bluuebunny/crossref_metadata_2025 huggingface dataset:
Number Density of Bright Lyman-Break Galaxies at z ∼ 6 in the Subaru Deep Field
Authors: Shimasaku Kazuhiro , Ouchi Masami , Furusawa Hisanori , Yoshida Makiko , Kashikawa Nobunari , Okamura Sadanori
Published: March 2014

We report on bright Lyman-break galaxies (LBGs) selected in a $767 \,\mathrm{arcmin}^2$ area of the Subaru Deep Field. The selection was made in the $i-z_{\mathrm{R}}$ versus $z_{\mathrm{B}}-z_{\mathrm{R}}$ plane, where $z_{\mathrm{B}}$ and $z_{\mathrm{R}}$ are new bandpasses with a central wavelength of 8842 Å and 9841 Å, respectively. We detected 12 LBG candidates down to $z_{\mathrm{R}} = 25.4$, and calculated the normalization of the rest-frame far-ultraviolet (FUV: $\simeq 1400 \,{Å}$) luminosity function at $M_{\mathrm{FUV}} =-21.6$ to be $\phi(-21.6) = (2.6 \pm 0.7) \times 10^{-5} \,\mathrm{mag}^{-1} \,\mathrm{Mpc}^{-3}$. This must be the most reliable measurement ever obtained of the number density of bright $z\sim 6$ LBGs, because it is more robust against both contamination and cosmic variance than previous values. The FUV luminosity density contributed from LBGs brighter than $M_{\mathrm{FUV}} =-21.3$ is $(2.8 \pm 0.8) \times 10^{24} \,\mathrm{erg} \,\mathrm{s}^{-1} \,\mathrm{Hz}^{-1} \,\mathrm{Mpc}^{-3}$, which is equivalent to a star-formation rate density of $(3.5 \pm 1.0) \times 10^{-4} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1} \,\mathrm{Mpc}^{-3}$. We find that the FUV luminosity density of bright galaxies increases by an order of magnitude from $z\sim 6$ to $\sim 3$, and then drops by $10^3$ from $z \sim 3$ to the present epoch. The evolutionary behavior of bright LBGs resembles that of luminous dusty star-forming galaxies and bright QSOs. The redshift of $z \sim 3$ appears to be a remarkable era in the cosmic history when massive galaxies were being intensively formed.
X-Ray Emission from a Supernova Remnant, G344.7−0.1, Observed in the ASCA Galactic Plane Survey
Authors: Yamauchi Shigeo , Ueno Masaru , Koyama Katsuji , Bamba Aya
Published: March 2014

X-ray emission from a cataloged radio supernova remnant (SNR), G344.7$-$0.1, was observed in the ASCA Galactic Plane Survey. The X-ray image showed extended emission with a diameter of $6' \hbox{--} 8'$. The X-ray spectrum exhibited emission lines from He-like Si, S, Ar, and Ca, which indicates that the X-rays have a thermal plasma origin. The spectrum was represented by a thin thermal plasma model with a temperature of 0.7–0.8 keV. The model fit showed that S and Ca are overabundant relative to the solar values. In addition to the emission lines from highly ionized atoms, an emission line at an energy of $\sim 6.4 \,\mathrm{keV}$ was found. This line is attributable to a K transition line from low-ionized iron. The strong Fe-K$\alpha$ line may suggest the existence of an Fe-rich plasma.
Millimeter Continuum Observations of McNeil’s Nebula Object
Authors: Tsukagoshi Takashi , Kitamura Yoshimi , Kawabe Ryohei , Saito Masao , Yokogawa Sozo , Kurono Yasutaka
Published: March 2014

We performed 98 and 110 GHz continuum monitoring observations of the FU Orionis candidate, McNeil’s Nebula Object (MNO), from 2004 February to May, with the Nobeyama Millimeter Array. In this study, we succeeded in detecting compact ($\sim 3000 \,\mathrm{AU}$) dust emission towards the position of LMZ 12, the millimeter counterpart of MNO. From monitoring observations, however, we could not find any distinct time variation of the total flux densities for the period from 2004 February to May. The Spectral Energy Distribution (SED) of MNO in $\lambda = 0.45 \hbox{--} 3 \,\mathrm{mm}$, which shows no increase in brightness after the outburst, is found to have a power-law form with an index of 2.5; the index corresponds to a $\mathrm{\beta}$ index of 0.5 for the dust mass opacity coefficient. If we consider the continuum emission from MNO as an optically thin thermal one from the dust in the envelope or the outer cold region of the accretion disk around MNO, the total flux densities of the emission give a mass of the circumstellar material of $0.04 \pm 0.01 \,{{{M}_{\odot}}}$, which is slightly larger than the disk mass of T Tauri stars ($\sim 0.01 \,{{{M}_{\odot}}}$). It is very likely, based on these results, that MNO experiences an FU Orionis outburst in the transient stage from a protostar to a T Tauri star. Furthermore, considering the non-detection of an millimeter outburst together with the outburst at optical and IR wavelengths, we suggest that the eruptive phenomenon occurs in the innermost hot region of the disk.
Discovery of a Fifth Image of the Large Separation Gravitationally Lensed Quasar SDSS J1004+4112
Authors: Naohisa Inada , Oguri Masamune , Keeton Charles R. , Eisenstein Daniel J. , Castander Francisco J. , Chiu Kuenley , Hall Patrick B. , Hennawi Joseph F. , Johnston David E. , Pindor Bartosz , Richards Gordon T. , Rix Hans-Walter , Schneider Donald P. , Zheng Wei
Published: March 2014

We report on the discovery of a fifth lensed image in the large separation lensed quasar system SDSS J1004$+$4112. A faint point source located ${0\rlap {.}{}^{\mathrm {\prime \prime }}2}$ from the center of the brightest galaxy in the lensing cluster was detected in images taken with the Advanced Camera for Surveys (ACS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope. The flux ratio between the point source and the brightest lensed component in the ACS image is similar to that in the NICMOS image. The location and brightness of the point source are consistent with lens model predictions for a lensed image. We therefore conclude that the point source is likely to be a fifth lensed image of the source quasar. In addition, the NICMOS image reveals the lensed host galaxy of the source quasar, which can strongly constrain the structure of the lensing critical curves, and thereby the mass distribution of the lensing cluster.
Water-Vapor Maser Survey for Active Galactic Nuclei: A Megamaser in NGC 6926
Authors: Sato Naoko , Yamauchi Aya , Ishihara Yuko , Sorai Kazuo , Kuno Nario , Nakai Naomasa , Balasubramanyam Ramesh , Hall Peter
Published: March 2014

We made a survey of water-vapor maser emission for 93 AGNs with the Nobeyama 45-m and Mopra 22-m telescopes from 1999 to 2002. A megamaser was detected in a Seyfert 2 galaxy, NGC 6926, at a distance of 80 Mpc, in 2002 June. [Greenhill et al. (2003a) have also reported a detection of the megamaser at the close date.] The peak flux density was 110 mJy, and the total isotropic luminosity was 340${L}_{\odot}$. The maser shows triply peaked spectrum, suggesting an edge-on disk. A narrow-line feature of the maser components at $V_{\mathrm{LSR}} = 6001 \,\mathrm{km} \,\mathrm{s}^{-1}$ was strongly variable with a time scale of a few tens of days, and the variation should be of intrinsic origin. We also showed a possibility of variability of water-vapor maser emission of a megamaser previously detected in a Seyfert/ultraluminous FIR galaxy, NGC 6240.
Non-LTE Line-Formation and Abundances of Sulfur and Zinc in F, G, and K Stars
Authors: Takeda Yoichi , Hashimoto Osamu , Taguchi Hikaru , Yoshioka Kazuo , Takada-Hidai Masahide , Saito Yuji , Honda Satoshi
Published: March 2014

Extensive statistical-equilibrium calculations on S I and Zn I were carried out, in order to investigate how the non-LTE effect plays a role in the determination of their abundances in F–K stars. Having checked on the spectra of representative F-type stars (Polaris, Procyon, $\alpha$ Per) and the Sun that our non-LTE corrections yield a reasonable consistency between the abundances derived from different lines, we tried an extensive non-LTE reanalysis of published equivalent-width data of S I and Zn I lines for metal-poor halo/disk stars. According to our calculations, S I 9212/9228/9237 lines suffer significant negative non-LTE corrections ($\lesssim 0.2 \hbox{--} 0.3 \,\mathrm{dex}$), while LTE is practically valid for S I 8683/8694 lines. As far as the very metal-poor regime is concerned, a marked discordance is observed between the $\mathrm{[S/Fe]}$ values from these two abundance indicators, in the sense that the former attains a nearly flat plateau (or even a slight downward bending) while the latter shows an ever-increasing trend with a further lowering of metallicity. The characteristics of $\mathrm{[Zn/Fe]}$ reported from recent LTE studies (i.e., an evident/slight increase of $\mathrm{[Zn/Fe]}$ with a decrease of $\mathrm{[Fe/H]}$ for very metal-poor/disk stars) were almost confirmed, since the non-LTE corrections for the Zn I 4722/4810 and 6362 lines (tending to be positive and gradually increasing toward lower $\mathrm{[Fe/H]}$) are quantitatively of less significance ($\lesssim 0.1 \,\mathrm{dex}$).
Development of a 1-m Robotic Telescope System
Authors: Han Wonyong , Mack Peter , Lee Chung-Uk , Park Jang-Hyun , Jin Ho , Kim Seung-Lee , Kim Ho-Il , Yuk In-Soo , Lee Woo-Baik , Bradstreet Matthew
Published: March 2014

Korea Astronomy & Space Science Institute (KASI) has installed a 1-m robotic telescope at Mt. Lemmon, AZ, in collaboration with a company, Astronomical Consultants & Equipment, Inc (ACE). The telescope system is totally designed to make fully robotic observations, and can be operated in both interactive and unattended robotic modes. The telescope is newly designed and manufactured regarding both mechanical and optical parts. The optical system is designed to collect 80% of the incident light within ${0\rlap {.}{}^{\mathrm {\prime \prime }}5}$ with an $f/7.5$ Ritchey-Chretien design. The telescope mount is an equatorial fork with a friction drive system, and it allows fully programmable tracking speeds with a typical range of $15'' \,\mathrm{s}^{-1}$ and an accuracy of $\pm 5'' \,\mathrm{hr}^{-1}$. The mount system includes an integral pointing model to correct for mechanical errors and misalignments, and an auto-guide unit is also available. To gather environmental information a weather station and an all sky camera are installed at the site. In this paper we introduce the system design and the performance of the mechanical and optical quality of the telescope system based on the results of test observations using some variable stars.
Electron Impact Excitation of Ti XVIII
Authors: Zhong Jia Yong , Zeng Jiao Long , Zhao Gang , Bari Muhanmmud Abbas , Zhang Jie
Published: March 2014

Two different methods were used to calculate the collision strengths of boron-like titanium. One was a close-coupling way using the Dirac Atomic $R$-matrix Code (DARC) of P. H. Norrington and I. P. Grant (private communication), and the other was based on a relativistic distorted-wave (RDW) approximation with a Flexible Atomic Code (FAC) by Gu (2003). For DARC, the lowest 125 fine-structure levels belonging to the ($1s^{2}$) $2s^{2}2p, 2s2p^{2}, 2p^{3}, 2s^{2}3l, 2s2p3l$, and $2p^{2}3l$ ($l=s, p$, and $d$) configurations were included in the calculations. The target model space encompassed the lowest 15 levels, and all $105 \Delta n=0$ transitions together with 40 partial waves were included in calculations of the collision strengths. For FAC, the configuration interactions included in the calculations of atomic structure and excitation were among the same configurations of DARC. The collision strengths for all 125 levels were calculated at 10 scattered electron energies (10–10000 eV). The effective collision strengths, obtained after integrating the collision strengths of two codes over a Maxwellian distribution of electron energies, were also calculated for the electron temperatures in the range (50–500 eV). For application to spectral modeling or diagnostics, we report a complete set of data for the energy levels, radiative rates, and effective collision strengths (only FAC) for all transitions.
Radiative Flow in a Luminous Disk
Authors: Fukue Jun
Published: March 2014

Radiatively driven flow in a luminous disk is examined in the subrelativistic regime of $(v/c)^1$, taking account of radiation transfer. The flow is assumed to be vertical, and the gravity and gas pressure are ignored. When internal heating is dropped, for a given optical depth and radiation pressure at the flow base (disk “inside”), where the flow speed is zero, the flow is analytically solved under the appropriate boundary condition at the flow top (disk “surface”), where the optical depth is zero. The loaded mass and terminal speed of the flow are both determined by the initial conditions; the mass-loss rate increases as the initial radiation pressure increases, while the flow terminal speed increases as the initial radiation pressure and the loaded mass decrease. In particular, when heating is ignored, the radiative flux $F$ is constant and the radiation pressure $P_0$ at the flow base with optical depth $\tau_0$ is bound in the range of $2/3 < cP_0/F < 2/3 + \tau_0$. In this case, at the limit of $cP_0/F = 2/3 + \tau_0$, the loaded mass diverges and the flow terminal speed becomes zero, while, at the limit of $cP_0/F = 2/3$, the loaded mass becomes zero and the terminal speed approaches $(3/8) \, c$, which is the terminal speed above the luminous flat disk under an approximation of the order of $(v/c)^1$. We also examine the case where heating exists, and find that the flow properties are qualitatively similar to the case without heating.
Detection of SiO Maser Emission in V838 Mon
Authors: Deguchi Shuji , Matsunaga Noriyuki , Fukushi Hinako
Published: March 2014

We report on the detection of 43 GHz SiO maser emission in V838 Mon, a prototype of a new class of eruptive variables, in which a red supergiant was formed after a nova-like eruption in 2002. The detection of SiO masers indicates that the star formed after the eruption is indeed a kind of cool mass-losing object with circumstellar masers. The measured radial velocity and the intensity of maser emission are consistent with the object being located at a distance of about 7 kpc from the sun. It also suggests that a considerable percentage of SiO masing objects in the Galaxy are formed by the same mechanism as that which created V838 Mon.
Magnetic-Reconnection and Current-Sheet Model for the Radio Arc and Threads in the Galactic Center
Authors: Sofue Yoshiaki , Kigure Hiromitsu , Shibata Kazunari
Published: March 2014

We propose a new mechanism to explain the radio arc and threads in the Galactic center by current sheets produced by local magnetic shears due to the interaction of a moving cloud and a vertical field based on three-dimensional magnetohydrodynamical simulations. Magnetic reconnection and acceleration of cosmic-ray electrons in the current sheet would result in a high contrast of the radio emissivity inside and outside the arc and threads.
PPPM and TreePM Methods on GRAPE Systems for Cosmological N-Body Simulations
Authors: Yoshikawa Kohji , Fukushige Toshiyuki
Published: March 2014

We present Particle–Particle–Particle–Mesh (PPPM) and Tree Particle–Mesh (TreePM) implementations on GRAPE-5 and GRAPE-6A systems, special-purpose hardware accelerators for gravitational many-body simulations. In our PPPM and TreePM implementations on GRAPE, the computational time is significantly reduced compared with the conventional implementations without GRAPE, especially under strong particle clustering, and is almost constant irrespective of the degree of particle clustering. We describe our survey of two simulation parameters, the PM grid spacing and the opening parameter for the most optimal combination of force accuracy and computational speed. We also describe the parallelization of these implementations on a PC–GRAPE cluster, in which each node has one GRAPE board, and present the optimal configuration of simulation parameters for good parallel scalability.
An Unbiased Search for Molecular Clouds in the Southern Galactic Warp
Authors: Nakagawa Masanori , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo
Published: March 2014

We made an unbiased search for molecular clouds in the Galactic Warp. This survey, covering an area of 56 square degrees at $l = 252^{\circ}$ to $266^{\circ}$ and $b =-5^{\circ}$ to $-1^{\circ}$, revealed 70 molecular clouds, while only 6 clouds were previously known in this sector at $R \gtrsim 14.5 \,\mathrm{kpc}$. The mass of the clouds is in a range from $7.8 \times 10^{2} \,{{{M}_{\odot}}}$ to $8.4 \times 10^{4} \,{{{M}_{\odot}}}$, significantly less than the most massive giant molecular clouds in the inner disk, $\sim 10^{6} \,{{{M}_{\odot}}}$, while the cloud mass spectrum characterized by a power law is basically similar to other parts of the Galaxy. The $X$ factor, $N(\mathrm{H}_{2}) / \int T({{12\atop} \mathrm{CO}}) \,dV$, derived from the molecular clouds in the Warp, is estimated to be $3.5(\pm1.8)$-times larger than that in the inner disk. The total molecular mass in the Warp is estimated to be $7.3 \times 10^5 \,{{{M}_{\odot}}}$, and the total mass in the far-outer Galaxy ($R \gtrsim 14.5 \,\mathrm{kpc}$) can be estimated to be $2 \times 10^7 \,{{{M}_{\odot}}}$. The spatial correlation between the CO and H i distribution appears to be fairly good, and the mass of the molecular gas is about 1% of that of the atomic gas in the far-outer Galaxy. This ratio is similar to that in the interarm, but is ten-times smaller than those of the spiral arms. Only 6 of the 70 Warp clouds show signs of star formation at the IRAS sensitivity, and the star-formation efficiency for high-mass stars in the Warp is found to be smaller than those in other molecular clouds in the Galaxy.
On the Relation of Brightness Temperatures in Coronal Holes at 5.7 and 17 GHz
Authors: Vladimir Maksimov P. , Prosovetsky Dmitry V. , Grechnev Victor V. , Krissinel Boris B. , Shibasaki Kiyoto
Published: March 2014

From the analysis of simultaneous observations with the Siberian Solar Radio Telescope and Nobeyama Radioheliograph we show that coronal holes are not uniform. In particular, in coronal holes small-scale features exist with anticorrelating brightness temperatures at 5.7 and 17 GHz. The features are disposed radially, which suggests radial heat transfer in them. We propose that the favorable heating mechanism within those features is dissipation of Alfvén waves.
Apsidal Motion and Photometric Elements of the Eccentric Eclipsing Binary V401 Lacertae
Authors: Bulut Ibrahim , Demircan Osman
Published: March 2014

New UBV photometric observations of the recently discovered eccentric orbit binary V401 Lacertae were analyzed by using the Wilson-Devinney program. Seven new minimum times were estimated by using new observations. The analysis of the light curves and all available minimum times has revealed that the system is detached, with the orbital eccentricity $e = 0.1734 \pm 0.0003$, the longitude of the periastron $\omega = {63\rlap {.}{}^{\mathrm {\circ }}93} \pm {0\rlap {.}{}^{\mathrm {\circ }}15}$, the rate of change of the longitude of periastron $\dot{\omega} = {0\rlap {.}{}^{\mathrm {\circ }}0200} \pm {0\rlap {.}{}^{\mathrm {\circ }}0024} \;\mathrm{cycle}^{-1}$, corresponding to an apsidal motion period of $U = 96.2 \pm 11.4 \,\mathrm{yr}$. The apsidal motion of the system has been confirmed by the significant difference on the longitude of periastron ($\omega$) obtained from two light curves (Hipparcos and ourselves) in two different epochs.
17 GHz Neutral Line Associated Sources: Birth, Motion, and Projection Effect
Authors: Uralov Arkadiy M. , Rudenko George V. , Rudenko Ilia G.
Published: March 2014

New results and the confirmation of some older suggestions concerning the nature of solar microwave Neutral Line associated Sources (NLSs) were obtained by using data acquired with the Nobeyama Radioheliograph at 17 GHz along with coronal magnetic field magnetograms extrapolated from full-disk longitudinal magnetograms. The used method of extrapolation is applicable for active regions with rather arbitrary position on the solar disk, and allows us to avoid projection effects in observed longitudinal magnetograms. An application of this method was demonstrated for the period of 2003 October–November. We found NLSs to be widespread at 17 GHz. The NLSs are located just above, or in close vicinity to, the inversion line of the radial component of the coronal magnetic field in the place of a close contact of opposite magnetic polarities, where a horizontal magnetic component has local maxima. We briefly address the birth, motions of NLSs, their transformations into sunspot-associated sources, and vice versa. We also add a set of observational facts in evidence for the presence of 17 GHz NLSs in active regions, which produce powerful flares.
Plasma Parameters in a Post-Eruptive Arcade Observed with CORONAS-F/SPIRIT, Yohkoh/SXT, SOHO/EIT, and in Microwaves
Authors: Grechnev Victor V. , Uralov Arkadiy M. , Zandanov Vasily G. , Rudenko George V. , Borovik Valery N. , Grigorieva Irina Y. , Slemzin Vladimir A. , Bogachev Sergey A. , Kuzin Sergei V. , Zhitnik Igor’ A. , Pertsov Andrey A. , Shibasaki Kiyoto , Livshits Moisey A.
Published: March 2014

The SPectroheliographIc X-Ray Imaging Telescope (SPIRIT) aboard the CORONAS-F spacecraft sometimes observes in the Mg XII 8.42 Å line ($T_\mathrm{max} \sim 9 \,\mathrm{MK}$) large, bright features existing for many hours high in the corona. This fact suggests that plasma beta there might not be small. We identify such a feature observed on 2001 October 22 at a height of 100 Mm with a hot part of a post-eruptive arcade. Using multi-spectral data and radio astronomy methods, we estimate the plasma parameters in the arcade and reveal the coronal magnetic configuration. Several hours after the eruption, the temperature in the arcade was 6–8 MK, and the plasma density was $(5 \hbox{--} 10) \cdot 10^{9} \,\mathrm{cm}^{-3}$. We confirm the results by the accord of the quantities obtained from different observations using different methods and by the extrapolation of the photospheric magnetograms into the corona, from which we have obtained a magnetic field strength of about 7 G at that height. Hence, indeed $\beta \ge 1$ in the post-eruptive arcade. The high-beta possibility had previously been stated, e.g., by Ichimoto et al. (1994), but still not investigated. We address this issue in terms of the “standard flare model” elaborated by Shibata and Yokoyama. During this event, Yohkoh/SXT observed McKenzie-Hudson dark moving features. Those features are filled with cold material, if they are not empty, and may affect the arcade.
A Measurement of the Quadrupole Power Spectrum in the Clustering of the 2dF QSO Survey
Authors: Yamamoto Kazuhiro , Nakamichi Masashi , Kamino Akinari , Bassett Bruce A. , Nishioka Hiroaki
Published: March 2014

We report on a measurement of the quadrupole power spectrum in the two degree field (2dF) QSO redshift (2QZ) survey. The analysis used an algorithm parallel to that for estimating the standard monopole power spectrum without first requiring computation of the correlation function or the anisotropic power spectrum. The error on the quadrupole spectrum was rather large, but the best-fit value of the bias parameter from the quadrupole spectrum is consistent with that from previous investigations of the 2 dF data.
Preflare Nonthermal Emission Observed in Microwaves and Hard X-Rays
Authors: Asai Ayumi , Nakajima Hiroshi , Shimojo Masumi , White Stephen M. , Hudson Hugh S. , Lin Robert P.
Published: March 2014

We present a detailed examination on nonthermal emissions during the preflare phase of the X4.8 flare that occurred on 2002 July 23. The microwave (17 GHz and 34 GHz) data obtained with the Nobeyama Radioheliograph at Nobeyama Solar Radio Observatory and the hard X-ray data taken with the Reuven Ramaty High Energy Solar Spectroscopic Imager obviously showed nonthermal features in the preflare phase. We also found a faint ejection associated with the flare in the EUV images taken with the Transition Region and Coronal Explorer. We discuss the temporal and spatial features of the nonthermal emissions in the preflare phase, and their relation with the ejection.
Discovery of a Featureless X-Ray Spectrum in the Supernova Remnant Shell of G330.2+1.0
Authors: Torii Ken’ichi , Uchida Hiroyuki , Hasuike Kazuto , Tsunemi Hiroshi , Yamaguchi Yasuhiro , Shibata Shinpei
Published: March 2014

We report here on the first pointed X-ray observation of the supernova remnant (SNR) G330.2$+$1.0. The X-ray morphology is characterized by an extended shell. Its X-ray spectrum is well represented by a single power-law function with a photon index of $\gamma \simeq 2.8$ and interstellar absorption of $n_{\mathrm{H}} \simeq 2.6 \times 10^{22} \; [\mathrm{cm}^{-2}]$. We interpret this emission as synchrotron radiation from accelerated electrons at the SNR shock, as seen in SN 1006. The surface brightness of the X-ray emission is anti-correlated with the radio emission, and the power-law spectrum is dominated at the western shell where the radio emission is weak. The co-existence of two distinct (radio bright/X-ray faint and radio faint/X-ray bright) shells in a single supernova remnant challenges our understanding of the particle acceleration and radiation mechanisms in different interstellar environments. The object may be a good target for searching TeV gamma-rays and molecular gas surrounding the blast shock. We also report on the nature of a bright point-like source (AX J1601$-$5143) to the south of the SNR.
Ten Milliparsec-Scale Structure of the Nucleus Region in Centaurus A
Authors: Horiuchi Shinji , Meier David L. , Preston Robert A. , Tingay Steven J.
Published: March 2014

We present the results of a VLBI Space Observatory Programme (VSOP) observation of the subparsec structure in Cen A at 4.9 GHz. The observation produced an image of the subparsec jet components with a resolution of three-times better than images from previous VLBI monitoring campaigns at 8.4 GHz, and twice better than the previous 22 GHz studies. Owing to its proximity, our Cen A space-VLBI image is one of the highest spatial-resolution images of an AGN ever made—0.01 pc per beam—comparable only to the recent 43 GHz VLBI images of M87. The elongated core region is resolved into several components of over 10 milliarcsec long (0.2 pc), including a compact component of brightness temperature $2.2 \times 10^{10} \,\mathrm{K}$. A counterjet was detected: if we assume jet-counterjet symmetry, a relatively slow jet speed, and a large viewing angle, as derived from previous observations, the image allows us to investigate the distribution of ionized gas around the core, which is opaque at this frequency due to free-free absorption. We also analyzed the jet geometry in terms of collimation. Assuming the strongest component to be the core, the jet opening angle at $\sim 5000 \,r_{\mathrm{S}}$ from the core is estimated to be $\sim 12^\circ$, with the collimation of the jet to $\sim 3^\circ$ continuing out to $\sim 20000 \,r_{\mathrm{S}}$. This result is consistent with previous studies of the jet in M87, which favor MHD disk outflow models. Future space VLBI observations at higher frequencies will probably be able to image the collimation region, within $1000 \, r_{\mathrm{S}}$ of the center of Cen A, together with the accretion disk itself.
Milliarcsecond-Scale Spectral Properties and Jet Motions in M 87
Authors: Dodson Richard , Edwards Philip G. , Hirabayashi Hisashi
Published: March 2014

We have combined high resolution VLBI Space Observatory Programme (VSOP) data at 1.6 and 4.8 GHz with Very Long Baseline Array (VLBA) data at higher frequencies and with similar resolutions to study the spectral properties of the core of M 87 with milliarcsec resolution. The VSOP data allows a more accurate measurement of the turnover frequency, and hence more reliable determination of associated physical parameters of the source. Comparison of the images with previously published images yields no evidence for significant motions of components in the parsec-scale jet. In addition, the brightness temperatures obtained from modelfits to the core are well below the inverse Compton limit, suggesting that the radio emission we are observing is not strongly Doppler boosted.
Time Delays for the Giant Quadruple Lensed Quasar SDSS J1004+4112: Prospects for Determining the Density Profile of the Lensing Cluster
Authors: Kawano Yozo , Oguri Masamune
Published: March 2014

We investigated the dependence of the time delays for the large-separation gravitationally lensed quasar SDSS J1004$+$4112 on the inner mass profile of the lensing cluster. Adopting a mass model whose innermost density profile was parameterized as $\rho \propto r^{-\alpha}$, we derived a series of mass models that can fit the observational data, and then compute the probability distribution functions of time delays. We find that larger $\alpha$ has longer time delays, longer tails at the higher end of the probability distribution, and larger model uncertainties. The ratios of the time delays slightly depend on the slope, $\alpha$. Among others, time delays between images C and A (or B) have little dependence on the inner slope, particularly when the time delays are short. The dependence of time delays on $\alpha$ is well fitted by a linear form, which reflects the well-known degeneracy between the mass profile and time delays. We performed a Monte Carlo simulation to illustrate how well the inner slope can be constrained from measurements of time delays. We found that measurements of more than one time delay resulted in reasonably tight constraints on the inner slope ($\sigma_{\alpha} \lesssim 0.25$), while only one time delay could not determine the inner slope very well. Our result indicates that time delays indeed serve as a powerful tool to determine the mass profile, despite the complexity of the lensing cluster.
The Virgo High-Resolution CO Survey: VI. Gas Dynamics and Star Formation along the Bar in NGC 4303
Authors: Koda Jin , Sofue Yoshiaki
Published: March 2014

We present CO interferometer observations of the barred galaxy NGC 4303 (M 61). This galaxy has a strong gas concentration at the central region and prominent offset ridges at the leading sides of the bar. Sharp velocity gradients are apparent across the ridges. The brightness temperature in the ridges is low, indicating the existence of unresolved molecular clouds. Additionally, an analysis of the newborn stellar clusters revealed in HST images suggests that the parent molecular clouds had masses of $10^{4-6} \,{{{M}_{\odot}}}$. The observed shear velocity gradient across the ridges is too small to break up giant molecular clouds. Therefore, the clouds are likely to survive passage through the ridges. We discuss a cloud orbit model in a bar potential for understanding the gas distribution, dynamics, and star formation in NGC 4303. The model reproduces the narrow offset ridges and sharp velocity gradients across the ridges, although no shock is associated with the ridges. We discuss cloud–cloud collisions (and close interactions) as a possible triggering mechanism for star formation. The newborn stellar clusters in NGC 4303 are located predominantly at the leading sides of the offset ridges. Cloud orbits are densely populated in the region where the clusters are found, suggesting a high collisional frequency and possibly a high rate of triggered star formation. Cloud-based dynamics is less dissipative than smooth hydrodynamic models, possibly extending the timescales of gas dynamical evolution and gas fueling to central regions in barred galaxies.
High-Resolution Studies of the Dense Molecular Cores toward Massive Star-Forming Regions
Authors: Saito Hiro , Saito Masao , Moriguchi Yoshiaki , Fukui Yasuo
Published: March 2014

We present the results of the imaging of dense molecular cores in three massive star-forming regions (IRAS 02461$+$6147, IRAS 03035$+$5819, and IRAS 06058$+$2138), which are associated with luminous infrared sources with $1 \hbox{--} 5 \times 10^{4} \,{{{L}_{\odot}}}$. The C${{18\atop} \mathrm{O}}$ ($J = 1 \hbox{--} 0$) molecular emission from the dense cores and the thermal dust and/or free-free emission at 98 GHz and 110 GHz in the hot core candidates have been imaged with a resolution of $\sim {4{}^{\mathrm {\prime \prime }}}$ using the Nobeyama Millimeter Array. We identified 28 C${{18\atop} \mathrm{O}}$ dense cores, whose mass, effective radius, and line-width range from 2.1 to 29${M}_{\odot}$, from 0.013 to 0.108 pc, and from 0.7 to $2.7 \,\mathrm{km} \,\mathrm{s}^{-1}$, respectively, and identified four thermal dust millimeter continuum sources (MCSs). We divided the C${{18\atop} \mathrm{O}}$ cores into two types, a turbulent core and a non-turbulent core. The non-turbulent cores are similar to the typical cores in the low-mass star-forming regions. The turbulent cores have a higher average $\mathrm{H}_2$ density than those of the non-turbulent cores, and the external pressure of these cores is 100–1000 times higher than that of low-mass star-forming regions. Three of the turbulent cores are associated with massive protostar candidates and the intensity peak of MCS. Massive stars are formed from the turbulent cores which are gravitationally bound. In order to form such a turbulent core a molecular cloud has a large kinetic motion and a large mass.
Superhumps Behavior during Normal Outbursts in ER Ursae Majoris: Spectroscopy and Photometry
Authors: Zhao Yinghe , Li Zongyun , Wu Xiaoan , Peng Qiuhe , Zhang Zhousheng , Li Zili
Published: March 2014

We undertook a 4-day spectroscopic observation and conducted a 13-day photometric study of an SU UMa-type dwarf nova, ER Ursae Majoris. The mean $K$-amplitude for the emission lines is $54 \pm 8 \,\mathrm{km} \,\mathrm{s}^{-1}$ and the $\gamma$ velocity is $8 \pm 4 \,\mathrm{km} \,\mathrm{s}^{-1}$ based on our spectroscopic results. A phase shift of 0.22 was also obtained. Our photometric observation confirms superhumps in normal outbursts of ER UMa, and reconciles contradictory observational results obtained by different authors. We find that superhumps possibly develop near each normal outburst maximum and fade out before the next outburst maximum. If the observed humps were not late superhumps, but ordinary superhumps, much more theoretical work should be done to explain the new phenomena.
Horizontal and Vertical Flow Structure in Emerging Flux Regions
Authors: Kozu Hiromichi , Kitai Reizaburo , Brooks David H. , Kurokawa Hiroki , Yoshimura Keiji , Berger Thomas E.
Published: March 2014

In order to obtain an overall view of the flow structure of convective gas in emerging flux regions (EFRs), we studied three EFRs in two solar active regions, NOAA 8218 and NOAA 10774. Using the Local Correlation Tracking method, we found several horizontally divergent flow structures, which were stable over a period of 1 hour, in 2 EFRs in NOAA 8218. The horizontal flow velocities and the sizes of the structures were around $500 \,\mathrm{m} \,\mathrm{s}^{-1}$ and about 4 mm in radius, respectively. We analyzed another dataset of NOAA 10774 using spectroscopic methods and found temporarily stable up-ward gas flows in the central part of the EFR. The line-of-sight velocities were around $150 \,\mathrm{m} \,\mathrm{s}^{-1}$ and the size of the flow patch was 2 to 5 mm in radius. These results support our previous findings that convective-cell-like flow appears in the central part of an EFR. We estimated from these results that the depth of the flow cell in EFRs is about 600 Km, and the turn-over time of the cell is about 2 hours.
Monte Carlo Modeling of Compton-Scattering Angles in a Mildly Relativistic Plasma
Authors: Seon Kwang-Il
Published: March 2014

If the inversion method is applied to random-number generation in a Monte Carlo simulation of Compton-scattering, we often encounter cubic equations. These may be solved using well-known numerical iterative methods, such as the Newton–Raphson, or bisection methods. These numerical methods, however, may lead to many iterations, which should be avoided for modeling efficiency. We present explicit inversion formulae of two cubic equations arising from the modeling of Compton-scattering angles in a mildly or weakly relativistic plasma. Explicit analytical methods are superior to any other rejection or numerical inversion methods in terms of the modeling efficiency, and will be useful for Monte Carlo simulations of X-ray reflection from cold material and the Sunyaev–Zel’dovich effect.
Implications for Cosmic Reionization from the Optical Afterglow Spectrum of the Gamma-Ray Burst 050904 at z = 6.3
Authors: Totani Tomonori , Kawai Nobuyuki , Kosugi George , Aoki Kentaro , Yamada Toru , Iye Masanori , Ohta Kouji , Hattori Takashi
Published: March 2014

The gamma-ray burst (GRB) 050904 at $z = 6.3$ provides the first opportunity to probe the intergalactic medium (IGM) by GRBs at the epoch of reionization. Here, we present a spectral modeling analysis of the optical afterglow spectrum taken by the Subaru Telescope, aiming to constrain the reionization history. The spectrum shows a clear damping wing at wavelengths redward of the Lyman break, and the wing shape can be fitted either by a damped Ly$\alpha$ system with a column density of $\log [N_{\mathrm{H {I}}} \,(\mathrm{cm}^{-2})] \sim 21.6$ at a redshift close to the detected metal absorption lines ($z_{\mathrm{metal}} = 6.295$), or by almost neutral IGM extending to a slightly higher redshift of $z_{\mathrm{IGM,u}} \sim 6.36$. In the latter case, the difference between the two redshifts may be explained by the acceleration of metal absorbing shells in the activities of the GRB or its progenitor. However, we exclude this possibility by using the light transmission feature around the Ly$\beta$ resonance, leading to a firm upper limit of $z_{\mathrm{IGM,u}} \leq 6.314$. We then show evidence that the IGM was already largely ionized at $z = 6.3$ with the best-fit neutral fraction of IGM, $x_{\mathrm{H {I}}} \; (\equiv n_{\mathrm{H {I}}} / n_{\mathrm{H}}) = 0.00$, and upper limits of $x_{\mathrm{H {I}}} < 0.17$ and 0.60 at 68% and 95% confidence levels, respectively. This is the first direct and quantitative upper limit on $x_{\mathrm{H {I}}}$ at $z \gt 6$. Various systematic uncertainties are examined, but none of them appears large enough to change our conclusion. To get further information on the reionization, it is important to increase the sample size of $z \gtrsim 6$ GRBs, in order to find GRBs with low column densities ($\log N_{\mathrm{H {I}}} \lesssim 20$) within their host galaxies and to make statistical studies of Ly$\alpha$ line emission from host galaxies.
Optical Monitoring of the Seyfert Galaxy NGC 4151 from 1997 to 2003
Authors: Guo Difu , Tao Jun , Qian Bochen
Published: March 2014

CCD photometric observations ($V, R$, and $I$) of the Seyfert galaxy NGC 4151 were carried out from 1997 May 9 to 2003 May 25. A possible microvariation was found simultaneously in three bands on 2003 May 2. If the microvariation was due to a hot spot on the accretion disk, then there is probably a supermassive black hole of around $5.4 \times 10^7 \,{{{M}_{\odot}}}$ at the center of the source. Combining our new data and data from literature, the historical light curves from 1968 to 2003 ($V$ band) and from 1910 to 2000 ($B$ band) were compiled and used to study the periodicity of the source. A possible period of around 15.8 yr was found.
Common Correlations between 60, 100, and 140$\, {\mu \mathrm {m}}$ Intensities in the Galactic Plane and Magellanic Clouds
Authors: Hibi Yasunori , Shibai Hiroshi , Kawada Mitsunobu , Ootsubo Takafumi , Hirashita Hiroyuki
Published: March 2014

We investigated the far-infrared SED of the Galaxy and the Magellanic Clouds by using the COBE (COsmic Background Explorer)/DIRBE (Diffuse InfraRed Background Experiment) ZSMA (Zodi-Subtracted Mission Average) maps at wavelengths of 60$\, {\mu \mathrm {m}}$, 100$\, {\mu \mathrm {m}}$, and 140$\, {\mu \mathrm {m}}$. We analyzed three regions: the galactic plane region with the galactic latitude $\vert b\vert < 5^{\circ}$, the Large Magellanic Cloud region, and the Small Magellanic Cloud region. Because the dust optical depth is much smaller in the far-infrared than in the visible, we could observe cumulative far-infrared radiation from regions with various interstellar radiation field in the line of sight. As a consequence of considering such an effect, we found a common far-infrared color correlation between the 140–100$\, {\mu \mathrm {m}}$ and 100–60$\, {\mu \mathrm {m}}$ intensity ratios in all three galaxies. Although this color correlation cannot be explained by any existing model, it fits very well the far-infrared color of nearby star-forming galaxies.
Energy Conversion Efficiency in Prompt Emissions of Gamma-Ray Bursts
Authors: Suzuki Motoko , Kawai Nobuyuki
Published: March 2014

Using 52 gamma-ray bursts observed and localized by BeppoSAX and HETE-2, a comprehensive analysis of the correlation between the properties of prompt emissions and the brightness of the afterglows was performed. We found a highly significant correlation between the isotropic total energy of prompt emission and luminosity of optical afterglow. There is also a correlation between the fluence in prompt emission and the magnitude of the optical afterglow. We then investigated the energy conversion efficiency in prompt emissions of gamma-ray bursts using 24 bursts with the known redshift. We calculated the kinetic energy of relativistic shells from the luminosities of the optical afterglows. The energy-conversion efficiency, as estimated by comparing this kinetic energy with the total radiated energy of prompt emission, is distributed between about 1% and 40%. This result suggests that the ratio of the Lorentz factor of two colliding shells is large, or the fraction of shock energy that goes into the electrons is small for the internal shock scenario.
Dynamical Friction on Satellite Galaxies
Authors: Fujii Michiko , Funato Yoko , Makino Junichiro
Published: March 2014

For a rigid model satellite, Chandrasekhar’s dynamical friction formula describes the orbital evolution quite accurately, when the Coulomb logarithm is chosen appropriately. However, it is not known if the orbital evolution of a real satellite with the internal degree of freedom can be described by the dynamical friction formula. We performed an $N$-body simulation of the orbital evolution of a self-consistent satellite galaxy within a self-consistent parent galaxy. We found that the orbital decay of the simulated satellite is significantly faster than an estimate from the dynamical friction formula. The main cause of this discrepancy is that the stars stripped out of the satellite are still close to the satellite, and increase the drag force on the satellite through two mechanisms. One is a direct drag force from particles in the trailing tidal arm, a non-axisymmetric force that slows the satellite down. The other is an indirect effect that is caused by the particles remaining close to the satellite after escaping. The force from them enhances the wake caused in the parent galaxy by dynamical friction, and this larger wake in turn slows the satellite down more than expected from the contribution of its bound mass. We found that these two have comparable effects, and that the combined effect can be as large as 20% of the total drag force on the satellite.
Bigradient Phase Referencing
Authors: Doi Akihiro , Fujisawa Kenta , Habe Asao , Honma Mareki , Kawaguchi Noriyuki , Kobayashi Hideyuki , Murata Yasuhiro , Omodaka Toshihiro , Sudou Hiroshi , Takaba Hiroshi
Published: March 2014

We propose bigradient phase referencing (BPR), a new radio-observation technique, and report on its performance using the Japanese very-long-baseline-interferometry network (JVN). In this method, a weak source is detected by phase-referencing using a primary calibrator, in order to play a role as a secondary calibrator for phase-referencing to a weak target. We will be given the opportunity to select a calibrator from lots of milli-Jansky sources, one of which may be located at a position closer to the target. With such a smaller separation, high-quality phase-referencing can be achieved. A subsequent more-sophisticated calibration can relocate the array’s focus to a hypothetical point much closer to the target; a higher quality of phase referencing is available. Our demonstrative observations with strong radio sources have proved the capabilities of the BPR in terms of the image dynamic ranges and astrometric reproducibility. The image dynamic range on a target has been improved by a factor of about six compared to that of normal phase-referencing; the resultant position difference of the target’s emission between two epochs was only $62 \pm 50$ microarcsecond, even with less than 2300-km baselines at 8.4 GHz and fast-switching between a target-calibrator pair separated by a ${2\rlap {.}{}^{\mathrm {\circ }}1}$.
Discovery of a New Dwarf Nova, TSS J022216.4+412259.9: WZ Sge-Type Dwarf Nova Breaking the Shortest Superhump Period Record
Authors: Imada Akira , Kubota Kaori , Kato Taichi , Nogami Daisaku , Maehara Hiroyuki , Nakajima Kazuhiro , Uemura Ryoko Ishioka Makoto
Published: March 2014

We report on the time-resolved CCD photometry of a newly discovered variable star, TSS J022216.4$+$412259.9 during an outburst in a 2005 November–December brightening. The obtained light curves unambiguously show 0.2–0.3 mag modulations, which we confirmed to be the superhump observed among SU UMa-type dwarf novae. We also performed a period search for data obtained during the outburst plateau phase, and revealed the existence of the two periodicities: 0.054868(98)d for the first two nights and 0.055544(26)d for the following plateau phase. This bi-periodicity is hardly observed in the usual SU UMa-type dwarf novae, but is characteristic of WZ Sge-type stars. We undoubtedly detected a rebrightening in the post-outburst stage, which is typical of short-period SU UMa-type dwarf novae, including WZ Sge-type stars. These observations suggest that TSS J022216.4$+$412259.9 may be a new WZ Sge star breaking the shortest superhump period so far of 0.05648 d for V592 Her among this class with a known superhump period.
Infrared 2–4 Micrometer Spectroscopy and Millimeter Interferometric HCN and HCO+ Observations of the Individual Merging Components of Arp 299
Authors: Imanishi Masatoshi , Nakanishi Kouichiro
Published: March 2014

We present ground-based infrared $K$–(2–2.5$\, {\mu \mathrm {m}}$) and $L$-band (2.8–4.1$\, {\mu \mathrm {m}}$) spectroscopy, as well as interferometric observations at $\lambda \sim 3 \,\mathrm{mm}$, for the individual merging components (A, B, and C) of the luminous infrared galaxy Arp 299. The presence and location of a buried active galactic nucleus (AGN) are investigated. Our sub-arcsec-resolution infrared spectra clearly reveal that the putative buried AGN resides in the nucleus B1 (a subcomponent of B), based on a very low equivalent width of 3.3$\, {\mu \mathrm {m}}$ polycyclic aromatic hydrocarbon emission, a weak 2.3$\, {\mu \mathrm {m}}$ CO absorption feature, and a large time variation of the $K$–and $L$-band continuum fluxes. Our interferometric observations simultaneously obtain HCN ($J = 1 \hbox{--} 0$) and $\mathrm{HCO}^{+}$ ($J = 1 \hbox{--} 0$) emission lines with $\sim 4 {{}^{\prime \prime }}$ resolution, and we find the HCN to $\mathrm{HCO}^{+}$ brightness-temperature ratios to be as low as those found in starburst nuclei in all of the major merging components of Arp 299. The low ratio even in the AGN-hosting nucleus B may be due to the presence of a large amount of high-density molecular gas whose chemistry is dominated by coexisting starbursts and/or shocks, rather than by the central strong X-ray-emitting AGN.