bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Gravitational Instability of an Isothermal Gaseous Slab under High External Pressure
Authors: Umekawa Michihisa , Matsumoto Ryoji , Miyaji Shigeki , Yoshida Tatsuo
Published: March 2014

We carried out two-dimensional hydrodynamic simulations to study the nonlinear growth of the gravitational instability of a self-gravitating isothermal gaseous slab confined by external pressure. When the external pressure is low, the Jeans instability creates dense collapsing clumps for long-wavelength perturbations. When the external pressure is high (Pext/P00 > 0.64 where P00 is the initial mid-plane pressure and Pext is the external pressure), an incompressible mode of gravitational instability creates clumps, the mass of which is smaller than the Jeans mass. The clumps merge due to mutual gravitational attraction. Although each clump cannot collapse gravitationally, when its mass exceeds the Jeans mass by merging, the merged clump collapses gravitationally. These results indicate that when the external pressure is high, star formation can be triggered by the merging of low-mass Jeans stable clumps. In high external pressure regions, we expect that the mass function of collapsing clumps in the clouds has a peak around the Jeans mass.
Spectroscopic Study of the Vela-Shrapnel
Authors: Tsunemi Hiroshi , Miyata Emi , Aschenbach Bernd
Published: March 2014

Several shrapnels have been detected in the vicinity of Vela SNR by the ROSAT all-sky survey. We present here the spectral properties of shrapnel ‘A’ observed with the ASCA satellite. A prominent Si-K emission line with relatively weak emission lines from other elements have been detected, revealing that the relative abundance of Si is a few ten-times higher than those of other elements. Combining with the ROSAT PSPC results, we obtained the electron temperature, kTe, to be 0.33 ± 0.01 keV. The total mass of shrapnel ‘A’ is estimated to be ∼ 0.01 M⊙. If it is an ejecta of a supernova explosion, the interstellar matter would be swept up in the leading edge while the ejecta material would be peeled off in the trailing edge, which should be confirmed by future observations.
Color and Morphology of Galaxies in the Region of the 3C 324 Clusters at z ∼ 1.2
Authors: Kajisawa Masaru , Yamada Toru
Published: March 2014

We investigated the color and morphology of optically selected galaxies in the region of clusters at z ∼ 1.2 near to the radio galaxy 3C 324 using archived data taken with the Hubble Space Telescope. The faint galaxies selected at the HST F702W band that contribute to the surface-density excess of the region have wide ranges of color, size, and morphology, which are not likely to be due to contamination by foreground galaxies. Namely, the rest-frame ultraviolet emission properties of the galaxies in the clusters are not very homogeneous; various amounts of star-formation activity may occur in a significant fraction of them. Although our analysis is purely statistical, we find that typical star-forming galaxies with blue colors have a relatively late-type morphology compared to the red quiescent population in the systems.
Central Kinematics and Rotation Curve of the Sb Galaxy NGC 4527 in CO, Hα and [N II] Lines
Authors: Sofue Yoshiaki , Tomita Akihiko , Honma Mareki , Tutui Yoshinori
Published: March 2014

We have obtained interferometer observations of the central region of the Sb galaxy NGC 4527 in the CO (J = 1–0) line emission using the Nobeyama Millimeter Array. We also obtained optical (Hα, [N II]) spectroscopy using the Okayama 188-cm reflector along the major axis. The kinematical structure and the distribution of H II regions show symmetry around the nucleus, while the distribution of molecular gas is asymmetric. The molecular-gas mass shares only 10% of the dynamical mass in the central 1 kpc radius region. Using position-velocity diagrams, we have derived a center-to-disk rotation curve. It rises steeply in the central region, attaining a maximum of about 250 km s−1 at 400 pc radius, and then decreases to a minimum at 2 kpc radius, followed by a disk and outer flat part. The rotation curve may provide us with the most similar case to that of the Milky Way Galaxy.
A Study of Dense Molecular Gas and Star Formation toward the Vela Molecular Ridge with NANTEN
Authors: Yamaguchi Nobuyuki , Mizuno Norikazu , Saito Hiro , Matsunaga Ken'ichi , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

New observations of the J=1−0 12CO, 13CO, and C18O emission lines have been extensively made toward the Vela Molecular Ridge (VMR) with NANTEN. The most prominent cloud is the giant molecular cloud, corresponding to the VMR-C region (Vela C). The present C18O distribution has been identified as 29 clouds. Among them, the most massive one is included in Vela C, having a total mass of ∼ 4.4 × 104M⊙. The rest of them are smaller C18O clouds of 102-103M⊙. Star formation in the region is almost exclusively occurring in the C18O clouds. The luminosities of the associated protostellar IRAS sources range from 5 L⊙ to 1.1 × 104L⊙, and the luminosity distribution is found to be well represented by the relation dNstar/dLIR ∞ L-1.65±0.14IR. We find that the ratios of the total luminosity of the sources associated with given C18O clouds to the cloud masses are significantly enhanced for those clouds associated with H II regions by an order of magnitude. This is interpreted as meaning that the formation of massive stars is enhanced due to the effects of H II regions, as is consistent with the preceding work. We have also newly found molecular outflow toward IRAS 08588–4347 as well as five possible candidates for outflows.
A Study of Dense Cloud Cores and Star Formation in Lupus: C18O J = 1−0 Observations with NANTEN
Authors: Hara Atsushi , Tachihara Kengo , Mizuno Akira , Onishi Toshikazu , Kawamura Akiko , Obayashi Ayano , Fukui Yasuo
Published: March 2014

We have made an extensive study of dense cloud cores and star formation in the Lupus dark-cloud complex. Millimeter-wave observations in the C18O (J = 1−0) emission at 2.6 mm wavelength were made with the “NANTEN,” a 4-m mm-wave telescope of Nagoya University at Las Campanas Observatory. Thirty-six dense cores were identified and mapped in the C18O emission at 2′ grid spacing with a 2′.7 beam. The typical mass, radius, H2 column density, and line width of the C18O cores are 9.7 M⊙ , 0.17 pc, 4.1 × 1021 cm-2, 0.90 km s-1, respectively. The mass spectrum of the C18O cores was fitted by a single power-law index of γ = −1.7± 0.6 for Mcore ≥ 3 M⊙ . The physical parameters of the dense C18O cores were derived and compared with those in Taurus, Ophiuchus North, and L 1333. The average characteristics of the C18O cores in Lupus are similar to those in Ophiuchus North and L 1333, although those in Taurus are found to be different, especially in the line width, virial ratio, and mass spectrum index among the four regions. By comparing the physical properties of the C18O cores with the distribution of YSOs and H13CO+ condensations in Lupus, we have confirmed a trend suggested in previous studies, that star formation preferentially occurs in cores having a small virial ratio, Mvir/Mcore, and a large H2 column density.
Discovery of an X-Ray Pulsar in the SMC: AX J0058-7203
Authors: Tsujimoto Masahiro , Imanishi Kensuke , Yokogawa Jun , Koyama Katsuji
Published: March 2014

We report on the discovery and analysis of an X-ray pulsar, AX J0058–7203, in the Small Magellanic Cloud. This pulsar exhibits coherent pulsations at P = 280.3 s with a double-peak structure. The X-ray spectrum is well fitted with a simple power-law model of photon index Γ ∼ 0.7. No significant change of the pulsation period over the observation was found. A comparison with ROSAT observations in the same field reveals that AX J0058–7203 is highly variable, and is most likely a Be star binary pulsar.
The First Light of the Subaru Telescope: A New Infrared Image of the Orion Nebula
Authors: Kaifu Norio , Usuda Tomonori , Hayashi Saeko S. , Itoh Yoichi , Akiyama Masayuki , Yamashita Takuya , Nakajima Yasushi , Tamura Motohide , Inutsuka Shuichiro , Hayashi Masahiko , Maihara Toshinori , Iwamuro Fumihide , Motohara Kentaro , Iwai Jun'ich , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Terada Hiroshi , Goto Miwa , Ando Hiroyasu , Aoki Tetsuo , Chikada Yoshihiro , Doi Mamoru , Ebizuka Noboru , Fukuda Takeo , Hamabe Masaru , Hasegawa Tetsuo , Horaguchi Toshihiro , Ichikawa Shinichi , Ichikawa Takashi , Imanishi Masatoshi , Imi Katsumi , Inata Motoko , Isobe Shuzo , Iye Masanori , Kamata Yukiko , Kanzawa Tomio , Karoji Hiroshi , Kashikawa Nobunari , Kataza Hirokazu , Kato Taichi , Kobayashi Naoto , Kobayashi Yukiyasu , Kodaira Keiichi , Kosugi George , Kurakami Tomio , Mikami Yoshitaka , Miyama Shoken M. , 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 Junichi , 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 , Tanaka Kyoko , Tanaka Wataru , Tomono Daigo , Torii Yasuo , Waseda Koichi , Watanabe Junichi , Watanabe Masaru , Yagi Masafumi , Yamashita Yasumasa , Yasuda Naoki , Yoshida Michitoshi , Yoshida Shigeomi , Yutani Masami
Published: March 2014

This paper describes the first light and subsequent test observations with the 8.2 m aperture Subaru Telescope constructed at the summit of Mauna Kea. Following the engineering first light, which started 1998 December, the astronomical first light and test observations were carried out in 1999 January with 4 testing instruments under seeing conditions of 0″.2*#x2013;0″.5 for near-infrared and 0″.3–0″.6 for optical wavelengths. The actively supported primary mirror was shown to achieve an overall imaging performance of 0″.1 (FWHM) or better in the absence of any atmospheric disturbance. The pointing accuracy of the telescope is about 1″ rms, and a closed-loop tracking accuracy of ≲ 0″.07 rms has been achieved. Infrared images of the Orion Nebula covering 5′ × 5′, obtained with J, K″, and H2v = 1–0 S(1) filters, have revealed much finer and fainter details of the BN/KL region, the bright bar, and other conspicuous features compared with previous observations. K′ band photometry of 516 point sources yielded a luminosity function with a peak at K′ ∼ 12 mag with a long tail in K′ ∼ 13 mag down to K″ ∼ 17 mag, suggesting a fairly large number of young brown dwarfs existing in the Trapezium cluster. Several new features around the Orion BN/KL region are also reported.
X-Ray Flares from an Hα Emission-Line Star in the Orion Region, Kiso A0904–105
Authors: Yamauchi Shigeo , Kamimura Reiko , Koyama Katsuji
Published: March 2014

We analyzed ASCA data, including the reflection nebula NGC 2023, and discovered two X-ray flares from an Hα emission-line star, Kiso A0904–105, located at ∼ 30′ to the southwest of NGC 2023. The separation time between the two flares was ∼ 4 hr. The temperatures of the first and second flares reached (5–7) × 107 K and the luminosities around the flare peaks were ∼ 1033 erg s−1 (0.5–10.0 keV energy band, assuming the distance of 400 pc), which are comparable to those of the giant X-ray flares from T Tauri stars. After the flare peaks, X-ray intensity exhibited an exponential decay. Comparing the flares with those from T Tauri stars, we found that the physical parameters in the flaring plasma were within the range of those obtained from T Tauri stars.
The Absence of Cyclotron Lines in Neutron-Star Atmospheres with Super-Strong Magnetic Fields
Authors: Nishimura Osamu , Sumiyoshi Kousuke , Ebisuzaki Toshikazu
Published: March 2014

We have numerically calculated the radiative transfer in neutron-star atmospheres threaded by a uniform super-strong magnetic field (∼ 109 T), where not only cyclotron resonant scattering, but also photon splitting, occurs. Here, the multiangle radiative transfer equations were solved for cyclotron resonant scattering, which depends strongly on the angle of photon propagation with respect to the magnetic field line. We also investigated the feature of the cyclotron lines reprocessed by the photon splitting in the atmospheres into which the power-law-type flux is injected. We have found that the cyclotron absorption lines are strongly reprocessed by photon splitting, and may not be detected at a magnetic field of about 4.41 × 109 T in the power-law-type spectra.
Instability of Embedded Polytropes
Authors: Horedt George Paul
Published: March 2014

The equivalence of two stability criteria (decreasing pressure with increasing radius versus increasing central density with increasing mass) is shown analytically for spherical polytropes without background medium, and numerically for embedded ones. Previous results concerning the instability under external pressure of incomplete (truncated) polytropes within a uniform background medium are shown to be not true. The spherical incomplete embedded polytrope is stable/unstable for the same polytropic indices and for the same background densities as the corresponding complete embedded polytrope.
Accretion Disks Phase Transitions: 2-D or Not 2-D?
Authors: Abramowicz Marek A. , Björnsson Gunnlaugur , Igumenshchev Igor V.
Published: March 2014

We argue that the proper way to treat thin-thick accretion-disk transitions should take into account the 2-D nature of the problem. We illustrate the physical inconsistency of the 1-D vertically integrated approach by discussing a particular example of the convective transport of energy.
Broad-Band X-Ray Study of a Transient Pulsar RX J0059.2–7138
Authors: Kohno Makoto , Yokogawa Jun , Koyama Katsuji
Published: March 2014

We report on the results of the ASCA and ROSAT observations on RX J0059.2-7138, a transient X-ray pulsar in the Small Magellanic Cloud. The barycentric pulse period has been precisely determined to be 2.763221 ± 0.000004 s. The pulse shape is almost identical in all of the energy bands. The pulse fraction increases with the photon energy below ∼ 2 keV, while it is nearly constant at ∼ 37% above ∼ 2 keV. The X-ray spectrum has been found to consist of two components. One is dominant above 2 keV, and exhibits sinusoidal pulsations. This component is well described by a typical model found in many X-ray binary pulsars, a power-law of photon index 0.4 with an exponential cut-off at 6.5 keV. The other is dominant below 1 keV and shows no significant pulsation. This component is represented by either a broken power-law with photon indices of 2.6 and 5.1 below and above a break energy of 0.9 keV, or a metal-poor thin-thermal plasma with a temperature of 0.37 keV. The phase-averaged luminosity is ∼ 1038 erg s-1 (0.1–10.0 keV) for both components. A hint of oxygen over-abundance is found in the absorbing column, possibly due to circumstellar gas ejected from an evolved companion.
1-GHz Bandwidth Digital Spectro-Correlator System for the Nobeyama Millimeter Array
Authors: Okumura Sachiko K. , Momose Munetake , Kawaguchi Noriyuki , Kanzawa Tomio , Tsutsumi Takahiro , Tanaka Atsushi , Ichikawa Teruaki , Suzuki Takakiyo , Ozeki Kensuke , Natori Kazuhito , Hashimoto Tamio
Published: March 2014

We have developed 1-GHz bandwidth digital spectro-correlator system for the Nobeyama Millimeter Array (NMA). It consists of 2Gsample/sec·2bit analog-to-digital (A/D) converters and an ultra-wide band digital correlator. We developed two kinds of special-purpose LSI having functions of delay compensation and correlation, respectively. With these LSIs, the ultra-wide band digital correlator realizes 1024-MHz bandwidth spectroscopy with 128-channel resolution for 15-correlation data. This system allows us to observe radio continuum emission with about a two-times better signal-to-noise ratio than that of the previous correlator system. We started common-use observations with this new system from 1997 March; the system has been extended in order to obtain 21-correlation data for a 7-element “Rainbow„ ( NMA + 45-m telescope ) interferometer system.
Super-Eddington Accretion-Disk Models for SS 433
Authors: Okuda Toru , Fujita Mitsutaka
Published: March 2014

We examine highly super-Eddington accretion disk models onto a neutron star for SS 433, based on two-dimensional hydrodynamical calculations. The super-Eddington accretion flows form a kind of standing shock elongated along the rotational axis of the disk. This results in a very rarefied, hot, optically thin region between the shock and the axis. The anisotropic radiation fields in this region accelerate the flows to relativistic jets of ∼ 0.2 c with a collimation angle of ∼ 10°–25°. The accretion disk is highly convective or turbulent near to the equatorial plane, and is very geometrically thick. Most of the input accreting matter is blown off from the system through the jets and the disk wind. The super-Eddington accretion disk models are promising to explain SS 433.
Discovery of a New Deeply Eclipsing SU UMa-Type Dwarf Nova, IY UMa (= TmzV 85)
Authors: Uemura Makoto , Kato Taichi , Matsumoto Katsura , Takamizawa Kesao , Schmeer Patrick , Jensen Lasse Teist , Vanmunster Tonny , Novák Rudolf , Martin Brian , Pietz Jochen , Buczynski Denis , Kinnunen Timo , Moilanen Marko , Oksanen Arto , Cook Lewis M. , Watanabe Tsutomu , Maehara Hiroyuki , Itoh Hiroshi
Published: March 2014

We discovered a new deeply eclipsing SU UMa-type dwarf nova, IY UMa, which experienced a superoutburst in 2000 January. Our monitoring revealed two distinct outbursts, which suggest a superoutburst interval of ∼ 800 d, or its half, and an outburst amplitude of 5.4 mag. From time-series photometry during the superoutburst, we determined a superhump and orbital period of 0.07588 d and 0.0739132 d, respectively.
ASCA Observations of the NGC 2264 Molecular Cloud
Authors: Nakano Makoto , Yamauchi Shigeo , Sugitani Koji , Ogura Katsuo
Published: March 2014

We have made ASCA observations of the molecular cloud associated with NGC 2264, and detected nine and five sources in the soft and hard X-ray band images, respectively. Most of them are identified with known pre-main-sequence stars or protostellar objects. Two Class I sources with intermediate luminosities and one Class II source associated with molecular outflow are promising candidates for X-ray emitters. An optically thin hot-plasma model with two components can reproduce the GIS X-ray spectra, including both of the Class I sources. The hard X-rays probably arise from these Class I sources, and are intrinsically very luminous, >1032 erg s−1 in the 0.7–10.0 keV energy band, and their luminosities lie between low-mass Class I sources and that of the W 3 massive core region. Since near-infrared survey data reveal that Class I sources are surrounded by embedded young clusters, the soft X-ray components could be explained by aggregates of low-mass pre-main-sequence stars.
Slim-Disk Model for Soft X-Ray Excess and Variability of Narrow-Line Seyfert 1 Galaxies
Authors: Mineshige Shin , Kawaguchi Toshihiro , Takeuchi Mitsuru , Hayashida Kiyoshi
Published: March 2014

Narrow-line Seyfert 1 galaxies (NLS1s) exhibit an extreme soft X-ray excess and large variability. We argue that both features can be basically accounted for by the slim-disk model. We assume that a central black-hole mass in NLS1 is relatively small, M ∼ 105–7M⊙ , and that a disk shines nearly at the Eddington luminosity, LE. Then, the disk becomes a slim disk and exhibits the following distinctive signatures: (1) The disk luminosity (particularly of X-rays) is insensitive to the mass-flow rates, Ṁ, since the generated energy is partly carried away to the black hole by trapped photons in accretion flow. (2) The spectra are multi-color blackbody. The maximum blackbody temperature is Tbb ≃ 0.2(M/105 M⊙ )−1/4 keV, and the size of the blackbody emitting region is small, rbb ≲ 3 rS (with rS being Schwarzschild radius), even for a Schwarzschild black hole. (3) All of the ASCA observation data of NLS1s fall onto the region of dot Ṁ/(LE/c2)>10 (with LE being the Eddington luminosity) on the (rbb,Tbb) plane, supporting our view that a slim disk emits soft X-rays at ∼ LE in NLS1s. (4) Magnetic energy can be amplified, at most, up to the equipartition value with the trapped radiation energy, which greatly exceeds the radiation energy emitted from the disk. Hence, energy release by consecutive magnetic reconnection will give rise to substantial variability in soft X-ray emission.
Spectroscopic Diagnostics of Symbiotic Stars III. Radial Velocity Analyses of HBV 475
Authors: Ikeda Yuji , Tamura Shin'ichi
Published: March 2014

We present highly resolved spectroscopic data of HBV 475 (= V 1329 Cyg) in the optical region, which have been obtained during the past 10 years at the Okayama Astrophysical Observatory. We analyzed line profiles of Hα, Hγ, HeII λ4686, [OIII] λ5007, and [FeVII] λ6086 using Gaussian de-convolution method, and investigated the variation of individual components of the profiles as a function of the orbital phase. We revised the mass function obtained from the orbital elements of the hot star as fh(M) ∼ 1.2 ± 0.3 M⊙. It differs considerably from previously published values, which were larger than 20 M⊙. However, our new mass function is more reasonable for a symbiotic system consisting of a red giant and a hot star, which is currently presumed to be a white dwarf. Finally, we suggest a descriptive model of line-emitting regions in the HBV 475 binary, which explains the basic variation in the line profiles and agrees with the main features of the HST image.
Metal Abundances in the Hot Interstellar Medium in Early-Type Galaxies Observed with ASCA
Authors: Matsushita Kyoko , Ohashi Takaya , Makishima Kazuo
Published: March 2014

We have analyzed ASCA data of 27 early-type galaxies, and studied the properties of their X-ray emitting ISM (InterStellar Medium) in detail. We found that overlapping lines and free-bound continuum cause strong coupling in the derived abundances of various elements. The abundance determination is also difficult due to the uncertainties in the Fe-L atomic physics, because the Fe-L lines couple with the O and Ne K-lines. However, when the abundances of α-elements are fixed, all of the plasma codes give similar Fe abundances with a scattering of only 20–30%. To relax the strong coupling among the elements, we included 20% systematic errors in the Fe-L region of the spectra. Then, in X-ray luminous galaxies, the derived abundance of Fe and α-elements both became ∼ 1 solar within a factor of 2. This result relaxes the previous severe discrepancy between the ISM and stellar metallicities. The ISM metallicity in X-ray fainter galaxies is still uncertain, but we can at least constrain that the contribution from type-Ia SN to the ISM abundance is lower than in X-ray luminous systems. These results strongly suggest that a large fraction of SN Ia products have escaped into intergalactic space.
Unusual Properties of X-Ray Emission near the Galactic Center
Authors: Tanaka Yasuo , Koyama Katsuji , Maeda Yoshitomo , Sonobe Takashi
Published: March 2014

The X-ray spectrum in a 1° × 1° region of the Galactic center observed with the ASCA satellite is examined in detail, following the first report by Koyama et al. (1996, AAA 65.155.208). The observed spectrum contains prominent emission lines from helium-like and hydrogen-like ions of various elements, and is essentially the same all over the region. If the observed spectrum is thermal emission from hot plasmas, it requires multi-temperature plasma components, each at a different degree of ionization and with a different amount of absorption. The absence of adiabatic cooling and of systematic changes in the degree of ionization over the region is against the Galactic center origin of hot plasmas. A significant broadening of the helium-like and hydrogen-like iron K-lines is confirmed. The line width corresponds to a rms velocity of ∼ 3300 km s−1, which far exceeds the sound velocity in a plasma of kT ∼ 14 keV measured with the Ginga satellite. These facts cast doubt on a thermal origin of the observed X-ray emission.
Detection Rate of Molecular Gas in Elliptical Galaxies: Constraints on Galaxy-Formation Theories
Authors: Fujita Yutaka , Nagashima Masahiro , Gouda Naoteru
Published: March 2014

We calculated the detection rate of cold gas in elliptical galaxies using a semi-analytic model of galaxy formation, and compared it with observations. We have shown that a model with a long star-formation time-scale ( ∼ 20 Gyr) is inconsistent with observations. Thus, some mechanisms of reducing the mass of interstellar medium, such as the consumption of molecular gas by star formation and/or reheating from supernovae, are certainly effective in galaxies. Our model predicts that star formation is induced when galaxies in a halo collide with each other and it reduces the cold gas left until the present. However, we find that the reduction through random collisions of satellite (non-central) galaxies in the mean-free time-scale in a halo is not required to explain the observations. For cD galaxies, the predicted detection rate of cold gas is consistent with observations as long as the transformation of hot gas into cold gas is prevented in halos whose circular velocities are larger than 500;km; s−1. Moreover, we find that the cold gas brought into cDs through capturing gas-rich galaxies is small. We also show that the fraction of galaxies with observable cold gas should be small for cluster ellipticals in comparison with that for field ellipticals. Our fiducial models and the models with a large reheating efficiency can reproduce the observations well, although a comparison with a larger and complete sample of elliptical galaxies will constrain the physical parameters in galaxy-formation theories more strictly.
ASCA Observations of Three Shakhbazyan's Compact Groups of Galaxies
Authors: Takahashi Isao , Fukazawa Yasushi , Kodaira Keiichi , Makishima Kazuo , Nakazawa Kazuhiro , Xu Haiguang
Published: March 2014

X-ray observations of three Shakhbazyan's Compact Groups of Galaxies are presented for the first time. Extended X-ray emission was detected from SCGG 202 and SCGG 223 with 0.5–2 keV luminosity of 1 ' 1042 erg s−1 and 3 ' 1042 erg s−1 (for H0 = 75 km s−1 Mpc−1), respectively, while no significant emission was detected from SCGG 205 with an upper limit of 0.7 ' 1042 erg s−1. The X-ray spectra of SCGG 202 and SCGG 223 can be described with thin-thermal plasma emission with a temperature of about 1 keV. The X-ray properties of SCGG 202 and SCGG 223 are in good agreement with those of other known groups of galaxies, proving the physical nature of their grouping.
Stellar Contents of the Galactic Giant H II Region NGC 3603
Authors: Pandey Anil K. , Ogura Katsuo , Sekiguchi Kaz
Published: March 2014

We present CCD UBVRI and Hα photometry for the starburst cluster associated with the galactic giant H II region NGC 3603. The mean reddening of the cluster members comes out to be $\langle E(B-V)\rangle=1.48\pm0.21 $ (s.d.). The surface distribution of the reddening shows a radial variation with a minimum near to the cluster center and two local maxima at radii ∼ 30″ and ∼ 70″. Our photometric data indicate an anomalous reddening law for the dust inside the cluster region, and the ratio of the total to the selective extinction, R, is found to be ∼ 4.3. A comparison of the observational and intrinsic colour-magnitude digrams (CMDs) yields a mean distance modulus of (m – M)0 = 14.0, which corresponds to a distance of 6.3 ± 0.6 kpc. This distance is smaller than those obtained in earlier works (e.g., 7.2 kpc, Melnick et al. 1989, AAA 49.132.013) but is in good agreement with the kinematic distance (6.1 ± 0.6 kpc) recently reported by De Pree et al. (1999, AAA 71.132.041). The cluster shows a large age spread, containing stars as old as up to several Myr. However, the mean age of the cluster is found to be ≤ 1 Myr. We estimate a minimum star formation efficiency of ∼ 25 % and a gas removal time of τ ∼ 4.6 Myr.
Overabundance of Calcium in the Young SNR RX J0852–4622: Evidence of Over-Production of 44Ti
Authors: Tsunemi Hiroshi , Miyata Emi , Aschenbach Bernd , Hiraga Junko , Akutsu Daisuke
Published: March 2014

Recently, COMPTEL has detected γ-rays of 1157 keV from 44Ti in the direction of the SNR RX J0852–4622 (Iyudin et al. 1998, AAA 70.125.077). Since 44Ti is a product of explosive nucleosynthesis and its half lifetime, τ1/2, is about 60 yr, RX J0852–4622 must be a young supernova remnant and radiation is dominated by the ejecta rather than by interstellar matter. We have detected an X-ray emission line at 4.1 ± 0.2 keV which is thought to come from highly ionized Ca. The emission line is so far only seen in the north-west shell region of RX J0852–4622. The X-ray spectrum can be well fitted with that of a thin hot plasma of cosmic abundances, except that of Ca, which is overabundant by a factor of 8 ± 5. Assuming that most of the Ca is 44Ca, which originates from 44Ti by radioactive decay, we estimate a total Ca mass of about 1.1 × 10−3M⊙. Combining the amount of 44Ca and the observed flux of the 44Ti γ-ray line, the age of RX J0852–4622 is around 1000 yr.
PROGRAPE-1: A Programmable, Multi-Purpose Computer for Many-Body Simulations
Authors: Hamada Tsuyoshi , Fukushige Toshiyuki , Kawai Atsushi , Makino Junichiro
Published: March 2014

We have developed PROGRAPE-1 (PROgrammable GRAPE-1), a programmable multi-purpose computer for many-body simulations. The main difference between PROGRAPE-1 and “traditional” GRAPE systems is that the former uses FPGA (Field Programmable Gate Array) chips as the processing elements, while the latter relies on a hardwired pipeline processor specialized to gravitational interactions. Since the logic implemented in FPGA chips can be reconfigured, we can use PROGRAPE-1 to calculate not only gravitational interactions, but also other forms of interactions, such as the van der Waals force, hydrodynamical interactions in the SPHr calculation, and so on. PROGRAPE-1 comprises two Altera EPF10K100 FPGA chips, each of which contains nominally 100000 gates. To evaluate the programmability and performance of PROGRAPE-1, we implemented a pipeline for gravitational interactions similar to that of GRAPE-3. One pipeline is fitted into a single FPGA chip, operated at 16 MHz clock. Thus, for gravitational interactions, PROGRAPE-1 provided a speed of 0.96 Gflops-equivalent. PROGRAPE will prove to be useful for a wide-range of particle-based simulations in which the calculation cost of interactions other than gravity is high, such as the evaluation of SPH interactions.
Large Angle Bending of the Light-Month Jet in Centaurus A
Authors: Fujisawa Kenta , Inoue Makoto , Kobayashi Hideyuki , Murata Yasuhiro , Wajima Kiyoaki , Kameno Seiji , Iguchi Satoru , Horiuchi Shinji , Sawada-Satoh Satoko , Kawaguchi Noriyuki , Edwards Philip G. , Hirabayashi Hisashi
Published: March 2014

An intercontinental VLBI observation of Cen A is presented. We found that the jet exhibits bending with an angle of 60° at 2 light-months from the core. Because of the large viewing angle of the jet in Cen A, this bending should be a real bend of this magnitude, rather than a projection effect. Two possible interpretations of the bending jet — jet collision with ambient matter, and a changing angle of jet ejection — have been considered and rejected. The possibility is discussed that the observed bending of Cen A is an apparent bend resulting from observing a limb-brightened jet with insufficient resolution, and compared with a numerical simulation of a jet. Another implication of the bending jet is discussed based on a similarity with two other AGNs, 3C 273 and Vir A, in which similar features have been reported on the light-months scale. The relationship between the mass and the structure scale in Vir A and Cen A is very similar. This feature in Cen A suggests that such mis-alignments on the light-month scale are common and are related to the formation mechanism of AGN jets.
ASCA X-Ray Observations of the NGC 2023 and NGC 2024 Regions
Authors: Yamauchi Shigeo , Kamimura Reiko , Koyama Katsuji
Published: March 2014

This paper presents the properties of X-ray sources in the regions of NGC 2023 and NGC 2024 observed with ASCA. We found 14 point-like sources in the NGC 2023 field. In the NGC 2024 field, on the other hand, we found extended X-ray emission in the central dust lane of NGC 2024, and resolved 5 point-like sources around the nebula. From the positional coincidence and moderate column density of NH ∼ 1.6×1022 H cm−2, the extended source is mostly attributable to an integrated emission from X-ray emitting young stellar objects (YSOs) found with ROSAT. However, the plasma temperature of ∼ 4 keV is higher than the ROSAT results as well as those of usual YSOs. Possible counterparts have been found for the other resolved sources, except two; one has large absorption at low energies and the other has moderate absorption. The plasma temperatures and luminosities from the point sources, except for an O-type star ζ Ori and a star exhibiting X-ray flares, are estimated to be ∼ 1-5 keV and 1030.6−1031.5 erg s−1 in the 0.5−10.0 keV energy band (assuming the distance of 400 pc), respectively. We found no X-ray peak at the position of a Class 0 protostar, NGC 2023-MM1.
Molecular Clouds around a Runaway O Star, ζ Ophiuchi
Authors: Tachihara Kengo , Abe Rihei , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo
Published: March 2014

Molecular clouds around a runaway O star, ζ Oph, have been surveyed with the NANTEN telescope, and their streaming motion caused by ζ Oph has been detected. ζ Oph is the earliest (O9.5 V) member of the Sco OB 2 association and is rapidly moving accompanied by an H II region, S 27. We detected 2 major filamentary cloud complexes, L 156 and L 204 complexes. Their total masses traced by the 12CO emission are 520 M⊙ and 1110 M⊙ , respectively. Denser molecular cloud cores detected in C18O are locally distributed on the near side of the L 204 complex to ζ Oph, and lower density gas spreads toward the opposite side. Both complexes have radial velocity shifts that are correlated with the gas density. It is suggested that the low-density gas is accelerated outward away from ζ Oph relative to the embedded dense cores. These density and velocity structures indicate a dynamical interaction between the H II region and the molecular clouds. We calculated the kinetic energies and momenta for seven individual clouds, and examined the effects of the stellar wind and photo-evaporation by the UV field of ζ Oph. It is found that the stellar wind can hardly input the momentum during the crossing time of the rapid movement of ζ Oph. UV radiation seems to be a more likely origin of the streaming gas motion.
On the Detection of Solar Coronal High-Velocity Fields Using the XUV Doppler Telescope
Authors: Kobayashi Ken , Hara Hirohisa , Kano Ryohei , Nagata Shin'ichi , Sakao Taro , Shimizu Toshifumi , Tsuneta Saku , Yoshida Tsuyoshi
Published: March 2014

The XUV Doppler Telescope (XDT) is a sounding rocket experiment designed to detect flows in the solar corona using filter ratios. The XDT, successfully launched on 1998 January 31, is a normal incidence telescope composed of narrow-bandpass multilayer mirrors and capable of obtaining images 2 Å above and 2 Å below the Fe XIV 211 Å (T = 1.7 MK) emission line. It has the potential to make a velocity map of the entire solar disk with just a few minutes of observation. The image ratio maps show features that translate to Doppler shifts of 200 km s−1 or more, including several `redshift' features located near footpoints of coronal loops. However, no corresponding velocity features were seen by the Solar and Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) in the Mg IX 368 Å (T = 1 MK) line, suggesting that the features are not caused by Doppler shift. Instead, the features seem to be related to contamination of lower temperature (T < 1 MK) emission lines and the nearby density-sensitive Fe XIII lines. We conclude that while no flows were positively identified by the XDT, this observing technique is capable of detecting flows of 1000 km s−1 independently, and 200 km s−1 when combined with simultaneous plasma diagnostic observation.
Sub-Parsec-Scale Acceleration of the Radio Jet in the Powerful Radio Galaxy NGC 6251
Authors: Sudou Hiroshi , Taniguchi Yoshiaki , Ohyama Youichi , Kameno Seiji , Sawada-Satoh Satoko , Inoue Makoto , Kaburaki Osamu , Sasao Tetsuo
Published: March 2014

In order to investigate the genesis of a powerful radio jet, we have mapped the central 10 pc region of the nearby radio galaxy, NGC 6251, with a 0.2 pc resolution using Very Long Baseline Interferometer (VLBI) at two radio frequencies, 5 GHz and 15 GHz. We have found the sub-parsec-scale counterjet for the first time in this radio galaxy. This discovery allows us to investigate the jet acceleration based on the relativistic beaming model.
Discovery of a 9-s X-Ray Pulsar, AX J0049–732, in the Small Magellanic Cloud
Authors: Ueno Masaru , Yokogawa Jun , Imanishi Kensuke , Koyama Katsuji
Published: March 2014

We report on an ASCA discovery of a new X-ray pulsar, AX J0049−732, in the Small Magellanic Cloud (SMC). The pulse shape is sinusoidal with a barycentric period of 9.1320 ± 0.0004 s. The X-ray spectrum was fitted by an absorbed power-law model with a photon index of 0.6+1.0−0.7 and a column density of 1.3+2.9−1.3 × 1022 cm−2. An unabsorbed flux at 0.7−10.0 keV was estimated to be 8 × 10−13 erg cm−2 s−1 corresponding to an X-ray luminosity of 4 × 1035 erg s−1 at the SMC distance of 62 kpc.
Discovery of the Slowest X-Ray Pulsar in the SMC, AX J0049.5–7323, with ASCA
Authors: Yokogawa Jun , Imanishi Kensuke , Ueno Masaru , Koyama Katsuji
Published: March 2014

The discovery of coherent pulsations with ASCA from an X-ray source, AX J0049.5−7323, is reported. The barycentric period was determined to be 755.5 ± 0.6 s, which is the longest among X-ray pulsators in the SMC. The X-ray spectrum has been found to be unchanged through ASCA observations, with a photon index of ∼ 0.8 and a luminosity of ∼ 5 × 1035 erg s−1 (0.7−10 keV). Archival data of the Einstein and the ROSAT satellites indicate that the flux has been ≲ 10−12 erg s−1 cm−2 (≲ 5 × 1035 erg s−1) for over 20 years and exhibits a variability with a factor of ≳ 10. We argue that AX J0049.5−7323 is an X-ray pulsar with a Be star companion.
Convection-Dominated, Magnetized Accretion Flows into Black Holes
Authors: Machida Mami , Matsumoto Ryoji , Mineshige Shin
Published: March 2014

Two-dimensional (2D) and three-dimensional (3D) hydrodynamical simulations have been intensively performed recently to clarify the accretion-flow structure in the low-radiation-efficiency limit. However, the results depend critically on the parameterized magnitude of the viscosity, which, in principle, should be determined self-consistently by MHD simulations. We analyzed the structure of 3D MHD accretion flows initially threaded by weak toroidal magnetic fields, and found for the first time large-scale convective motions dominating near to the black hole. Radial profiles of each physical quantity include: the density, $ \rho \propto r^{-0.5}$; radial velocity, $ v_r\propto r^{-1.5}$; temperature, $ T \propto r^{-1.0}$; and field strength, $ B^2 \propto r^{-1.5}$. Although the flow structure, itself, appears to be similar to those obtained by hydrodynamic simulations, the observational appearance is distinct. Unlike non-magnetic models, in which radiation is dominant at the outermost convective zones because of outward energy flow by convection, substantial accretion energy can be released in the vicinity of a black hole in MHD flow via magnetic reconnection. Such reconnection leads to sporadic flare events, thus producing variability in out-going radiation, as is commonly observed in objects with black-hole accretion.
Water-Vapor Maser Emission from the Seyfert 2 Galaxy IC 2560: Evidence for a Super-Massive Black Hole
Authors: Ishihara Yuko , Nakai Naomasa , Iyomoto Naoko , Makishima Kazuo , Diamond Philip , Hall Peter
Published: March 2014

We present an H$_2$O maser emission study of the Seyfert galaxy IC 2560 based on single-dish and VLBI observations. The maser emission was detected in multiple velocity ranges: one around the systemic velocity, one blue-shifted from the systemic velocity by $\sim220$-$420~$km$~$s$^{-1}$, and one red-shifted by $\sim210$-$350~$km$~$s$^{-1}$. This was the first detection of high-velocity features in this galaxy. The velocity of the systemic features drifts at a mean rate of $2.62\pm0.09~$km$~$s$^{-1}~$yr$^{-1}$. Assuming a compact Keplerian disk at the nucleus, the inner and outer radii of this disk are 0.07 and 0.26 pc, respectively. The central mass confined within the disk inner radius is $2.8\times10^6~M_{\odot}$, and its density is at least $2.1\times10^9~M_{\odot}~\mbox{pc}^{-3}$. Such a high density strongly suggests the existence of a black hole at the nucleus. The maser spots of the systemic features are distributed over $\lt 0.3~$mas (0.04 pc). The continuum source at the same position as the maser source is $\lt 1.0~$mas (0.13 pc) in size, and its brightness temperature of $2.7\times10^{11}~$K confirms IC 2560 to be an AGN. The 2-10 keV luminosity based on ASCA data is $1.0\times10^{41}~$erg$~$s$^{-1}$, which makes IC 2560 one of the low-luminosity AGNs. Adopting the standard accretion model, the mass-accretion rate needs to be $2\times10^{-5}~M_{\odot}~\mbox{yr}^{-1}$ in order to explain the X-ray luminosity.
Low-Temperature Optical Properties of Silicate Particles in the Far-Infrared Region
Authors: Chihara Hiroki , Koike Chiyoe , Tsuchiyama Akira
Published: March 2014

The far-infrared absorption spectra of crystalline circumstellar dust analogues (orthoenstatite, clinoenstatite, diopside, and forsterite) were measured at room temperature (295 K) and liquid-helium temperature (4.2 K). The wavelength ranges of the measurements were $20\hbox{-}80\,{\mu \mathrm {m}}$ and $30\hbox{-}80\,{\mu \mathrm {m}}$ at 295 K and 4.2 K, respectively. The absorption bands were detected very clearly not only at room temperature, but also at liquid-helium temperature. The temperature effects were clearly observed at liquid-helium temperature, such as (1) an increase in the spectral index of the continuum, (2) an enhancement in the absorption band strength, (3) a decrease in the band width, and (4) the absorption peaks of all bands of all samples shifted toward a shorter wavelength. These results suggest that a reconsideration of the identification should be required for some absorption bands which have been recognized as unidentified bands because of a disagreement in the peak position between the observed data and the laboratory data obtained at room temperature. Our experimental data can be obtained from the web-site (http://www.kyoto-phu.ac.jp/labo/butsuri/).
Bondi Accretion onto a Luminous Object
Authors: Fukue Jun
Published: March 2014

Spherical accretion of ionized gas onto a gravitating object is examined under the influence of central radiation. In classical Bondi accretion onto a non-luminous source with mass $ M$, the accretion rate $ \dot{M}_\mathrm{B}$ is expressed as $ \dot{M}_\mathrm{B}= \lambda(\gamma) \times 4\pi G^2 M^2\rho_\infty c_{\mathrm{s}\infty}^{-3}$, where $ \rho_\infty$ is the density at infinity and $ c_{\mathrm{s}\infty}$ the sound speed at infinity. We first found that the normalized accretion rate $ \lambda(\gamma)$ is approximated by $ \lambda(\gamma) = -(5/4)\gamma+ (19/8)$, instead of a rigorous expression. When the central object is a “spherical” source, the accretion rate $ \dot{M}$ reduces to $ \dot{M}_\mathrm{B} (1-\Gamma)^2$, where $ \Gamma$ is the central luminosity normalized by the Eddington one. If the central luminosity is produced by the accretion energy, the steady canonical luminosity is determined and the normalized luminosity does not exceed unity, as expected. On the other hand, when the central object is a “disk” source, such as an accretion disk, the accretion rate becomes $ \dot{M}/\dot{M}_\mathrm{B} = 1 -2\Gamma_\mathrm{d} + (4/3)\Gamma_\mathrm{d}^2$ for $ \Gamma_\mathrm{d} \leq 1/2$, and $ \dot{M}/\dot{M}_\mathrm{B} = 1 /(6\Gamma_\mathrm{d})$ for $ \Gamma_\mathrm{d} > 1/2$, where $ \Gamma_\mathrm{d}$ is the normalized disk luminosity. We also found steady canonical solutions, where the normalized luminosity can exceed unity for sufficiently large accretion rates. The anisotropic radiation field of accretion disks greatly modifies the accretion nature.
Optical Follow-up of the GRB 010222 Afterglow by Subaru Telescope
Authors: Watanabe Jun-ichi , Kinoshita Daisuke , Komiyama Yutaka , Tetsuharu Fuse , Urata Yuji , Yoshida Fumi
Published: March 2014

The optical afterglow of a gamma ray burst, GRB 010222, which was discovered by the BeppoSAX Team as the brightest one ever detected, was observed by Suprime-Cam of the Subaru Telescope at Mauna Kea. The obtained $R$-band magnitude was $ 18.59 \pm 0.04$ at February 22.51 UT, $ 18.99 \pm 0.04$ at February 22.65 UT, and $ 21.76\pm 0.03$ at February 25.64 UT. The light curve made from all data reported so far shows the decay of the brightness with a broken power law, of which the indices are $ -0.92 \pm 0.01$ before and $ -1.27 \pm 0.01$ after the break. The break point of the light curve is $ 0.73 \pm 0.02 \;\mathrm{d}$ after the burst, which is the earliest example ever observed. A brief summary of our follow-up observations, together with the importance of the optical follow-up capable by the Subaru telescope, is described in this letter.
A Molecular Cloud and an Expanding Cavity Adjacent to the Nonthermal Filaments of the Galactic Center Radio Arc
Authors: Oka Tomoharu , Hasegawa Tetsuo , Sato Fumio , Tsuboi Masato , Miyazaki Atsushi
Published: March 2014

Large-scale CO images taken with the $2 \times 2$ focal-plane array receiver on the 45 m telescope of Nobeyama Radio Observatory reveal parsec-scale structure of molecular gas around the Galactic center radio arc. The LVG analysis shows that the gas kinetic temperature is considerably enhanced ($T_\mathrm{k} \geq 70 \,\mathrm{K}$) in CO 0.13–0.13, a cloud which seems to be in contact with the nonthermal filaments of the Galactic center radio arc. This lends support for an interaction between CO 0.13–0.13 and the nonthermal filaments. The interaction with the strong magnetic field in and around the nonthermal filaments may heat up the molecular gas in CO 0.13–0.13 through shock dissipation and/or magnetic viscosity.

We also find an expanding cavity adjacent to the nonthermal filaments. The shell has a radius of $\sim 5 \,\mathrm{pc}$ and an expansion velocity of $25 \,\mathrm{km} \,\mathrm{s}^{-1}$. This expanding cavity might have been formed by several hundred supernovae or a single hypernova within $3 \times 10^5 \,\mathrm{yr}$. Magnetic tubes in this region could have been swept up by the expanding cavity, and compressed by interactions with CO 0.13–0.13. An interaction between the cloud and magnetic field may accelerate electrons to relativistic energies through shock acceleration or magnetic field reconnection.
Subaru Deep Near-Infrared Imaging of the Field of a Possible Proto-Cluster Near the Radio Galaxy 53W002 at $z=2.4$
Authors: Yamada Toru , Motohara Kentaro , Iwamuro Fumihide , Maihara Toshinori , Kajisawa Masaru , Tanaka Ichi , Kodama Tadayuki , Terada Hiroshi , Goto Miwa , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Takata Tadafumi , Sekiguchi Kazuhiro , Iye Masanori , Sasaki Toshiyuki , Usuda Tomonori , Kosugi George , Simpson Chris
Published: March 2014

We present the results of deep $K^\prime$ - and $J$-band imaging of the field of a proto-cluster region near the radio galaxy 53W002 at $z=2.390$ with the Subaru Telescope. The data were analyzed together with deep optical and near-infrared (NIR) images taken with the Hubble Space Telescope to investigate the properties of ten optically compact emission-line galaxies and candidates. Excluding the three objects which may contain active galactic nuclei, many are faint or undetected at $K^\prime$ ($\lambda_\mathrm{rest} \approx 6000 \,{Å}$), and are therefore revealed to be intrinsically small starbursting objects. On the other hand, we detect few objects with colors and magnitudes expected for quiescent massive galaxies at $z=2.4$ in the field.