110 research outputs found
CO mapping of the nuclear region of NGC 6946 and IC 342 with Nobeyama millimeter array
CO observations of nearby galaxies with nuclear active star forming regions (and starburst galaxies) with angular resolutions around 7 seconds revealed that molecular bars with a length of a few kiloparsecs have been formed in the central regions of the galaxies. The molecular bar is interpreted as part of shock waves induced by an oval or barred potential field. By shock dissipation or dissipative cloud-cloud collisions, the molecular gas gains an infall motion and the nuclear star formation activity is fueled. But the distribution and kinematics of the molecular gas in the nuclear regions, which are sites of active star formation, remain unknown. Higher angular resolutions are needed to investigate the gas in the nuclear regions. Researchers made aperture synthesis observations of the nuclear region of the late-type spiral galaxies NGC 6946 and IC 342 with resolutions of 7.6 seconds x 4.2 seconds (P.A. = 147 deg) and 2.4 seconds x 2.3 seconds (P.A. = 149 deg), respectively. The distances to NGC 6496 and IC 342 are assumed to be 5.5 Mpc and 3.9 Mpc, respectively. Researchers have found 100-300 pc nuclear gas disk and ring inside a few kpc molecular gas bars. Researchers present the results of the observations and propose a possible mechanism of active star formation in the nuclear region
Characterization of sensitivity and responses of a 2-element prototype wavefront sensor for millimeter-wave adaptive optics attached to the Nobeyama 45 m telescope
We report the results of the performance characterization of a prototype
wavefront sensor for millimetric adaptive optics (MAO) installed on the
Nobeyama 45 m radio telescope. MAO is a key component to realize a future
large-aperture submillimeter telescope, such as Large Submillimeter Telescope
(LST) or Atacama Large Aperture Submillimeter Telescope (AtLAST). The
difficulty of MAO is, however, real-time sensing of wavefront deformation with
~10 um accuracy across the aperture. Our wavefront sensor operating at 20 GHz
measures the radio path length between a certain position of the primary mirror
surface to the focal point where a 20 GHz coherent receiver is placed. With the
2-element prototype, we sampled two positions on the primary mirror surface (at
radii of 5 m and 16 m) at a sampling rate of 10 Hz. Then an excess path length
(EPL) between the two positions was obtained by differentiating the two optical
paths. A power spectral density of the EPL shows three components: a
low-frequency drift (1/f^n), oscillations, and a white noise. A comparison of
EPL measurements under a variety of wind conditions suggests that the former
two are likely induced by the wind load on the telescope structure. The power
of the white noise corresponds to a 1sigma statistical error of 8 um in EPL
measurements. The 8 um r.m.s. is significant with respect to the mirror surface
accuracy required by the LST and AtLAST (~20-40 um r.m.s.), which demonstrates
that our technique is also useful for the future large-aperture submillimeter
telescopes.Comment: 10 pages, 9 figures. Published in SPIE Pro
Construction of a consensus linkage map for red clover (Trifolium pratense L.)
<p>Abstract</p> <p>Background</p> <p>Red clover (<it>Trifolium pratense </it>L.) is a major forage legume that has a strong self-incompatibility system and exhibits high genetic diversity within populations. For several crop species, integrated consensus linkage maps that combine information from multiple mapping populations have been developed. For red clover, three genetic linkage maps have been published, but the information in these existing maps has not been integrated.</p> <p>Results</p> <p>A consensus linkage map was constructed using six mapping populations originating from eight parental accessions. Three of the six mapping populations were established for this study. The integrated red clover map was composed of 1804 loci, including 1414 microsatellite loci, 181 amplified fragment length polymorphism (AFLP) loci and 204 restriction fragment length polymorphism (RFLP) loci, in seven linkage groups. The average distance between loci and the total length of the consensus map were 0.46 cM and 836.6 cM, respectively. The locus order on the consensus map correlated highly with that of accession-specific maps. Segregation distortion was observed across linkage groups. We investigated genome-wide allele frequency in 1144 red clover individuals using 462 microsatellite loci randomly chosen from the consensus map. The average number of alleles and polymorphism information content (PIC) were 9.17 and 0.69, respectively.</p> <p>Conclusion</p> <p>A consensus genetic linkage map for red clover was constructed for the first time based on six mapping populations. The locus order on the consensus map was highly conserved among linkage maps and was sufficiently reliable for use as a reference for genetic analysis of random red clover germplasms.</p
Mapping candidate QTLs related to plant persistency in red clover
Red clover (Trifolium pratense L.) is a diploid (2n = 14), self-incompatible legume that is widely cultivated as a forage legume in cold geographical regions. Because it is a short-lived perennial species, improvement of plant persistency is the most important objective for red clover breeding. To develop a marker-assisted selection (MAS) approach for red clover, we identified candidate QTLs related to plant persistency. Two full-sib mapping populations, 272 × WF1680 and HR × R130, were used for QTL identification. Resistance to Sclerotinia trifoliorum and Fusarium species, as well as to winter hardiness, was investigated in the laboratory and in field experiments in Moscow region (Russia), and Sapporo (Japan). With the genotype data derived from microsatellite and other DNA markers, candidate QTLs were identified by simple interval mapping (SIM), Kruskal–Wallis analysis (KW analysis) and genotype matrix mapping (GMM). A total of 10 and 23 candidate QTL regions for plant persistency were identified in the 272 × WF1680 and the HR × R130 mapping populations, respectively. The QTLs identified by multiple mapping approaches were mapped on linkage group (LG) 3 and LG6. The significant QTL interactions identified by GMM explained the higher phenotypic variation than single effect QTLs. Identification of haplotypes having positive effect QTLs in each parent were first demonstrated in this study for pseudo-testcross mapping populations in plant species using experimental data. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-009-1253-5) contains supplementary material, which is available to authorized users
Formation of a Massive Black Hole at the Center of the Superbubble in M82
We performed 12CO(1-0), 13CO(1-0), and HCN(1-0) interferometric observations
of the central region (about 450 pc in radius) of M82 with the Nobeyama
Millimeter Array, and have successfully imaged a molecular superbubble and
spurs. The center of the superbubble is clearly shifted from the nucleus by 140
pc. This position is close to that of the massive black hole (BH) of >460 Mo
and the 2.2 micron secondary peak (a luminous supergiant dominated cluster),
which strongly suggests that these objects may be related to the formation of
the superbubble. Consideration of star formation in the cluster based on the
infrared data indicates that (1) energy release from supernovae can account for
the kinetic energy of the superbubble, (2) the total mass of stellar-mass BHs
available for building-up the massive BH may be much higher than 460 Mo, and
(3) it is possible to form the middle-mass BH of 100-1000 Mo within the
timescale of the superbubble. We suggest that the massive BH was produced and
is growing in the intense starburst region.Comment: 9 pages, 3 figures, to appear in ApJ Lette
Star formation efficiency in the Barred Spiral Galaxy NGC 4303
We present new CO(J=1-0) observations of the barred galaxy NGC 4303
using the Nobeyama 45m telescope (NRO45) and the Combined Array for Research in
Millimeter-wave Astronomy (CARMA). The H images of barred spiral
galaxies often show active star formation in spiral arms, but less so in bars.
We quantify the difference by measuring star formation rate and efficiency at a
scale where local star formation is spatially resolved. Our CO map covers the
central 2\farcm3 region of the galaxy; the combination of NRO45 and CARMA
provides a high fidelity image, enabling accurate measurements of molecular gas
surface density. We find that star formation rate and efficiency are twice as
high in the spiral arms as in the bar. We discuss this difference in the
context of the Kennicutt-Schimidt (KS) law, which indicates a constant star
formation rate at a given gas surface density. The KS law breaks down at our
native resolution ( 250 pc), and substantial smoothing (to 500 pc) is
necessary to reproduce the KS law, although with greater scatter.Comment: 17 pages, 10 figures, published by ApJ;
http://adsabs.harvard.edu/abs/2010ApJ...721..383
Aperture Synthesis Observations of CO, HCN, and 89GHz Continuum Emission toward NGC 604 in M 33: Sequential Star Formation Induced by Supergiant Hii region
We present the results from new Nobeyama Millimeter Array observations of
CO(1-0), HCN(1-0), and 89-GHz continuum emissions toward NGC 604, known as the
supergiant H ii region in a nearby galaxy M 33. Our high spatial resolution
images of CO emission allowed us to uncover ten individual molecular clouds
that have masses of (0.8 -7.4) 10M_{\sun } and sizes of 5 -- 29 pc,
comparable to those of typical Galactic giant molecular clouds (GMCs).
Moreover, we detected for the first time HCN emission in the two most massive
clouds and 89 GHz continuum emission at the rims of the "H shells".
Three out of ten CO clouds are well correlated with the H shells both
in spatial and velocity domains, implying an interaction between molecular gas
and the expanding H ii region. Furthermore, we estimated star formation
efficiencies (SFEs) for each cloud from the 89-GHz and combination of
H and 24-m data, and found that the SFEs decrease with
increasing projected distance measured from the heart of the central OB star
cluster in NGC 604, suggesting the radial changes in evolutionary stages of the
molecular clouds in course of stellar cluster formation. Our results provide
further support to the picture of sequential star formation in NGC604 initially
proposed by Tosaki et al. (2007) with the higher spatially resolved molecular
clouds, in which an isotropic expansion of the H ii region pushes gases outward
and accumulates them to consecutively form dense molecular clouds, and then
induces massive star formations.Comment: 23 pages, 8 figures, accepted for publication in Ap
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