bluuebunny/crossref_metadata_2025_split huggingface dataset:
An AKARI Search for Intracluster Dust of Globular Clusters
Authors: Matsunaga Noriyuki , Mito Hiroyuki , Nakada Yoshikazu , Fukushi Hinako , TanabÉ Toshihiko , Ita Yoshifusa , Izumiura Hideyuki , Matsuura Mikako , Ueta Toshiya , Yamamura Issei 
Published: March 2014

Abstract
We report on observations of 12 globular clusters with the Far-Infrared Surveyor (FIS) aboard the AKARI satellite. Our goal is to search for emission from cold dust within clusters. We detected diffuse emissions toward NGC6402 and 2808, but the IRAS 100$\mu$m maps show the presence of strong background radiation. They are likely to have been emitted from the Galactic cirrus. We also detected 28 point-like sources mainly in WIDE-S images (90$\micron$). At least several of them are not associated with clusters, but background galaxies identified in external catalogs. We present the spectral energy distributions (SEDs) by combining near-and-mid infrared data obtained with the Infrared Camera (IRC), if possible. Those SEDs suggest that most of the point sources are background galaxies. For most of the other clusters, we have confirmed a lack of intracluster dust. We evaluated the upper limits of the intracluster dust mass to be between 10$^{-5}$ and 10$^{-3}\MO$, depending on the dust temperature. The inferred lifetime of the intracluster dust is shorter than 5Myr ($T_{\mathrm{d}}$$=$ 70K) or 50Myr (35K). Such a short lifetime indicates some mechanism(s) are at work to remove the intracluster dust. We also discuss its impact on the chemical evolution of globular clusters.
Spatial Distributions of Dust and Polycyclic Aromatic Hydrocarbons in the Nearby Elliptical Galaxy NGC4589 Observed with AKARI
Authors: Kaneda Hidehiro , Suzuki Toyoaki , Onaka Takashi , Okada Yoko , Sakon Itsuki 
Published: March 2014

Abstract
We report on near- to far-infrared (IR) observations of the nearby elliptical galaxy NGC4589 by AKARI. NGC4589 has a complex stellar rotation field with a position angle difference of 45$^{\circ}$ between the kinematic and morphological axes, although its morphology shows a smooth optical profile that closely follows the de Vaucouleurs law. The galaxy has a minor-axis dust lane, which is twisted toward the main stellar rotation. These properties strongly support that the galaxy is a relatively old merger remnant. We have obtained the spatial distributions of dust from far-IR emission and near-IR absorption, separately. We have also estimated the distribution of polycyclic aromatic hydrocarbons (PAHs) from the difference between images in the mid-IR bands. The spatial distributions of the dust and PAHs resemble each other, both showing significant deviations from the smooth stellar distribution. They extend to the main stellar rotation and the direction of the twisted inner dust lane, thus following the relics of the merger. Therefore, a large fraction of the dust and PAHs in NGC4589 are likely to originate from a past merger event.
Systematic Infrared 2.5—5μm Spectroscopy of Nearby Ultraluminous Infrared Galaxies with AKARI
Authors: Imanishi Masatoshi , Nakagawa Takao , Ohyama Yoichi , Shirahata Mai , Wada Takehiko , Onaka Takashi , Oi Nagisa 
Published: March 2014

Abstract
We report on the results of systematic infrared 2.5-5$\mu$m spectroscopy of 45 nearby ultraluminous infrared galaxies (ULIRGs) at $z \lt$ 0.3 using AKARI IRC. This paper investigates whether the luminosities of these ULIRGs are dominated by starburst activity, or alternatively, whether optically elusive buried active galactic nuclei (AGNs) are energetically important, based on the strengths of 3.3$\mu$m polycyclic aromatic hydrocarbon (PAH) emission and dust absorption features at 3-4$\mu$m. Because of the AKARI IRC's spectroscopic capability in the full 2.5-5$\mu$m wavelength range, we can apply this energy diagnostic method to ULIRGs at $z\gt$ 0.15. We estimate the intrinsic luminosities of extended (several kpc), modestly obscured ($A_{V} \lt$ 15mag) starburst activity based on the observed 3.3$\mu$m PAH emission luminosities measured in AKARI IRC slitless spectra, and confirm that such starbursts are energetically unimportant in nearby ULIRGs. In roughly half of the observed ULIRGs classified optically as non-Seyferts, we find signatures of luminous buried AGNs. The fraction of ULIRGs with detectable buried AGN signatures increases with increasing infrared luminosity. Our overall results support the scenario that luminous buried AGNs are important in many ULIRGs at $z \lt$ 0.3 classified optically as non-Seyferts, and that the optical undetectability of such buried AGNs occurs merely because of a large amount of nuclear dust, which can make the sightline of even the lowest dust column density opaque to the ionizing radiation of the AGNs.
Galaxy Clusters at 0.9 &lt; z &lt; 1.7 in the AKARI NEP Deep Field
Authors: Goto Tomotsugu , Hanami Hitoshi , Im Myungshin , Imai Koji , Inami Hanae , Ishigaki Tsuyoshi , Mok Lee Hyung , Matsuhara Hideo , Nakagawa Takao , Ohyama Youichi , Oyabu Shinki , Pearson Chris P. , Takagi Toshinobu , Wada Takehiko 
Published: March 2014

Abstract
There is a huge gap between the properties of red-sequence selected massive galaxy clusters at $z\lt1$ and Lyman-break selected proto-clusters at $z\gt3$. It is important to understand when and how the $z\gt3$ proto-clusters evolve into passive clusters at $z\lt1$. We aim to fill this cluster desert by using space-based N4 (4$\mu$m) imaging with AKARI. The $z'-$N4 color is a powerful separator of cluster galaxies at $z$$\gt$ 1, taking advantage of the 4000Å break and the 1.6$\mu$m bump. We carefully selected 16 promising cluster candidates at 0.9 $\lt$$z$$\lt$ 1.7, which all show an obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared $S_{15\micron}/S_{9\micron}$ flux ratio is an extinction-free indicator of galaxy star-formation activity due to the redshifted PAH emission lines (6.2, 7.7, and 8.6$\mu$m). We show statistically that the cluster galaxies have a lower $S_{15\micron}/S_{9\micron}$ flux ratio than do field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9 $\lt$$z$$\lt$ 1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.
Identification of Potential Weak Target Radio Quasars for ASTRO-G In-Beam Phase-Referencing
Authors: Frey Sándor , GabÁnyi Krisztina Éva , Asaki Yoshiharu 
Published: March 2014

Abstract
We apply an efficient selection method to identify potential weak Very Long Baseline Interferometry (VLBI) target quasars simply using optical (SDSS) and low-resolution radio (FIRST) catalogue data. Our search is restricted to within 12 from known compact radio sources that are detectable as phase-reference calibrators for ASTRO-G at 8.4 GHz frequency. These calibrators have estimated correlated flux density $&gt;$20 mJy on the longest ground–space VLBI baselines. The search radius corresponds to the primary beam size of the ASTRO-G antenna. We show that $\sim$20 quasars with at least mJy-level expected flux density can be pre-selected as potential in-beam phase-reference targets for ASTRO-G at 8.4 GHz frequency. Most of them have never been imaged with VLBI. The sample of these dominantly weak sources offers a good opportunity to study their radio structures with unprecedented angular resolution provided by Space VLBI. The method of in-beam phase-referencing is independent from the ability of the orbiting radio telescope to do rapid position-switching manoeuvres between the calibrators and the nearby reference sources, and less sensitive to the satellite orbit determination uncertainties.
A Large-Scale 13CO Mapping of the W 49 A Molecular Cloud Complex
Authors: Miyawaki Ryosuke , Hayashi Masahiko , Hasegawa Testuo 
Published: March 2014

Abstract
We present $^{13}$CO ($J$$=$ 1-0) and C$^{18}$O ($J$$=$ 1-0) maps of the W 49 A molecular cloud complex observed at a resolution of 17$''$ (HPBW). Fourteen features (MHH-1 to MHH-14) were identified in the $^{13}$CO velocity channel maps, most of them distributed within an area of 6$'$ (20 pc) in diameter with their total mass amounting to 1.7 $\times$ 10$^{6}M_\odot$. The features have a three-dimensional velocity dispersion of 8 km s$^{-1}$, which leads to a mean free time per feature of 10$^{6}$yr. This suggests that they are interacting one another in a region of $\sim$20 pc in diameter. The feature MHH-1, which corresponds to W 49 N, is unique in that it exhibits a large velocity width (15 km s$^{-1}$ FWHM) and is compact in size (2.3 pc $\times$ 3.0 pc FWHM), while containing a large mass of 2.4 $\times$ 10$^{5}M_\odot$. This indicates that the free-fall time of MHH-1 is on the order of 10$^{5}$yr, an order of magnitude smaller than that of the entire complex. It has turned out that MHH-1 has a smaller spatial width at $V_{\rm LSR}$$\lesssim$ 8 km s$^{-1}$ than at $\gtrsim$8 km s$^{-1}$. This result, together with the line-profile characteristics of various optically thin lines, suggests that at least two massive clouds with different radial velocities exist toward MHH-1. The massive compact feature may have been produced by the interaction of the two different velocity clouds.
A New Mechanism for Massive Binary Black-Hole Evolution
Authors: Hayasaki Kimitake 
Published: March 2014

Abstract
It is still unknown how a binary black hole (BBH) evolves after its semi-major axis has reached the sub-parsec scale, where dynamical friction with neighboring stars is no longer effective (the so-called final-parsec problem). In this paper, we propose a new mechanism by which a massive BBH can naturally coalesce within a Hubble time. We consider the evolution of a BBH with a triple disk composed of an accretion disk around each black hole and one circumbinary disk surrounding them. While the circumbinary disk removes the orbital angular momentum of the BBH via a binary-disk resonant interaction, the mass transfer from the circumbinary disk to each black hole adds some fraction of its angular momentum to the orbital angular momentum of the BBH. We find that there is a critical value of the mass-transfer rate where extraction of the orbital angular momentum from the BBH is balanced with the addition of orbital angular momentum to the BBH. The semi-major axis of the BBH decays with time, whereas the orbital eccentricity of the BBH grows with time, if the mass-transfer rate is smaller than the critical one, and vice versa. Its evolutionary timescale is characterized by the product of the viscous timescale of the circumbinary disk and the ratio of the total black-hole mass to the mass of the circumbinary disk. Most massive BBHs are able to merge within a Hubble time by the proposed mechanism, which helps to solve the final parsec problem.
Correlations between Flare Parameters and Magnetic Parameters in Solar Flares
Authors: Yamamoto Tetsuya T. , Sakurai Takashi 
Published: March 2014

Abstract
We investigated correlations between flare parameters and magnetic parameters by picking up the largest and smaller flares in each sample region. The flare parameters that we used were the X-ray peak flux, characteristic duration time, and X-ray energy. These values were derived from Geostationary Operational Environmental Satellites (GOES) X-ray light curves (1–8Å). The magnetic parameters used were the averaged longitudinal field strength, averaged shear field strength, and characteristic length of flare ribbons. These magnetic parameters were derived from flaring areas. We used vector magnetograms obtained with the Solar Flare Telescope (National Astronomical Observatory of Japan) and SoHO/MDI (Michelson Doppler Imager) magnetograms. In this paper the regionally largest flare is defined as the flare whose X-ray peak flux exceeds one-fifth of the X-ray peak flux of the most intense flare in each region, and all the other flares are defined as smaller flares. From 1997 to 2003, we selected 20 flares as the regionally largest flares and 15 flares as smaller flares. We found that the X-ray peak flux of the regionally largest flares has definite correlations with the magnetic parameters, and the characteristic duration time has a definite correlation only with the characteristic length of flare ribbons. The regionally largest flares and smaller flares show different relations between the flare parameters and the magnetic parameters. They show, on the other hand, a single relation between the X-ray energy and the magnetic free energy index derived from the photospheric magnetic parameters.
Proper Motions with Subaru I. Methods and a First Sample in the Subaru Deep Field
Authors: Richmond Michael W. , Morokuma Tomoki , Doi Mamoru , Komiyama Yutaka , Yasuda Naoki , Okamura Sadanori , Gal-Yam Avishay 
Published: March 2014

Abstract
We search for stars with proper motions in a set of twenty deep Subaru images, covering about 0.28 square degrees to a depth of $i^\prime$$\simeq$ 25, taken over a span of six years. In this paper, we describe in detail our reduction and techniques to identify moving objects. We present a first sample of 99 stars with motions of high significance, and discuss briefly the populations from which they are likely drawn. Based on photometry and motions alone, we expect that 9 of the candidates may be white dwarfs. We also find a group of stars which may be extremely metal-poor subdwarfs in the halo.
Deep 15 $\mu$m AKARI Observations in the CDFS: Estimating Dust Luminosities for a MIR-Selected Sample and for Lyman Break Galaxies and the Evolution of LdustLUV with the Redshift
Authors: Burgarella Denis , Buat Véronique , Takeuchi Tsutomu T. , Wada Takehiko , Pearson Chris 
Published: March 2014

Abstract
Deep observations of the Chandra Deep Field South have been secured at 15$\mu$m with AKARI/IRC infrared space telescope. From these observations, we define a sample of mid infrared-selected galaxies at 15$\mu$m and we also obtain 15$\mu$m flux densities for a sample of Lyman Break Galaxies at $z$$\sim $ 1 already observed at 24$\mu$m with Spitzer/MIPS. Number counts for the mid infrared-selected sample show a bump around a 15$\mu$m flux density of 0.2 mJy that can be attributed to galaxies at $z$$\gt$ 0.4 and at $z$$\gt$ 0.8 for the fainter part of the bump. This bump seems to be shifted as compared to other works and a possible origin can be the Cosmic variance. On the two above samples at $z$$\sim $ 1 we have tested the validity of the conversions from luminosities $\nu f_{\nu}$ at 8$\mu$m to total dust luminosities by comparing with luminosities estimated from 12$\mu$m data used as a reference. Some calibrations seem better when compared to $L_{\rm dust}$ evaluated from longer wavelength luminosities. We also find that the rest-frame 8$\mu$m luminosities provide good estimates of $L_{\rm dust}$. By comparing our data to several libraries of spectral energy distributions, we find that models can explain the diversity of the observed $f_{24} / f_{15}$ ratio quite reasonably. However, when we analyse the luminosity dependence of this ratio, we find important discrepancies. Finally, we revisit the evolution of $L_{\rm dust} / L_{\rm UV}$ ratio with the redshift $z$ by re-calibrating previous $L_{\rm dust}$ at $z$$\sim $ 2 based on our results and added new data points at higher redshifts. The decreasing trend is amplified as compared to the previous estimate.
No Evidence for Variability of Intervening Absorption Lines toward GRB 060206: Implications for the Mg ii Incidence Problem
Authors: Aoki Kentaro , Totani Tomonori , Hattori Takashi , Ohta Kouji , Kawabata Koji S. , Kobayashi Naoto , Iye Masanori , Nomoto Ken’ichi , Kawai Nobuyuki 
Published: March 2014

Abstract
We examined the variability of absorption line strength of intervening systems along the line of sight to GRB 060206 at z$=$ 4.05, utilizing low-resolution optical spectra obtained by the Subaru telescope from six to ten hours after the burst. Strong variabilities of Fe ii and Mg ii lines at z$=$ 1.48 during $t$$=$ 5–8 hr have been reported for this GRB, and those have been used to support the idea of clumpy Mg ii cloudlets, which was originally proposed to explain the anomalously high incidence of Mg ii absorbers in the GRB spectra compared to quasars. However, our spectra with a higher signal-to-noise ratio do not show any evidence for variability in $t$$=$ 6–10 hr. There is a clear discrepancy between our data and those of Hao et al. (2007, ApJ, 659, L99) in the overlapping time interval. Furthermore, the line strengths in our data are in agreement with those observed at $t$$\sim$ 2 hr by Thöne et al. (2008, A&A, 489, 37). We also detected Fe ii and Mg ii absorption lines for a system at z$=$ 2.26; these lines do not show evidence for variability either. Therefore, we conclude that there is no strong evidence for the variability in the intervening absorption lines toward GRB 060206, offering poor support for the Mg ii cloudlet hypothesis by the GRB 060206 data.
Two Types of Magnetohydrodynamic Sheath Jets
Authors: Kaburaki Osamu 
Published: March 2014

Abstract
Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double-layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma being balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature decreases like a virial one, and neither the pressure-gradient nor the MHD forces, which are both determined consistently, cannot completely overcome the gravity, even at infinity. The second type is realized under an isothermal situation, and the gravity is cancelled exactly by the pressure-gradient force. Hence, the jets of this type are accelerated purely by the MHD force. It is also suggested that these two types correspond, respectively, to the jets from type I and II radio galaxies in the Fanaroff-Riley classification.
A Large Expanding Molecular Arc in the Sagittarius B1 Complex
Authors: Tanaka Kunihiko , Oka Tomoharu , Nagai Makoto , Kamegai Kazuhisa 
Published: March 2014

Abstract
Results of molecular line observations toward the Sagittarius B1 complex are reported. Maps of the HCN, HCO$^+$ and SiO J$=$ 1–0 emissions were taken with the NRO 45-m telescope. With these data, combined with the ASTE CO J$=$ 3–2 survey data, we have investigated the spatial structure, kinematics and physical conditions of two peculiar molecular features: CO0.55$+$0.07 and SiO0.56$-$0.01. The CO arc, CO0.55$+$0.07, shows clear expanding motion with sizes of 8.5 $\times$ 6.8 pc$^2$ and an expansion velocity of 40 km s$^{-1}$. The SiO shell, SiO0.56$-$0.01, has a size of 3.0 $\times$ 3.4 pc$^2$, and surrounds an X-ray Fe line source, G0.570$-$0.018. The mass and the kinetic energy of CO0.55$+$0.07 are estimated to be 10$^{5.5}{M_\odot}$ and 10$^{51.5}$erg, respectively. The kinetic energy of SiO0.56$-$0.01 is $\sim$10$^{50.4}$erg. An LVG analysis shows that the typical density and kinetic temperature are 10$^{3.8}$cm$^{-3}$ and 28 K, respectively. High-density clumps with a density of 10$^{4.0{-}4.5}$cm$^{-3}$ associated with CO0.55$+$0.07 and SiO0.56$-$0.01 have been found, supporting the idea that they consist of swept-up material. The huge kinetic energy of CO0.55$+$0.07 is considered to be injected by a series of supernova explosions that took place within $\sim$2 $\times$ 10$^{5}$yr, which would suggest that it is a ‘bubble’ created by a massive stellar cluster, whose mass is estimated to be 10$^{3.5{-}4.5}{M_\odot}$. The origin of SiO0.56$-$0.01 is rather unclear, but we suggest that it could be related to the X-ray source G0.570$-$0.018.
CCD Photometry of a Newly Confirmed SU UMa-Type Dwarf Nova, NSV 4838
Authors: Imada Akira , Yasuda Tatsuki , Omodaka&gt; Toshihiro , Oizumi Shota , Yamamoto Hiroyuki , Tanada Shunsuke , Arao Yoshihiro , Kodama Kie , Suzuki Miho , Matsuo Takeshi , Maehara Hiroyuki , Kato Taichi , Sugiyasu Kei , Moritani Yuuki , Sumiyoshi Masanao , Nakajima Kazuhiro , Pietz Johen , Yanagisawa Kenshi , Nogami Daisaku 
Published: March 2014

Abstract
We present time-resolved CCD photometry of a dwarf nova, NSV 4838 (UMa 8, SDSS J102320.27$+$440509.8), during 2005 June and 2007 February outbursts. The two light curves showed superhumps with mean periods of 0.0699(1)d for the 2005 outburst and 0.069824(83)d for the 2007 outburst. Using its known orbital period of 0.0678 d, we estimated the mass ratio of the system to be $q$$=$ 0.13 based on an empirical relation. Although the majority of SU UMa-type dwarf novae having similar superhump periods show negative period derivatives, we found that the superhump period increased at $\dot{P}/P_{\rm sh}$$=$$+$7($+$3, $-$4) $\times$ 10$^{-5}$ during the 2007 superoutburst. We also investigated long-term light curves of NSV 4838, from which we derived 340 d as a supercycle of this system.
Suzaku Observation Adjacent to the South End of the Radio Arc
Authors: Fukuoka Ryosuke , Koyama Katsuji , Ryu Syukyo G. , Tsuru Takeshi Go 
Published: March 2014

Abstract
Suzaku observed the Galactic center region near the Radio Arc at $\sim$20$^\prime$; southeast of Sagittarius A*. In an 18$^\prime$ × 18$^\prime$ field of view, we found four distinct X-ray sources: a bright star and a diffuse source associated with star clusters in the soft band (0.5–2.0 keV), a small clump in a higher energy band (4–6 keV), and a peculiar clump in the 6.4 keV line band. The latter two clumps are located at the south end of the Radio Arc. This paper reports on the results, and discusses the origin of these X-ray sources, with a particular emphasis on small clumps.
Direct Observation of the Extended Molecular Atmosphere of $o$ Ceti by Differential Spectral Imaging with an Adaptive Optics System
Authors: Takami Hideki , Goto Miwa , Gaessler Wolfgang , Hayano Yutaka , Iye Masanori , Kamata Yukiko , Kanzawa Tomio , Kobayashi Naoto , Minowa Yosuke , Oya Shin , Pyo Tae-Soo , Saint-Jacques David , Takato Naruhisa , Terada Hiroshi , Tokunaga Alan T. , Tsuji Takashi 
Published: March 2014

Abstract
We present new measurements of the diameter of $o$ Ceti (Mira) as a function of wavelength in the 2.2$\mu$m atmospheric window using the adaptive optics system and the infrared camera and spectrograph mounted on the Subaru Telescope. We found that the angular size of the star at the wavelengths of CO and H$_2$O absorption lines were up to twice as large as the continuum photosphere. This size difference is attributable to optically thick CO and H$_2$O molecular layers surrounding the photosphere. This measurement is the first direct differential spectroscopic imaging of stellar extension that resolves individual molecular lines with high spectral-resolution observations. This observation technique is extremely sensitive to differences in spatial profiles at different wavelengths; we show that a difference in diameter much smaller than the point spread function can be measured.