bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable Line Profiles Due to Non-Axisymmetric Patterns in an Accretion Disc around a Rotating Black Hole
Authors: Karas Vladimír , Martocchia Andrea , Šubr Ladislav
Published: March 2014

We have explored spectral line profiles due to spiral patterns in accretion discs around black holes. A parametrization was employed for the shape and emissivity of spiral waves, which can be produced by non-axisymmetric perturbations affecting the disc density and ionization structure. The effects of the light-travel time, energy shift, and gravitational focusing near to a rotating black hole were taken into account. A high-resolution ray-tracing code was used to follow the time variations of the synthetic line profile. A variety of expected spectral features were examined and the scheme applied to a broad iron line observed in MCG$-$6–30–15.
The FR-I Radio Galaxies NGC 315 and NGC 4261 Observed with ASCA
Authors: Matsumoto Yukari , Fukazawa Yasushi , Nakazawa Kazuhiro , Iyomoto Naoko , Makishima Kazuo
Published: March 2014

FR-I radio galaxies NGC 315 and NGC 4261 were observed in X-rays with ASCA for $\sim 37 ~\mathrm{ks}$ and $\sim 54~\mathrm{ks}$, respectively. Hard X-ray emission from a point-like source at the nucleus was detected at a 2–10 keV luminosity of $3.1 \times 10^{41}$ and $9.2 \times 10^{40}~\mathrm{erg}~\mathrm{s}^{-1}$, respectively, for assumed distances of 66 Mpc and 29 Mpc (for $H_0 = 75~\mathrm{km}~\mathrm{s}^{-1}~\mathrm{Mpc}^{-1}$). The 2–10 keV spectra of NGC 315 and NGC 4261 were both fitted successfully with a power-law of photon index $2.02 \pm 0.34$ and $1.45 \pm 0.11$, respectively, plus emission from hot gas. The NGC 315 nucleus is mildly absorbed. No X-ray variability was detected from either object, with typical upper limits of several tens per cent. These results imply the presence of a low-luminosity active galactic nucleus in both galaxies, and reconfirm the previous recognition that the FR-I nuclei are significantly less X-ray luminous than the FR-II ones.
The Fundamental Plane of Spiral Galaxies: Search from Observational Data
Authors: Han JinLin , Deng Zugan , Zou Zhenlong , Wu Xue-Bing , Jing Yipeng
Published: March 2014

The fundamental plane of spiral galaxies was searched from observational data, which can be approximately represented in observational parameters by $L \propto V^2 R$, where $L, R$, and $V$ are the luminosity, the linear size of galactic disk, and the rotation velocity. This plane exists at all optical bands in our samples of more than 500 spiral galaxies in total. It is more fundamental than the relationship between any two of the parameters, and can reduce the residual of the Tully–Fisher $L$–$V$ relations by about 50%. Noticed that the power index of $V$ is doubled from that of $R$, which implies that the total mass and the mass distribution of galaxies plays an important role in forming the fundamental plane. Involving the third parameter of galactic size has a strong physical implication on galaxy formation and the dark-mass distribution.
The 2000–2001 Superoutburst of the WZ Sge-Type Star RZ Leonis: A Clue to Understanding the Origin of Viscosity in Quiescent Dwarf Nova Disks
Authors: Ishioka Ryoko , Kato Taichi , Uemura Makoto , Iwamatsu Hidetoshi , Matsumoto Katsura , Stubbings Rod , Mennickent Ronald , Billings Gary W. , Kiyota Seiichiro , Masi Gianluca , Pietz Jochen , Novak Rudolf , Martin Brian E. , Oksanen Arto , Moilanen Marko , Torii Ken’ichi , Kinugasa Kenzo , Kawakita Hideyo
Published: March 2014

We report here on time-resolved photometric observations of the superoutburst of a dwarf nova, RZ Leo, which occurred during 2000 December–2001 January. We reveal the following characteristics of the outburst based on our observations: long duration, large amplitude, and the existence of two types of superhumps — “early superhumps” and “normal superhumps”. In addition to the extremely low frequency of the outbursts, the characteristics of the outburst strongly indicate that RZ Leo is the fifth member of the WZ Sge-type dwarf novae.

The orbital period of RZ Leo is 0.07651 d, which is remarkably longer than the “canonical” period of other WZ Sge stars ($\sim 0.058\,\mathrm{d}$). The longer period indicates a non-degenerate secondary of RZ Leo, which suggests that the idea of a low quiescence viscosity due to a degenerate brown dwarf secondary may not be correct. The present discovery of RZ Leo as being a WZ Sge star provides the first clear indication that the decay of magnetic turbulence in accretion disks of quiescent WZ Sge stars plays an important role in producing the proposed low quiescent viscosity.
SPH Simulations of Spiral Shocks in Discs around Black Holes
Authors: Belvedere Gaetano , Lanzafame Giuseppe
Published: March 2014

Spiral structures and shocks often appear in astrophysical gas dynamics and particular in accretion-disc simulations; however, they are difficult to follow numerically. In this paper we consider a black hole of 8$ {M}_{\odot}$ as a primary and a small secondary of 0.5 $ {M}_{\odot}$, following the idea that a low $ M_{2}/M_{1}$ would favour spiral structure and possibly spiral shock onset through gas compression induced by strong gravitational attraction. In the framework of Smooth Particle Hydrodynamics (SPH), we performed two 2D models and two 3D models. Simulations in either pair are distinguished by the adopted $ \gamma$ value (low and high compressibility cases). Indeed, both 2D models reveal the existence of spiral structures in the disc bulk. Furthermore, spiral shocks at the outer disc edge are evident for the high compressibility 2D model. Spiral structures appear to develop also for the 3D high compressibility model. Instead, for the 3D low compressibility model, no clear conclusion can be drawn as the number of particles (and thus the SPH resolution) is low.
Chandra Observations of a Young Embedded Magnetic B Star in the $\rho$ Ophiuchus Cloud
Authors: Hamaguchi Kenji , Corcoran Michael F. , Imanishi Kensuke
Published: March 2014

This paper reports on an analysis of two Chandra X-ray observations of the young magnetic B star $\rho$ Ophiuchus S1. X-ray emission from the star was detected in both observations. The average flux was almost the same in both, but during each observation the flux showed significant time variations by a factor of two on time-scales of 20–40 ks. Each spectrum could be fit by either an absorbed power-law model with a photon index of $\sim 3$ or a thin-thermal plasma model with a temperature of $\sim 2 \,\mathrm{keV}$ and an extremely low metal abundance ($\lesssim 0.1$ solar). The spectrum of the first observation has a weak-line feature at about 6.8 keV, which might correspond to highly ionized iron $\mathrm{K}\alpha$. In contrast, the spectrum of the second observation apparently shows a weak edge absorption component at $E \sim4 \,\mathrm{keV}$. The continuum emission and $\log (L_\mathrm{X} / L_{\mathrm{bol}}) \sim-6$ are similar to those of young intermediate-mass stars (Herbig Ae/Be stars), although the presence of a strong magnetic field (inferred from the detection of non-thermal radio emission) has drawn an analogy between $\rho$ Ophiuchus S1 and magnetic chemically peculiar (MCP) stars. If the X-ray emission is thermal, the small abundances that we derived might be related to the inverse first-ionization potential (FIP) effect, though there is no significant trend as a function of FIP from our model fits. If the emission is non-thermal, it might be produced by high-energy electrons in the magnetosphere.
Evolution of Elliptical Galaxies at $z \gtrsim 1$ Revealed from a Large, Multicolor Sample of Extremely Red Objects
Authors: Miyazaki Masayuki , Shimasaku Kazuhiro , Kodama Tadayuki , Okamura Sadanori , Furusawa Hisanori , Ouchi Masami , Nakata Fumiaki , Doi Mamoru , Hamabe Masaru , Kimura Masahiko , Komiyama Yutaka , Miyazaki Satoshi , Nagashima Chie , Nagata Tetsuya , Nagayama Takahiro , Nakajima Yasushi , Nakaya Hidehiko , Pickles Andrew J. , Sato Shuji , Sekiguchi Kazuhiro , Sekiguchi Maki , Sugitani Koji , Takata Tadafumi , Tamura Motohide , Yagi Masafumi , Yasuda Naoki
Published: March 2014

We studied the evolution of elliptical galaxies at $z \gtrsim 1$ using a sample of 247 Extremely Red Objects (EROs) with $R-K_\mathrm{s} \ge 3.35$ (AB) and $K_\mathrm{s} \le 22.1$ (AB) constructed from $BVR \, i'z'JHK_\mathrm{s}$ multicolor data of a $114 \,\mathrm{arcmin}^2$ area in the Subaru/XMM-Newton Deep Field taken with the Subaru Telescope and the UH 2.2 m telescope. By fitting template spectra of old galaxies (OGs) and young, dusty starbursts (DSs) to the multicolor data, we classified EROs into these two classes and estimated their redshifts. We found that 58% of the EROs in our sample belong to the OG class and that these OGs have a wide range of colors at any redshift. We derived rest-frame $B$-band luminosity functions of OGs in our sample at $z=1 \hbox{-} 1.5$ and $1.5 \hbox{-} 2.5$, and found that the number density of galaxies obeying passive evolution drops at $z \gtrsim 1.5$ by a factor of three or more. The spatial correlation length of OGs is estimated to be $r_0 \gtrsim 8 \,h^{-1} \,\mathrm{Mpc}$, which is comparable to, or larger than, those of present-day early-type galaxies of similar luminosities. We also discussed properties of DSs in our data.
SDSS J1335+0118: A New Two-Image Gravitational Lens
Authors: Oguri Masamune , Inada Naohisa , Castander Francisco J. , Gregg Michael D. , Becker Robert H. , Ichikawa Shin-ichi , Pindor Bartosz , Brinkmann Jonathan , Eisenstein Daniel J. , Frieman Joshua A. , Hall Patrick B. , Johnston David E. , Richards Gordon T. , Schechter Paul L. , Schneider Donald P. , Szalay Alexander S.
Published: March 2014

We report on the discovery of the two-image gravitationally lensed quasar SDSS J1335$+$0118. The object was selected as a lens candidate from the Sloan Digital Sky Survey. The imaging and spectroscopic follow-up observations confirm that the system exhibits two gravitationally lensed images of a quasar at $z=1.57$. The image separation is ${1\rlap {.}{}^{\mathrm {\prime \prime }}56}$. We also detect an extended component between the two quasar images, likely to be a lensing galaxy. Preliminary mass modeling predicts a differential time delay, $\Delta t$ of $\sim30 \, h^{-1} \mathrm{day}$, assuming the redshift of the lens galaxy to be $0.5$.
The Anisotropic Transfer of Resonance Photons in Hot Plasmas on Magnetized White Dwarfs
Authors: Terada Yukikatsu , Ishida Manabu , Makishima Kazuo
Published: March 2014

In order to confirm the anisotropic effect of resonance photons in hot accretion columns on white dwarfs in magnetic cataclysmic variables, proposed by Terada et al. (2001), systematic studies with ASCA of 7 polars and 12 intermediate polars were performed. The equivalent widths of He-like Fe $\mathrm{K}\alpha$ lines of polars were found to be systematically modulated at their spin periods in such a way that it increases at the pole-on phase. This implies that the anisotropic mechanism is commonly operating among polars. On the other hand, those of intermediate polars are statistically consistent with being unmodulated with an upper limit of 1.5-times modulation. This may be due to a different accretion manner, like an aurora curtain (Rosen et al. 1988), so that the plasma also becomes optically thin along the horizontal axis for the resonance lines, or because of larger optical depths for Compton scattering if the emission regions have the same coin-like shapes as polars.
The Evolution of Galaxies in and around Clusters at High-Redshift
Authors: Fujita Yutaka , Goto Tomotsugu
Published: March 2014

In this paper, we focus on ram-pressure stripping and evaporation of disk galaxies in and around a cluster. We show that the evolution of the disk surface density affects the efficiency of ram-pressure stripping of galaxies at $z\gtrsim 1$. We also consider the saturation of thermal conduction in detail and show that it cannot be ignored at larger radii of a cluster, which makes the time-scale of the evaporation larger. Both the ram-pressure stripping and evaporation could affect the evolution of galaxies even around a cluster. In particular, the observed gradual decline of the star-formation rates of galaxies in and around clusters could be explained by evaporation without resorting to speculative strangulation (stripping of warm gas in galactic halos).
The Peculiar 2004 Superoutburst in the Helium Dwarf Nova, 2003aw
Authors: Daisaku Nogami , Monard Berto , Retter Alon , Liu Alex , Uemura Makoto , Ishioka Ryoko , Imada Akira , Kato Taichi
Published: March 2014

We conducted a time-resolved photometric campaign of helium dwarf nova, 2003aw, in 2004 May–June. 2003aw stayed at 14.7–15.7 mag for the first several days during this campaign, which is the plateau phase of this superoutburst. This variable then rapidly decayed to $\sim 18.0 \,\mathrm{mag}$, still brighter by about 2 mag than its quiescence magnitude, and maintained this brightness for about 20 days, having short flares of $\sim 2 \,\mathrm{mag}$. A long fading tail followed it. We detected superhumps with a period of 0.02357(4)d [= 2036(3)s] during the plateau phase. The whole light curve of the superoutburst in 2003aw, taking into account the present data and those in the literature, perfectly resembles that of the 1996–1997 superoutburst of the peculiar WZ Sge-type hydrogen-rich dwarf nova, EG Cnc.
Search for CCH—, NCO—, and NCS— Negative Ions in Molecular Clouds
Authors: Morisawa Yusuke , Hoshina Hiromichi , Kato Yoshiyasu , Simizu Zenzo , Kuma Susumu , Sogoshi Norihito , Fushitani Mizuho , Watanabe Shiori , Miyamoto Yuki , Momose Takamasa , Kasai Yasuko , Kawaguchi Kentarou
Published: March 2014

Despite several suggestions concerning the existence of negatively charged molecules and negative atomic ions in molecular clouds, few attempts have been made to search for negative ions in molecular clouds. In the present study, we extensively searched for three negative molecular ions ($\mathrm{CCH}^{-}, \mathrm{NCO}^{-}$, and $\mathrm{NCS}^{-}$) in a dark cloud, L134N, using the Nobeyama 45-m radio telescope. The three negative ions are molecules whose rotational constants have been reported based on laboratory experiments. After a long accumulation, a trace amount of an unidentified emission line was detected at a frequency close to the theoretical prediction of the $J = 1 \hbox{--} 0$ transition of $\mathrm{CCH}^{-}$. If this unidentified line is attributable to $\mathrm{CCH}^{-}$, the observed emission intensity would provide an estimation of the column density of $\mathrm{CCH}^{-}$ in L134N to be $1.0 \times 10^{11} \,\mathrm{cm}^{-2}$, which corresponds to a fractional abundance of $5 \times 10^{-12}$ relative to hydrogen. However, our recent observation using the IRAM 30-m telescope did not reproduce the $J = 1 \hbox{--} 0$ signal, nor detect any trace of the $J = 2 \hbox{--} 1$ transition. Thus, the identification of $\mathrm{CCH}^{-}$ in L134N is not yet confirmed. As for other ions, signals of neither $\mathrm{NCO}^{-}$ nor $\mathrm{NCS}^{-}$ were detected in L134N. Although we also searched for the three negative ions in a translucent cloud, CB228, and a star-forming region, SgrB2, no signals were detected. The upper limit abundances of the ions in these clouds are discussed.
Geometrical Effect of Supercritical Accretion Flows: Observational Implications of Galactic Black-Hole Candidates and Ultraluminous X-Ray Sources
Authors: Watarai Ken-ya , Ohsuga Ken , Takahashi Rohta , Fukue Jun
Published: March 2014

We consider the dependence of the viewing angle in supercritical accretion flows and discuss the observational implications of galactic black-hole candidates and ultraluminous X-ray sources. Model spectra of supercritical accretion flows strongly depend on the inclination angle. For example, the maximum temperature of the supercritical disk (the accretion rate and the black-hole mass are $\dot{M} = 1000 \,L_{\mathrm{E}}/c^2$ and $M = 10 \,{{{M}_{\odot}}}$, respectively) is $kT_{\mathrm{in}} \sim 2.0 \,\mathrm{keV}$ for a low-inclination angle, $i \lesssim 40^\circ$, while $k T_{\mathrm{in}} \sim 0.6 \,\mathrm{keV}$ for a high-inclination angle, $i \gtrsim 60^\circ$. This spectral softening originates from self-occultation of the disk, i.e., the outer disk blocks emission from the disk inner region, even if we take into account the effect of general relativity (light bending, Doppler boosting). This is because, when the mass accretion rate exceeds the critical rate, then the shape of the disk is geometrically thick due to enhanced radiation pressure. We also find that the spectral properties of low-$i$ and low accretion-rate disks are very similar to those of high-$i$ and high accretion-rate disks. That is, if an object has a high $i$ and a high accretion rate, such a system suffers from self-occultation and the spectrum will be extremely soft. Therefore, we cannot distinguish these disks by only the difference in their spectrum shapes. Conversely, if we use the self-occultation properties, we could constrain the inclination angle of the system. We suggest that some observed high-temperature ultraluminous X-ray sources have low-inclination angles, i.e., near face-on geometry, $i \lesssim 40^{\circ}$, and the Galactic black-hole candidate XTE J1550$-$564 possesses relatively high-inclination angles, $i \gtrsim 60^{\circ}$.
Extremely High-Velocity Gas in the Galaxy Arp 220, Revealed with Ammonia Absorption Lines
Authors: Takano Shuro , Nakanishi Kouichiro , Nakai Naomasa , Takano Toshiaki
Published: March 2014

We observed ammonia $(J, K) = (1, 1), (2, 2), (3, 3)$, and $(4, 4)$ transitions at a wavelength of 1.3 cm toward a prototypical ultraluminous infrared galaxy, Arp 220, with the Nobeyama 45-m radio telescope. We detected extremely wide absorption lines at the $(1, 1)$ and $(3, 3)$ transitions. The maximum total velocity width was $\sim 1800 \,\mathrm{km} \,\mathrm{s}^{-1}$. Such wide molecular absorption lines were detected for the first time in galaxies. The absorption lines are formed by ammonia only in front of the central compact continuum emission ($\sim {1{}^{\mathrm {\prime \prime }}} = 370 \,\mathrm{pc}$). The present results clearly indicate the existence of extremely high-velocity motion in the central compact region of Arp 220. A possible origin of such motion is rapidly rotating gas, suggesting the existence of an active galactic nucleus, or outflowing or inflowing gas.
Three-Dimensional Magnetohydrodynamic Simulation of Nonlinear Magnetic Buoyancy Instability of Flux Sheets with Magnetic Shear
Authors: Nozawa Satoshi
Published: March 2014

A series of three-dimensional magnetohydrodynamic simulations is used to study the nonlinear evolution of the magnetic buoyancy instability of a magnetic flux sheet with magnetic shear. A horizontal flux sheet that is initially placed below the solar photosphere is susceptible to both the interchange instability and the Parker instability (the undular mode of the magnetic buoyancy instability). The growth rate in the linear stage of the instability in the numerical simulation is consistent with that predicted by linear theory. In the nonlinear stage, the development depends on the initial perturbation as well as the initial magnetic field configuration (i.e., the presence of magnetic shear). When an initial perturbation is assumed to be periodic, the emerging flux rises to the corona and the magnetic field expands like a potential field, as observed in 2D simulations. When an initial non-periodic perturbation or random perturbations are assumed, the magnetic flux expands horizontally when the magnetic field emerges a little into the photosphere. The distribution of the magnetic field and gas tends to be in a new state of magnetohydrostatic equilibrium. When magnetic shear is present in the initial magnetic flux sheets, the interchange mode is stabilized so that the emerging loop is higher than in the no magnetic shear case. We discuss how the presented results are related to the emerging flux observed on the Sun.
Chandra Observations of A 2670 and A 2107: A Comet Galaxy and cDs with Large Peculiar Velocities
Authors: Fujita Yutaka , Sarazin Craig L. , Sivakoff Gregory R.
Published: March 2014

We present an analysis of Chandra observations of the galaxy clusters A 2670 and A 2107. Their cD galaxies have large peculiar velocities ($\gt200 \,\mathrm{km} \,\mathrm{s}^{-1} \gt200 \,\mathrm{km} \,\mathrm{s}^{-1}$) and thus the clusters appear to be undergoing mergers. In A 2670, we find a comet-like structure around one of the brightest galaxies. At the leading edge of the structure, there is a cold front. The mass of the X-ray gas in the comet-like structure suggests that the galaxy was in a small cluster or group, and its intracluster medium is being stripped by ram-pressure. The regions of cool interstellar medium of the cD galaxies in A 2670 and A 2107 are very compact. This is similar to the brightest galaxies in the Coma cluster, which is also a merging cluster. In each galaxy, the short cooling time of the ISM requires a heating source; the compact nature of the ISM makes it unlikely that the heating source is a central active galactic nucleus.
Dual-Frequency VSOP Imaging of the Jet in S5 0836+710
Authors: Lobanov Andrei P. , Krichbaum Thomas P. , Witzel Arno , Zensus J. Anton
Published: March 2014

The luminous high-redshift ($z=2.17$) quasar S5 0836$+$710 was observed in 1997 October with the VSOP at 1.6 GHz and 5 GHz. We report here a previously unpublished image made from the data at 1.6 GHz, and compare the structure of a relativistic jet in this quasar at two frequencies. We present a spectral index image tracing the spectral properties of the jet up to $\sim 40$ milliarcsec distance from the nucleus. The curved jet ridge line observed in the images and the spectral index distribution can be described by a Kelvin–Helmholtz instability developing in a relativistic outflow with a Mach number of $\sim 6$. In this description, the overall ridge line of the jet is formed by the helical surface mode of the Kelvin–Helmholtz instability, while areas of flatter spectral index embedded into the flow correspond to pressure enhancements produced by the elliptical surface mode of the instability. An alternative explanation involving a sequence of slowly dissipating shocks cannot be ruled out at this point.
Distance Measurement of Spiral Arms in the Galactic-Center Direction Using Radial-Velocity Gradients
Authors: Sofue Yoshiaki
Published: March 2014

We propose a method to determine the distances of spiral arms in the galactic-center (GC) direction using radial-velocity gradients of approximately straight ridges in longitude–velocity (LV) diagrams of the CO and H I line emissions. We show that the velocity gradient of an LV ridge is uniquely related to the distance. The arms and rings in the central region show large velocity gradients, while nearby arms appear as ridges with small velocity gradients. Applying this method, we determine the distances of the arms on the Sun–GC line, which has remained most difficult in the commonly used kinematical-distance method.
Chemical Abundances in the Secondary Star of the Black Hole Binary V4641 Sagittarii (SAX J1819.3−2525)
Authors: Sadakane Kozo , Arai Akira , Aoki Wako , Arimoto Nobuo , Takada-Hidai Masahide , Ohnishi Takashi , Tajitsu Akito , Beers Timothy C. , Iwamoto Nobuyuki , Tominaga Nozomu , Umeda Hideyuki , Maeda Keiichi , Nomoto Ken’ichi
Published: March 2014

We report on detailed spectroscopic studies performed for the secondary star in the black hole binary (micro-quasar) V4641 Sgr in order to examine its surface chemical composition and to see if its surface shows any signature of pollution by ejecta from a supernova explosion. High-resolution spectra of V4641 Sgr observed in the quiescent state in the blue-visual region are compared with those of the two bright well-studied B9 stars (14 Cyg and $\nu$ Cap) observed with the same instrument. The effective temperature of V4641 Sgr ($10500 \pm 200 \,\mathrm{K}$) is estimated from the strengths of He I lines, while its rotational velocity, $v \sin i$ ($95 \pm 10 \,\mathrm{km} \,\mathrm{s}^{-1}$), is estimated from the profile of the Mg II line at 4481 Å. We obtain abundances of 10 elements and find definite over-abundances of N (by 0.8 dex or more) and Na (by 0.8 dex) in V4641 Sgr. From line-by-line comparisons of eight other elements (C, O, Mg, Al, Si, Ti, Cr, and Fe) between V4641 Sgr and the two reference stars, we conclude that there is no apparent difference in the abundances of these elements between V4641 Sgr and the two normal late B-type stars, which have been reported to have solar abundances. An evolutionary model of a massive close binary system has been constructed to explain the abundances observed in V4641 Sgr. The model suggests that the progenitor of the black hole forming supernova was as massive as $\sim 35 \,{{{M}_{\odot}}}$ on the main-sequence and, after becoming a $\sim 10 \,{{{M}_{\odot}}}$ He star, underwent a “dark” explosion which ejected only N–and Na-rich outer layer of the He star without radioactive ${{56\atop} \mathrm{Ni}}$.
MOIRCS Deep Survey. I: DRG Number Counts
Authors: Kajisawa Masaru , Konishi Masahiro , Suzuki Ryuji , Tokoku Chihiro , Uchimoto Katsuno Yuka , Yoshikawa Tomohiro , Akiyama Masayuki , Ichikawa Takashi , Ouchi Masami , Omata Koji , Tanaka Ichi , Nishimura Tetsuo , Yamada Toru
Published: March 2014

We used very deep near-infrared imaging data taken with the Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru Telescope to investigate the number counts of Distant Red Galaxies (DRGs). We observed a $4' \times 7'$ field in the Great Observatories Origins Deep Survey-North (GOODS-N), and our data reached $J=24.6$ and $K=23.2$ ($5\,\sigma$, Vega magnitude). The surface density of DRGs selected by $J-K \gt 2.3 J-K \gt 2.3$ is $2.35 \pm 0.31 \,\mathrm{arcmin}^{-2}$ at $K < 22$ and $3.54 \pm 0.38 \,\mathrm{arcmin}^{-2}$ at $K < 23$, respectively. These values are consistent with those in the GOODS-South and FIRES. Our deep and wide data suggest that the number counts of DRGs turn over at $K \sim 22$, and the surface density of the faint DRGs with $K \gt 22$ is smaller than that expected from the number counts at the brighter magnitude. The result indicates that while there are many bright galaxies at $2 < z < 4$ with the relatively old stellar population and/or heavy dust extinction, the number of faint galaxies with a similar red color is relatively small. Different behavior patterns of the number counts of the DRGs and bluer galaxies with $2 < z_{\mathrm{phot}} < 4$ at $K \gt 22$ suggest that the mass-dependent color distribution, where most of the low-mass galaxies are blue, while more massive galaxies tend to have redder colors, had already been established at that epoch.
Steady Models of Optically Thin, Magnetically Supported Black Hole Accretion Disks
Authors: Oda Hiroshi , Machida Mami , Nakamura Kenji E. , Matsumoto Ryoji
Published: March 2014

We obtained steady solutions of optically thin, single-temperature, magnetized black hole accretion disks, assuming thermal bremsstrahlung cooling. Based on the results of 3D MHD simulations of accretion disks, we assumed that the magnetic fields inside the disk are turbulent and dominated by an azimuthal component. We decomposed the magnetic fields into an azimuthally averaged mean field and fluctuating fields. We also assumed that the azimuthally averaged Maxwell stress is proportional to the total pressure. The radial advection rate of the azimuthal magnetic flux, $\dot \Phi$, is prescribed as being proportional to $\varpi^{-\zeta}$, where $\varpi$ is the radial coordinate and $\zeta$ is a parameter that parameterizes the radial variation of $\dot \Phi$. We found that when the accretion rate, $\dot M$, exceeds the threshold for the onset of the thermal instability, a magnetic pressure-dominated new branch appears. Thus, the thermal-equilibrium curve of an optically thin disk has a ‘Z’-shape in the plane of the surface density and temperature. This indicates that as the mass accretion rate increases, a gas pressure-dominated optically thin hot accretion disk undergoes a transition to a magnetic pressure dominated, optically thin cool disk. This disk corresponds to the X-ray hard, luminous disk in black hole candidates observed during the transition from a low/hard state to a high/soft state. We also obtained global steady transonic solutions containing such a transition layer.
A Multiband Study of the Optically Dark GRB 051028
Authors: Urata Yuji , Huang Kui-Yun , Kuo Ping-Hung , Ip Wing-Huen , Qiu Yulei , Masuno Keisuke , Tashiro Makoto , Abe Keiichi , Onda Kaori , Kodaka Natsuki , Kuwahara Makoto , Tamagawa Toru , Usui Fumihiko , Ioka Kunihito , Lee Yi-Hsi , Wei Jianyan , Deng Jinsong , Zheng Weikang , Makishima Kazuo
Published: March 2014

Observations were made of the optical afterglow of GRB 051028 with the Lulin observatory 1.0m telescope and the Wide-Field Telescope for GRB Early Timing (WIDGET) robotic telescope system. $R$-band photometric data were obtained on 2005 October 28 (UT), or 0.095–0.180 d after the burst. There is a possible plateau in the optical light curve around 0.1 d after the burst; the afterglow of GRB 051028 resembles optically bright afterglows (e.g., GRB 041006, GRB 050319, GRB 060605) in shape of the light curve, but not in brightness. The brightness of the GRB 051028 afterglow is 3 mag fainter than that of one of the dark events, GRB 020124. Optically dark GRBs have been attributed to dust extinction within the host galaxy or a high redshift. However, a spectrum analysis of the X-rays implies that there is no significant absorption by the host galaxy. Furthermore, according to a theoretical calculation of the Ly$\alpha$ absorption to find the limit of the GRB 051028’s redshift, the expected $R$-band absorption is not high enough to explain the darkness of the afterglow. The present results disfavor either the high-redshift hypothesis or the high-extinction scenario for optically dark bursts; rather, they are consistent with the possibility that the brightness of the optical afterglow is intrinsically dark.
A Possible Estimate of the Doppler Factors for Blazars
Authors: Xiang Yang , Dai Ben-Zhong
Published: March 2014

We have studied the beaming effect and multi-band properties of blazars using a sample of 31 blazars. In the sample, the observed variability timescale, the mass of the central super-massive black hole (SMBH), and the flux densities at 4 energy bands (radio, optical, X-ray, and $\gamma$-ray) of each object were compiled from the literature. The Doppler factor was estimated in two cases: (1) considering that the Doppler factor is the same throughout the entire energy band, and calculating by using the observed variability timescale; (2) the Doppler factor is a function of frequency, i.e., the Doppler factor is variable in a different energy band. Based on the Doppler factor estimated in both cases, we find that the intrinsic flux densities at different energy bands are significantly correlated with each other.
BRIDGE: A Direct-Tree Hybrid $N$-Body Algorithm for Fully Self-Consistent Simulations of Star Clusters and Their Parent Galaxies
Authors: Fujii Michiko , Iwasawa Masaki , Funato Yoko , Makino Junichiro
Published: March 2014

We developed a new direct-tree hybrid $N$-body algorithm for fully self-consistent $N$-body simulations of star clusters in their parent galaxies. In such simulations, star clusters need high accuracy, while galaxies need a fast scheme because of the large number of particles required to model it. In our new algorithm, the internal motion of the star cluster is calculated accurately using the direct Hermite scheme with individual timesteps, and all other motions are calculated using the tree code with a second-order leapfrog integrator. The direct and tree schemes are combined using an extension of the mixed variable symplectic (MVS) scheme. Thus, the Hamiltonian corresponding to everything other than the internal motion of the star cluster is integrated with the leapfrog, which is symplectic. Using this algorithm, we performed fully self-consistent $N$-body simulations of star clusters in their parent galaxy. The internal and orbital evolutions of the star cluster agreed well with those obtained using the direct scheme. We also performed fully self-consistent $N$-body simulation for large-$N$ models ($N=$ 2$\times$10$^6$). In this case, the calculation speed was seven-times faster than what would be if the direct scheme was used.
Discovery of a Possible X-Ray Counterpart to HESS J1804—216
Authors: Bamba Aya , Koyama Katsuji , Hiraga Junko S. , Hughes John P. , Kohmura Takayoshi , Kokubun Motohide , Maeda Yoshitomo , Matsumoto Hironori , Senda Atsushi , Takahashi Tadayuki , Tsuboi Yohko , Yamauchi Shigeo , Yuasa Takayuki
Published: March 2014

Suzaku deep observations have discovered two highly significant nonthermal X-ray sources, Suzaku J1804$-$2142 (Src 1) and Suzaku J1804$-$2140 (Src 2), positionally coincident with the unidentified TeV $\gamma$-ray source, HESS J1804$-$216. The X-ray sources are not time variable and show no counterpart in other wavebands, except for the TeV source. Src 1 is unresolved at Suzaku spatial resolution, whereas Src 2 is extended or composed of multiple sources. The X-ray spectra are highly absorbed, hard, and featureless, and are well fitted by absorbed power-law models with best-fit photon indices and absorption columns of $-0.3_{-0.5}^{+0.5}$ and $0.2_{-0.2}^{+2.0} \times 10^{22} \,\mathrm{cm}^{-2}$ for Src 1, and $1.7_{-1.0}^{+1.4}$ and $1.1_{-0.6}^{+1.0} \times 10^{23} \,\mathrm{cm}^{-2}$ for Src 2. The measured X-ray absorption to the latter source is significantly larger than the total Galactic neutral hydrogen column in that direction. The unabsorbed 2–10 keV band luminosities are $7.5 \times 10^{32} (d/5 \,\mathrm{kpc})^2 \,\mathrm{erg} \,\mathrm{s}^{-1}$ (Src 1) and $1.3 \times 10^{33} (d/5 \,\mathrm{kpc})^2 \,\mathrm{erg} \,\mathrm{s}^{-1}$ (Src 2), where $d$ is the source distance. Among the handful of TeV sources with known X-ray counterparts, HESS J1804$-$216 has the largest ratio of TeV $\gamma$-ray to hard X-ray fluxes. We discuss the nature of the emission and propose the Suzaku sources as plausible counterparts to the TeV source, although further observations are necessary to confirm this.
Precision Fe Kα and Fe Kβ Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku
Authors: Yaqoob Tahir , Murphy Kendrah D. , Griffiths Richard E. , Haba Yoshito , Inoue Hajime , Itoh Takeshi , Kelley Richard , Kokubun Motohide , Markowitz Alex , Mushotzky Richard , Okajima Takashi , Ptak Andrew , Reeves James , Serlemitsos Peter J. , Takahashi Tadayuki , Terashima Yuichi
Published: March 2014

We present detailed time-averaged X-ray spectroscopy in the 0.5–10 keV band of the Seyfert 1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometer (XIS). There is an Fe K line emission complex that we model with broad and narrow lines and we show that the intensities of the two components are decoupled at a confidence level $ \gt3\sigma$. The broad line ($\mathrm{EW} = 118^{+32}_{-61} \,\mathrm{eV}$) could originate in an accretion disk (inclined at $ \gt30^{\circ}$). The narrow Fe $\mathrm{K}\alpha$ line ($\mathrm{EW} =163^{+47}_{-26} \,\mathrm{eV}$) is unresolved by the XIS at 99% confidence and likely originates in distant matter. A significant (narrow) Fe $\mathrm{K}\beta$ line is also detected and we describe a new robust method to constrain the ionization state of Fe in the distant line emitter (e.g. the putative obscuring torus). The method does not require any knowledge of possible gravitational and Doppler energy shifts and we deduce that the predominant ionization state of Fe in the distant matter is lower than Fe VIII (at 99% confidence), conservatively taking into account residual calibration uncertainties and theoretical and experimental uncertainties in the Fe K fluorescent line energies. We argue that the narrow Fe $\mathrm{K}\alpha$ and Fe $\mathrm{K}\beta$ lines likely originate in a Compton-thin structure.
The Suzaku High Resolution X-Ray Spectrometer
Authors: Kelley Richard L. , Mitsuda Kazuhisa , Allen Christine A. , Arsenovic Petar , Audley Michael D. , Bialas Thomas G. , Boyce Kevin R. , Boyle Robert F. , Breon Susan R. , Brown Gregory V. , Cottam Jean , DiPirro Michael J. , Fujimoto Ryuichi , Furusho Tae , Gendreau Keith C. , Gochar Gene G. , Gonzalez Oscar , Hirabayashi Masayuki , Holt Stephen S. , Inoue Hajime , Ishida Manabu , Ishisaki Yoshitaka , Jones Carol S. , Keski-Kuha Ritva , Kilbourne Caroline A. , McCammon Dan , Morita Umeyo , Moseley S. Harvey , Mott Brent , Narasaki Katsuhiro , Ogawara Yoshiaki , Ohashi Takaya , Ota Naomi , Panek John S. , Porter F. Scott , Serlemitsos Aristides , Shirron Peter J. , Sneiderman Gary A. , Szymkowiak Andrew E. , Takei Yoh , Tveekrem June L. , Volz Stephen M. , Yamamoto Mikio , Yamasaki Noriko Y.
Published: March 2014

The X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with non-dispersive, high-resolution X-ray spectroscopy. As designed, the instrument covers the energy range 0.3 to 12 keV, which encompasses the most diagnostically rich part of the X-ray band. The sensor consists of a 32-channel array of X-ray microcalorimeters, each with an energy resolution of about 6 eV. The very low temperature required for operation of the array (60 mK) is provided by a four-stage cooling system containing a single-stage adiabatic demagnetization refrigerator, a superfluid-helium cryostat, a solid-neon dewar, and a single-stage, Stirling-cycle cooler. The Suzaku/XRS is the first orbiting X-ray microcalorimeter spectrometer and was designed to last more than three years in orbit. The early verification phase of the mission demonstrated that the instrument worked properly and that the cryogen consumption rate was low enough to ensure a mission lifetime exceeding 3 years. However, the liquid-He cryogen was completely vaporized two weeks after opening the dewar guard vacuum vent. The problem has been traced to inadequate venting of the dewar He and Ne gases out of the spacecraft and into space. In this paper we present the design and ground testing of the XRS instrument, and then describe the in-flight performance. An energy resolution of 6 eV was achieved during pre-launch tests and a resolution of 7 eV was obtained in orbit. The slight degradation is due to the effects of cosmic rays.
AKARI Infrared Imaging of Reflection Nebulae IC4954 and IC4955
Authors: Ishihara Daisuke , Onaka Takashi , Kaneda Hidehiro , Suzuki Toyoaki , Kataza Hirokazu , Sakon Itsuki , Okada Yoko , Doi Yasuo , Fujishiro Naofumi , Fujiwara Hideaki , Ita Yoshifusa , Kii Tuneo , Kim Woojung , Makiuti Sin’itirou , Matsumoto Toshio , Matsuhara Hideo , Murakami Hiroshi , Nakagawa Takao , Ohyama Youichi , Oyabu Shinki , Serjeant Stephen , Shibai Hiroshi , Takagi Toshinobu , TanabÉ Toshihiko , Uemizu Kazunori , Ueno Munetaka , Usui Fumihiko , Wada Takehiko , Watarai Hidenori , Yamamura Issei
Published: March 2014

We present the observations of the reflection nebulae IC4954 and IC4955 region with the Infrared Camera and the Far-Infrared Surveyor (FIS) on board the infrared astronomical satellite AKARI during its performance verification phase. We obtained 7 band images from 7 to 160$\mu $m with higher spatial resolution and higher sensitivities than previous observations. The spatial variation in the mid-infrared color suggests that the star-formation in IC4954/4955 is progressing from south-west to north-east. The FIS 4-band data from 65$\mu $m to 160$\mu $m allow us to correctly estimate the total infrared luminosity from the region, which is about one sixth of the energy emitted from the existing stellar sources. Five candidates for young stellar objects have been detected as point sources for the first time in the 11$\mu $m image and it is suggested that that current star-formation has been triggered by previous star-formation activities. A wide area map of the size of about $1^\circ$ around the IC4954/4955 region was created from the AKARI mid-infrared All-Sky Survey data. Together with the H I 21 cm data, it suggests a large hollow structure of a degree scale, on whose edge the IC4954/4955 region has been created, indicating star formation over three generations in largely different spatial scales.
Hinode's Observational Result on the Saturation of Magnetic Helicity Injected into the Solar Atmosphere and Its Relation to the Occurrence of a Solar Flare
Authors: Magara Tetsuya , Tsuneta Saku
Published: March 2014

This paper is intended to present key features of the evolution toward the onset of a solar flare, using Hinode's observations on the photospheric magnetic field. Hinode can provide the temporal development of the photospheric field as a vector quantity, which shows that magnetic shear is initially developed in a flare-productive active region (AR 10930), and then decreases toward the onset of an X-class flare. The magnetic helicity in this active region first increases rapidly, while it become saturated in the late phase. We explain the physical origin of these features in terms of the emergence of a magnetic flux tube into the solar atmosphere, and investigate how they relate to the occurrence of a flare. We also discuss how the magnetic helicity evolves in different types of flares, showing that its evolution can be used for flare prediction.
Star-Forming Galaxies at z ≈ 0.24 in the Subaru Deep Field and the Sloan Digital Sky Survey
Authors: Morioka Taichi , Nakajima Aki , Taniguchi Yoshiaki , Shioya Yasuhiro , Murayama Takashi , Sasaki Shunji S.
Published: March 2014

We made a search for H$\alpha $ emitting galaxies at z$\approx $ 0.24 in the Subaru Deep Field (SDF) using an archival data set obtained with the Subaru telescope. We carefully selected H$\alpha $ emitters in the narrow-band filter NB816, using $B$, $V$, $R_{\rm C}$, $i^\prime$, and z$^\prime$ broad-band colors. We obtained a sample of 258 emitting galaxies with observed equivalent widths of (H$\alpha $$+$ [NII]6548,6584) greater than 12Å. We also analyzed a sample of H$\alpha $ emitters taken from the Sloan Digital Sky Survey (SDSS) to constrain the luminous end of the H$\alpha $ luminosity function. Using the same selection criteria as those for the SDF, and after excluding AGNs, we obtained 317 H$\alpha $ emitting star-forming galaxies. Combining these two samples of H$\alpha $ emitters found in both SDF and SDSS, we derived an H$\alpha $ luminosity function with best-fit Schechter function parameters of $\alpha $$=$$-$1.31$^{+0.17}_{-0.17}$, log$\phi^{*}$$=$$-$2.46$^{+0.34}_{-0.40}$Mpc$^{-3}$, and log$L^{*}$$=$ 41.99$^{+0.08}_{-0.07}$ergss$^{-1}$. The extinction-corrected H$\alpha $ luminosity density is 4.45$^{+2.96}_{-1.75}$$\times$ 10$^{39}$ergss$^{-1}$Mpc$^{-3}$. Using the Kennicutt relation between the H$\alpha $ luminosity and star-formation rate, the star-formation rate density in the survey volume was estimated at 0.035$^{+0.024}_{-0.014}M_{\odot}$yr$^{-1}$Mpc$^{-3}$. The angular two-point correlation function of H$\alpha $ emitters over 875 arcmin$^2$ at z$=$ 0.24 was well-fitted by a power-law form with $w(\theta)$$=$ 0.047$^{+0.017}_{-0.013} \theta^{-0.66 \pm 0.08}$, corresponding to the correlation function $\xi(r)$$=$ [$r/$(2.6$^{+1.0}_{-0.8}$Mpc)]$^{-1.66\pm0.08}$. The small correlation length of H$\alpha $ emitters may imply a weak clustering of active star-forming galaxies.
Clustering Properties of Low-Luminosity Star-Forming Galaxies at z = 0.24 and 0.40 in the Subaru Deep Field
Authors: Nakajima Aki , Shioya Yasuhiro , Nagao Tohru , Saito Tomoki , Murayama Takashi , Sasaki Shunji S. , Yokouchi Asuka , Taniguchi Yoshiaki
Published: March 2014

We present our analysis on the clustering properties of star-forming galaxies selected by narrow-band excesses in the Subaru Deep Field. Specifically, we focus on H$\alpha $ emitting galaxies at $z$$=$ 0.24 and $z$$=$ 0.40 in the same field, to investigate possible evolutionary signatures of clustering properties of star-forming galaxies. Based on an analysis on 228 H$\alpha $ emitting galaxies with 39.8 $\lt$ log$L$(H$\alpha $) $\lt$ 40.8 at $z$$=$ 0.40, we find that their two-point correlation function can be estimated as $\xi$$=$ ($r/$1.62$^{+0.64}_{-0.50}$Mpc)$^{-1.84\pm0.08}$. This is similar to that of H$\alpha $ emitting galaxies in the same H$\alpha $ luminosity range at $z$$=$ 0.24, $\xi$$=$ ($r/$1.88$^{+0.60}_{-0.49}$Mpc)$^{-1.89 \pm0.07}$. These correlation lengths are smaller than those for a brighter galaxy sample studied by Meneux et al. (2006) in the same redshift range. The evolution of the correlation length between $z$$=$ 0.24 and $z$$=$ 0.40 is interpreted by the gravitational growth of the dark-matter halos.
Detection of Polarimetric Variations Associated with the Shortest Time-Scale Variability in S5 0716+714
Authors: Sasada Mahito , Uemura Makoto , Arai Akira , Fukazawa Yasushi , Kawabata Koji S. , Ohsugi Takashi , Yamashita Takuya , Isogai Mizuki , Sato Shuji , Kino Masaru
Published: March 2014

We present the results of near-infrared and optical observations of the BL Lac object S5 0716$+$714, carried out with the KANATA telescope. S5 0716$+$714 has both a long-term, high-amplitude variability and a short-term variability within one night. The shortest variability (microvariability) time-scale is important for understanding the geometry of jets and the magnetic field, because it provides a possible minimum size of variation sources. Here, we report on the detection of 15-min variability in S5 0716$+$714, which is one of the shortest time scales in optical and near-infrared variations observed in blazars. The detected microvariation had an amplitude of 0.061$\pm$0.005mag in the $V$ band and a blue color of $\Delta$($V-J$) $=$$-$0.025$\pm$0.011. Furthermore, we successfully detected an unprecedented, short time-scale polarimetric variation, which correlated with the brightness change. We revealed that the microvariation had a specific polarization component. The polarization degree of the variation component was higher than that of the total flux. These results suggest that the microvariability originated from a small and local region where the magnetic field was aligned.
AKARI/IRC Deep Survey in the North Ecliptic Pole Region
Authors: wada Takehiko , Matsuhara Hideo , Oyabu Shinki , Takagi Toshinobu , Lee Hyung Mok , Im Myungshin , Ohyama Youichi , Goto Tomotsugu , Pearson Chris P. , White Glenn J. , Serjeant Stephen , Wada Kensuke , Hanami Hitoshi
Published: March 2014

We have made a deep and wide imaging survey with all nine AKARI/IRC bands from 2 to 24$\mu$m within a half degree of the North Ecliptic Pole. The survey covered a circular area of 0.38deg$^2$ centered at RA $=$ 17h56m, Dec $=$ 66°37' where a deep optical multi-band survey has been conducted by Subaru/Suprime-Cam. The 5$\sigma$ sensitivity of the survey for point sources is 11.0, 48, 117, and 275$\mu$Jy at wavelengths 3, 7, 15, and 24$\mu$m, respectively. The survey is limited by sky noise at wavelengths from 7 to 24$\mu$m, and limited by source confusion from 2 to 4$\mu$m. We have also made a point source catalog at each band, consisting of more than 5000 sources with a 50% completeness limit of 93$\mu$Jy at 15$\mu$m. Our results are consistent with the pilot survey at faint fluxes and has better statistical significance at the bright fluxes. This is the first near- and mid-infrared sub-mJy extragalactic survey with contiguous wavelength coverage from 2 to 24$\mu$m and a large band-merged catalogue. It will provide powerful and unique diagnostics of obscured star-formation and AGN activities in the galaxies up to $z=2$.