bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Local Isolated Magnetic Flux Tubes in a Rapidly Rotating Stellar Atmosphere
Authors: Chou Wenchien , Tajima Toshiki , Matsumoto Ryoji , Shibata Kazunari
Published: March 2014

The dynamics of magnetic flux tubes in a rapidly rotating stellar atmosphere is considered. We focus on the effects and signatures of the instability of the flux tube emergence influenced by the Coriolis force. We present the results from a linear stability analysis and discuss its possible signatures during the course of the evolution of G-type and M-type stars. We carried out three-dimensional magnetohydrodynamical simulations of local isolated magnetic flux tubes under a magnetic buoyancy instability in co-rotating Cartesian coordinates. We have found that the combination of the buoyancy instability and the Coriolis effect gives rise to a mechanism to twist the emerging magnetic flux tube into a helical structure. The tilt angle, east-west asymmetry, and magnetic helicity of the twisted flux tubes in the simulations have been studied in detail. The linear and nonlinear analyses provide hints as to what kind of pattern of large spots in young M-type main-sequence stars might be observed. We have found that young and old G-type stars may have different distributions of spots, while M-type stars may always have low-latitude spots. The size of stellar spots may decrease when a star becomes older, due to a decrease in the magnetic field. A qualitative comparison with solar observations is also presented.
Hoyle-Lyttleton Accretion onto Accretion Disks
Authors: Fukue Jun , Ioroi Masayuki
Published: March 2014

We investigate Hoyle-Lyttleton accretion for the case where the central source is a luminous accretion disk. In Hoyle-Lyttleton accretion onto a “spherical” source, accretion takes place in an axially symmetric manner around a so-called accretion axis and the accretion rate Ṁ is given as ṀHL(1 − Γ)2, where ṀHL is the accretion rate of the classical Hoyle-Lyttleton accretion and Γ is the central luminosity normalized by the Eddington one. If the central object is a compact star with a luminous accretion disk, the radiation field becomes “non-spherical”. In such a case the axial symmetry around the accretion axis breaks down and the accretion rate Ṁ depends on an inclination angle i between the accretion axis and the symmetry axis of the disk. In the case of pole-on accretion (i = 0) the accretion rate becomes smaller than that of the spherical case. We found that the accretion rate is approximately expressed as dot Ṁ ∼ ṀHL(1− Γ)(1 − 2Γ). In the case of edge-on accretion (i = 90°) the shape of the accretion cross-section varies from a circle (Γ = 0), an ellipse, a hollow ellipse (Γ ∼ 0.5), and a twin lobe (Γ ≳ 0.65). The accretion rate is larger than that of the spherical case, and approximately expressed as Ṁ ∼ ṀHL(1 − Γ) for Γ ≤ 0.65 and Ṁ ∼ ṀHL(2 − Γ)2/5 for Γ ≥ 0.65. Once the accretion disk forms and the anisotropic radiation fields are produced around the central object, the accretion plane (and the direction of jets) will be maintained automatically. Thus, the anisotropic radiation field of accretion disks drastically changes the accretion nature, which gives a clue to the formation of accretion disks around an isolated black hole. Hoyle-Lyttleton type accretion onto the accretion disk may take place in various astrophysical situations, including the galactic center X-ray source 1E 1740.7–2942.
Radiative Winds in Supersoft X-Ray Sources with Passive Disks
Authors: Fukue Jun , Hachiya Masao
Published: March 2014

In supersoft X-ray sources (SSXSs) the central source, which is supposed to be a nuclear-burning white dwarf, is very luminous. In such a case the central luminosity (nuclear energy) dominates the disk luminosity (accretion energy). Therefore, the surrounding disk is not active, but passive, in the sense that irradiation heating dominates viscous heating. We examined the radiative environment and radiatively accelerated winds in such luminous SSXSs with passive disks. The radiation fields are generally enhanced in the polar direction due to the existence of the disk. We found that the wind configuration bifurcates according to the origin of wind gas; the wind tends to be a polar flow if it originates from the central star, whereas it becomes equatorial flow if it originates from the disk. The latter disk winds blow off the surface of the disk, confined in the vertical direction by the radiation fields. In both cases the terminal speed of the wind is of the order of ∧JGM(T — 1)/i?*, where M is the white-dwarf mass, R* the white-dwarf radius, and V the white-dwarf luminosity normalized by the Eddington luminosity. The polar flow is slightly faster than the equatorial flow, reflecting the bipolarity of radiation fields and the mass evaporation from the disk.
ASCA Observation of Kepler's Supernova Remnant
Authors: Kinugasa Kenzo , Tsunemi Hiroshi
Published: March 2014

We report the results of Kepler's supernova remnant (SNR) observed with ASCA. We clearly detected many emission lines from heavy elements on the SIS spectrum. Since we could not fit the data with a simple non-equilibrium ionization (NEI) hot-plasma model, we applied realistic SNR models employing either the Sedov model or the Chevalier model. As a result, the spectrum was not reproduced by the Sedov model, but was well-reproduced by the Chevalier model, except for the Fe-K line blends. The emission from the ejecta heated by reverse shock dominates that from the interstellar matter heated by the fore shock. The relative abundances of the ejecta strongly suggest that Kepler's SN is a SN la. However, the Fe-K line blends could not be reproduced well by only the Chevalier model from an astrophysical point of view. We found that the Fe-K line emission was well produced by an additional iron component. This component must have a relatively higher temperature and a lower ionization time scale than those of the ejecta component. This additional iron component may result from mixing of the inner region. This must be an iron-dominant plasma which is a fossil of the SN la explosion.
ASCA Observation of the Low-Luminosity Seyfert 1.5 Galaxy NGC 5033
Authors: Terashima Yuichi , Kunieda Hideyo , Misaki Kazutami
Published: March 2014

We present the results of an ASCA observation of the low-luminosity Seyfert 1.5 galaxy NGC 5033. A point-like X-ray source with a luminosity of 2.3×1041 erg s−1 in the 2–10 keV band (at 18.7 Mpc; Tully 1988, AAA 045.002.054) was detected at the nucleus. The X-ray light curve shows variability on a timescale of ∼ 104 s with an amplitude of ∼ 20%. The X-ray continuum is represented by a weakly absorbed (NH ≈ 9×1020 cm−2) power-law with a photon index of 1.72±0.04, which is quite similar to Seyfert 1 galaxies with higher luminosities. An Fe Kα emission line is detected at 6.40+0.08−0.06 keV (redshift corrected) and the equivalent width is 290±100 eV. The line width is unresolved. The narrower line width and larger equivalent width compared to Seyfert 1s imply that fluorescent Fe Kα emission from matter further out from the center than the accretion disk significantly contributes to the observed Fe Kα line. We suggest that fluorescent Fe Kα emission from the putative torus contributes to the observed Fe Kα line.
Quasi-Periodic Features Due to Clumps Orbiting around a Black Hole
Authors: Karas Vladimír
Published: March 2014

The expected Fourier power-spectrum density is examined with regard to the shape and quality factor Q of features which are predicted to appear in a signal from clumps orbiting near a marginally stable orbit of a compact body. It is shown that clumps distributed randomly in a narrow range of radii produce quasi-periodic oscillations with Q≈102, similar to those observed in many low-mass X-ray binaries.
Apparent Double SiO Maser Sources
Authors: Deguchi Shuji , Fujii Takahiro , Izumiura Hideyuki , Matsumoto Shigeru , Nakada Yoshikazu , Wood Peter R. , Yamamura Issei
Published: March 2014

During the course of a SiO maser survey of galactic disk IRAS sources at 43 GHz, we found two cases of doubly peaked SiO maser sources in the 40″ half-power beam of the Nobeyama 45-m telescope. The double peaks in the spectra of these sources (IRAS 18019-1822 and 18465-0717) have velocity separations of 73 and 147 km s−1, indicating that each peak comes from a separate source. Infrared imaging observations found pairs of candidate counterparts for each source with angular separations of about 20″. Combining the observational data, we conclude that these objects are apparent-double SiO sources, which are by chance seen in the same direction. The discovery rate for pairs of SiO maser sources in a single telescope beam is found to be consistent with the surface density of SiO maser sources in the galactic disk. These sources can be used to measure the parallaxes and proper motions with VLBI in the future.
Imaging Polarimetry and Color of the Inner Coma of Comet Hale-Bopp(C/1995 O1)
Authors: Furusho Reiko , Suzuki Bunji , Yamamoto Naotaka , Kawakita Hideyo , Sasaki Toshiyuki , Shimizu Yasuhiro , Kurakami Tomio
Published: March 2014

Optical-imaging polarimetry of comet Hale-Bopp (C/1995 O1) was performed on 1997 March 17, using the Okayama Optical Polarimetry and Spectroscopy system (OOPS), which was mounted on the 91-cm reflector at Okayama Astrophysical Observatory. Using two different narrow-band filters for the continuum, color maps and polarization maps of dust particles of comet Hale-Bopp were obtained. A dust “jet„ structure (also called ‘arc structure’) was seen in the intensity, polarization, and color maps. The polarization degree of the arc structure was higher than in other parts of the coma, and the color of the arc structure was bluer compared to other coma regions.
Is Galactic Star-Formation Activity Increased during Cluster Mergers?
Authors: Fujita Yutaka , Takizawa Motokazu , Nagashima Masahiro , Enoki Motohiro
Published: March 2014

We have investigated the effect of pressure from the intracluster medium on disk galaxies in merging clusters. The ram-pressure on the galaxies rapidly increases when two clusters collide. This leads to stripping of the interstellar medium (ISM) and a decrease in the star-formation rate (SFR) of the galaxies. On the other hand, the increase of the SFR caused by compression of the ISM is less significant. Thus, a cluster merger does not trigger, but weakens, the star-formation activity of galaxies. In the central region of colliding clusters, blue galaxies with high velocity should exist, although most galaxies become red. Following a decrease in the blue galaxy fraction in clusters, the fraction of post-starburst galaxies increases. After a merger, many galaxies in the cluster restart star-formation activity and the segregation of blue and red galaxies becomes prominent.
Metal Enrichment in the Early Galactic Halo
Authors: Ikuta Chisato , Arimoto Nobuo
Published: March 2014

The early history of metal enrichment in the galactic halo was studied. We investigated the chemical inhomogeneity by using a stochastic chemical evolution model. The model confronts the metallicity distribution function of long-lived halo stars, which has been found to be a clue to obtain the best model prescriptions. We have found that star formation in the halo virtually terminated by ∼ 1 Gyr and that the halo has never been chemically homogeneous in its star-formation history. This conclusion does not depend whether the mass loss from the halo is taken into account or not. The observed ratios of a-elements with respect to iron do not show scatters on a [a/Fe]-[Fe/H] plane, but this does not imply that interstellar matter in the halo was homogeneous because a chemical evolution path on this diagram is degenerate in the star-formation rate. On the other hand, an apparent spread of the [Sr/Fe] ratio among metal-poor halo stars does not reflect an inhomogeneous metal enrichment; instead, it is due to a sharp increase in the production rate of strontium, which is probably synthesised in slightly less-massive stars than the progenitor of iron-producing type II supernovae.
A Search for the CO (J = 1–0) Emission Line toward the Quasar H1413+117
Authors: Tsuboi Masato , Miyazaki Atsushi , Imaizumi Satoshi , Nakai Naomasa
Published: March 2014

We have searched for the CO (J = 1-0) line emission toward the gravitational lensed “Cloverleaf„ quasar, H1413+117, at z – 2.56 using the 45-m telescope of Nobeyama Radio Observatory. The r.m.s. noise of the resultant spectrum was 1 < 7rms = 0.6 mK in TUB or 1.6 mJy for a velocity resolution of 50 km s−1. We obtained the 5 αims upper limit of the velocity-integrated CO (J = 1–0) line flux, / S^dv < 1.4 Jy km s- The lower limit of the intrinsic ratio of the brightness temperature is TB[ CO (J = 3-2)]/TB[ CO (J = 1-0)] > 0.79 at z = 2.56. This value corresponds to TB[CO(J = 3-2)]/TB[CO (J - 1-0)] >= 0.72–0.75 at z = 0 from a LVG calculation. This temperature ratio is consistent with those in the central regions of nearby IR luminous galaxies.
High-Resolution VSOP Imaging of the Southern Blazar PKS 1921-293 at 1.6 GHz
Authors: Shen Zhi-Qiang , Edwards Philip G. , Lovell James E. J. , Fujisawa Kenta , Kameno Seiji , Inoue Makoto
Published: March 2014

We present a high-resolution 1.6 GHz VSOP image of the southern blazar PKS 1921-293. The image shows a typical core-jet morphology, consistent with ground-based VLBI images. However, the addition of data from the space antenna has greatly improved the angular resolution (especially along the north-south direction for this source), thus allowing us to clearly identify the core. Model fitting has revealed an inner jet component of ∼ 1.5 mas north of the core. This jet feature may be moving on a common curved path connecting the jet within a few parsecs to the 10-parsec-scale jet. The compact core has a brightness temperature of 2.6 × 1012 K (in the rest frame of the quasar), an indication of relativistic beaming. We analyzed the source in terms of three models involving the inverse Compton catastrophe, an inhomogeneous relativistic jet, and the equipartition of energy between the radiating particles and the magnetic field. Our analysis of this 7-ray-quiet blazar shows no preference to any particular one of these models.
TV Observation of the Leonid Meteor Shower in 1998: No Strong Activity over Japan
Authors: Watanabe Jun-ichi , Abe Shinsuke , Fukushima Hideo , Kinoshita Daisuke
Published: March 2014

We carried out a high-sensitivity TV observation of the Leonid meteor shower at the Nobeyama Radio Observatory, from 15h20m UT through 20h24m UT on 1998 November 17. We detected 58 Leonid meteors, along with 99 sporadic meteors. The peak of the activity, as expected around 20h UT, was not clearly observed. The average influx rate of meteoroids was 1.4 × 10−5 km−2 s−1 (mag < +8) during our observation.
VLBA Observation of SiO Masers in the M Giant IRC –10414
Authors: Imai Hiroshi , Deguchi Shuji , Miyoshi Makoto
Published: March 2014

We have mapped an M giant star, IRC ⤓10414, in the SiO J = 1–0 v = 1 line at 43.1 GHz with the VLBA‡ with a spatial resolution of better than 0.5 mas. The maser spots spread over on a circle having a radius of about 7.1 mas. A velocity gradient in the east-west direction of ∼ 0.7 km s−1 mas−1 is found. Monitoring observations with Nobeyama 45-m telescope have shown that the intensity ratio of the SiO J = 1 – 0 v = 1 to v = 2 maser line was quite unusual (5–40) for the period of 1997–1999 in this object; this ratio was known to be close to unity in many late-type stellar objects, but was known to deviate strongly from unity in young stellar objects. The unusual line intensity ratio of this star may suggest a chemical or geometrical anomaly of the envelope of IRC –10414. A possible ring/disk model is discussed in order to explain the distribution of the maser spots in this object.
Origin of High-Speed Non-Thermal Flow Due to the Collisions of Molecular Cloud Clumps
Authors: Kamaya Hideyuki
Published: March 2014

It is well-known that there is non-thermal flow in molecular clouds. Its origin is frequently discussed in the context of star-formation. Interestingly, non-thermal flow has two components of the velocity field. One of the two is the so-called turbulent component, and its velocity dispersion is expressed as σc, which is called the core-component. The other is the wing-component, and its dispersion is denoted as σw. There is a characteristic relation between those two components, σw ∼ 3 × σc. In this paper, we present a simple derivation of this core-wing relation, assuming that the wing component originates in the collisions of small clumps, which have been suggested observationally in molecular clouds and their cores. Throughout our discussions, we insist that the core-wing relation is a reminiscence of the shock property in a moment of collisions of the clumps.
ASCA Observation of a Radio-Loud Quasar and a New Candidate for a Cluster of Galaxies
Authors: Akimoto Fumie , Furuzawa Akihiro , Tawara Yuzuru , Kamata Yuichi , Yamashita Koujun
Published: March 2014

During an X-ray observation of the distant galaxy cluster CL 0107+31 (z = 0.69) with ASCA, an extended X-ray source was detected in the field of view. Based on an image analysis in two different energy bands of 1–3 keV and 3–10 keV, we found that this source consists of a hard point-like component and an additional soft diffuse X-ray source extended over ≥ 3′ in radius. However, due to poor photon statistics, we could not distinguish whether their X-ray spectra are thermal or non-thermal. The peak position of the central X-ray source coincides with a radio-loud quasar, NRAO 58. NRAO 58 is found to have a power-law spectrum with a photon index $1.6^{+0.3}_{-0.2}$ and a (2–10 keV) luminosity of ∼ 4×46 erg s−1 (in the quasar rest frame). The extended component is likely to be a candidate for a nearby galaxy group which accidentally coincides with the quasar.
Gamma-Ray Emission from Pulsar Outer Magnetosphere: Spectra of Curvature Radiation
Authors: Hirotani Kouichi , Shibata Shinpei
Published: March 2014

We consider the structure of a stationary outer-gap accelerator around an oblique rotator. Pulsar wind may bring about charge depletion in the magnetosphere near to the light cylinder; the charge depletion, in turn, would cause a large electric field along the magnetic field lines. Positrons or electrons migrating in the gap are accelerated by this field to radiate γ-ray photons by curvature radiation. These γ-ray photons produce yet more radiating particles by colliding with surface blackbody X-ray photons, leading to a pair-production cascade in the gap. The replenished charges partially screen the longitudinal electric field, which is self-consistently solved together with the distribution of e±'s and γ-ray photons. We find that both the peak energy and the luminosity of γ-rays are a decreasing function of the surface blackbody temperature. Applying the results to PSR B1706 – 44, we can predict that its unobserved X-ray spectrum has a blackbody temperature of about 100 eV.
Radiative Disk Winds from a Self-Similar Slim Disk
Authors: Watarai Ken-ya , Fukue Jun
Published: March 2014

We investigated the radiation fields of a self-similar slim disk and the behavior of wind particles, which are driven by the radiation pressure of a self-similar slim disk. When the accretion rate is of the order of a critical rate, the accretion disk must puff up in the vertical direction to form a so-called slim disk. In contrast to a standard alpha disk, this slim disk has two major features: i) the disk is geometrically (mildly) thick, and ii) the radial motion is comparable to the rotational motion (advection). These effects make the opening angle of the disk less than 180°, and the disk radiation fields are expected to enhance towards the center. However, we found that trajectories of wind particles are accelerated along the disk surface. This indicates that the shape of the disk strongly influence the motion of plasma particles. Furthermore, particles lose angular momentum by radiation drag, while gaining angular momentum from rotating radiation fields. Taking into consideration the Compton drag, the income and expenditure of angular momentum of wind particles is positive, and they tend to spread out in a radial direction.
Search for Molecular Clouds toward Intermediate-to-High Latitude IRAS Sources in the Southern Sky
Authors: Yonekura Yoshinori , Hayakawa Takahiro , Mizuno Norikazu , Mine Yoshihiro , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

We have conducted a search for molecular clouds toward southern IRAS point sources at intermediate-to-high galactic latitude (|b| ≥ 10° in 12CO (J = 1−0) emission with the NANTEN telescope. The main purpose of the survey was to find a new sample of star-forming clouds unknown to date. Of the 29 targets, we detected CO emission toward 5 IRAS sources, i.e., 04591–0856, 05044–0325, 05050–0614, 06345–3023, and 13543–3941. Among 5 detections, the molecular cloud associated with 06345–3023 (G 239.2–16.3) was detected for the first time. If we assume the distance as being 1.5 kpc, this\ source is ∼ 430 pc away from the galactic plane. Three sources 04591–0856 (G 208.3–28.4), 05044–0325 (G 203.5–24.7), and 05050–0614 (G 206.4–25.9) are located west to the Orion molecular clouds, and 13543-3941 (G 316.4+21.2) is located in the cometary globule CG 12. Four of the 5 clouds show a cometary shape with a “head-tail” distribution, and three of them have the IRAS source located at the edge opposite to the tail. We find that all of the CO clouds are associated with the optical nebulosities, which are likely to be reflection nebulae. A comparison of the present CO clouds with those in Ophiuchus, Taurus, Chamaeleon, and L 1333 indicates that star-forming clouds tend to have a high column density, as well as a smaller ratio of the virial mass to the LTE mass.
A Dark-Cloud Complex in Aquila: Small Molecular Clouds Possibly Associated with the Aquila Rift
Authors: Kawamura Akiko , Onishi Toshikazu , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

A 12CO(J = 1−0) survey for local molecular clouds was performed toward dark clouds in Aquila (26° < l ≤ 42° and −25° ≤ b < −2°) by using the 4-meter millimeter wave telescope, NANTEN, at Las Campanas Observatory, Chile. A cloud complex consisting of 64 small clouds has been discovered in −25° ≲ b ≲ −12°; at a distance of 220 pc, its height from the galactic plane is ∼ 50–100 pc and the total mass is ∼ 4 × 103M⊙. The spatial and velocity distributions of the complex suggest that it may be connected to the Great Rift in Aquila. This complex, as a whole, has a significantly large virial mass compared with the mass derived from the CO intensities by an order of magnitude, though H I gas of ∼ 104M⊙, possibly associated, may contribute to bind them gravitationally. The individual CO clouds have velocity dispersion and mass similar to those of the high-latitude clouds; also, the clouds are not in gravitational equilibrium. There is no indication of active star formation.
NANTEN Observations of the Southern Coalsack in 13CO and C18O J = 1−0 Emission
Authors: Kato Shigeo , Mizuno Norikazu , Asayama Shin-ichiro , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

We made observations of the 13CO and C18O J = 1−0 emission toward the Southern Coalsack. The 13CO observations covered the whole extent of the main cloud with a 2′.7 beam at an 8′ or 4′ grid spacing. The 13CO emitting gas is highly clumpy, consisting of small “cloudlets” of ≲ 0.4 pc diameter. The densest and most massive cloudlet, whose mass is ∼ 200 M⊙ , is coincident with the region of the heaviest visual extinction, located at the western edge of the cloud. The total mass of the 13CO emitting gas amounts to ∼ 600 M⊙ , corresponding to only ∼ 17% of the total cloud mass estimated from 12CO observations. In addition, toward the densest region in 13CO we made C18O J = 1−0 observations. We found five C18O dense cores, in agreement with well-known optically dark globules, and identified these dense cores to be potential sites of star formation, as indicated by their high column density, which is typical of star-forming cores. On the other hand, a comparison of the 13CO and C18O distributions with young stellar objects detected as IRAS point sources indicates no sign of recent star formation in the Southern Coalsack.
NANTEN Observations of Dense Cores in the Corona Australis Molecular Cloud
Authors: Yonekura Yoshinori , Mizuno Norikazu , Saito Hiro , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

We carried out a C18O survey for dense molecular cores in the Corona Australis (CrA) molecular cloud with the NANTEN telescope. We observed 2.2 deg2 at a 2′ grid spacing with a 2′.7 beam, and 1980 positions were observed. We identified 8 C18O cores, whose typical line width, average column density, radius, mass, and average number density were 0.66 km s-1, 1.1×1022 cm-2, 0.13 pc, 18 M⊙ , and 1.4 × 104 cm-3, respectively. We found that Δ Vcomp, 〈 N(H2)〉, R, M, and n(H2) become larger along with an increase in the star-formation activity, whereas the ratio Mvir/M becomes smaller. A comparison of the present cores with those in Chamaeleon, Lupus, Ophiuchus, Taurus, and L 1333 indicates that star-forming cores tend to have a high column density, as well as a smaller Mvir/M ratio.
VLBA Polarimetry Observation of the BL Lacertae Object 0300+470
Authors: Nan Ren Dong , Zhang Hai Yan , Gabuzda Denise C. , Inoue Makoto
Published: March 2014

New polarimetry VLBA images of the BL Lac object BL 0300+470 at 5 GHz (1995.33) and 8 GHz (1994.95) are presented. The source shows a variable compact, one-side core jet structure. The magnetic fields indicated by the polarization position-angles of the components appear to be parallel to the jet at the position of the inner knot at the 5 GHz band and to be predominantly transverse to the jet direction in the core region at 8 GHz band, which is typical of the core region polarization in BL Lac objects.
Gas, Iron, and Gravitational Mass in Galaxy Clusters: The General Lack of Cluster Evolution at z < 1.0
Authors: Matsumoto Hironori , Tsuru Takeshi Go , Fukazawa Yasushi , Hattori Makoto , Davis David S.
Published: March 2014

We have analyzed the ASCA data of 29 nearby clusters of galaxies systematically, and obtained temperatures, iron abundances, and X-ray luminosities of their intracluster medium (ICM). We also estimated the ICM mass using the β model, and then evaluated the iron mass contained in the ICM and derived the total gravitating mass. This gives the largest and most homogeneous information about the ICM derived only by ASCA data. We compared these values with those of distant clusters whose temperatures, abundances, and luminosities were also measured with ASCA, and have found no clear evidence of evolution for the clusters at z < 1.0. Only the most distant cluster at z = 1.0, AX J2019.3+1127, has an anomalously high iron abundance, but its iron mass in the ICM may be among normal values for the other clusters, because the ICM mass may be smaller than the other clusters. This may suggest a hint of evolution of clusters at z ∼ 1.0.
Comments on a Formation Scenario of the Two-Component Protogalaxy by Galactic Magnetic Fields
Authors: Kamaya Hideyuki
Published: March 2014

Within the framework of the two-component protogalaxy model, the components of which are dense cold clouds and diffuse coronal gas, we discuss the stability condition of the dense clouds against the Kelvin-Helmholtz instability (KHI). Interestingly, the stability condition of the clouds against KHI determines the global properties of the protogalaxies. Especially, in this paper, the effect of the magnetic field against KHI is examined. The author hypothesizes the two-component mixture to be magnetized. It is known that when the relative speed between two contacting fluids is smaller than the Alfvén speed, it is possible for KHI to be suppressed due to the magnetic field. Obviously, the efficiency of stabilization against KHI by this effect is related to the global property of the two-component protogalaxies. Hence, we find that the two-component model of the protogalaxy is compatible with the scenario of galaxy formation via a magnetic field.
ASCA Observations of RX J1838.4–0301
Authors: Song Liming , Mihara Tatehiro , Matsuoka Masaru , Negoro Hitoshi , Corbet Robin
Published: March 2014

The results of ASCA observations of RX J1838.4–0301 are presented. The source was found to be faint and there was no obvious X-ray flare during the ASCA observation. No evidence for pulsations was found near to the 5.45 s period previously reported from ROSAT observations. The source energy spectrum cannot be fitted well with either a single-component power law, thermal bremsstrahlung, or blackbody emission model, while a variety of two component models do give acceptable fits. The flux which we derive is consistent with that measured in the quiescent state with ROSAT. On the basis of the ROSAT and ASCA results, we suggest that RX J1838.4–0301 may be a transient source in which the quiescent state has a fairly constant flux level. However, our results do not yet enable a clear determination of whether this source is an anomalous X-ray pulsar or some other type of object.
Tridimensional Spectrophotometric Study of the Extended Emission-Line Regions of the Infrared-Luminous Merger Markarian 266
Authors: Ishigaki Tsuyoshi , Yoshida Michitoshi , Aoki Kentaro , Ohtani Hiroshi , Sugai Hajime , Hayashi Tadashi , Ozaki Shinobu , Hattori Takashi , Ishii Motomi
Published: March 2014

An extensive tridimensional spectrophotometric study of the extended emission-line regions of Mrk 266, a merging system of a Seyfert galaxy and a LINER, was performed. We obtained its narrow-band images of Hα, [OIII] λ5007, and [SII] λλ 6716, 6731 using an imaging Fabry-Perot interferometer with a tunable filter and area spectroscopic data by means of a slit-scan. From these data were found high-excitation regions characterized by large [OIII]/Hβ (∼ 10) and large HeII λ 4686/Hβ (≥ 0.2). These regions can be considered as being photoionized by a power-law continuum from the Seyfert nucleus. If the continuum is radiated isotropically, an ionizing luminosity of 1055–56 photons s−1 is required. This implies that the Seyfert nucleus is one of the most luminous Seyfert nuclei, and can dominate the heating of dust, emitting the enormous amount of infrared emission of Mrk 266 (∼ 3 × 1011L⊙). The line ratios and emission-line luminosities of the LINER nucleus can be interpreted as an indication of a central starburst with a bolometric luminosity of about 2–6 × 1010L⊙ and a large-scale outflow (“superwind”). Finally, we remark on the evolutionary nature of activities of Mrk 266.
Asymmetric Free-Free Absorption towards a Double Lobe of OQ 208
Authors: Kameno Seiji , Horiuchi Shinji , Shen Zhi-Qiang , Inoue Makoto , Kobayashi Hideyuki , Hirabayashi Hisashi , Murata Yasuhiro
Published: March 2014

We present 1.66 GHz VSOP (VLBI Space Observatory Programme) observations of a GHz-peaked spectrum (GPS) source, OQ 208. Two compact lobes with a 10 pc separation in the NE-SW direction are identified with those observed with ground VLBI at higher frequencies. We find that the two lobes are highly asymmetric in terms of a flux density ratio NE:SW of ∼ 60:1 at 1.66 GHz, larger than that at higher frequencies. Both lobes show a steeply rising spectrum between 1.66 and 2.32 GHz, which implies free-free absorption by an ambient plasma, rather than synchrotron self-absorption. The absorption features show different peak frequencies, and indicate a larger optical depth towards the fainter SW lobe. This suggests the existence of an external absorber embedding the lobes. Hence, we can estimate the electron temperature, Te, and the electron density, ne, of the absorber. Considering the optical depth and X-ray luminosity, we derive the electron temperature and density in the ranges of 104 < Te < 6 × 107 K and 600 < ne < 7 × 105 cm−3, respectively. These properties coincide with those of NLR (Narrow Line Region). We point out that the NLR plasma affects evolution of radio galaxies, paticularly GPS sources.
Infrared Imaging of the Gravitational Lens PG 1115+080 with the Subaru Telescope
Authors: Iwamuro Fumihide , Motohara Kentaro , Maihara Toshinori , Iwai Jun'ichi , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Terada Hiroshi , Goto Miwa , Oya Shin , Akiyama Masayuki , Ando Hiroyasu , Aoki Tetsuo , Chikada Yoshihiro , Doi Mamoru , Fukuda Takeo , Hamabe Masaru , Hayashi Masahiko , Hayashi Saeko S. , Horaguchi Toshihiro , Ichikawa Shinichi , Ichikawa Takashi , Imanishi Masatoshi , Imi Katsumi , Inata Motoko , Isobe Shuzo , Itoh Yoichi , Iye Masanori , Kaifu Norio , Kamata Yukiko , Kanzawa Tomio , Karoji Hiroshi , Kashikawa Nobunari , Kato Taichi , Kobayashi Naoto , Kobayashi Yukiyasu , Kodaira Keiichi , Kosugi George , Kurakami Tomio , Mikami Yoshitaka , Miyashita Akihiko , Miyata Takashi , Miyazaki Satoshi , Mizumoto Yoshihiko , Nakagiri Masao , Nakajima Koich , Nakamura Kyoko , Nariai Kyoji , Nishihara Eiji , Nishikawa Jun , Nishimura Shiro , Nishimura Tetsuo , Nishino Tetsuo , Noguchi Kunio , Noguchi Takeshi , Noumaru Jun'ichi , Ogasawara Ryusuke , Okada Norio , Okita Kiichi , Omata Koji , Oshima Norio , Otsubo Masashi , Sasaki Goro , Sasaki Toshiyuki , Sekiguchi Maki , Sekiguchi Kazuhiro , Shelton Ian , Simpson Chris , Suto Hiroshi , Takami Hideki , Takata Tadafumi , Takato Naruhisa , Tamura Motohide , Tanaka Kyoko , Tanaka Wataru , Tomono Daigo , Torii Yasuo , Usuda Tomonori , Waseda Koichi , Watanabe Juni'chi , Watanabe Masaru , Yagi Masafumi , Yamashita Takuya , Yamashita Yasumasa , Yasuda Naoki , Yoshida Michitoshi , Yoshida Shigeomi , Yutani Masami
Published: March 2014

We present high spatial resolution images of the gravitational-lens system PG 1115+080 taken with the near-infrared camera (CISCO) on the Subaru telescope. The FWHM of the combined image is 0″.32 in the K′-band, yielding spatial resolution of 0″.14 after a deconvolution procedure. This is a first detection of an extended emission adjacent to the A1/A2 components, indicating the presence of a fairly bright emission region with a characteristic angular radius of ∼ 5 mas (40 pc). The near-infrared image of the Einstein ring was extracted in both the J and K′ bands. The J – K′ color is found to be significantly redder than that of a synthetic model galaxy with an age of 3 Gyr, the age of the universe at the quasar redshift.
Subaru Observations for the K-Band Luminosity Distribution of Galaxies in Clusters near to 3C 324 at z ∼ 1.2
Authors: Kajisawa Masaru , Yamada Toru , Tanaka Ichi , Maihara Toshinori , Iwamuro Fumihide , Terada Hiroshi , Goto Miwa , Motohara Kentaro , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Iye Masanori , Imanishi Masatoshi , Chikada Yoshihiro , Simpson Chris , Sasaki Toshiyuki , Kosugi George , Usuda Tomonori , Kanzawa Tomio , Kurakami Tomio
Published: March 2014

We investigate the K-band luminosity distribution of galaxies in the region of clusters at z ∼ 1.2 near to the radio galaxy 3C 324. The imaging data were obtained during the commissioning period of the Subaru telescope. There is a significant excess of the surface number density of the galaxies with K = 17–20 mag in the region within ∼ 40″ from 3C 324. At this bright end, the measured luminosity distribution shows a drop, which can be represented by the exponential cut off of the Schechter-function formula; the best-fitted value of the characteristic magnitude, K*, is ∼ 18.4±0.8. This measurement follows the evolutionary trend of the K* of the rich clusters observed at an intermediate redshift, which is consistent with passive evolution models with a formation redshift zf ≳ 2. At K ≳ 20 mag, however, the excess of the galaxy surface density in the region of the clusters decreases abruptly, which may imply that the luminosity function of the cluster galaxies has a negative slope at the faint end. This may imply strong luminosity segregation between the inner and outer parts of the clusters, or some deficit of faint galaxies in the cluster central region of the cluster.
Color–Magnitude Sequence in the Clusters at z ∼ 1.2 near the Radio Galaxy 3C 324
Authors: Kajisawa Masaru , Yamada Toru , Tanaka Ichi , Maihara Toshinori , Iwamuro Fumihide , Terada Hiroshi , Goto Miwa , Motohara Kentaro , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Iye Masanori , Imanishi Masatoshi , Chikada Yoshihiro , Yoshida Michitoshi , Simpson Chris , Sasaki Toshiyuki , Kosugi George , Usuda Tomonori , Sekiguchi Kazuhiro
Published: March 2014

We have investigated the optical and near-infrared colors of K′-selected galaxies in clusters at z ∼ 1.2 near to the radio galaxy 3C 324 using images obtained with the Subaru telescope and archival HST data. The distribution of colors of the galaxies in the cluster region is found to be fairly broad, and it may imply significant scatter in their star-formation histories, although the effect of contamination of field galaxies is uncertain. The red sequence of galaxies whose R – K colors are consistent with passive evolution models for old galaxies is found to be truncated at K′ ∼ 20 mag, and there are few fainter galaxies with similar red colors in the cluster region. We find that the bulge-dominated galaxies selected by quantitative morphological classification form a broad sequence in the color-magnitude diagram, whose slope is much steeper than that expected from metallicity variations within a passively evolving coeval galaxy population. We argue that the observed color-magnitude sequence can be explained by metallicity and age variations, and the fainter galaxies with K′ > 20 mag may be 1–2 Gyr younger than the brighter galaxies. Some spatial segregation of the color and K′-band luminosity is seen in the sky distribution; the redder and the brighter objects tend to be located near 3C 324.
High-Resolution Images of the Ring Nebula Taken with the Subaru Telescope
Authors: Komiyama Yutaka , Yagi Masafumi , Miyazaki Satoshi , Okamura Sadanori , Tamura Shin'ichi , Fukushima Hideo , Doi Mamoru , Furusawa Hisanori , Fuse Tetsuharu , Hamabe Masaru , Hayashi Masahiko , Hayashino Tomoki , Imi Katsumi , Iye Masanori , Kaifu Norio , Karoji Hiroshi , Kawasaki Wataru , Kimura Masahiko , Kosugi George , Nakata Fumiaki , Noumaru Junichi , Okada Norio , Sasaki Toshiyuki , Sawada Yasuhiro , Sekiguchi Maki , Shelton Ian , Shimasaku Kazuhiro , Suzuki Katsuyuki , Takata Tadafumi , Taniguchi Yoshiaki , Usuda Tomonori , Yamashita Takuya , Yasuda Naoki
Published: March 2014

We present high-resolution images of the Ring Nebula in the Hα, V, and B bands taken with the Subaru telescope. The Hα image reveals the fine structure of the inner and outer halos in unprecedented detail. The innermost part of the inner halo just outside of the main ring may be identified as a new component in terms of the surface brightness hierarchy seen in the Ring Nebula. A filamentary structure consisting of loops and knots, which gives a petal-like appearance to the inner halo, is also seen in this new component. The outer halo is found to show a limb-brightened knotty structure similar to the inner halo, but at much fainter levels. The typical size of the knots, however, is clearly different between the two halos. The median size measured on the Hα image is 1″.2 and 3.″2 in the inner and outer halos, respectively. The corresponding lifetime, which is defined by the size divided by the thermal velocity, is 400 years and 1200 years. The tri-color image was made with Hα, V, and B images after being sharpened by the maximum-entropy method. The image shows the fine structure of the main ring and the enhanced bands of emission running across the central hole with a resolution comparable to the image taken with the Hubble Space Telescope. The features newly found in the present images may give some support, but more challenges, to the unified model proposed by Guerrero et al.
Temporal 1/fα Fluctuations from Fractal Magnetic Fields in Black-Hole Accretion Flow
Authors: Kawaguchi Toshihiro , Mineshige Shin , Machida Mami , Matsumoto Ryoji , Shibata Kazunari
Published: March 2014

Rapid fluctuation with a frequency dependence of 1/fα (with α ≃ 1–2) is characteristic of radiation from black-hole objects. Its origin remains poorly understood. We examined three-dimensional magnetohydrodynamical simulation data, finding that a magnetized accretion disk exhibits both 1/fα fluctuation (with α ≃ 2) and a fractal magnetic structure (with the fractal dimension of D ∼ 1.9). The fractal field configuration leads to reconnection events with a variety of released energy and duration, thereby producing 1/fα fluctuations.
Stability of a Dynamically Collapsing Gas Sphere
Authors: Hanawa Tomoyuki , Matsumoto Tomoaki
Published: March 2014

We discuss the stability of dynamically collapsing gas spheres. We use a similarity solution for a dynamically collapsing sphere as the unperturbed state. In the similarity solution the gas pressure is approximated by a polytrope of P = K ργ. We examined three types of perturbations: bar ( l = 2) mode, spin-up mode, and Ori-Piran mode. When γ < 1.097 , it is unstable against the bar mode. It is unstable against the spin-up mode for any γ . When γ < 0.961 , the similarity solution is unstable against the Ori-Piran mode. The unstable mode grows in proportion to | t - t0 | -σ , while the central density increases in proportion to ρc ∝ (t - t0) -2 in the similarity solution. The growth rate, σ, is obtained numerically as a function of γ for the bar mode and the Ori-Piran mode. The growth rate of the bar mode is larger for a smaller γ . The spin-up mode has a growth rate of σ = 1/3 for any γ.
Deep X-Ray Observations of Supernova Remnants G359.1–0.5 and G359.0–0.9 with ASCA
Authors: Bamba Aya , Yokogawa Jun , Sakano Masaaki , Koyama Katsuji
Published: March 2014

We present the results of deep ASCA observations of two shell-like radio supernova remnants (SNRs) located in the direction to the galactic center (GC) region. Unlike the radio morphology, G359.1-0.5 shows center-filled X-rays with prominent Kα lines of He-like silicon and H-like sulfur. The plasma requires at least two temperature components: a silicon-dominated cool plasma of 0.6 keV temperature and a sulfur-dominated higher temperature plasma of 4.4 keV. Because the absorption column is ∼ 6× 1022 H cm-2, this SNR would be near to the GC. The spherical plasma is attributable to supernova ejecta with the total mass of Si and S being about 0.1 M⊙ and 0.3 M⊙, respectively. X-rays from G359.0-0.9 trace the partial shell structure of the radio emission. The spectrum is well fitted to a single-temperature plasma of 0.4 keV with a non-solar abundance of magnesium or iron. Because the absorption column is not very large, ∼ 1.8× 1022 H cm-2, G359.0-0.9 would be in front of the GC region. The total supernova energy, interstellar density near to the X-ray emitting shell, and age of the SNR are estimated to be 1.2× 1051 erg, 0.5 cm-3, and 1.8× 104 yr, respectively. We also discuss possible implications on the origin of the large-scale hot plasma surrounding the GC.
Two-Epoch Space VLBI Observations of the Gamma-Ray Loud Quasar PKS 1741–038
Authors: Wajima Kiyoaki , Lovell James E. J. , Kobayashi Hideyuki , Hirabayashi Hisashi , Fujisawa Kenta , Tsuboi Masato
Published: March 2014

We present the results of high-resolution imaging of the gamma-ray loud quasar PKS 1741–038 with the HALCA satellite and ground radio telescopes. Observations were made at two epochs at an interval of nine months with the first-epoch observation at 1.6 and 5 GHz and with the second-epoch observation at 5 GHz. The source shows a very compact structure, but is clearly resolved in the space-ground baseline visibility data. The core component of the source has a brightness temperature, Tb, greater than 1012 K in the source's rest frame at each frequency. We applied three individual jet models in order to derive the Doppler factor, δ . The core component has δ ∼ 14, considering the Tb limit due to the inverse Compton catastrophe, while a 2.5-times larger δ is obtained assuming that the particles and magnetic field are in equipartition. Two-epoch images at 5 GHz show almost no change of the structure. Assuming that the component motion in this interval is less than our resolution, we derived the upper limit of the viewing angle as being 4.°8. The smaller viewing angle and higher Doppler factor favor the inverse Compton gamma-ray emission model; we conclude that the gamma-ray emission from this source is highly Doppler-boosted.
A Universal Phase Function for Jovian Clouds from the Visible to Near-IR Wavelength Region. I. Zone Phase Function
Authors: Satoh Takehiko , Itoh Seigo , Kawabata Kiyoshi , Tenma Takafumi , Akabane Tokuhide
Published: March 2014

A set of wavelength-dependent scattering phase functions for Jupiter's clouds has been obtained; the Mie theory was employed to simulate well-defined scattering phase functions deduced from an analysis of the Pioneer 10 photometry data (Tomasko et al. 1978, AAA 021.099.011). A reasonable fit to the cloud-phase functions for the bright zone (STrZ) was obtained with a particle effective radius, reff, of 0.96 μ m and the real part of the refractive index, nr, being 1.591 for the blue and 1.535 for the red, slightly higher than the nominal values for ammonia ice. The derived Mie phase functions were tested against several STrZ data. The appropriateness of these phase functions has been demonstrated through the fact that they reproduce not only the observed limb-to-limb intensity profiles, but also the correct wavelength dependence of the haze optical thickness for a wide wavelength range from visible to near-infrared.
Contribution and Properties of the Green- and Red-Line Coronal Loops in the K-Corona
Authors: Takeda Aki , Kurokawa Hiroki , Kitai Reizaburo , Ishiura Kiyomi
Published: March 2014

A set of high-resolution images of corona obtained during the total solar eclipse on 1991 July 11, was carefully analyzed to investigate the properties of the loop structures observed in the green (530.3 nm) and red (637.4 nm) emission lines and in the continuum. With the help of a structure-enhancement algorithm, we have quantitatively shown that: (1) The green- and red-line loops are quite separately distributed in space. (2) For most structures seen in the continuum in the active-region corona, components can be identified in the green or red line. (3) In the innermost corona, structures in the red-line tend to contribute more to the total column density than the green-line structures. We present two schematic models to explain the spatial relation of the green-line, the red-line, and the continuum loops. Next, we studied individual loops in the green and red lines, and derive that their electron densities are almost the same. We also propose a method to determine the ‘background contribution’ of the green and red lines to the total column density derived from the continuum intensity. It is found that the total column density in the analyzed region can be reasonably explained by a mixture of the 530.3 nm component with a line-of-sight length comparable to the size of the active region, and the 637.4 nm component, which tends to concentrate in loop structures. We thereby conclude that the observed corona is well explained by a plasma of temperatures ranging from 2 MK to 1 MK.
The Nuclear Region of the Seyfert 2 Galaxy NGC 3079
Authors: Sawada-Satoh Satoko , Inoue Makoto , Shibata Katsunori M. , Kameno Seiji , Migenes Victor , Nakai Naomasa , Diamond Philip J.
Published: March 2014

We present a discussion on high-resolution studies of the nuclear region of NGC 3079 using observations of an H2O maser and continuum emission as well as H I absorption with a global VLBI network including the VLBA, the phased VLA and the Effelsberg 100 m telescope. Multi-frequency observations of the continuum emission reveal the spectra of continuum components and suggest a core-jet morphology. The H2O maser spots lie in a series of clusters distributed along a north-south direction, while we rule out any possibility that the masering disk lies along the north-south direction. H I absorption features towards the continuum components have a velocity gradient opposite to that observed in the galaxy as a whole. We identify the nucleus and rotation axis of the central 10 pc region, and discuss the properties of a postulated rotating torus in the nuclear region.