arXiv subjects

Y. Taniguchi

Publications and source records attributed to Y. Taniguchi.

263 records · Page 15Linked to original sources

arXiv1999

Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic-Wind and Nuclear-Inflow in NGC 3256

We find in a detailed morphological study (at 15 pc resolution) that the extended massive star formation process, shows: (i) extended triple asymmetrical spiral arms structure (r = 5 kpc); and (ii) the spiral arms emanate from three different nuclei. The main optical nucleus shows a small spiral-disk (r = 500 pc) which is a continuation of the external one and reach the very nucleus. And this very nucleus shows blue elongate structure (63 pc x 30 pc), and luminous blue star cluster properties. We study the kinematics of this system and present a detailed Halpha velocity field for the central region (r = 5 kpc). In the main optical nucleus we found a clear "outflow component" associated to galactic-winds and a "inflow radial motion" (in the spiral-disk nuclear structure, r = 700 pc). In addition we detected the outflow component in the central and external regions (r < 5-6 kpc), with a very wide opening angle of 140. We found that the mean value of the inflow region (at PA = 80) is practically perpendicular to the axis of the bipolar outflow (at PA = 160). We analyze in detail the physical conditions in the giant H II regions located in the asymmetric spiral arms, the two main optical nuclei, and the outflow component. In the central region (r = 5-6 kpc) we detected that the nuclear starburst and the extended giant H II regions have very similar properties. We suggest that the interaction between dynamical effects, the galactic--wind (outflow), low-energy cosmic rays, and the molecular+ionized gas (probably in the inflow phase) could be the possible mechanism that generate the "similar extended properties in the massive star formation, at scale of 5-6 kpc!". We analyze for NGC3256 the possible evolution from luminous IR galaxy to QSOs.

astro-ph↗

arXiv1999

Lattice QCD with Domain-Wall Fermions

We study the quenched lattice QCD using domain-wall fermions at $β=6.0$. Behaviors of both pion mass and the explicit breaking term in the axial Ward-Takahashi identity support the existence of the chiral zero modes. We observe a good agreement between the pion decay constants $f_π$ from both the conserved axial current and the local current perturbatively renormalized at 1-loop. Finally the possible existence of the parity broken phase is also examined in this model.

hep-lat↗

arXiv1999

Quenched QCD with domain-wall fermions on coarse lattices

We investigate the existence of chiral zero modes at a^{-1} \simeq 1 GeV in quenched domain-wall QCD. Simulations are carried out for the plaquette and an RG-improved gauge actions on a 12^3x24xN_s lattice with N_s=10-50. We find that the pion mass in the chiral limit remains non-vanishing as N_s\to\infty for both gauge actions. Possible origins of this non-vanishing pion mass are discussed.

hep-lat↗

arXiv1998

New Near-Infrared Spectroscopy of the High Redshift Quasar B 1422+231 at z=3.62

We present new near-infrared (rest-frame UV-to-optical) spectra of the high redshift, gravitationally lensed quasar B 1422+231 (z=3.62). Diagnostic emission lines of FeII, [OIII]5007, and Hb, commonly used to determine the excitation, ionization, and chemical abundances of radio-quiet and radio-loud quasars, were detected. Our new data show that the ratio FeII(UV)/Hb=18.1+-4.6 and FeII(optical)/Hb=2.3+-0.6 are higher than those reported by Kawara et al. (1996) by factors of 1.6 and 3.3, respectively, although the ration [OIII]5007/Hb=0.19+-0.02 is nearly the same between the two measurements. The discrepancy of the line flux ratios between the measurements is likely due to improved data and fitting procedures rather that to intrinsic variability. While approximately half of the high-z quasars observed to date have much more extreme FeII(optical)/Hb ratios, the line ratio measured for B 422+231 are consistent with the observed range of FeII(optical) ratios of low-z quasars.

astro-ph↗

arXiv1998

Dusty star forming galaxies at high redshift

The global star formation rate in high redshift galaxies, based on optical surveys, shows a strong peak at a redshift of z=1.5, which implies that we have already seen most of the formation. High redshift galaxies may, however, emit most of their energy at submillimeter wavelengths if they contain substantial amounts of dust. The dust would absorb the starlight and reradiate it as far-infrared light, which would be redshifted to the submillimeter range. Here we report a deep survey of two blank regions of sky performed at submillimeter wavelengths (450 and 850-micron). If the sources we detect in the 850-micron band are powered by star formation, then each must be converting more than 100 solar masses of gas per year into stars, which is larger than the maximum star formation rates inferred for most optically-selected galaxies. The total amount of high redshift star formation is essentially fixed by the level of background light, but where the peak occurs in redshift for the submillimeter is not yet established. However, the background light contribution from only the sources detected at 850-micron is already comparable to that from the optically-selected sources. Establishing the main epoch of star formation will therefore require a combination of optical and submillimeter studies.

astro-ph↗

arXiv1998

A Geometrical Relationship between Broad-Line Clouds and an Accretion Disk around Active Galactic Nuclei

Recent hard X-ray spectroscopy of active galactic nuclei has strongly suggested that double-peaked, very broad Fe K emission arises from an accretion disk around the central engine. Model fitting of the observed Fe K emission line profile makes it possible to estimate a probable inclination angle of the accretion disk. In order to study the geometrical relationship between the accretion disk and broad emission-line regions (BLRs), we investigate the correlation between the inclination angle of the accretion disk and the velocity width of BLRs for 18 type-1 Seyfert galaxies. We found that there may be a negative correlation between them, i.e., Seyfert nuclei with a more face-on accretion disk tend to have larger BLR velocity widths, suggesting that the BLRs are not coplanar with respect to the accretion disk. The most probable interpretation may be that the BLRs arise from outer parts ({\it r} $\sim$ 0.01 pc) of a warped accretion disk illuminated by the central engine.

astro-ph↗

arXiv1998

Dynamical Mass of Type 2 Seyfert Nuclei

We have derived the masses of central objects ($M_{BH}$) of nine type 2 Seyfert nuclei using the observational properties of the hidden broad H$β$ emission. We obtain the average dynamical mass, log$(M_{BH} / M_\odot) \simeq 8.00 \pm 0.51 - 0.475 log (τ_{es}/1)$ where $τ_{es}$ is the optical depth for electron scattering. If $τ_{es} \sim 1$, this average mass is almost comparable with those of type 1 Seyfert nuclei. However, if $τ_{es} \ll 1$, as is usually considered, the average mass of type 2 Seyfert nuclei may be more massive than that of type 1s. We discuss implications for issues concerning both the current unified model of Seyfert nuclei and physical conditions of the electron scattering regions.

astro-ph↗

arXiv1997

One loop calculation in lattice QCD with domain-wall quarks

One loop corrections to the domain-wall quark propagator are calculated in massless QCD. It is shown that no additative counter term to the current quark mass is generated in this theory, and the wave function renormalization factor of the massless quark is explicitly evaluated. We also show that an analysis with a simple mean-field approximation can explain properties of the massless quark in numerical simulations of QCD with domain-wall quarks.

hep-lat↗

arXiv1997

One loop calculation of QCD with domain-wall quarks

We calculate one loop corrections to the domain-wall quark propagator in QCD. We show how the wave function is renormalized in this theory. Especially we are interested in the behavior of the massless fermion mode, which exists near the domain wall at the tree level. We show that this massless mode is stable against the quantum correction.

hep-lat↗

arXiv1997

A New Superwind Wolf-Rayet Galaxy Mrk 1259

We report the discovery of a starburst-driven wind (superwind) from the starburst nucleus galaxy Mrk 1259. The estimated number ratio of Wolf-Rayet (WR) to O stars amounts to ~0.09. While the nuclear emission-line region is due to usual photoionization by massive stars, the circumnuclear emission-line regions show anomalous line ratios that can be due to cooling shocks. Since the host galaxy seems to be a face-on disk galaxy and the excitation conditions of the circumnuclear emission-line regions show the spatial symmetry, we consider that we are seeing the superwind nearly from a pole-on view. Cooling shock models may explain the observed emission line ratios of the circumnuclear regions although a factor of 2 overabundance of nitrogen is necessary. All these suggest that the high-mass enhanced starburst occurred ~5X10^6 years ago in the nuclear region of Mrk 1259.

astro-ph↗

arXiv1996

Dynamical Gauge Boson and Strong-Weak Reciprocity

It is proposed that asymptotically nonfree gauge theories are consistently interpreted as theories of composite gauge bosons. It is argued that when hidden local symmetry is introduced, masslessness and coupling universality of dynamically generated gauge boson are ensured. To illustrate these ideas we take a four dimensional Grassmannian sigma model as an example and show that the model should be regarded as a cut-off theory and there is a critical coupling at which the hidden local symmetry is restored. Propagator and vertex functions of the gauge field are calculated explicitly and existence of the massless pole is shown. The beta function determined from the $ Z $ factor of the dynamically generated gauge boson coincides with that of an asymptotic nonfree elementary gauge theory. Using these theoretical machinery we construct a model in which asymptotic free and nonfree gauge bosons coexist and their running couplings are related by the reciprocally proportional relation.

hep-th↗