bluuebunny/crossref_metadata_2025 huggingface dataset:
Strong Emission-Line Galaxies at Low Redshifts in the Field around the Quasar SDSSp J104433.04−012502.2
Authors: Ajiki Masaru , Shioya Yasuhiro , Taniguchi Yoshiaki , Murayama Takashi , Nagao Tohru , Sasaki Shunji S. , Sumiya Ryoko , Morioka Taichi , Hatakeyama Yuichiro , Yokouchi Asuka , Takahashi Mari I. , Koizumi Osamu
Published: March 2014

We discuss the observational properties of strong emission-line galaxies at low redshifts found by our deep imaging survey for high-redshift Ly$\alpha$ emitters. In our survey, we used a narrow-band filter, NB816 ($\lambda_{\mathrm{center}} = 8150 \,{Å}$ with $\mbox{FWHM} = 120 \,\mbox{Å}$ FWHM$= 120 \,{Å}$), and an intermediate-band filter, IA827 ($\lambda_{\mathrm{center}} = 8270 \,{Å}$ with $\mbox{FWHM} = 340 \,\mbox{Å}$ FWHM$= 340 \,{Å}$). In this survey, 62 NB816-excess ($\gt 0.9 \,\mathrm{mag} \gt 0.9 \,\mathrm{mag}$) and 21 IA827-excess ($\gt 0.8 \,\mathrm{mag} \gt 0.8 \,\mathrm{mag}$) objects were found. Among them, we found 20 NB816-excess and 4 IA827-excess Ly$\alpha$ emitter candidates. Therefore, it turns out that 42 NB816-excess and 17 IA827-excess objects are strong emission-line objects at lower redshifts. Since 4 objects in the two low-$z$ samples are common, the total number of strong low-$z$ emitters is 55. Applying our photometric redshift technique, we identified 7 $\mathrm{H}\alpha$ emitters at $z \approx 0.24$, 20 $\mathrm{H}\beta$–[O III] ones at $z \approx 0.65$, and 11 [O II] ones at $z \approx 1.19$. However, we could not determine reliable photometric redshifts of the remaining 17 emitters. The distributions of their rest frame equivalent widths are consistently understood based on recent studies of galaxy evolution from $z \sim 1$ to $z \sim 0$.
Reliability Checks on the Indo-US Stellar Spectral Library Using Artificial Neural Networks and Principal Component Analysis
Authors: Singh Harinder P. , Yuasa Manabu , Yamamoto Nawo , Gupta Ranjan
Published: March 2014

The Indo-US coudé feed stellar spectral library (CFLIB) made available to the astronomical community recently by Valdes et al. (2004, ApJS, 152, 251) contains spectra of 1273 stars in the spectral region 3460 to 9464 Å at a high resolution of 1 Å (FWHM) and a wide range of spectral types. Cross-checking the reliability of this database is an important and desirable exercise since a number of stars in this database have no known spectral types and a considerable fraction of stars has not so complete coverage in the full wavelength region of 3460–9464 Å resulting in gaps ranging from a few Å to several tens of Å. We use an automated classification scheme based on Artificial Neural Networks (ANN) to classify all 1273 stars in the database. In addition, principal component analysis (PCA) is carried out to reduce the dimensionality of the data set before the spectra are classified by the ANN. Most importantly, we have successfully demonstrated employment of a variation of the PCA technique to restore the missing data in a sample of 300 stars out of the CFLIB.
Three-Dimensional Simulation of Solar Emerging Flux Using the Earth Simulator I. Magnetic Rayleigh-Taylor Instability at the Top of the Emerging Flux as the Origin of Filamentary Structure
Authors: Isobe Hiroaki , Miyagoshi Takehiro , Shibata Kazunari , Yokoyama Takaaki
Published: March 2014

We present the results of three-dimensional magnetohydrodynamic simulations of solar emerging flux and its interaction with preexisting coronal field. In order to resolve the fine structures and the current sheets, we used high-resolution grids with up to $800 \times 400 \times 620$ points; the calculation was carried out using the Earth Simulator. The model set up is an extension of a previous two-dimensional simulation by Yokoyama and Shibata (1995) to include the variation along the third direction. Based on the same simulation result, we reported in our previous paper (Isobe et al. 2005): (1) Dense filaments similar to H$\alpha$ arch filament system are spontaneously formed in the emerging flux by the magnetic Rayleigh–Taylor type instability. (2) Filamentary current sheets are created in the emerging flux due to a nonlinear development of the magnetic Rayleigh-Taylor instability, which may cause an intermittent, nonuiform heating of the corona. (3) A magnetic reconnection between the emerging flux and preexisting coronal field occurs in a spatially intermittent way. In this paper we describe the simulation model and discuss the origin and the properties of the magnetic Rayleigh-Taylor instability in detail. It is shown that the top-heavy configuration that causes the instability is formed by the intrinsic dynamics of the emerging flux.
New Corroborative Evidence for the Overdensity of Galaxies around the Radio-Loud Quasar SDSS J0836+0054 at z = 5.8
Authors: Ajiki Masaru , Taniguchi Yoshiaki , Murayama Takashi , Shioya Yasuhiro , Nagao Tohru , Sasaki Shunji S. , Hatakeyama Yuichiro , Morioka Taichi , Yokouchi Asuka , Takahashi Mari I. , Koizumi Osamu
Published: March 2014

Recently, Zheng et al. (2006) found evidence for an overdensity of galaxies around a radio-loud quasar, SDSS J0836$+$0054, at $z = 5.8$ (a $5 \,\mathrm{arcmin}^2$ field). We examined our deep optical imaging data ($B, V, r^\prime, i^\prime, z^\prime$, and NB816) taken with the Suprime-Cam on the Subaru Telescope. The NB816 narrow-band filter ($\lambda_{\mathrm{c}} = 815 \,\mathrm{nm}$ and $\Delta\lambda = 12 \,\mathrm{nm}$) is suitable to search for Ly$\alpha$ emitters at $z \approx 5.7$. We found a new strong Ly$\alpha$ emitter at $z \approx 5.7$ close to object B, identified by Zheng et al. (2006). Further, the non-detection of nine objects selected by Zheng et al. (2006) in our $B, V$, and $r^{\prime}$ images provides corroborative evidence to indicate that they are high-$z$ objects.
Binary-Shaped Pupil Coronagraphs for High-Contrast Imaging Using a Space Telescope with Central Obstructions
Authors: Tanaka Shinichiro , Enya Keigo , Abe Lyu , Nakagawa Takao , Kataza Hirokazu
Published: March 2014

We present sets of configurations of binary-shaped pupil coronagraphs optimized for a realistic space telescope to directly detect extrasolar giant planets. For the purpose of mid-infrared observations, the target contrast ratio is set to $10^{-7}$. We made a systematic assessment of the performance of two recently proposed pupil shapes, “checkerboard” and “concentric ring” masks, where a large central obstruction due to a secondary mirror and its related support spiders was introduced into the telescope pupil. It turned out that, if the secondary mirror diameter is smaller than $\sim 15 \%$ of the diameter of the primary, the checkerboard-type masks are more promising in terms of the total high-contrast area. With such a small secondary, we propose to modify the original symmetrical checkerboard apodization function. This modification enables us to achieve a $10^{-7}$ contrast at an inner working angle (IWA) of $4.0 \,\lambda/D$. On the other hand, when the secondary mirror size cannot be reduced to that level, the concentric ring masks are preferable because of their larger transmission. It was also found that the transmission through the optimal binary masks exhibits two characteristic features as the IWA increases: firstly, abrupt increases and secondly, plateaus. We attribute this nature of the binary apodization functions to the existence of threshold IWAs that allow large openings in the pupil.
Spectropolarimetric Study on Circumstellar Structure of Microquasar LS I+61°303
Authors: Nagae Osamu , Kawabata Koji S. , Fukazawa Yasushi , Yamashita Takuya , Ohsugi Takashi , Uemura Makoto , Chiyonobu Shingo , Isogai Mizuki , Cho Toshinari , Suzuki Masaaki , Okazaki Akira , Okita Kiichi , Yanagisawa Kenshi
Published: March 2014

We present an optical linear spectropolarimetry study of the microquasar LS I$+61^{\circ}$303. The continuum emission is mildly polarized (up to 1.3%) and shows almost no temporal change. We found a distinct change of polarization across the $\mathrm{H}\alpha$ emission line, indicating the existence of a polarization component intrinsic to the microquasar. We estimated the interstellar polarization component from polarization of the $\mathrm{H}\alpha$ line and derived the intrinsic polarization component. The wavelength dependence of the intrinsic component is well explained by Thomson scattering in an equatorial disk of a Be-type mass donor. The position angle (PA) of the intrinsic polarization is $\sim 25^{\circ}$, and represents the rotational axis of the Be disk. This PA is nearly perpendicular to the PA of a radio jet found during quiescent phases. Assuming an orthogonal disk–jet geometry around the compact star, the rotational axis of the accretion disk is almost perpendicular to that of the Be disk. Moreover, according to the orbital parameters of the microquasar, the compact star is likely to get across the Be disk around their periastron passage. We discuss the peculiar circumstellar structure of this microquasar inferred based on our observation, and suggest a possible connection with its high-energy activities.
Verification of the Effectiveness of VSOP-2 Phase Referencing with a Newly Developed Simulation Tool, ARIS
Authors: Asaki Yoshiharu , Sudou Hiroshi , Kono Yusuke , Doi Akihiro , Dodson Richard , Pradel Nicolas , Murata Yasuhiro , Mochizuki Nanako , Edwards Philip G. , Sasao Tetsuo , Fomalont Edward B.
Published: March 2014

The next-generation space VLBI mission, VSOP-2, is expected to provide unprecedented spatial resolution at 8.4, 22, and 43 GHz. In this report, phase referencing with VSOP-2 is examined in detail based on a simulation tool called ARIS. The criterion for successful phase referencing was set to keep the phase errors below one radian. Simulations with ARIS reveal that phase referencing achieves good performance at 8.4 GHz, even under poor tropospheric conditions. At 22 and 43 GHz, it is recommended to conduct phase referencing observations under good or typical tropospheric conditions. The satellite is required to have an attitude-switching capability with a one-minute or shorter cycle, and an orbit determination accuracy higher than $\sim$10 cm at apogee; the phase referencing calibrators are required to have a signal-to-noise ratio larger than four for a single scan. The probability to find a suitable phase referencing calibrator was estimated by using VLBI surveys. From the viewpoint of calibrator availability, VSOP-2 phase referencing at 8.4 GHz is promising. However, the chance of finding suitable calibrators at 22 and 43 GHz is significantly reduced; it is important to conduct specific investigations for each target at those frequencies.
Observational Characteristics of the First Protostellar Cores
Authors: Omukai Kazuyuki
Published: March 2014

First protostellar cores are young stellar objects in the earliest evolutionary stage. They are hydrostatic objects formed soon after the central portions of star-forming cores become optically thick to dust emission. We consider their characteristics in the emitted radiation, and discuss their evolution with increasing mass of the cores. Particular attention is paid to detailed radiative and chemical processes in the postshock relaxation layer located at the surface of the core, where the majority of radiation is emitted. Most of the radiation is originally emitted in the dust continuum in mid-infrared wavelength ($\sim$ 10–30 $\mu$m), which reprocessed to far-infrared with $\sim$ 100–200 $\mu$m. Although some fraction ($\sim$ 0.1) of the radiation energy is emitted in the H$_2$O lines at the accretion shock, most is absorbed and reemitted in the dust continuum in the envelope. The H$_2$O lines account for at most $\sim 1/100$ of the observed luminosity. If a cavity is present in the envelope due to outflow or rotation, the dust and H$_2$O line emission in the mid-infrared wavelength from the shock can be observed directly, or as a reflection nebula. Among forthcoming observational facillities, SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is the most suitable for detecting either direct or processed radiation from first-core objects.
Lyman Break Galaxies at z$\sim$5: Rest-Frame UV Spectra. II
Authors: Ando Masataka , Ohta Kouji , Iwata Ikuru , Akiyama Masayuki , Aoki Kentaro , Tamura Naoyuki
Published: March 2014

We present spectroscopy results of Lyman break galaxies (LBGs) at z$\sim$5 in the J0053$+$1234 field. Among five bright candidates with z$'$$\;<\;$25.0 mag, two objects are confirmed to be at z$\;\sim\;$5. The equivalent widths (EWs) of Ly$\alpha$ emission of the 2 LBGs are not so strong as to be detected as Ly$\alpha$ emitters, and one of them shows strong low-ionization interstellar (LIS) metal absorption lines. Two faint objects with z$'$$\geq$25.0 mag are also confirmed to be at z$\;\sim\;$5, and their spectra show strong Ly$\alpha$ emission in contrast to bright ones. These results suggest a deficiency of strong Ly$\alpha$ emission in bright LBGs at z$\;\sim\;$5, as discussed in our previous paper. Combined with our previous spectra of LBGs at z$\;\sim\;$5, obtained around the Hubble Deep Field-North (HDF-N), we made a composite spectrum of luminous ($M_{1400} \leq -$21.5 mag) LBGs at z$\;\sim\;$5. The resultant spectrum shows weak Ly$\alpha$ emission and strong LIS absorptions, which suggest that the bright LBGs at z$\;\sim\;$5 have chemically evolved at least to $\sim$0.1 solar metallicity. For a part of our sample in the HDF-N region, we obtained near-to-mid infrared data, which constrain the stellar masses of these objects. With the stellar mass and the metallicity estimated from the LIS absorptions, the metallicities of the LBGs at z$\;\sim\;$5 tend to be lower than those of galaxies with the same stellar mass at z$\lesssim 2$, although the uncertainty is very large.
The Impact of Type Ia Supernova Explosions on the Companion in a Binary System
Authors: Meng Xiangcun , Chen Xuefei , Han Zhanwen
Published: March 2014

Using a simple analytic method, we can calculate the impact effect between the ejecta of a SN Ia and its companion to survey the influence of the initial parameters of the progenitor’s system, which is useful for searching the companion in an explosion remnant. The companion models are obtained from Eggleton’s evolution code. The results are divided into two groups based on the mass-transfer stage. For a given condition, more hydrogen-rich material is stripped from the envelope of a Hertzsprung-gap companion than that of a main-sequence companion, while a larger kick velocity and a larger luminosity are gained for a main-sequence companion. The kick velocity is too low to significantly affect the final spatial velocity of the companion, which is mainly affected by the initial parameters of the progenitor systems. The spatial velocity of the stripped material has an upper limit within the range of 8000–9500 km s$^{-1}$, which only depends on the total kinetic energy of the explosion. The stripped mass, the ratio of the stripped mass to the companion mass and the kick velocity of the companion all significantly depend on the initial companion mass and the orbital period. Our model may naturally explain the spatial velocity of the star G in the remnant of Tycho’s supernova, while an energy-loss mechanism is needed to interpret its luminosity.
A Complete Survey of the Central Molecular Zone in NH$_3$
Authors: Nagayama Takumi , Omodaka Toshihiro , Handa Toshihiro , Iahak Hayati Bebe Hajra , Sawada Tsuyoshi , Miyaji Takeshi , Koyama Yasuhiro
Published: March 2014

We present a map of the major part of the central molecular zone (CMZ) of simultaneous observations in the NH$_3 (J,K) =$ (1,1) and (2,2) lines using the Kagoshima 6 m telescope. The mapped area is $-$1$\rlap{.}{}^{\circ}$000 $\leq l \leq$ 1$\rlap{.}{}^{\circ}$625 and $-$0$\rlap{.}{}^{\circ}$375 $\leq b \leq$ 0$\rlap{.}{}^{\circ}$250. The kinetic temperatures derived from the (2,2) to (1,1) intensity ratios are 20–80 K, or exceed 80 K. The gases corresponding to temperatures of 20–80 K and $\geq$ 80 K contain 75% and 25% of the total NH$_3$ flux, respectively. These temperatures indicate that the dense molecular gas in the CMZ is dominated by gas that is warmer than the majority of the dust present there. A comparison of our observations with a CO survey by Sawada et al. (2001, ApJS, 136, 189) shows that the NH$_3$ emitting region is surrounded by a high-pressure region on the longitude–velocity ($l - v$) plane. Although NH$_3$ emission traces dense gas, it does not extend over a high-pressure region. Therefore, the high-pressure region is less dense and has to be hotter. This indicates that the molecular-cloud complex in the Galactic center region has a “core” of dense and warm clouds that are traced by the NH$_3$ emission, and an “envelope” of less-dense and hotter gas clouds. Besides heating by ambipolar diffusion, the hot plasma gas emitting the X-ray emission may heat the hot “envelope”.
Subsystems in a Stable Planetary System
Authors: Tanikawa Kiyotaka , Ito Takashi
Published: March 2014

Our planetary system is dynamically stable for the lifetime of the Sun according to long-term numerical integrations of the planetary orbits (2002, MNRAS, 336, 483). We first list up possible subsystems of a stable planetary system, and then discuss three forms of subsystems that may contribute to maintaining the stability of the system, and whose role may have escaped analysis by dynamical astronomers. We stress that multiplanet subsystems may have a variety of mechanisms for maintaining stability. This is in contrast with the stability problem of massless bodies, such as asteroids, satellites, and comets.
Observation of C$_8$H$^-$ toward IRC +10216
Authors: Kentarou Kawaguchi , Fujimori Ryuji , Aimi Sayaka , Takano Shuro , Okabayashi Emi Y. , Gupta Harshal , BrÜnken Sandra , Gottlieb Carl A. , McCarthy Michael C. , Thaddeus Patrick
Published: March 2014

Five rotational lines of the C$_8$H$^-$ ion were observed in the circumstellar envelope of IRC $+$10216 with the Nobeyama 45 m telescope. An improved value of the column density of the C$_8$H radical yielded a [C$_8$H$^-$]$/$[C$_8$H] ratio of 37%—nearly 4 times larger than the [C$_6$H$^-$]$/$[C$_6$H] ratio (8.6%) and nearly 1500 times the [C$_4$H$^-$]$/$[C$_4$H] ratio (0.024%), which may indicate more efficient formation of longer carbon chain anions. The excitation temperature of C$_8$H$^-$ (16$\;\pm\;$2 K) derived here is somewhat lower than that of the two smaller anions C$_6$H$^-$ (32 K) and C$_4$H$^-$ (23 K) in IRC $+$10216.
Discoveries of Diffuse Iron Line Sources from the Sgr B Region
Authors: Koyama Katsuji , Inui Tatsuya , Hyodo Yoshiaki , Matsumoto Hironori , Tsuru Takeshi Go , Maeda Yoshitomo , Murakami Hiroshi , Yamauchi Shigeo , Kissel Steven E. , Chan Kai-Wing , Soong Yang
Published: March 2014

The radio complex Sgr B region was observed with the X-ray Imaging Spectrometer (XIS) on board Suzaku. This region exhibits diffuse iron lines at 6.4, 6.7, and 6.9 keV, which are $\mathrm{K}\alpha$ lines of Fe I (neutral iron), Fe XXV (He-like iron), and Fe XXVI (H-like iron), respectively. The high energy resolving power of the XIS provided separate maps of the K-shell transition lines from Fe I (6.4 keV) and Fe XXV (6.7 keV). Although the 6.7 keV line is smoothly distributed over the Sgr B region, a local excess is found near $(l, b) = ({0\rlap {.}{}^{\mathrm {\circ }}61}, {0\rlap {.}{}^{\mathrm {\circ }}01})$, possibly due to a new SNR. The plasma temperature is $kT\sim 3 \,\mathrm{keV}$ and the age is estimated to be younger than $7 \times 10^{3} \,\mathrm{yr}$. The 6.4 keV image is clumpy with local excesses near Sgr B2 and at $(l, b) = ({0\rlap {.}{}^{\mathrm {\circ }}74},- {0\rlap {.}{}^{\mathrm {\circ }}09})$. Like Sgr B2, this excess may be another candidate of an X-ray reflection nebula.
X-Ray Spectrum of Sagittarius A East
Authors: Koyama Katsuji , Uchiyama Hideki , Hyodo Yoshiaki , Matsumoto Hironori , Tsuru Takeshi Go , Ozaki Masanobu , Maeda Yoshitomo , Murakami Hiroshi
Published: March 2014

Sgr A East is a young SNR located in the Galactic Center (GC) region. Since the GC region is occupied by diffuse X-ray emission (GCDX) with a strong 6.7 keV line, an estimation of the GCDX is crucial to study the X-ray spectrum of Sgr A East. The flux and spectrum of the GCDX are found to be smoothly distributed around and across Sgr A East, and hence a reliable GCDX subtraction can be made. This paper presents the X-ray spectrum of Sgr A East with the XIS on board Suzaku. In addition to the previously reported $\mathrm{K}\alpha$ lines from S XV, Ar XVII, Ca XIX, and Fe XXV (all He-like atoms), we found $\mathrm{K}\alpha$ lines from S XVI, Ar XVIII, Fe XXVI (all hydrogenic atoms), and Ni XXVII (He-like), $\mathrm{K}\beta$ lines from S XV, Ar XVII, and Fe XXV, and a $\mathrm{K}\gamma$ line from Fe XXV. Plasma diagnostics using these lines revealed the presence of at least a two-temperature plasma. The overall spectrum can be fitted with a two-temperature ($\sim 1.2 \,\mathrm{keV}$ and $\sim 6 \,\mathrm{keV}$) plasma in ionization equilibrium plus a power-law component.
Suzaku Observation of Two Ultraluminous X-Ray Sources in NGC 1313
Authors: Mizuno Tsunefumi , Miyawaki Ryohei , Ebisawa Ken , Kubota Aya , Miyamoto Masao , Winter Lisa M. , Ueda Yoshihiro , Isobe Naoki , Dewangan Gulab C. , Done Chris , Griffiths Richard E. , Haba Yoshito , Kokubun Motohide , Kotoku Jun’ichi , Makishima Kazuo , Matsushita Kyoko , Mushotzky Ricard F. , Namiki Masaaki , Petre Robert , Takahashi Hiromitsu , Tamagawa Toru , Terashima Yuichi
Published: March 2014

Two ultraluminous X-ray sources (ULXs) in the nearby Sb galaxy NGC 1313, named X-1 and X-2, were observed with Suzaku on 2005 September 15. During the observation for a net exposure of 28 ks (but over a gross time span of 90 ks), both objects varied in intensity by about 50%. The 0.4–10 keV X-ray luminosities of X-1 and X-2 were measured as $2.5 \times 10^{40} \,\mathrm{erg} \,\mathrm{s}^{-1}$ and $5.8 \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$, respectively, with the former exhibiting the highest ever reported for this ULX. The spectrum of X-1 can be explained by the sum of a strong and variable power-law component with a high-energy cutoff, and a stable multicolor blackbody with an innermost disk temperature of $\sim 0.2 \,\mathrm{keV}$. These results suggest that X-1 was in a “very high” state, where disk emission is strongly Comptonized. The absorber within NGC 1313 toward X-1 is suggested to have a subsolar oxygen abundance. The spectrum of X-2 is best represented, in its fainter phase, by a multicolor blackbody model with an innermost disk temperature of 1.2–1.3 keV, and becomes flatter as the source becomes brighter. Hence, X-2 is interpreted to be in a slim-disk state. These results suggest that the two ULXs have black hole masses of some dozens to a few hundred of solar masses.
Umbral Fine Structures in Sunspots Observed with Hinode Solar Optical Telescope
Authors: Kitai Reizaburo , Watanabe Hiroko , Nakamura Tahei , Otsuji Ken-ichi , Matsumoto Takuma , UeNo Satoru , Nagata Shin’ichi , Shibata Kazunari , Muller Richard , Ichimoto Kiyoshi , Tsuneta Saku , Suematsu Yoshinori , Katsukawa Yukio , Shimizu Toshifumi , Tarbell Theodore D. , Shine Richard A. , Title Alan M. , Lites Bruce
Published: March 2014

A high resolution imaging observation of a sunspot umbra was made with the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the blue and green continua were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components, and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution, and morphological evolution. The brightness of UDs is confirmed to depend on the brightness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of the space observation, we could for the first time follow the temporal behavior of these events. The derived properties of the internal structure of the umbra are discussed from the viewpoint of magnetoconvection in a strong magnetic field.
Observations of Sunspot Oscillations in G Band and Ca II H Line with Solar Optical Telescope on Hinode
Authors: Nagashima Kaori , Sekii Takashi , Kosovichev Alexander G. , Shibahashi Hiromoto , Tsuneta Saku , Ichimoto Kiyoshi , Katsukawa Yukio , Lites Bruce , Nagata Shin’ichi , Shimizu Toshifumi , Shine Richard A. , Suematsu Yoshinori , Tarbell Theodore D. , Title Alan M.
Published: March 2014

Exploiting high-resolution observations made by the Solar Optical Telescope on board Hinode, we investigate the spatial distribution of the power spectral density of the oscillatory signal in and around the active region NOAA 10935. The G-band data show that in the umbra the oscillatory power is suppressed in all frequency ranges. On the other hand, in Ca II H intensity maps oscillations in the umbra, so-called umbral flashes, are clearly seen with the power peaking around 5.5 mHz. The Ca II H power distribution shows the enhanced elements with the spatial scale of the umbral flashes over most of the umbra, but there is a region with suppressed power at the center of the umbra. The origin and property of this node-like feature remain unexplained.
Response of the Solar Atmosphere to Magnetic Flux Emergence from Hinode Observations
Authors: Li Hui , Sakurai Takashi , Ichimito Kiyoshi , Suematsu Yoshinori , Tsuneta Saku , Katsukawa Yukio , Shimizu Toshifumi , Shine Richard A. , Tarbell Theodore D. , Title Alan M. , Lites Bruce , Kubo Masahito , Nagata Shin’ichi , Kotoku Jun , Shibasaki Kiyoto , Saar Steven H. , Bobra Monica
Published: March 2014

In the present work, we used optical and X-ray data from the Hinode satellite to study the response of the solar chromosphere and the corona to the emerging flux in the photosphere. In total, twelve emerging flux regions (EFRs) were selected to conduct this study. The average separation of the two polarities and the lifetime of these EFRs were 3$\rlap {.} {}^{\prime\prime}$2 and 40 min, respectively. All of these regions showed corresponding enhanced emission in the Ca II H line and soft X-rays with different filters, indicating that these small-scale and short-lived EFRs heat the chromosphere and the corona to some extent.
A Measurement of Proper Motions of SiO Maser Sources in the Galactic Center with the VLBA
Authors: Oyama Tomoaki , Miyoshi Makoto , Deguchi Shuji , Imai Hiroshi , Shen Zhi-Qiang
Published: March 2014

We report on the high-precision astrometric observations of maser sources around the Galactic Center in the SiO $J=1$-0 $v=1$ and 2 lines with the VLBA during 2001–2004. With phase-referencing interferometry referred to the radio continuum source Sgr A*, accurate positions of masers were obtained for three detected objects: IRS 10EE (7 epochs), IRS 15NE (2 epochs), and SiO 6(only 1 epoch). Because circumstellar masers of these objects were resolved into several components, proper motions for the maser sources were derived with several different methods. Combining our VLBA results with those of the previous VLA observations, we obtained the IRS 10EE proper motion of 76$\pm$3kms$^{-1}$ (at 8kpc) to the south relative to Sgr A*. Almost null proper motion of this star in the east–west direction results in a net transverse motion of the infrared reference frame of about 30$\pm$9kms$^{-1}$ to the west relative to Sgr A*. The proper-motion data also suggests that IRS 10EE is an astrometric binary with an unseen massive companion.
Aperture Synthesis Imaging of a High-Velocity Compact Cloud near the Galactic Center
Authors: Oka Tomoharu , Hasegawa Tetsuo , White Glenn J. , Sato Fumio , Tsuboi Masato , Miyazaki Atsushi
Published: March 2014

We observed CO $J =$ 1-0 and HCN $J =$ 1-0 line emission toward a high-velocity, compact molecular cloud, CO0.02-0.02, near the center of our Galaxy, using the Nobeyama Millimeter Array (NMA). A CO velocity-integrated map with a resolution of 4.3”$\times$2.4” shows two oval clumps with sizes of 0.8pc. These clumps are seperated by 1.2pc, being located at the eastern and southwestern peripheries of the CO0.02-0.02 cloud. The overall distribution of HCN emission coincides with that taken with the Nobeyama 45m telescope. The HCN velocity-integrated map with a resolution of 6.1”$\times$3.4” shows two prominent peaks in the cloud center. Both NMA maps at $V_{\rm LSR}$$\sim$110kms$^{-1}$ show an arc-shaped edge in the southeast, which may correspond to the edge of the “emission cavity” found in the CO $J =$ 3-2 integrated-intesity map. We also noticed a faint radio continuum “arc” that encircles the bulk of the CO0.02-0.02 cloud. These results support the notion that CO0.02-0.02 has been accelerated, heated, and compressed in a series of supernova shocks that occurred within the last (3-5)$\times$10$^{4}$yr. We suggest that a massive compact cluster with an age of 10-30Myr is responsible for the formation of the CO0.02-0.02 cloud.
Cooperative Observation of Ellerman Bombs between the Solar Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope
Authors: Matsumoto Takuma , Kitai Reizaburo , Shibata Kazunari , Nagata Shin’ichi , Otsuji Kenichi , Nakamura Tahei , Watanabe Hiroko , Tsuneta Saku , Suematsu Yoshinori , Ichimoto Kiyoshi , Shimizu Toshifumi , Katsukawa Yukio , Tarbell Theodore D. , Lites Bruce W. , Shine Richard A. , Title Alan M.
Published: March 2014

High-resolution CaIIH broad-band filter images of NOAA10933 on 2007 January 5 were obtained by the Solar Optical Telescope aboard the Hinode satellite. Many small-scale ($\sim$1") bright points were observed outside the sunspot and inside the emerging flux region. We identified some of these bright points with Ellerman bombs (EBs) by using H$\alpha$ images taken by the Domeless Solar Telescope at Hida observatory. The sub-arcsec structures of two EBs seen in CaIIH were studied in detail. Our observation showed the following two aspects: (1) The CaIIH bright points identified with EBs were associated with the bipolar magnetic field structures, as reported by previous studies. (2) The structure of the CaIIH bright points turned out to consist of the following two parts: a central elongated bright core (0.7" $\times$ 0.5") located along the magnetic neutral line and a diffuse halo (1.2" $\times$ 1.8").
Subaru/MOIRCS Near-Infrared Imaging in the Proto-Cluster Region at z = 3.1
Authors: Uchimoto Yuka Katsuno , Suzuki Ryuji , Tokoku Chihiro , Ichikawa Takashi , Konishi Masahiro , Yoshikawa Tomohiro , Omata Koji , Nishimura Tetsuo , Yamada Toru , Tanaka Ichi , Kajisawa Masaru , Akiyama Masayuki , Matsuda Yuichi , Yamauchi Ryosuke , Hayashino Tomoki
Published: March 2014

We present the results of deep near-infrared imaging observations of the $z=3.1$ proto-cluster region in the SSA 22a field taken by MOIRCS mounted on the Subaru Telescope. We observed a 21.7 arcmin$^2$ field to depths of $J=$ 24.5, $H=$ 24.3, and $K=$ 23.9 (5$\sigma$). We examined the distribution of the $K$-selected galaxies at $z \sim 3$ by using a simple color cut for distant red galaxies (DRGs) as well as a photometric-redshift selection technique. The marginal density excess of DRGs and the photo-$z$ selected objects were found around the two most luminous Ly$\alpha$ blobs (LABs). We investigated the correlation between the $K$-selected objects and the LABs, and found that several galaxies with stellar mass, $M_* = 10^{9}$–$10^{11} M_\odot$, exist in the vicinity of LABs, especially around the two most luminous ones. We also found that 7 of the 8LABs in the field have plausible $K_{\rm s}$-band counterparts, and the sum of the stellar mass possibly associated with LABs correlates with their luminosity and surface brightness, which implies that the origin of Ly$\alpha$ emission may be closely correlated with their previous star-formation phenomena.
High-Resolution Spectroscopy of T Tauri Stars
Authors: Taguchi Yuske , Itoh Yoichi , Mukai Tadashi
Published: March 2014

We have conducted high-resolution spectroscopic observations of a sample of both classical and weak-line T Tauri stars embedded in the Taurus-Auriga molecular cloud using the Okayama Astrophysical Observatory’s 188 cm telescope equipped with HIDES (HIgh Dispersion Echelle Spectrograph). Utilizing the ratios of equivalent widths of specific lines, we efficiently eliminated the effects of “veiling” and determined the atmospheric parameters individually for each object. Eight pairs of temperature-sensitive line-ratios were selected to derive the effective temperature with high precision and reliability. As for the surface gravity, we have developed a new method to determine the value. The method was first tested on observed spectral standards, and the derived surface gravities had a less than 5% deviation from the values in the literature. The derived surface gravities are well within the range of the assumed values for T Tauri stars.
Modeling Nonlinear Evolution of Baryon Acoustic Oscillations: Convergence Regime of $N$-body Simulations and Analytic Models
Authors: Nishimichi Takahiro , Shirata Akihito , Taruya Atsushi , Yahata Kazuhiro , Saito Shun , Suto Yasushi , Takahashi Ryuichi , Yoshida Naoki , Matsubara Takahiko , Sugiyama Naoshi , Kayo Issha , Jing Yipeng , Yoshikawa Kohji
Published: March 2014

We used a series of cosmological $N$-body simulations and various analytic models to study the evolution of the matter power spectrum in real space in a $\Lambda$ cold dark matter universe. We compared the results of $N$-body simulations against three analytical model predictions; standard perturbation theory, renormalized perturbation theory, and a closure approximation. We included the effects from a finite simulation box size under comparison. We determined the values of the maximum wavenumbers, $k^{\rm lim}_{1\%}$ and $k^{\rm lim}_{3\%}$, below which the analytic models and the simulation results agree with accuracy to within 1 and 3 percent. We then provided a simple empirical function that describes the convergence regime determined by comparisons between our simulations and the analytical models. We found that if we use the Fourier modes within the convergence regime alone, the characteristic scale of baryon acoustic oscillations can be determined with an accuracy of 1% from future surveys with a volume of a few $h^{-3}$Gpc$^3$ at z$\sim$ 1 or z$\sim$ 3 in the absence of any systematic distortion of the power spectrum.
North Ecliptic Pole Wide Field Survey of AKARI: Survey Strategy and Data Characteristics
Authors: Lee Hyung Mok , Kim Seong Jin , Im Myungshin , Matsuhara Hideo , Oyabu Shinki , Wada Takehiko , Nakagawa Takao , Ko Jongwan , Shim Hyun Jin , Lee Myung Gyoon , Hwang Narae , Takagi Toshinobu , Pearson Chris
Published: March 2014

We present the survey strategy and the data characteristics of the North Ecliptic Pole (NEP) Wide Survey of AKARI. The survey was carried out for about one year starting from 2006 May with 9 passbands from 2.5 to 24 $\mu$m and the areal coverage of about 5.8 degree$^2$ centered on NEP. The survey depth reaches to 21.8 AB magnitude near infrared (NIR) bands, and $\sim$18.6 AB magnitude at the mid infrared (MIR) bands such as 15 and 18 $\mu$m. The total number of sources detected in this survey is about 104000, with more sources in NIR than in the MIR. We have cross matched infrared sources with optically identified sources in CFHT imaging survey which covered about 2 degree$^2$ within NEP-Wide survey region in order to characterize the nature of infrared sources. The majority of the MIR sources at 15 and 18 $\mu$m bands are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs. We found that a large fraction (60%–80%) of bright sources in 9 and 11 $\mu$m is stars while stellar fraction decreases toward fainter sources. We present the histograms of the sources at MIR bands at 9, 11, 15, and 18 $\mu$m. The number of sources per magnitude thus varies as $m^{0.6}$ for longer wavelength sources while shorter wavelength sources show steeper variation with $m$, where $m$ is the AB magnitude.
Global Radiation-Magnetohydrodynamic Simulations of Black-Hole Accretion Flow and Outflow: Unified Model of Three States
Authors: Ohsuga Ken , Mineshige Shin , Mori Masao , Kato Yoshiaki
Published: March 2014

Black-hole accretion systems are known to possess several distinct modes (or spectral states), such as low/hard state and high/soft state. Since the dynamics of the corresponding flows is distinct, theoretical models were separately considered for each state. We here propose a unified model based on our new, global, two-dimensional radiation-magnetohydrodynamic simulations. By controlling a density normalization we could for the first time reproduce three distinct modes of accretion flow and outflow with one numerical code. When the density is large (model A), a geometrically thick, very luminous disk forms, in which photon trapping takes place. When the density is moderate (model B), the accreting gas can effectively be cooled by emitting radiation, thus generating a thin disk, i.e., a soft-state disk. When the density is too low for radiative cooling to be important (model C), a disk becomes hot, thick, and faint; i.e., a hard-state disk. The magnetic energy is amplified within the disk up to about twice, 30%, and 20% of the gas energy in models A, B, and C, respectively. Notably, the disk outflows with helical magnetic fields, which are driven either by radiation-pressure force or magnetic-pressure force, are ubiquitous in any accretion modes. Finally, our simulations are consistent with the phenomenological $\alpha$-viscosity prescription; that is, the disk viscosity is proportional to the pressure.
Superhump Development during the 2005 Superoutburst of 1RXS J053234+624755
Authors: Imada Akira , Henden Arne , Kato Taichi , Moritani Yuuki , Sumiyoshi Masanao , Tanada Syunsuke , Omodaka Toshihiro , Ishioka Ryoko , Uemura Makoto , Yanagisawa Kenshi , Nogami Daisaku
Published: March 2014

We report on time-resolved CCD photometry of the 2005 March/April superoutburst of a recently confirmed SU UMa-type dwarf nova, 1RXS J053234+624755. The superoutburst was accompanied by a precursor in which conspicuous superhumps were visible from the second night of the precursor. This is a rare example where superhumps were observed during a precursor. Concerning an estimated mass ratio of 0.07 for the system, the present observations contrast with the well-known Lubow relation. We also found that the superhump period increased as the superoutburst proceeded, despite the fact that the superoutburst showed a precursor. If the superhump-period change is closely related to the disk radius of the superoutburst, systems having a small mass ratio could display an increasing superhump period, even if the superoutburst contains a precursor.
Solar-Radiation Heating Effects on 3200 Phaethon
Authors: Ohtsuka Katsuhito , Nakato Aiko , Nakamura Tomoki , Kinoshita Daisuke , Ito Takashi , Yoshikawa Makoto , Hasegawa Sunao
Published: March 2014

Apollo-type near-Earth asteroid 3200 Phaethon, having a small perihelion distance of $q$$\sim$ 0.14 AU, is classified as F- or B-type, one of subclasses among the C-complex (C-, G-, B-, and F-types) asteroids. The F/B-type asteroids and dehydrated CI and CM carbonaceous chondrites, which are regarded as being linked to each other, underwent a thermal history of high-temperature heatings at more than hundreds of degrees and dehydration for a certain period of time after aqueous alteration in their parent bodies. However, their primary heating mechanism and its timing are less certain and still controversial. We have investigated solar-radiation heating effects on Phaethon at the present planetary-epoch. As a consequence, we have found that the effects on Phaethon, if it is still hydrated, might indeed be a likely candidate for the primary metamorphic heat source. We also found that solar-radiation heating on Phaethon is a function of the latitude, since Phaethon has a highly tilted polar axis. Thus, the northern hemisphere would be selectively more heated than the southern hemisphere. Therefore, we hypothesized that the northern hemisphere, especially the north pole–northern midlatitude region, would be more thermally metamorphosed and dehydrated, if solar-radiation heating is the primary metamorphic heat source of Phaethon. This may provide the latitude-dependent color variations on Phaethon’s surface, although this has not been proven by the existing Phaethon’s spectral data.
The Nature of Unresolved Soft X-Ray Emission from the Galactic Disk
Authors: Masui Kensuke , Mitsuda Kazuhisa , Yamasaki Noriko Y. , Takei Yoh , Kimura Shunsuke , Yoshino Tomotaka , McCammon Dan
Published: March 2014

Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the galactic absorption in midplane directions, it decreases at most by about 20% in midplane. Suzaku observation of the direction, ($\ell$, $b$) $=$ (235$^\circ$, 0$^\circ$), showed an O vii${\rm K} \alpha$ emission intensity comparable with that of the MBM-12 on cloud Suzaku observation, but revealed a narrow bump peaked at $\sim$0.9 keV. The latter component is partly filling the decrease of the extragalactic component in midplane. The feature can be well represented by a thin thermal emission with a temperature of about 0.8 keV. Because of the high pressure implied for spatially extended hot gas, the emission is likely a sum of unresolved faint sources. We consider a large fraction of the emission originates from faint dM stars. We constructed a model spectrum for spatially unresolved dM stars that consistently explains the observed spectrum and the surface brightness. The model also suggests that the emission from dM stars decreases very rapidly with increasing $b$, and thus that it cannot compensate entirely the decrease of the extragalactic component at $b$$\sim$ 2$^\circ$–10$^\circ$.
Suzaku Observations of SS Cygni in Quiescence and Outburst
Authors: Ishida Manabu , Okada Shunsaku , Hayashi Takayuki , Nakamura Ryoko , Terada Yukikatsu , Mukai Koji , Hamaguchi Kenji
Published: March 2014

We present results from the Suzaku observations of the dwarf nova SS Cyg in quiescence and outburst in 2005 November. The high sensitivity of the HXD PIN and the high spectral resolution of the XIS enabled us to determine the plasma parameters with unprecedented precision. The maximum temperature of the plasma in quiescence, 20.4$^{+4.0}_{-2.6}$(stat)$\pm$3.0(sys)keV, is significantly higher than that in outburst, 6.0$^{+0.2}_{-1.3}$keV. The elemental abundances are close to the solar ones for medium-$Z$ elements (Si, S, Ar), whereas they decline both in lighter and heavier elements, except for that of carbon, which is 2 solar, at least. The solid angle of the reflector subtending over an optically thin thermal plasma is $\Omega^{\rm Q}/(2\pi)$$=$ 1.7$\pm$0.2(stat)$\pm$0.1(sys) in quiescence. A 6.4 keV iron K$\alpha$ line is resolved into narrow and broad components. These facts indicate that both the white dwarf and the accretion disk contribute to the reflection. We consider the standard optically thin boundary layer as being the most plausible picture for the plasma configuration in quiescence. The solid angle of the reflector in outburst, $\Omega^{\rm O}\!\!/(2\pi)$$=$ 0.9$^{+0.5}_{-0.4}$, and a broad 6.4 keV iron line indicate that the reflection in outburst originates from the accretion disk and an equatorial accretion belt. The broad 6.4 keV line suggests that the optically thin thermal plasma is distributed on the accretion disk like solar corona.
Timing and Spectral Study of AXJ1745.6$-$2901 with Suzaku
Authors: Hyodo Yoshiaki , Ueda Yoshihiro , Yuasa Takayuki , Maeda Yoshitomo , Makishima Kazuo , Koyama Katsuji
Published: March 2014

The eclipsing low-mass X-ray binary AX J1745.6$-$2901 was observed with Suzaku in its outburst phase. Combining the Chandra observation made 1.5 month earlier than Suzaku, we determined the orbital period to be 30063.76$\pm$0.14 s. We found deep flux dips prior to the eclipse phase of the orbit. The X-ray spectrum of the persistent phase is described by a combination of a direct and a scattered-in components by dust emission. During the eclipse, the X-ray spectrum becomes only the dust scattering (scattered-in) component. The optical depth of the dust scattering is $\sim$ 10.5 at 1 keV. The direct component is composed of a blackbody likely from the neutron-star surface and a disk-blackbody. No power-law component is found in the hard energy band up to 30 keV. A clear edge at $\sim$ 7.1 keV in the deep dip spectrum indicates that the major portion of Fe in the absorber is neutral, or in a low ionization state. We discovered four narrow absorption lines near the K-shell transition energies of Fe XXV, Fe XXVI, and Ni XXVII. The absorption line features are well explained by the solar abundance gas in a bulk motion of $\sim$ 10$^{3}$kms$^{-1}$.
VERA Observations of H$_2$O Maser Sources in Three Massive Star-Forming Regions and Galactic Rotation Measurements
Authors: Oh Chung Sik , Kobayashi Hideyuki , Honma Mareki , Hirota Tomoya , Sato Katsuhisa , Ueno Yuji
Published: March 2014

We present the results of VLBI observations of three H$_2$O maser sources in massive star-forming regions: IRAS 06058$+$2138, IRAS 19213$+$1723, and AFGL 2789. We determined the annual parallaxes and proper motions for these sources by a phase-referencing method. The estimated distances to IRAS 06058$+$2138 and AFGL 2789 are 1.76$\pm$0.11 kpc and 3.07$\pm$0.30 kpc, which are located in the Perseus spiral arm. The distance to IRAS 19213$+$1723 is 3.98$\pm$0.57 kpc, placing it in the Carina–Sagittarius arm. With estimated 3-dimensional velocity components, we have shown that the galactic rotation curve is flat in the range of 6.4 kpc $\le R \le$ 13 kpc as combining with S 269, which was observed with VERA. We have also found that the overall rotation curve of the Galaxy do not depend on $\Theta_0$. The maser sources also show deviations from flat rotation curves by a few kilometers per second. We discuss possible reasons for these peculiar motions.
Revisit to the Nuclear Spin Temperature of NH$_{3}$ in Comet C/2001 Q4 (NEAT) Based on High-Dispersion Spectra of Cometary NH$_{2}$
Authors: Shinnaka Yoshiharu , Kawakita Hideyo , Kobayashi Hitomi , Kanda Yu-ichi
Published: March 2014

The Ortho-to-Para abundance ratio (OPR) of cometary molecules is considered to be one of primordial characters of comeary ices, which has information concerning their formation. In order to determine the OPR of cometary ammonia (NH$_{3}$), high-dispersion spectra in the optical wavelength region have been the most powerful tool, since NH$_{2}$ is a photo-dissociation product of NH$_{3}$, and NH$_{2}$ has a strong electronic transition in the optical region. Here we present an improved procedure to derive the OPR of NH$_{2}$ (OPR of NH$_{3}$ is derived from that of NH$_{2}$) from the high-dispersion spectra of NH$_{2}$ in comets. We consider (1) the contamination of NH$_{2}$ lines by the C$_{2}$ Swan-band lines, (2) the influence by the telluric absorption lines, and (3) multiple measurements of OPR from different vibronic bands of NH$_{2}$ in the optical region, to achieve a more accurate determination of OPRs than that in previous studies. We applied the new method to the spectrum of comet C/2001 Q4 (NEAT) for which the OPR of NH$_{2}$ was determined in the previous study. The derived OPR of NH$_{2}$ is 3.23$ \pm $0.03, and this is more accurate than before. The OPR of NH$_{3}$ is estimated to be 1.12$ \pm $0.02, which corresponds to a nuclear spin temperature ($T_\mathrm{spin}$) of 30$^{+2}_{-1} $K. The $T_\mathrm{spin}$ value of NH$_{3}$ is basically consistent with the temperature inferred from the mixing ratio of CO with respect to H$_{2}$O found in the same comet.