bluuebunny/crossref_metadata_2025 huggingface dataset:
Smoothed Particle Hydrodynamics Coupled with Radiation Transfer
Authors: Susa Hajime
Published: March 2014

We have constructed a brand-new radiation hydrodynamics solver based upon Smoothed Particle Hydrodynamics, which works on a parallel computer system. The code is designed to investigate the formation and evolution of first-generation objects at $z \gtrsim 10$, where the radiative feedback from various sources plays important roles. The code can compute the fraction of chemical species e, $\mathrm{H}^{+}$, H, $\mathrm{H}^{-}, \mathrm{H}_2$, and $\mathrm{H}_2^{+}$ by fully implicit time integration. It also can deal with multiple sources of ionizing radiation, as well as radiation at Lyman–Werner band. We compare the results for a few test calculations with the results of one-dimensional simulations, in which we find good agreements with each other. We also evaluate the speedup by parallelization, which is found to be almost ideal, as long as the number of sources is comparable to the number of processors.
Kinematics of SiOJ = 8–7 Emission towards the HH 212 Jet
Authors: Takami Michihiro , Takakuwa Shigehisa , Momose Munetake , Hayashi Masa , Davis Christopher J. , Pyo Tae-Soo , Nishikawa Takayuki , Kohno Kotaro
Published: March 2014

We present SiO $J = 8 \hbox{--} 7$ (347.3 GHz) observations towards HH 212 (Herbig-Haro object 212) using the ASTE (Atacama Submillimeter Telescope Experiment) telescope. Our observations with a $22^{\prime\prime}$-diameter beam show that the SiO emission is highly concentrated within $1'$ of the driving source. We carefully compare the SiO observations with archival $\mathrm{H}_2$ 1–0 S(1) images and published $\mathrm{H}_2$ echelle spectra. We find that, although the SiO velocities closely match the radial velocities seen in $\mathrm{H}_2$, the distributions of $\mathrm{H}_2$ and SiO emission differ markedly. We attribute the latter to the different excitation conditions required for $\mathrm{H}_2$ and SiO emission, particularly the higher critical density ($n_{\mathrm{H}_2} \sim 10^8 \,\mathrm{cm}^{-3}$) of the SiO $J = 8 \hbox{--} 7$ emission. The kinematic similarities imply that the $\mathrm{H}_2$ and SiO are associated with the same internal working surfaces. We conclude that the SiO $J = 8 \hbox{--} 7$ emission has a potential for probing the jet/wind launching region through interferometric observations in the future, particularly for the youngest, most deeply embedded protostars where IR observations are not possible.
Discovery of a λ Bootis Like Abundance Pattern in the Pulsating Algol-Type System RZ Cassiopeiae
Authors: Narusawa Shin-ya , Ozaki Shinobu , Kambe Eiji , Sadakane Kozo
Published: March 2014

The abundances of eight elements (C through Fe) were determined in the primary star of the short-period Algol-type binary RZ Cas relative to the A3 V spectroscopic standard star $\alpha$ PsA. Definite under-abundances (by $-0.45 \,\mathrm{dex}$ or more) of Mg, Si, Ti, Cr, and Fe were established. On the other hand, light elements C and O show solar abundances, and Ca is slightly under-abundant ($\sim-0.3 \,\mathrm{dex}$). This abundance pattern demonstrates that RZ Cas shows a characteristic of mild $\lambda$ Boo-type stars. This finding raises a question on the physical relations between the metallicity (abundance anomaly), the pulsational characteristics, and the mass accretion processes.
Deep Extragalactic Surveys around the Ecliptic Poles with AKARI (ASTRO-F)
Authors: Matsuhara Hideo , Wada Takehiko , Matsuura Shuji , Nakagawa Takao , Kawada Mitsunobu , Ohyama Youichi , Pearson Chris P. , Oyabu Shinki , Takagi Toshinobu , Serjeant Stephen , White Glenn J. , Hanami Hitoshi , Watarai Hidenori , Takeuchi Tsutomu T. , Kodama Tadayuki , Arimoto Nobuo , Okamura Sadanori , Lee Hyung Mok , Pak Soojong , Im Myung Shin , Lee Myung Gyoon , Kim Woojung , Jeong Woong-Seob , Imai Koji , Fujishiro Naofumi , Shirahata Mai , Suzuki Toyoaki , Ihara Chiaki , Sakon Itsuki
Published: March 2014

AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10–180$\, {\mu \mathrm {m}}$, and deep pointed surveys of selected areas at 2–180$\, {\mu \mathrm {m}}$. The deep pointed surveys with AKARI will significantly advance our understanding of galaxy evolution, the structure formation of the universe, the nature of buried AGNs, and the cosmic infrared background. We describe here the important characteristics of the AKARI mission, the orbit, and attitude control system, and investigate the optimum survey area based on the updated pre-flight sensitivities of AKARI, taking into account the cirrus confusion noise as well as the surface density of bright stars. The North Ecliptic Pole is concluded to be the best area for 2–26$\, {\mu \mathrm {m}}$ deep surveys, while the low-cirrus noise regions around the South Ecliptic Pole are worth considering for 50–180$\, {\mu \mathrm {m}}$ pointed surveys to high sensitivities limited by the galaxy confusion noise. Current observational plans concerning these pointed surveys are described in detail. Comparing these surveys with deep surveys using the Spitzer Space Telescope, the AKARI deep surveys are particularly unique in respect of their continuous wavelength coverage over the 2–26$\, {\mu \mathrm {m}}$ range in broad-band deep imaging, and their slitless spectroscopy mode over the same wavelength range.
Non-Uniform Temperature Distribution in the Galaxy Clusters 2A 0335+096 and Abell 496 Observed by XMM-Newton
Authors: Tanaka Takeshi , Kunieda Hideyo , Hudaverdi Murat , Furuzawa Akihiro , Tawara Yuzuru
Published: March 2014

We present the XMM-Newton results of the galaxy clusters 2A 0335$+$096 and A496. From an investigation of 2-dimensional ICM profiles, we obtained new features related to dynamical activities in the ICM. In 2A 0335$+$096, we found a spiral cool tail around the central cold core, which is trailing from the opposite side of the cold front observed by Chandra. The deprojected temperature of the tail is 1.7 keV. The spiral feature apparently shows a turnaround motion of the core. We suggest that the cool tail feature represents evidence for turbulent viscous stripping of the remaining subcluster core. For A496, we found another cold front $4^{\prime}$ south of the X-ray emission peak. From the pressure profile across the cold front, we derived an upper limit to the Mach number of a gas body of 0.2. Regarding the temperature distribution in the outer region, we found non-uniformity on the cluster scale for both clusters, which suggests that both clusters experienced a merger in the past. We argue that the gas dynamical motions seen in the central regions of both clusters can be attributed to the past merger.
Phase Stability Measurement of an Optical Two-Tone Signal Applied to a Signal Reference Source for Millimeter and Sub-Millimeter Wave Interferometer
Authors: Yamada Masumi M. , Kiuchi Hitoshi , Kawanishi Tetsuya , Sakamoto Takahide , Tsuchiya Masahiro , Amagai Jun , Izutsu Masayuki
Published: March 2014

Local signal generation with high phase stability is one of the key elements of an interferometer system. In the ALMA (Atacama Large Millimeter/submillimeter Array) project, we have plans to generate and transmit a micro/millimeter-wave LO (Local Oscillator) reference signal as an optical two-tone signal. To realize this, we introduce a method to generate an optical two-tone signal by double sideband suppressed carrier modulation with a lithium niobate ($\mathrm{LiNbO}_3$) Mach–Zehnder optical modulator. The phase instability of the LO signal causes a loss of coherence in the interferometer. We measured the phase instability and estimated the coherence loss while assuming the highest frequency of ALMA LO. The observed Allan standard deviation for 22 GHz was $1.9 \times 10^{-14}$ at 1 s. Additional noise was found at a longer time scale than 4 s; however, the reason is not well understood at this stage. If this additional noise was classified as white frequency noise, the estimated coherence loss was 5.2% when 938 GHz frequency and a 100-s integration time were assumed. On the other hand, if this additional noise was caused by some other effect, for example phase fluctuation of the amplifier, the coherence loss was estimated to be 0.33% at 938 GHz frequency (100 s).
Does a Galaxy Fly?
Authors: Fujita Yutaka
Published: March 2014

Disk galaxies in a cluster of galaxies move in hot gas that fills the cluster. Generally, they move at transonic or supersonic velocities. If ram-pressure stripping is insufficient to destroy the gas disk, the galaxies should be affected by the wind of the surrounding hot gas, similar to an airfoil. In this paper, it is considered whether the aerodynamic interaction can be strong enough to force a disk galaxy to deviate from the orbit that it would have been in. It is shown that while the lift force is not effective, the drag force could affect face-on disk galaxies in poor clusters on a long time scale.
VLBI Observations of the Most Radio-Loud, Narrow-Line Quasar SDSS J094857.3 + 002225
Authors: Doi Akihiro , Nagai Hiroshi , Asada Keiichi , Kameno Seiji , Wajima Kiyoaki , Inoue Makoto
Published: March 2014

We observed the narrow-line quasar SDSS J094857.3$+$002225, which is known to have the highest radio loudness in the narrow-line Seyfert 1 galaxies (NLS1s), at 1.7–15.4 GHz with the Very Long Baseline Array (VLBA). This is the first very-long-baseline interferometry (VLBI) investigation of a radio-loud NLS1. We independently discovered (1) very high brightness temperatures from its compactness in a VLBA image and (2) flux variation among the VLBA observation and our other observations with the VLBA and the Very Large Array (VLA). A Doppler factor larger than 2.7–5.5 was required to meet an intrinsic limit of brightness temperature in the rest frame. This is evidence for highly relativistic nonthermal jets in an NLS1. We suggest that the Doppler factor is one of the most important parameters in the determination of the radio loudness of NLS1s. The accretion disk of SDSS J094857.3$+$002225 is probably in a very high state, rather than the high/soft state, by analogy with X-ray binaries with strong radio outbursts and superluminal jets, such as GRS 1915$+$105.
Spin of Stellar-Mass Black Holes Estimated by a Model of Quasi-Periodic Oscillations
Authors: Kato Shoji , Fukue Jun
Published: March 2014

We have proposed in previous papers that the high-frequency pair of quasi-periodic oscillations observed in black-hole binaries with a frequency ratio of $3:2$ are inertial-acoustic oscillations (nearly horizontal oscillations with no node in the vertical direction) or g-mode oscillations, which are resonantly excited on warped relativistic disks. The resonance occurs through horizontal motions. In this model, the dimensionless spin parameter, $a_*$, of the central sources can be estimated when their masses are known from other observations. This estimate is done for three sources (GRO J1665$-$40, XTE J1550$-$564, GRS 1915$+$105). For all of them, we have $a_*\leq 0.45$.
Electromagnetic Extraction of Energy from Kerr Black Holes
Authors: Okamoto Isao
Published: March 2014

The energy extraction process from Kerr black holes is elucidated compared with that from pulsars in force-free degenerate electrodynamics (FFDE). It is argued for the force-free magnetosphere of a Kerr black hole in a steady axisymmetric state that the function of unipolar inductors in the presence of global magnetic fluxes threading the horizon is equipped by a frame-dragging effect in the Kerr spacetime metric to the upper null surface, $\mathrm{S}_{\mathrm{N}}$, with the axial distance, $\varpi_{\mathrm{N}}$, where the local value of the angular velocity of the frame-dragging, $\omega$, is equal to the rotational frequency of each field line, i.e., $\omega(\varpi_{\mathrm{N}}) = \Omega_{\mathrm{F}}$, and the rotational velocity of each field line, $\boldsymbol{v}_{\mathrm{F}}$, measured by “zero-angular-momentum-observers” changes in sign. There must be a pair-creation gap at $\mathrm{S}_{\mathrm{N}}$, from which the paired winds, ingoing and outgoing, are initiated. The poloidal electric current, $I$, for each wind is determined by solving the eigenvalue problem with the “criticality condition” imposed at the fast surfaces nearly at the horizon and at infinity, and the “current-closure condition” at $\mathrm{S}_{\mathrm{N}}$ determines the ultimate eigenvalues of $\Omega_{\mathrm{F}}$ and $I$ in terms of the hole’s angular velocity, $\Omega_{\mathrm{H}} = \omega(r_{\mathrm{H}})$, and the distribution of the magnetic flux at the horizon. It is not in the ordinary ergosphere, but in the effective ergosphere in the region of $\Omega_{\mathrm{H}} \gt \omega \gt \Omega_{\mathrm{F}}$ and $\boldsymbol{v}_{\mathrm{F}}<0$ that general-relativistic effects play the most significant role for electromagnetic extraction of the hole’s energy. The flow there must be regarded as an ingoing magneto-centrifugal wind, rather than an accretion flow. In a kind of extreme state that “force-free” field lines be frozen in “massless” particles in FFDE, the “membrane paradigm” combined with the DC circuit model is useful in black hole as well as pulsar magnetospheres.
Relativistic Radiative Flow in a Luminous Disk II
Authors: Fukue Jun , Akizuki Chizuru
Published: March 2014

Radiatively driven transfer flow perpendicular to a luminous disk is examined in the relativistic regime of $(v/c)^2$, while taking into account the gravity of the central object. The flow is assumed to be vertical, and the gas pressure as well as the magnetic field are ignored. Using a velocity-dependent variable Eddington factor, we can solve the rigorous equations of the relativistic radiative flow accelerated up to relativistic speeds. For sufficiently luminous cases, the flow resembles the case without gravity. For less-luminous or small initial radius cases, however, the flow velocity decreases due to gravity. Application to a supercritical accretion disk with mass loss is briefly discussed.
Pulsar Magnetohydrodynamic Winds
Authors: Okamoto Isao , Sigalo Friday B.
Published: March 2014

The acceleration and collimation/decollimation of relativistic magnetocentrifugal winds are discussed concerning a cold plasma from a strongly magnetized, rapidly rotating neutron star in a steady axisymmetric state based on ideal magnetohydrodynamics. There exist unipolar inductors associated with the field line angular frequency, $\alpha$, at the magnetospheric base surface, $S_{\mathrm{B}}$, with a huge potential difference between the poles and the equator, which drive electric current through the pulsar magnetosphere. Any “current line” must emanate from one terminal of the unipolar inductor and return to the other, converting the Poynting flux to the kinetic flux of the wind at finite distances. In a plausible field structure satisfying the transfield force-balance equation, the fast surface, $S_{\mathrm{F}}$, must exist somewhere between the subasymptotic and asymptotic domains, i.e., at the innermost point along each field line of the asymptotic domain of $\varpi_{\mathrm{A}}^2 / \varpi^2 \ll 1$, where $\varpi_{\mathrm{A}}$ is the Alfvénic axial distance. The criticality condition at $S_{\mathrm{F}}$ yields the Lorentz factor, $\gamma_{\mathrm{F}} = \mu_{\varepsilon}^{1/3}$, and the angular momentum flux, $\beta$, as the eigenvalues in terms of the field line angular velocity, $\alpha$, the mass flux per unit flux tube, $\eta$, and one of the Bernoulli integrals, $\mu_{\delta}$, which are assumed to be specifiable as the boundary conditions at $S_{\mathrm{B}}$. The other Bernoulli integral, $\mu_{\varepsilon}$, is related to $\mu_{\delta}$ as $\mu_{\varepsilon} = \mu_{\delta} [1-(\alpha^2 \varpi_{\mathrm{A}}^2 / c^2)]^{-1}$, and both $\mu_{\varepsilon}$ and $\varpi_{\mathrm{A}}^2$ are eigenvalues to be determined by the criticality condition at $S_{\mathrm{F}}$. Ongoing MHD acceleration is possible in the superfast domain. This fact may be helpful in resolving a discrepancy between the wind theory and the Crab-nebula model. It is argued that the “anti-collimation theorem” holds for relativistic winds, based on the curvature of field streamlines determined by the transfield force balance. The “theorem” combines with the “current-closure condition” as a global condition in the wind zone to produce a two-component “quasi-conical” field structure as one of the basic properties of MHD outflows of centrifugal origin in the pulsar magnetosphere.
ASTE Observations of Warm Gas in Low-Mass Protostellar Envelopes: Different Kinematics between Submillimeter and Millimeter Lines
Authors: Takakuwa Shigehisa , Kamazaki Takeshi , Saito Masao , Yamaguchi Nobuyuki , Kohno Kotaro
Published: March 2014

With the ASTE telescope, we have observed three low-mass protostellar envelopes around L483, B335, and L723 in the submillimeter CS ($J$ = 7$-$6) and HCN ($J$ = 4$-$3) lines. We detected both the CS and HCN lines toward all targets, and the typical CS intensity ($\sim$ 1.0 K in $T_{\rm B}$) was twice higher than that of the HCN line. Mapping observations of L483 in these lines have shown that the submillimeter emissions are resolved, exhibit a western extension from the central protostar, and that the deconvolved size is $\sim$ 5500 AU $\times$ 3700 AU (PA = 78$^{\circ}$) in the HCN emission. The extent of the submillimeter emission in L483 implies the presence of higher temperature ($\gtrsim$ 40 K) gas at 4000 AU away from the central protostar, which suggests that we need to take 2-dimensional radiative transfer models with a bipolar cavity into account. The position–velocity diagrams of these submillimeter lines along the axis of the associated molecular outflow exhibit that the sense of the submillimeter velocity gradient is opposite to that of the millimeter observation or the associated molecular outflow, both in L483 and in B335. We suggest that expanding gas motions at the surface of the flattened envelope, which is irradiated by the central protostar directly, are the origin of the observed submillimeter velocity structure.
The Galactic Center Molecular Tornado Driven by Magnetic Squeezing Mechanism
Authors: Sofue Yoshiaki
Published: March 2014

Based on an analysis of the CO line-survey data, we report on peculiar properties of a helical-spur object of molecular gas at a radial velocity of $V_{\rm lsr}\sim 70$km s$^{-1}$ extending vertically from the galactic plane at $l = 1{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 2$ to high latitudes of $b\sim \pm 0{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 6 $. We call the object the Galactic Center molecular Tornado (GCT). The tornado is 170 pc ($1{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 2$) long and 14 pc ($6'$) wide, and is spinning at a rotation velocity of $\sim 30$km s$^{-1}$ in the same sense as, but with much steeper velocity gradient than, the galactic rotation. The coherent collimation and helical structure suggest that the tornado is related to an ordered vertical magnetic field. We propose a magnetic squeezing mechanism such that a vertical magnetic tube or a root of a large-scale prominence-like magnetic flux is twisted and squeezed by a molecular cloud in galactic rotation, and the gas is pushed out along the magnetic tube. The angular momentum of the cloud is lost along the twisting magnetic tube, which promotes gravitational collapse of the cloud and enhances star formation.
The Effect of FIR Emission from SDSS Galaxies on the SFD Galactic Extinction Map
Authors: Yahata Kazuhiro , Yonehara Atsunori , Suto Yasushi , Turner Edwin L. , Broadhurst Tom , Finkbeiner Douglas P.
Published: March 2014

We compare the most successful and widely used map of Galactic dust extinction, provided by Schlegel, Finkbeiner, and Davis (1998, hereafter SFD), to the galaxy number counts in the Sloan Digital Sky Survey (SDSS) photometric/spectroscopic DR4 sample. We divide the SDSS survey area into 69 disjoint subregions according to the dust extinction provided by SFD and compare the surface number density of galaxies in each subregion. As expected, the galaxy surface number density decreases with increasing extinction, but only for SFD extinction values above about 0.1 to 0.2 magnitudes (depending on the band). At lower values of the SFD extinction, we find that the sky surface density of galaxies increases with increasing extinction, precisely the opposite of the effect expected from Galactic dust. We also find that the average color of the SDSS photometric galaxy sample is slightly bluer at higher SFD extinctions in this regime, again the opposite of the effect expected from Galactic dust. Even though these anomalies occur only for sight-lines with low SFD extinction values, they affect approximately 68% of the high galactic latitude sky in which galaxies and their clustering properties are normally studied. Although it would be possible to explain these effects with a mysterious component of Galactic dust, which is anti-correlated with the 100$\mu$m flux on which the SFD extinction map is based, this model is not physically plausible. Moreover, we find that the surface number density of SDSS photometric quasars does not show any similar effect, as would be expected if the explanation were an unknown Galactic dust component. Considering these results, we suggest that the far infrared (FIR) brightness of the sky in regions of true low dust extinction is significantly “contaminated” by the FIR emission from background galaxies. We show that such an explanation is both qualitatively and quantitatively consistent with the available data. Based on this interpretation we conclude that systematic errors in the SFD extinction map due to extragalactic FIR emission are quite small, on the order hundredths of a magnitude, but nevertheless statistically detectable. Unfortunately, however, these errors are also entangled in a complex way with a signal of great interest to many “precision cosmology” applications, namely the large-scale clustering of galaxies.
Discovery of a New X-Ray Burst/Millisecond Accreting Pulsar, HETE J1900.1-2455
Authors: Suzuki Motoko , Kawai Nobuyuki , Tamagawa Toru , Yoshida Atsumasa , Nakagawa Yujin E. , Tanaka Kaoru , Shirasaki Yuji , Matsuoka Masaru , Ricker George R. , Vanderspek Roland , Butler Nat , Lamb Donald Q. , Graziani Carlo , Pizzichini Graziella , Sato Rie , Arimoto Makoto , Kotoku Jun’ichi , Maetou Miki , Yamauchi Makoto
Published: March 2014

A class of low-mass X-ray binary sources is known to be both X-ray burst sources and millisecond pulsars at the same time. A new source of this class was discovered by High Energy Transient Explorer 2 (HETE-2) on 2005 June 14 as a source of type-I X-ray bursts, which was named HETE J1900.1$-$2455. Five X-ray bursts from HETE J1900.1$-$2455 were observed during the summer of 2005. A time-resolved spectral analysis of these bursts has revealed that their spectra are consistent with the blackbody radiation throughout the bursts. The bursts show an indication of radius expansion. The bolometric flux remained almost constant during the photospheric radius expansion, while blackbody temperature dropped during the same period. Assuming that the flux reached the Eddington limit on a standard 1.4 solar-mass neutron star with a helium atmosphere, we estimate the distance to the source to be $\sim$ 4 Kpc.
Binary Black Hole Accretion Flows in Merged Galactic Nuclei
Authors: Hayasaki Kimitake , Mineshige Shin , Sudou Hiroshi
Published: March 2014

We consider accretion flows from circumbinary disks onto supermassive binary black holes on a subparsec scale of the galactic center based on a smoothed particles hydrodynamics (SPH) code. Simulation models are presented for four cases; that is, a circular binary and an eccentric one, each with equal and unequal masses. We find that the circumblack-hole disks are formed around each black hole regardless of the simulation parameters. There are two-step mechanisms that cause accretion flow. First, tidally induced elongation of the circumbinary disk triggers mass inflow toward two closest points on the circumbinary disk. Then, the gas is increasingly accumulated on these two points owing to the gravitational attraction of black holes. Second, when the gas can pass across the maximum loci of the effective binary potential, it starts to overflow via their two points, and freely infalls to each black hole. In circular binaries, the gas continues to be supplied from the circumbinary disk, (i.e., the gap between the circumbinary disk and the binary black hole is always closed). In eccentric cases, the mass supply undergoes periodic on/off transitions during one orbital period because of the variation of the periodic potential. The gap starts to close after the apoastron, and to open again after the next periastron passage. Due to the gap closing/opening cycles, the mass-capture rates are eventually strongly phase dependent. This could provide observable diagnosis for the presence of supermassive binary black holes in merged galactic nuclei.
New Approach to Study Non-Gravitational Motion of a Comet Normal to the Orbital Plane
Authors: Naoya MIURA , Ishiguro Masateru , Sarugaku Yuki , Ueno Munetaka
Published: March 2014

An edge-on view of the 22P/Kopff image showed that the nucleus was not on the locus of the maximum brightness of its dust cloud, which is likely to be a neck-line structure composed of large dust particles ejected 409 days before the observation. Assuming that the non-gravitational recoil force normal to the orbital plane generated a displacement of the nucleus, we demonstrate a modeled image similar to that of the observation. The obtained normal component of the non-gravitational acceleration is consistent with the predicted value extrapolated by data obtained during 1958–1983.
Near-Infrared Imaging Polarimetry of the NGC 2071 Star-Forming Region with SIRPOL
Authors: Tamura Motohide , Kandori Ryo , Hashimoto Jun , Kusakabe Nobuhiko , Nakajima Yasushi , Sato Shuji , Nagashima Chie , Kurita Mikio , Nagata Tetsuya , Nagayama Takahiro , Hough James H. , Matsumoto Tomoaki , Chrysostomou Antonio
Published: March 2014

We conducted deep JHK$_{\rm s}$ imaging polarimetry of a $\sim$ 8$' \times$ 8$'$ area of the NGC 2071 star-forming region. Our polarization data revealed various infrared reflection nebulae (IRNe) associated with the central IR young star cluster NGC 2071IR and identified their illuminating sources. There are at least 4 IRNe in NGC 2071IR, and several additional IRNe were identified around nearby young stars in the same field-of-view. Each illuminating source coincides with a known near-IR source, except for IRS 3, which is only a part of IRN 2 and is illuminated by the radio source 1c. Aperture polarimetry of each cluster source was used to detect unresolved circumstellar disk/outflow systems. Aperture polarimetry of the other point-like sources within the field was conducted in this region for the first time. The magnetic field structures (from $\sim$ 1 pc down to $\sim$ 0.1 pc) were derived using both aperture polarimetry of the point-like sources and imaging polarimetry of the shocked H$_2$ emission that is seen as the dominant knotty nebulae in the $K_{\rm s}$ band image; both are of dichroic origin and the derived field directions are consistent with each other. The magnetic field direction projected on the sky is also consistent with that inferred from the 850$\mu$m thermal continuum emission polarimetry of the central 0.2 pc region, but is running roughly perpendicular ($\sim$ 75$^{\circ}$) to the direction of the large-scale outflow. We argue that the field strength is too weak to align the outflow in the large-scale field direction via magnetic braking.
Near-Infrared Imaging Polarimetry of the Star-Forming Region NGC 2024
Authors: Kandori Ryo , Tamura Motohide , Kusakabe Nobuhiko , Nakajima Yasushi , Nagayama Takahiro , Nagashima Chie , Hashimoto Jun , Ishihara Akika , Nagata Tetsuya , Hough James H.
Published: March 2014

We conducted wide-field $JHK_{\rm s}$ imaging polarimetry toward NGC 2024, which is a massive star-forming region in the Orion B cloud. We found a prominent and extended polarized nebula over NGC 2024, and constrained the location of the illuminating source of the nebula through an analysis of polarization vectors. A massive star, IRS 2b with a spectral type of O8-B2, is located in the center of the symmetric vector pattern. Five small polarized nebulae associated with YSOs were discovered on our polarization images. These nebulae are responsible for the structures of circumstellar matter (i.e., disk/envelope systems) that produce strongly polarized light through dust scattering. For the point-like sources, we performed software aperture polarimetry in order to measure integrated polarizations, with which we detected candidate sources associated with circumstellar material. We found five young brown dwarfs with highly polarized integrated emission. These sources serve as direct evidence for the existence of a disk/envelope system around brown dwarfs. We investigated the fraction of highly polarized sources against the intrinsic luminosity of stars ($\propto$ mass), and found that the source detection rate remains constant from low luminosity (brown dwarfs) to higher luminosity (solar-type) stars. This result indicates that the relative disk scale-hight is rather independent of the stellar mass. We investigated the magnetic field structure of NGC 2024 through measurements of dichroic polarization. The average position angle of projected magnetic fields across the region is found to be 110${}^{\circ}$. We found a good consistency in magnetic field structures obtained using near-infrared dichroic polarization and sub-mm/far-infrared dust emission polarization, indicating that the dichroic polarizations at near-infrared wavelengths trace magnetic field structures inside dense ($A_{V} \lesssim 50$ mag) molecular clouds.
First NIR Polarimetry of 30 Doradus
Authors: Nakajima Yasushi , Kandori Ryo , Tamura Motohide , Kusakabe Nobuhiko , Hashimoto Jun , Nagayama Takahiro , Nagata Tetsuya , Hatano Hirofumi , Kato Daisuke , Hough James H.
Published: March 2014

We have carried out the first near-infrared (NIR) polarimetric imaging observations of the central part (7$\rlap{.}^{\prime}$7 $\times$ 7$\rlap{.}^{\prime}$7 $\sim 110 {\rm\; pc} \times 110 {\rm\; pc}$) of 30 Doradus. The totals of 106, 131, and 34 sources have significant polarization degrees at $J, H$, and $K_{\rm s}$, respectively. The $E$-vectors toward 30 Dor were mapped with unprecedentedly high resolutions. As previously noticed by optical observations, there is an overall tendency for the $E$-vectors to be roughly aligned in the east-west direction. In addition, our observations reveal a more complex structure of their alignment. The position angles of the $E$-vectors are not uniform, but show a gradual spatial variation. It is plausible to assume that they trace the magnetic field toward 30 Dor. One of the expanding shells toward 30 Dor, Shell 5, is clearly enveloped by $E$-vectors. The expanding shell has probably swept the magnetic field together into the rim, while creating the curved structure. We obtained the ratios of polarization degree among the NIR wavelengths: $P_H / P_J = 0.76\pm0.02$ and $P_{K_{\rm s}} / P_H = 0.87\pm0.06$. These fit a power-law dependence of $P \propto \lambda^{-0.9}$.
Stellar Contents of Two Intermediate Age Clusters: NGC 1912 and NGC 1907
Authors: Pandey Anil K. , Sharma Saurabh , Upadhyay Karunakar , Ogura Katsuo , Sandhu Tejbir S. , Mito Hiroyuki , Sagar Ram
Published: March 2014

We present CCD photometry in a wide field around two open clusters, NGC 1912 and NGC 1907. The stellar surface density profiles indicate that the radii of the clusters NGC 1912 and NGC 1907 are $\sim14^{\prime}$ and $\sim6^{\prime}$ respectively. The core of the cluster NGC 1907 is found to be $1\rlap{.}^{\prime}6\pm 0\rlap{.}^{\prime}3$, whereas the core of the cluster NGC 1912 could not be defined due to its significant variation with the limiting magnitude. The clusters are situated at distances of $1400\pm100$ pc (NGC 1912) and $1760\pm100$ pc (NGC 1907), indicating that in spite of their close locations on the sky they may be formed in different parts of the Galaxy. Although the mass functions for the clusters are quite noisy, in the given mass range the slopes of the mass functions for clusters NGC 1912 and NGC 1907 turn out to be $-1.12\pm0.30$ and $-1.23\pm0.21$, respectively, which are in agreement with the Salpeter value. Because the ages of the clusters are much higher than the estimated relaxation time-scales, dynamical relaxation may be one of the reasons for the observed mass segregation in the clusters. A comparison of the observed CMDs of the clusters with the synthetic CMDs gives a photometric binary content as $30\pm10\%$ (mass range $1.0 \le M_\odot \le 3.1$) and $20\pm10\%$ (mass range $1.2\le M_\odot \le 3.2$) in the case of NGC 1912 and NGC 1907, respectively.
CCD Photometric Study of the Contact Binary TX Cnc in the Young Open Cluster NGC 2632
Authors: Liu Liang , Qian Sheng-Bang , Boonrucksar Soonthornthum , Zhu Li-Ying , He Jia-Jia , Yuan J.-Z.
Published: March 2014

TX Cnc is a member of the young open cluster NGC2632. In the present paper, four CCD epochs of light minimum and a complete $V$ light curve of TX Cnc are presented. A period investigation based on all available photoelectric or CCD data showed that it is superimposed on a long-term increase ($dP/dt=+3.97\times{10^{-8}}$d yr$^{-1}$), and weak evidence suggests that it includes a small-amplitude period oscillation ($A_3=0\rlap{.}^{\rm d} 0028$; $T_3=26.6$yr). The light curves in the $V$ band obtained in 2004 were analyzed with the 2003 version of the W-D code. It was shown that TX Cnc is an overcontact binary system with a degree of contact factor $f=24.8\% (\pm0.9\%)$. The absolute parameters of the system were calculated: $M_1=1.319\pm0.007M_{\odot}, M_2=0.600\pm0.01M_{\odot}$; $R_1=1.28\pm0.19R_{\odot}, R_2=0.91\pm0.13R_{\odot}$. TX Cnc may be on the TRO-controlled stage of the evolutionary scheme proposed by Qian (2001a, b, 2003a), and may contain an invisible tertiary component ($m_3\approx0.097M_{\odot}$). If this is true, the tertiary component has played an important role in the formation and evolution of TX Cnc by removing angular momentum from the central system (Pribulla & Rucinski 2006). In this way the contact binary configuration can be formed in the shortlife time of a young open cluster via AML.
The Core Radius of a Star Cluster Containing a Massive Black Hole
Authors: Heggie Douglas C. , Hut Piet , Mineshige Shin , Makino Junichiro , Baumgardt Holger
Published: March 2014

We present a theoretical framework which establishes how the core radius of a star cluster varies with the mass of an assumed central black hole. Our result is that $r_{\rm c}/r_{\rm h}\propto (M_{\rm bh}/M)^{3/4}$ when the system is well relaxed. The theory compares favourably with a number of simulations of this problem, which extend to black hole masses of order 10% of the cluster mass. Though strictly limited as yet to clusters with stars of equal mass, our conclusion strengthens the view that clusters with large core radii are the most promising candidates in which to find a massive black hole.
First Determination of the Actinide Thorium Abundance for a Red Giant of the Ursa Minor Dwarf Galaxy
Authors: Aoki Wako , Honda Satoshi , Sadakane Kozo , Arimoto Nobuo
Published: March 2014

The thorium abundance of the red giant COS 82 in the Ursa Minor dwarf spheroidal galaxy was determined based on the high-resolution spectrum. This is the first detection of actinides in an extragalactic object. A detailed abundance pattern was determined for 12 other neutron-capture elements from atomic number 39 to 68. These elements are significantly over-abundant with respect to other metals, like Fe ($\gt$ 1 dex), and their abundance pattern agrees well with those of the r-process-enhanced, very metal-poor stars known in the galactic halo, while the metallicity of this object ([Fe$/$H] $\sim -$1.5) is much higher than these field stars ([Fe$/$H] $\sim-3.0$). The results indicate that the mechanism and the astrophysical site that are responsible for neutron-capture elements in COS 82 are similar to that for field r-process-enhanced stars, while the condition of low-mass star formation is quite different. An estimate of the age of this object based on the Th abundance ratio is discussed.
Chandra Detections of Diffuse X-Ray Emission from Globular Clusters
Authors: Okada Yuu , Kokubun Motohide , Yuasa Takayuki , Makishima Kazuo
Published: March 2014

Using Chandra, extended X-ray emission was detected from the direction of 6 globular clusters: 47 Tucanae, NGC 6752, M 5, $\omega$ Centauri, M 80, and NGC 6266. These X-ray sources, extending to a few arcmin, are located $1'-6'$ away from the cluster centers, and some are found in the direction of cluster motion through the Galactic halo. All of these sources are concluded to be diffuse, rather than an assembly of faint discrete X-ray sources. Those in 47 Tuc and NGC 6752 have similar spectra, described by a power law with a photon index of $\sim 2$, or a thin-thermal model with a temperature of $\sim 3 \!-\!4$ keV. Furthermore, they both have 843 MHz radio counterparts. The diffuse emission from $\omega$ Cen exhibits a $\sim 1.0$ keV thermal spectrum, while that from M 5 shows an even softer ($\sim$ 0.05 keV) spectrum. While the diffuse source in $\omega$ Cen could be a background contaminant, the others are likely to be physically associated with the globular clusters. Then, the absorption-corrected 0.5–4.5 keV luminosity of the sources in 47 Tuc and NGC 6752 becomes $(3\!-\!6)\times 10^{32}$ erg s$^{-1}$. These results are discussed in the context of shocks produced by the cluster motion through the Galactic halo, and the associated gas heating and particle acceleration.
Measurement of the Rossiter–McLaughlin Effect in the Transiting Exoplanetary System TrES-1
Authors: Narita Norio , Enya Keigo , Sato Bun’ei , Ohta Yasuhiro , Winn Joshua N. , Suto Yasushi , Taruya Atsushi , Turner Edwin L. , Aoki Wako , Tamura Motohide , Yamada Toru , Yoshii Yuzuru
Published: March 2014

We report a measurement of the Rossiter–McLaughlin effect in the transiting extrasolar planetary system TrES-1, via simultaneous spectroscopic and photometric observations with the Subaru and MAGNUM telescopes. By modeling the radial velocity anomaly that was observed during a transit, we determine the sky-projected angle between the stellar spin axis and the planetary orbital axis to be $\lambda = 30^{\circ}\pm 21^{\circ}$. This is the third case for which $\lambda$ has been measured in a transiting exoplanetary system, and the first demonstration that such measurements are possible for relatively faint host stars ($V \sim$ 12, as compared to $V \sim$ 8 for the other systems). We also derive a time of mid-transit, constraints on the eccentricity of the TrES-1b orbit ($e =$ 0.048$\pm$0.025), and upper limits on the mass of the Trojan companions ($\lesssim$ 14 $M_{\oplus}$) at the 3$\sigma$ level.
Dramatic Spectral and Photometric Changes of Pleione (28 Tau) between 2005 November and 2007 April
Authors: Tanaka Ken’ichi , Sadakane Kozo , Narusawa Shin-ya , Naito Hiroyuki , Kambe Eiji , Katahira Jun-ichi , Hirata Ryuko
Published: March 2014

Recent photometric and spectroscopic observations of Pleione are reported. Pleione showed brightness declines in both the $B$ and $V$ bands by $\sim$ 0$\rlap {.}{^{\rm m}}$25 between 2006 January and 2007 March. Significant decreases in the strengths and widths of the long-lived emission components in H$\alpha$ and H$\beta$ were observed during this period, while additional outer double-emission components appeared in these lines. Many metallic shell lines strengthened during the observation period, being accompanied by central quasi-emission components. We interpret these spectral changes in terms of a double disk: the progressive decline of a misaligned old disk in due course of precession and the formation and growth of a new disk in the star’s equatorial plane.
Astrometry of Galactic Star-Forming Region Sharpless 269 with VERA: Parallax Measurements and Constraint on Outer Rotation Curve
Authors: Honma Mareki , Bushimata Takeshi , Choi Yoon Kyung , Hirota Tomoya , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Miyaji Takeshi , Nagayama Takumi , Nakagawa Akiharu , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sato Katsuhisa , Sasao Tetsuo , Shibata Katsunori M. , Shintani Motonobu , Suda Hiroshi , Tamura Yoshiaki , Tsushima Miyuki , Yamashita Kazuyoshi
Published: March 2014

We have performed high-precision astrometry of H$_2$O maser sources in the Galactic star-forming region Sharpless 269 (S269) with VERA. We successfully detected a trigonometric parallax of $189 \pm 8 \mu$as, corresponding to a source distance of $5.28^{+0.24}_{-0.22}$ kpc. This is the smallest parallax ever measured, and the first one detected beyond 5 kpc. The source distance as well as the proper motions were used to constrain the outer rotation curve of the Galaxy, demonstrating that the difference of rotation velocities at the Sun and at S269 (which is 13.1 kpc away from the Galaxy’s center) is less than 3%. This gives the strongest constraint on the flatness of the outer rotation curve, and provides a direct confirmation of the existence of a large amount of dark matter in the Galaxy’s outer disk.
Distance to Orion KL Measured with VERA
Authors: Hirota Tomoya , Bushimata Takeshi , Choi Yoon Kyung , Honma Mareki , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kim Mi Kyoung , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Maruyama Kenta , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nakagawa Akiharu , Nakamura Kayoko , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sasao Tetsuo , Sato Katsuhisa , Sato Mayumi , Shibata Katsunori M. , Shintani Motonobu , Tamura Yoshiaki , Tsushima Miyuki , Yamashita Kazuyoshi
Published: March 2014

We present the initial results of multiepoch VLBI observations of 22 GHz H$_{2}$O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry). With the VERA dual-beam receiving system, we carried out phase-referencing VLBI astrometry, and successfully detected the annual parallax of Orion KL to be 2.29$\;\pm\;$0.10 mas, corresponding to a distance of 437$\;\pm\;$19 pc from the Sun. The distance to Orion KL was determined for the first time with the trigonometric parallax method in these observations. Although this value is consistent with that previously reported, 480$\;\pm\;$80 pc, which was estimated from a statistical parallax method using the proper motions and radial velocities of the H$_{2}$O maser features, our new results provide a much more accurate value with an uncertainty of only 4%. In addition to the annual parallax, we detected an absolute proper motion of the maser feature, suggesting an outflow motion powered by the radio source I along with the systematic motion of source I itself.
Self-Gravitational Magnetohydrodynamics with Adaptive Mesh Refinement for Protostellar Collapse
Authors: Matsumoto Tomoaki
Published: March 2014

A new numerical code, called SFUMATO, for solving self-gravitational magnetohydrodynamics (MHD) problems using adaptive mesh refinement (AMR) is presented. A block-structured grid is adopted as the grid of the AMR hierarchy. The total variation diminishing (TVD) cell-centered scheme is adopted as the MHD solver, with hyperbolic cleaning of the divergence error of the magnetic field also implemented. The MHD solver exhibits a second-order accuracy in convergence tests of linearized MHD waves. The self-gravity is solved using a multigrid method composed of (1) a full multigrid (FMG)-cycle on the AMR hierarchical grids, (2) a V-cycle on these grids, and (3) an FMG-cycle on the base grid. The multigrid method exhibits spatial second-order accuracy, fast convergence, and scalability. The numerical fluxes are conserved by using a refluxing procedure in both the MHD solver and the multigrid method. Several tests are performed and the results indicate that the solutions are consistent with previously published results.
Radiative Column and Light Curve of X-Ray Binary Pulsars
Authors: Karino Shigeyuki
Published: March 2014

We examine the published light curves (LCs) of 117 X-ray binary pulsars, while focusing on the dependence of their light curves on the observed energy bands. It is found that the energy dependence of the LCs appears only when the X-ray luminosity is larger than $\sim\;$5 $\times {10^{36}}\;$ergs$^{-1}$. Assuming that the behavior of light curve is related to the radiative accretion column on the neutron-star surface, this energy threshold can be considered as observational proof of the accretion column formation proposed by Basko and Sunyaev. Once we can grasp the existence of a radiative column, we can also obtain several useful pieces of information about the neutron-star properties. As an instance, we performed a statistical analysis of the orientation angle of the magnetic axis, and we found that the inclination angle of the magnetic axis should be small in order to explain the observed statistics.
Observations of B335 in the Millimeter Continuum and the 226 GHz H$_2$CO Line
Authors: Choi Minho
Published: March 2014

The protostar B335 was observed in the 1.3 mm continuum and in the H$_2$CO 3$_{12} \rightarrow$ 2$_{11}$ line with an angular resolution of about 8$^{\prime\prime}$. The mass of the inner envelope, detected by the dust continuum emission, is about 0.02$M_\odot$. The H$_2$CO spectrum at the protostellar position shows a blue-skewed double-peak profile, suggesting that the kinematics of the inner envelope is dominated by infall motion. When the blueshifted and the redshifted peaks were imaged separately, however, a small east–west displacement was found between the maximum positions. This displacement suggests that some part of the H$_2$CO emission might come from the outflowing gas. A combined effect of the infalling envelope and the outflow on the radiative transfer is discussed. This effect can make the line profile asymmetry severer than what is expected from infall-only models.
Missing Dwarf Problem in Galaxy Clusters
Authors: Kase Hiroyuki , Makino Junichiro , Funato Yoko
Published: March 2014

We investigated the formation and evolution of CDM subhalos in galaxy-sized and cluster-sized halos by means of $N$-body simulations. Our aim was to make clear what the “dwarf galaxy problem” is. It has been argued that the number of subhalos in simulated galaxy-sized halos is too large compared with the observed number of dwarfs in the local group, while that in cluster-sized halos is consistent with the observed number of galaxies in clusters, such as the Virgo cluster. We simulated nine halos with several different mass resolutions and physical scales. We found that the dependence of the cumulative number of subhalos, $N_c$, on their maximum circular velocity, $V_c$, is given by $N_c\propto V_c^{-3}$, down to the reliability limit, independent of the mass of the main halo. This implies that simulations for cluster-sized halos give too many halos with $V_c \sim$140 km s$^{-1}$ or less. Previous comparisons of cluster-sized halos gave a much smaller number of subhalos in this regime, simply because of their limited resolution. Our result implies that any theory that attempts to resolve the missing dwarf problem should also explain the discrepancy of the simulation and observation in cluster-sized halos.