bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seyfert-Type Dependences of Narrow Emission-Line Ratios and Physical Properties of High-Ionization Nuclear Emission-Line Regions in Seyfert Galaxies
Authors: Nagao Tohru , Murayama Takashi , Taniguchi Yoshiaki 
Published: March 2014

Abstract
In order to examine how narrow emission-line flux ratios depend on the Seyfert type, we compiled various narrow emission-line flux ratios of 355 Seyfert galaxies from the literature. We present in this paper that the intensity of the high-ionization emission lines, [Fe VII]$ \lambda6087$, [Fe X]$ \lambda6374$, and [Ne V]$ \lambda3426$, tend to be stronger in Seyfert 1 galaxies than in Seyfert 2 galaxies. In addition to these lines, [O III]$ \lambda4363$ and [Ne III]$ \lambda3869$, whose ionization potentials are not high ($ &lt; 100 \,\mathrm{eV}$), but whose critical densities are significantly high ($ \gtrsim 10^7 \,\mathrm{cm}^{-3}$), also exhibit the same tendency. On the other hand, the emission-line flux ratios among low-ionization emission lines do not show such a tendency. We point out that the most plausible interpretation of these results is that the high-ionization emission lines arise mainly from highly-ionized, dense gas clouds, which are located very close to nuclei, and thus can be hidden by dusty tori. To examine the physical properties of these highly-ionized dense gas clouds, photoionization model calculations were performed. As a result, we find that the hydrogen density and the ionization parameter of these highly-ionized dense gas clouds are constrained to be $ n_\mathrm{H}&gt; 10^6 \,\mathrm{cm}^{-3}$ and $ U &gt; 10^{-2}$, respectively. These lower limits are almost independent both from the metallicity of gas clouds and from the spectral energy distribution of the nuclear ionizing radiation.
Estimation of Central Black Hole Masses in Low-Luminosity Active Galactic Nuclei
Authors: Awaki Hisamitsu , Terashima Yuichi , Hayashida Kiyoshi , Sakano Masaaki 
Published: March 2014

Abstract
We analyzed six low-luminosity active galactic nuclei (hereafter LLAGNs), which consist of two bright LINERs (low-ionization nuclear emission line region) with broad H$ \alpha$, and of four bright low-luminosity Seyferts observed by the X-ray satellite ASCA. We examined the time variabilities of these targets, and found that most targets show no significant time variabilities, although these galaxies belong to LLAGNs. By applying Fourier analysis to their light curves in the 2–10keV band, we obtained the lower limits of their time variability scales, which correspond to their central black hole masses greater than several times $10^{6}\,{{{M}_{\odot}}}$. Our result suggests that these LLAGNs are harbors of super-massive black holes, but the emitting powers are only $ &lt; 1 \%$ of the Eddington luminosities of the central engines in the LLAGNs due to their small accretion rates. Since a black hole would grow by mass accretion, it is hard to create such a super-massive black hole under a small accretion rate. Therefore, the mass-accretion rates in the past must have been larger than those at present, and the galaxies have probably been as luminous as QSOs. This will be a hint to find out the cause of the lack of QSOs in the local universe.
An X-Ray Emitting Supernova Remnant Candidate, M 33 X-4
Authors: Okada Yuu , Takahashi Hiromitsu , Makishima Kazuo 
Published: March 2014

Abstract
Based on ASCA observations of the Local-Group spiral galaxy M 33, a report is made on the X-ray properties of luminous X-ray source called X-4, which is located in a giant H ii region in M 33. The 0.8-8.0keV spectrum of X-4 is described by a two-component model, consisting of a thin thermal plasma emission with a temperature of $ \sim 1.0 \,\mathrm{keV}$, and a power law emission with a photon index of $ \sim 2.0$. The two spectral components cross over at $ \sim 3.0 \,\mathrm{keV}$. These spectral properties are similar to those of a young supernova remnant (SNR), except that the 0.8-8.0keV luminosity of M 33 X-4, $ \sim 1.0 \times 10^{38} \,\mathrm{erg} \,\mathrm{s}^{-1}$, is considerably higher than those of the SNRs in the Milky Way. There is also evidence of excess absorption, or an over-abundance of $ \alpha$-elements relative to iron. If this source is an SNR, the hard component is thought to be synchrotron radiation from high-energy particles, produced either by shock acceleration, like in SN 1006, or by a central neutron star, like in the Crab Nebula.
CO Survey of Nearby Spiral Galaxies with the Nobeyama 45-m Telescope: I. The Data
Authors: Nishiyama Kohta , Nakai Naomasa 
Published: March 2014

Abstract
We mapped the 12CO($J = 1 -0$) emission along the major and minor axes of disks or bars of 25 nearby galaxies using the Nobeyama 45-m telescope with a spatial resolution of $0.01$–$0.12 D_{25}$ ($D_{25}$: de Vaucouleurs’ diameter), and detected the CO emission at 8–42 positions along each axis. The galaxy sample includes morphological type Sab and Scd as well as barred and nonbarred. These data are useful to statistically study the internal distribution and dynamics of molecular gas in galaxies and to deduce common characteristic properties. In this paper, we describe the sample and observations, present all spectra and measured line parameters, and examine the relations between the global molecular gas mass and the Hubble type, the total mass of the galaxies, and the star-formation rate.
CO Survey of Nearby Spiral Galaxies with the Nobeyama 45-m Telescope: II. Distribution and Dynamics of Molecular Gas
Authors: Nishiyama Kohta , Nakai Naomasa , Kuno Nario 
Published: March 2014

Abstract
We have studied the distribution and dynamics of molecular gas in galaxies by observing CO emission mainly along the major and minor axes of 28 nearby spiral galaxies with the 45-m telescope of the Nobeyama Radio Observatory. The observations showed that the surface density of molecular gas indicates an exponential distribution in the region of the flat (differential) rotation curve for all spiral galaxies. This could be because the radial distribution is determined by gas inflow due to the viscosity of molecular clouds. The surface density of molecular gas in barred galaxies also shows a characteristic distribution in the region of the bar, suggesting gas inflow along the bar by the bar potential and perpendicular to the bar by viscosity. Such a transfer of molecular gas increases the gas density in the central region, probably causing the evolution of the rotation curve, which is determined by the mass distribution, on the time scale of the galaxy age. We compared the radial distribution of the surface density of H I with that of $\mathrm{H}_{2}$, and found same scale length of the exponential distribution in the Virgo galaxies and a much larger scale length in field galaxies for H I. This could be due to a difference in the viscosity coefficient of the H I gas.
A Hyperenergetic CO Shell in the Galactic Center Molecular Cloud Complex
Authors: Oka Tomoharu , Hasegawa Tetsuo , Sato Fumio , Tsuboi Masato , Miyazaki Atsushi 
Published: March 2014

Abstract
We report on the detection of a high-velocity feature, CO 1.27$+$0.01, in the Galactic-center molecular-cloud complex. In our 12CO images taken with the NRO 45 m telescope, CO 1.27$+$0.01 appears as the second prominent high-velocity feature, next to CO 0.02–0.02, having a velocity width of $\Delta V \simeq 100 \,\mathrm{km} \,\mathrm{s}^{-1}$ and a size of $9 \,\mathrm{pc} \times 12 \,\mathrm{pc}$. It seems to consist of two expanding shells with sizes of $\sim 10 \,\mathrm{pc}$. The major shell has a kinetic energy of about an order of magnitude larger than the gravitational energy, indicating that the shell is apparently gravitationally unbound. We propose that CO 1.27$+$0.01 may have been accelerated by a series of supernova explosions which occurred within the last $\sim 6 \times 10^4 \,\mathrm{yr}$. No association of a nonthermal radio continuum source suggests a strong magnetic field ($B \gtrsim 0.4 \,\mathrm{mG}$) in the vicinity of CO 1.27$+$0.01.
Possible Kreutz Sungrazing Comets Found in Historical Records
Authors: Hasegawa Ichiro , Nakano Syuichi 
Published: March 2014

Abstract
In historical records, twenty four candidates of possible Kreutz sungrazing comets have been found, and their times of perihelion passage estimated. Translated original records of comets with presumed ephemerides are given. Some uncertain candidates are also presented. Although already suggested by Marsden (1967, Astron. Jahresber. 67.9133), our calculations on the motions of comets 1882 R1 and 1965 S1 confirm that the progenitor of these comets is a comet that appeared in 1106; some trials on the linkage of sungrazing comets are discussed.
Detection of Eight Molecular Supershells in the Southern Milky Way with NANTEN
Authors: Matsunaga Ken’ichi , Mizuno Norikazu , Moriguchi Yoshiaki , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo 
Published: March 2014

Abstract
We carried out a new CO survey for molecular supershells in the southern Milky Way with NANTEN. We covered an area of $300^{\circ} \lt l \lt 350^{\circ}$ and $-9^{\circ} \lt b \lt 9^{\circ}$ at $4^{\prime}$ or $8^{\prime}$ grid spacings with a 2.$^\prime$6 beamsize. In addition to the disk component at $\vert b\vert \lt 2^{\circ}$, we found numerous filamentary or arc-like CO distributions by inspecting the velocity channel maps. As a result, we identified 8 supershell candidates, 3 of which are associated with CO holes in the galactic disk. Six of the supershells had not been identified by the previous studies, while 2 of them were known from H i and low-resolution CO surveys. The size of the supershells ranges from 100 pc to 450 pc and the average is 230 pc; their age ranges from $2.2 \times 10^6 \;\mathrm{yr}$ to $1.1 \times 10^7 \,\mathrm{yr}$. We note that two of the supershells are also associated with observable indications of supershells at other wavelengths, including H i, far-infrared, soft X-ray, and SNRs. The implications of these findings are discussed in terms of the impact of supershells on star formation in the Galaxy.
A 12CO $J = 1 \hbox{--} 0$) Survey of Molecular Clouds toward the Vela Supernova Remnant with NANTEN
Authors: Moriguchi Yoshiaki , Yamaguchi Nobuyuki , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo 
Published: March 2014

Abstract
The molecular distribution toward the whole extent of the Vela SNR has been obtained at a linear resolution of 0.15 pc in 12CO ($J = 1 \hbox{--} 0$) emission with the NANTEN telescope. The CO distribution is generally anti-correlated with the SNR. The X-ray distribution has a sharp boundary toward the CO clouds, especially in the east, suggesting an interaction between them. There is only weak CO emission in the west, and the X-ray emission extends smoothly toward this direction. This indicates that the absence of dense gas probably allowed hot gas to escape freely. The CO clouds are highly filamentary, exhibiting a spatial correlation with regions of optical shocked features on a large scale. In the north of the SNR, enhanced X-ray emission is found toward network-like optical filaments. We suggest that this enhancement is due to the evaporation of molecular gas by shock heating caused by the interaction between the blast wave and the molecular gas. Comparisons with a few simple theoretical models of SNR evolution and expansion indicate that the clouds are mostly pre-existent, are being accelerated, and are evaporating now.
12CO Molecular Cloud Survey and Global Star Formation in Lupus
Authors: Tachihara Kengo , Toyoda Shuichiro , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo , Neuhäuser Ralph 
Published: March 2014

Abstract
The Lupus star-forming region has been surveyed for molecular clouds in 12CO with the NANTEN radio telescope, and a cloud mass of $1.7 \times 10^{4} \,{{{M}_{\odot}}}$ has been revealed. We were able to detect 105 molecular clouds, most of which are relatively small and of low mass. The members of the Sco OB 2 association and the X-ray detected pre-main-sequence stars (PMSs) are distributed all around this region. The OB stars and the molecular clouds show exclusive distributions. Large fractions of the PMSs are located away from the molecular clouds, and are thus isolated. The origin of the isolated PMSs is discussed. About 40% of the PMSs have candidates of their parent clouds less massive than 20${M}_{\odot}$ within 4 pc, which suggests in-situ star formation in the small clouds and their rapid dissipation. The separations from the PMSs to the clouds are typically larger than those in the Chamaeleon region, probably because of coexisting OB stars. From the cloud structures and the distributions of the OB stars, PMSs, and H i expanding shell, it is suggested that the molecular clouds have been effectively dissipated by the OB stars and a shock wave, which may also have triggered star formation in Lupus and the $\rho$ Oph clouds.
On the Mass Spectrum of Giant Molecular Clouds in the Large Magellanic Cloud
Authors: Fukui Yasuo , Mizuno Norikazu , Yamaguchi Reiko , Mizuno Akira , Onishi Toshikazu 
Published: March 2014

Abstract
Based on a new sensitive survey of the giant molecular clouds (GMCs) in the Large Magellanic Cloud, we derived the mass spectrum for them. In the mass range from $\sim8\times10^4\,{{{M}_{\odot}}}$ to $3\times10^6\,{{{M}_{\odot}}}$, a power law with an index value of $-1.9\pm0.1$ shows the best fit to the data. This is consistent with numerical simulations that explain both the H i and CO clumpy distributions by Wada et al. (2000; ApJ, 540, 797), but is significantly steeper than that of the GMCs in the Galaxy. This may be consistent with the drastic dissipation of the GMCs in the LMC due to higher UV radiation fields than in the Galaxy.
Average Curves of Emissivity of the Highest Pulses in Long and Short Gamma-Ray Bursts
Authors: Liang En-Wei , Xie Guang-Zhong , Su Cheng-Yue 
Published: March 2014

Abstract
The average curves of emissivity (ACEs) of the highest pulses in long and short groups of gamma-ray bursts(GRBs) observed by BATSE on board CGRO have been studied by an alignment method and a wavelet package de-noising technique. A developed pulse-finding has been applied to identify the highest pulses from the profiles of GRBs. A sample including 116 long GRBs and 95 short GRBs was selected. The results show that the ACEs of the pulses in the short group are shorter and narrower than that in the long group. The ACEs of pulses in two groups have a significant difference, which was measured by the K–S test. Compared to the ACEs, the normalized ACEs of the pulses in the two groups seem to be similar. We present a brief discussion of our results. Based on our results and the discussion, we conclude that two groups of bursts may be generated from different sizes of emission regions. These sources likely have an intrinsic difference. However, the emission mechanisms are the same. These results support the most accepted taxonomy of GRBs, and present an interpretation of why two groups of bursts have a notable difference in the burst–s duration, but other observed properties have no distinguishable difference.
Short-Period Noncontact Close Binary Systems. VI. V392 Orionis
Authors: Narusawa Shin-ya , Yamasaki Atsuma , Fukata Mitsuo , Takeda Masao , Nakamura Yasuhisa , Okazaki Akira 
Published: March 2014

Abstract
Photometric and spectroscopic observations in the optical region of the short-period eclipsing binary system V392 Ori (A5 V, $P = 0.6593 \,\mathrm{d}$) were performed and light and radial velocity curves were obtained. The light curves taken at various times are slightly different from one another. Analyses of the light and radial velocity curves yielded photometric and spectroscopic elements of the system. The derived mass function is quite small, $f(M) = 0.0108 \,{{{M}_{\odot}}}$. The masses of the primary and secondary components were found to be 1.2${M}_{\odot}$ and 0.3${M}_{\odot}$, respectively, and the radii are 1.7${R}_{\odot}$ and 0.9${R}_{\odot}$. V392 Ori was found to belong to a group of low-mass binary systems. Due to the semidetached nature of the system, the loss of mass/angular momentum from the system may occasionally occur, inducing a probable effect on the light curves of the system. We compare the system with other low-mass binary systems and discuss the evolutionary status of the system.
A Multi-Band Photometric Study of Tidal Debris in a Compact Group of Galaxies: Seyfert’s Sextet
Authors: Nishiura Shingo , Shioya Yasuhiro , Murayama Takashi , Sato Yasunori , Nagao Tohru , Taniguchi Yoshiaki , Sanders David B. 
Published: March 2014

Abstract
In order to investigate the properties of the prominent tidal debris feature extending to the northeast of a compact group of galaxies, Seyfert’s Sextet, we analyzed multi-band ($U$, $B$, $V$, $VR$, $R$, $I$, $J$, $H$, and $K^{\prime }$) photometric imaging data and obtained the following results: 1) The radial surface brightness distribution of this tidal debris in Seyfert’s Sextet (TDSS) in each band appears to be well approximated by an exponential profile. 2) The observed $B-V$ color of TDSS is similar to those of dwarf elliptical galaxies in nearby clusters. 3) Comparing the spectral energy distribution (SED) of TDSS with theoretical photometric evolution models and with the SED of the stars in the outer part of HCG 79b, we find that its SED is comparable to that of a $\sim 10 \,\mathrm{Gyr}$-old stellar population with solar metallicity, similar to the stellar population in the outer part of HCG 79b. This suggests that TDSS consists of stars that may have been liberated from HCG 79b by strong galaxy interactions, not a pre-existing dwarf galaxy as previously thought.
Observations of SiO Maser Sources within a Few Parsec from the Galactic Center
Authors: Deguchi Shuji , Fujii Takahiro , Miyoshi Makoto , Nakashima Jun-ichi 
Published: March 2014

Abstract
Mapping and monitoring observations of SiO maser sources near the Galactic center were made with the Nobeyama 45-m telescope at 43 GHz. Rectangular mapping an area of approximately $200^{\prime\prime} \times 100^{\prime\prime}$ in a ${30{}^{\mathrm {\prime \prime }}}$ grid, and triangular mapping in a ${20{}^{\mathrm {\prime \prime }}}$ grid toward the Galactic center, resulted in 15 detections of SiO sources; the positions of the sources were obtained with errors of 5 – ${10{}^{\mathrm {\prime \prime }}}$ , except for a few weak sources. Three-year monitoring observations found that the component at $V_\mathrm{lsr} =-27 \,\mathrm{km} \,\mathrm{s}^{-1}$ of IRS 10 EE flared to about 1.5 Jy during 2000 March–May, which was a factor of more than 5 brighter than its normal intensity. Using the radial velocities and positions of the SiO sources, we identified 5 which are counterparts of previously observed OH 1612 MHz sources. The other 10 SiO sources have no OH counterparts, but two were previously detected with VLA, and four are located close to the positions of large-amplitude variables observed at near-infrared wavelengths. A least-squares fit to a plot of velocities versus Galactic longitudes gives a rather high speed for the rotation of the star cluster around the Galactic center. The observed radial-velocity dispersion is roughly consistent with a value obtained before. It was found that all of the SiO sources with OH 1612 MHz counterparts have periods of light variation longer than 450 days, while SiO sources without OH masers often have periods shorter than 450 days. This fact suggests that lower-mass AGB stars are more often detected in SiO masers than in the OH 1612 MHz line.
Peak Frequency of the Synchrotron Emission and Classificatory Criteria of BL Lacertae Objects
Authors: Dong Yun-Ming , Mei Dong-Cheng , Liang En-Wei 
Published: March 2014

Abstract
In this short paper, we quantitatively consider how the peak frequency of the synchrotron emission can be used to distinguish RBLs and XBLs. A sample of RBLs and XBLs presented by Sambruna et al. (1996, AAA065.159.120) was employed and the peak frequency, $ \nu_{\mathrm{p}}$, of the synchrotron emission of each source was calculated by considering the proper physical origin of the X-ray emission for different classes of BL Lac objects. A plot of $ \alpha_{\mathrm{rx}} \hbox{--} \log \nu_{\mathrm{p}}$ can be divided into four different regions by lines of $ \alpha_{\mathrm{rx}} = 0.75$ and $ \log \nu_{\mathrm{p}} = 14.7 \pm 0.4$. All RBL-like objects, defined by $\alpha_{\mathrm{rx}} \gt 0.75$$ \alpha_{\mathrm{rx}} \gt 0.75$, are located in the upper-left region, while all XBL-like objects, defined by $ \alpha_{\mathrm{rx}} \leq 0.75$, are inside the lower-right region. No sources are in the lower-left and upper-right regions, suggesting that the classificatory criteria in terms of the peak frequency should be $ \log \nu_{\mathrm{p}} = 14.7 \pm 0.4$. This provides evidence supporting what Giommi et al. (1995, AAA063.158.163) proposed: RBL-like and XBL-like objects can be distinguished by the difference in the peak frequency of the synchrotron emission. The sometime confusing and observationally dependent RBL–XBL terminology should be replaced by the more physical LBL–HBL one.
Radial Distributions of the HCN/CO Ratio in Nearby CO Bright Galaxies
Authors: Sorai Kazuo , Nakai Naomasa , Kuno Nario , Nishiyama Kohta 
Published: March 2014

Abstract
Simultaneous observations of HCN and CO lines were made along the major axes of six nearby CO bright galaxies with the Nobeyama 45-m telescope. The beam-averaged HCN/CO ratios are 0.01 to 0.1. The distributions of the HCN/CO ratio along the major axes (and the minor axis for M 51) show different patterns from one galaxy to another. By adding data obtained from the outer disk, however, we found gradual decreases in the HCN and CO intensities and the HCN/CO ratio with increasing radius in M 51 from the nuclear region to 3 kpc, similar to our previous result for NGC 253. The HCN/CO ratio is very sensitive to the observing beam size on a linear scale. The ratio, which reflects the fraction of dense molecular gas, correlates with the star-formation activity derived from the far-infrared luminosity.