bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 $\boldsymbol{v}_{\mathrm{F}}&lt;0$ 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.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.