70 research outputs found
A Dynamical Study of Galaxies in the Hickson Compact Groups
In order to investigate dynamical properties of spiral galaxies in the
Hickson compact groups (HCGs), we present rotation curves of 30 galaxies in 20
HCGs. We found as follows. 1) There is not significant relation between
dynamical peculiarity and morphological peculiarity in HCG spirals. 2) There is
no significant relation between the dynamical properties and the frequency
distribution of nuclear activities in HCG spirals. 3) There are no significant
correlations between the dynamical properties of HCG spirals and any group
properties (i.e., the size, the velocity dispersion, the galaxy number density,
and the crossing time). 4) Asymmetric and peculiar rotation curves are more
frequently seen in the HCG spirals than in field spirals and in cluster ones.
However, this tendency is more obviously seen in late-type HCG spirals. These
results suggest that the dynamical properties of HCG spirals do not strongly
correlate with the morphology, the nuclear activity, and the group properties.
Our results also suggest that more frequent galaxy collisions occur in the HCGs
than in the field and in the clusters.Comment: 24 pages test (aasms4 LaTeX), 50 page tables (aasms4 LaTeX), and 16
Postscript figures, Accepted for The Astronomical Journa
The Nuclear Activity of the Galaxies in the Hickson Compact Groups
In order to investigate the nuclear activity of galaxies residing in compact
groups of galaxies, we present results of our optical spectroscopic program
made at Okayama Astrophysical Observatory. We have performed optical
spectroscopy of 69 galaxies which belong to 31 Hickson Compact Groups (HCGs) of
Galaxies. Among them, three galaxies have discordant redshifts. Further,
spectral quality is too poor to classify other three galaxies. Therefore, we
describe our results for the remaining 63 galaxies.
Our main results are summarized below. (1) We have found in our sample; 28
AGN, 16 HII nuclei, and 19 normal galaxies which show no emission line. We used
this HCG sample for statistical analyses. (2) Comparing the frequency
distributions of activity types between the HCGs and the field galaxies whose
data are taken from Ho, Filippenko, & Sargent (382 field galaxies), we find
that the frequency of HII nuclei in the HCGs is significantly less than that in
the field. However, this difference may be due to selection bias that our HCG
sample contains more early-type galaxies than the field, because it is known
that HII nuclei are rarer in early-type galaxies than in later ones. (3)
Applying correction this morphological bias to the HCG sample, we find that
there is no statistically significant difference in the frequency of occurrence
of emission-line galaxies between the HCGs and the field. This implies that the
dense galaxy environment in the HCGs does not affect triggering both the AGN
activity and the nuclear starburst. We discuss some implications on the nuclear
activity in the HCG galaxies.Comment: 33 pages (3 aasms4 LaTeX files), 5 figures (5 Postscript files:
excluded Figure 1), Accepted for publication in The Astronomical Journa
Subaru Spectroscopy of the Gravitational Lens HST 14176+5226: Implications for a Large Cosmological Constan
We present new optical spectroscopy of the lens elliptical galax in the
``Einstein Cross'' lens system HST 14176+5226, using the Faint Object Camera
and Spectrograph (FOCAS) of the Subaru t Our spectroscopic observations are
aimed at measuring the stella dispersion of the lens galaxy, located at high
redshift of z_L= as an important component to lens models. We have measured
this 230 +- 14 km s^{-1} (1 sigma) inside 0.35 effective radi based on the
comparison between the observed galaxy spectrum and templates of three G-K
giants by means of the Fourier cross-corr To extract the significance of this
information on the geometry universe which also affects the lensing of the
background image, to fit three different lens models to the available data of
the Provided that the lens galaxy has the structural and dynamical p (i.e., its
radial density profile, core radius, and velocity ani similar to those of local
elliptical galaxies, we calculate the function for the simultaneous
reproduction of both the observed and newly measured velocity dispersion of the
lens. Although the interval depends rather sensitively on the adopted lens
models o parameters, our experiments suggest the larger likelihood for a
cosmological constant, Omega_Lambda: formal 1 sigma lower Omega_Lambda in the
flat universe ranges 0.73 to 0.97, where lower limit is basically unavailable.
This method for determinin model is thus dependent on lens models but is
insensitive to oth ambiguities, such as the dust absorption or the evolutionary
eff galaxies. Exploring spectroscopic observations of more lens gala redshift
may minimize the model uncertainties and thus place a m constraint on
Omega_Lambda.Comment: 23 pages, 5 figures, accepted for publication in The Astronomical
Journa
Synthesis of Nitrogen-Doped Carbon Nanocoils with Adjustable Morphology using Ni–Fe Layered Double Hydroxides as Catalyst Precursors
Nitrogen-doped carbon nanocoils (CNCs) with adjusted morphologies were synthesized in a one-step catalytic chemical vapour deposition (CVD) process using acetonitrile as the carbon and nitrogen source. The nickel iron oxide/nickel oxide nanocomposites, which were derived from nickel–iron layered double hydroxide (LDH) precursors, were employed as catalysts for the synthesis of CNCs. In this method, precursor-to-catalyst transformation, catalyst activation, formation of CNCs, and nitrogen doping were all performed in situ in a single process. The morphology (coil diameter, coil pitch, and fibre diameter) and nitrogen content of the synthesized CNCs was individually adjusted by modulation of the catalyst composition and CVD reaction temperature, respectively. The adjustable ranges of the coil diameter, coil pitch, fibre diameter, and nitrogen content were confirmed to be approximately 500±100 nm, 600±100 nm, 100±20 nm, and 1.1±0.3 atom%, respectively
Low- and Medium-Dispersion Spectropolarimetry of Nova V475 Sct (Nova Scuti 2003): Discovery of an Asymmetric High-Velocity Wind in a Moderately Fast Nova
We present low-resolution () and medium-resolution ()
spectropolarimetry of Nova V475 Sct with the HBS instrument, mounted on the
0.91-m telescope at the Okayama Astrophysical Observatory, and with FOCAS,
mounted on the 8.2-m Subaru telescope. We estimated the interstellar
polarization toward the nova from the steady continuum polarization components
and H line emission components. After subtracting the interstellar
polarization component from the observations, we found that the H
emission seen on 2003 October 7 was clearly polarized. In the polarized flux
spectrum, the H emission had a distinct red wing extending to km s and a shoulder around km s, showing a
constant position angle of linear polarization \theta_{\rm *}\simeq
155\arcdeg\pm 15\arcdeg. This suggests that the nova had an asymmetric outflow
with a velocity of km s or more, which is six
times higher than the expansion velocity of the ionized shell at the same
epoch. Such a high-velocity component has not previously been reported for a
nova in the `moderately fast' speed class. Our observations suggest the
occurrence of violent mass-loss activity in the nova binary system even during
the common-envelope phase. The position angle of the polarization in the
H wing is in good agreement with that of the continuum polarization
found on 2003 September 26 (--0.6 %), which disappeared
within the following 2 d. The uniformity of the PA between the continuum
polarization and the wing polarization on October 7 suggests that the axis of
the circumstellar asymmetry remained nearly constant during the period of our
observations.Comment: 27 pages, 7 figures, accepted for publication in A
Current Performance and On-Going Improvements of the 8.2 m Subaru Telescope
An overview of the current status of the 8.2 m Subaru Telescope constructed
and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of
Japan is presented. The basic design concept and the verified performance of
the telescope system are described. Also given are the status of the instrument
package offered to the astronomical community, the status of operation, and
some of the future plans. The status of the telescope reported in a number of
SPIE papers as of the summer of 2002 are incorporated with some updates
included as of 2004 February. However, readers are encouraged to check the most
updated status of the telescope through the home page,
http://subarutelescope.org/index.html, and/or the direct contact with the
observatory staff.Comment: 18 pages (17 pages in published version), 29 figures (GIF format),
This is the version before the galley proo
Unexpected A-form formation of 4′-thioDNA in solution, revealed by NMR, and the implications as to the mechanism of nuclease resistance
Fully modified 4′-thioDNA, an oligonucleotide only comprising 2′-deoxy-4′-thionucleosides, exhibited resistance to an endonuclease, in addition to preferable hybridization with RNA. Therefore, 4′-thioDNA is promising for application as a functional oligonucleotide. Fully modified 4′-thioDNA was found to behave like an RNA molecule, but no details of its structure beyond the results of circular dichroism analysis are available. Here, we have determined the structure of fully modified 4′-thioDNA with the sequence of d(CGCGAATTCGCG) by NMR. Most sugars take on the C3′-endo conformation. The major groove is narrow and deep, while the minor groove is wide and shallow. Thus, fully modified 4′-thioDNA takes on the A-form characteristic of RNA, both locally and globally. The only structure reported for 4′-thioDNA showed that partially modified 4′-thioDNA that contained some 2′-deoxy-4′-thionucleosides took on the B-form in the crystalline form. We have determined the structure of 4′-thioDNA in solution for the first time, and demonstrated unexpected differences between the two structures. The origin of the formation of the A-form is discussed. The remarkable biochemical properties reported for fully modified 4′-thioDNA, including nuclease-resistance, are rationalized in the light of the elucidated structure
Prime Focus Spectrograph (PFS) for the Subaru Telescope: Overview, recent progress, and future perspectives
PFS (Prime Focus Spectrograph), a next generation facility instrument on the
8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed,
optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394
reconfigurable fibers will be distributed over the 1.3 deg field of view. The
spectrograph has been designed with 3 arms of blue, red, and near-infrared
cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure
at a resolution of ~1.6-2.7A. An international collaboration is developing this
instrument under the initiative of Kavli IPMU. The project is now going into
the construction phase aiming at undertaking system integration in 2017-2018
and subsequently carrying out engineering operations in 2018-2019. This article
gives an overview of the instrument, current project status and future paths
forward.Comment: 17 pages, 10 figures. Proceeding of SPIE Astronomical Telescopes and
Instrumentation 201
Lovastatin insensitive 1, a novel pentatricopeptide repeat protein, is a potential regulatory factor of isoprenoid biosynthesis in Arabidopsis
Higher plants have two metabolic pathways for isoprenoid biosynthesis: the cytosolic mevalonate (MVA) pathway and the plastidal non-mevalonate (MEP) pathway. Despite the compartmentalization of these two pathways, metabolic flow occurs between them. However, little is known about the mechanisms that regulate the two pathways and the metabolic cross-talk. To identify such regulatory mechanisms, we isolated and characterized the Arabidopsis T-DNA insertion mutant lovastatin insensitive 1 (loi1), which is resistant to lovastatin and clomazone, inhibitors of the MVA and MEP pathways, respectively. The accumulation of the major products of these pathways, i.e. sterols and chlorophyll, was less affected by lovastatin and clomazone, respectively, in loi1 than in the wild type. Furthermore, the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity analysis showed higher activity of HMGR in loi1-1 treated with lovastatin than that in the WT. We consider that the lovastatin-resistant phenotype of loi1-1 was derived from this post-transcriptional up-regulation of HMGR. The LOI1 gene encodes a novel pentatricopeptide repeat (PPR) protein. PPR proteins are thought to regulate the expression of genes encoded in organelle genomes by post-transcriptional regulation in mitochondria or plastids. Our results demonstrate that LOI1 is predicted to localize in mitochondria and has the ability to bind single-stranded nucleic acids. Our investigation revealed that the post-transcriptional regulation of mitochondrial RNA may be involved in isoprenoid biosynthesis in both the MVA and MEP pathways.Peer reviewe
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