the action leads to the Chern-Simons gravity in the continuum limit. The action is explicitly constructed by lattice dreibein and spin connection and is shown to be invariant under lattice local Lorentz transformation and gauge diffeomorphism. The action includes the constraint which can be interpreted as a gauge fixing condition of the lattice gauge diffeomorphism.

hep-th↗