425 research outputs found
Proper motions with Subaru II. A sample in the Subaru/XMM-Newton Deep Survey field
We search for stars with proper motions in a set of deep Subaru images,
covering about 0.48 square degrees to a depth of , taken over a
span of five and a half years. We follow the methods described in
\citet{Richmond2009} to reduce and analyze this dataset. We present a sample of
69 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 14 of the candidates may be white dwarfs. Our candidate with the
largest proper motion is surprisingly faint and likely to prove interesting:
its colors and motions suggest that it might be an M dwarf moving at over 500
km/sec or an L dwarf in the halo.Comment: 10 pages, 5 figures. Accepted by Publications of the Astronomical
Society of Japan, to appear in volume 62, February 2010. Revised version:
removed PASJ LaTeX tutorial which was mistakenly appended to pape
A theoretical study of the effect of upstream transpiration cooling on the heat-transfer and skin-friction characteristics of a compressible, laminar boundary layer
Proper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
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 ~ 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.Comment: 12 pages, 8 figures, submitted to PAS
A comparison between vertical winds in the lower thermosphere and magnetic field perturbations on the ground
Vertical winds in the lower thermosphere are estimated from OI557.7-nm Doppler shifts obtained with a Fabry-Perot interferometer at the Poker Flat Research Range (65.12N, 147.43W in geographic coordinate), Alaska. The temporal variation of vertical winds was compared with the horizontal component of the magnetic field obtained at Poker Flat and two other sites, Gakona (62.12N, 145.14W) and Fort Yukon (66.36N, 145.22W). Two nights of observations were examined and the results were shown here. The results showed that temporal variations of vertical winds were similar to that of magnetic field variation during each substorm. In some cases the results of cross correlation between these two parameters showed that the magnetic field perturbation leads vertical winds in the earlier period of the substorm. The difference increased gradually and reached a maximum at around the center of the recovery phase. From there, the differences decreased. The mechanism for the relation between the two parameters is still unclear, but this result suggests an intimate relation between ionospheric currents and vertical wind in the thermosphere
Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region
We have performed a systematic study of several regions in the sky where the
number of galaxies exhibiting star formation (SF) activity is greater than
average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced
sample. By statistically comparing the KUG and non-KUG distributions, we
discovered four KUG-rich regions with a size of . One of these regions corresponds spatially to a filament of length
Mpc in the Lynx-Ursa Major region (). We call this ``the Lynx-Ursa
Major (LUM) filament''. We obtained surface photometry of 11 of
the KUGs in the LUM filament and used these to investigate the integrated
colors, distribution of SF regions, morphologies, and local environments. We
found that these KUGs consist of distorted spiral galaxies and compact galaxies
with blue colors. Their star formation occurs in the entire disk, and is not
confined to just the central regions. The colors of the SF regions imply that
active star formation in the spiral galaxies occurred yr ago,
while that of the compact objects occurred yr ago. Though the
photometric characteristics of these KUGs are similar to those of interacting
galaxies or mergers, most of these KUGs do not show direct evidence of merger
processes.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The
Title of the previous one was truncated by the author's mistake, and is
corrected. Main body of the paper is unchange
The Optical/Near-Infrared Light Curves of SN 2002ap for the First 140 Days after Discovery
Supernova (SN) 2002ap in M74 was observed in the bands for the
first 40 days following its discovery (2002 January 29) until it disappeared
because of solar conjunction, and then in June after it reappeared. The
magnitudes and dates of peak brightness in each band were determined. While the
rate of increase of the brightness before the peak is almost independent of
wavelength, the subsequent rate of decrease becomes smaller with wavelength
from the to the band, and is constant at wavelengths beyond . The
photometric evolution is faster than in the well-known ``hypernovae''
SNe~1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The
bolometric light curve of SN 2002ap for the full period of observations was
constructed. The absolute magnitude is found to be much fainter than that of SN
1998bw, but is similar to that of SN 1997ef, which lies at the faint end of the
hypernova population. The bolometric light curve at the early epochs was best
reproduced with the explosion of a C+O star that ejects 2.5~M_\sun with
kinetic energy . A comparison of the
predicted brightness of SN 2002ap with that observed after solar conjunction
may imply that -ray deposition at the later epochs was more efficient
than in the model. This may be due to an asymmetric explosion.Comment: 15 pages, 6 figures, quality of figure1 is reduced for smaller
filesize, accepted for publication in Ap
Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective
<p>Abstract</p> <p>Background</p> <p>The teleost order Lophiiformes, commonly known as the anglerfishes, contains a diverse array of marine fishes, ranging from benthic shallow-water dwellers to highly modified deep-sea midwater species. They comprise 321 living species placed in 68 genera, 18 families and 5 suborders, but approximately half of the species diversity is occupied by deep-sea ceratioids distributed among 11 families. The evolutionary origins of such remarkable habitat and species diversity, however, remain elusive because of the lack of fresh material for a majority of the deep-sea ceratioids and incompleteness of the fossil record across all of the Lophiiformes. To obtain a comprehensive picture of the phylogeny and evolutionary history of the anglerfishes, we assembled whole mitochondrial genome (mitogenome) sequences from 39 lophiiforms (33 newly determined during this study) representing all five suborders and 17 of the 18 families. Sequences of 77 higher teleosts including the 39 lophiiform sequences were unambiguously aligned and subjected to phylogenetic analysis and divergence time estimation.</p> <p>Results</p> <p>Partitioned maximum likelihood analysis confidently recovered monophyly for all of the higher taxa (including the order itself) with the exception of the Thaumatichthyidae (<it>Lasiognathus </it>was deeply nested within the Oneirodidae). The mitogenomic trees strongly support the most basal and an apical position of the Lophioidei and a clade comprising Chaunacoidei + Ceratioidei, respectively, although alternative phylogenetic positions of the remaining two suborders (Antennarioidei and Ogcocephaloidei) with respect to the above two lineages are statistically indistinguishable. While morphology-based intra-subordinal relationships for relatively shallow, benthic dwellers (Lophioidei, Antennarioidei, Ogcocephaloidei, Chaunacoidei) are either congruent with or statistically indistinguishable from the present mitogenomic tree, those of the principally deep-sea midwater dwellers (Ceratioidei) cannot be reconciled with the molecular phylogeny. A relaxed molecular-clock Bayesian analysis of the divergence times suggests that all of the subordinal diversifications have occurred during a relatively short time period between 100 and 130 Myr ago (early to mid Cretaceous).</p> <p>Conclusions</p> <p>The mitogenomic analyses revealed previously unappreciated phylogenetic relationships among the lophiiform suborders and ceratioid familes. Although the latter relationships cannot be reconciled with the earlier hypotheses based on morphology, we found that simple exclusion of the reductive or simplified characters can alleviate some of the conflict. The acquisition of novel features, such as male dwarfism, bioluminescent lures, and unique reproductive modes allowed the deep-sea ceratioids to diversify rapidly in a largely unexploited, food-poor bathypelagic zone (200-2000 m depth) relative to the other lophiiforms occurring in shallow coastal areas.</p
Population-genetic nature of copy number variations in the human genome
Copy number variations (CNVs) are universal genetic variations, and their association with disease has been increasingly recognized. We designed high-density microarrays for CNVs, and detected 3000–4000 CNVs (4–6% of the genomic sequence) per population that included CNVs previously missed because of smaller sizes and residing in segmental duplications. The patterns of CNVs across individuals were surprisingly simple at the kilo-base scale, suggesting the applicability of a simple genetic analysis for these genetic loci. We utilized the probabilistic theory to determine integer copy numbers of CNVs and employed a recently developed phasing tool to estimate the population frequencies of integer copy number alleles and CNV–SNP haplotypes. The results showed a tendency toward a lower frequency of CNV alleles and that most of our CNVs were explained only by zero-, one- and two-copy alleles. Using the estimated population frequencies, we found several CNV regions with exceptionally high population differentiation. Investigation of CNV–SNP linkage disequilibrium (LD) for 500–900 bi- and multi-allelic CNVs per population revealed that previous conflicting reports on bi-allelic LD were unexpectedly consistent and explained by an LD increase correlated with deletion-allele frequencies. Typically, the bi-allelic LD was lower than SNP–SNP LD, whereas the multi-allelic LD was somewhat stronger than the bi-allelic LD. After further investigation of tag SNPs for CNVs, we conclude that the customary tagging strategy for disease association studies can be applicable for common deletion CNVs, but direct interrogation is needed for other types of CNVs
Critical properties of S=1/2 Heisenberg ladders in magnetic fields
The critical properties of the Heisenberg two-leg ladders are
investigated in a magnetic field. Combining the exact diagonalization method
and the finite-size-scaling analysis based on conformal field theory, we
calculate the critical exponents of spin correlation functions numerically. For
a strong interchain coupling, magnetization dependence of the critical
exponents shows characteristic behavior depending on the sign of the interchain
coupling. We also calculate the critical exponents for the Heisenberg
two-leg ladder with a diagonal interaction, which is thought as a model
Hamiltonian of the organic spin ladder compound
. Numerical results are compared with
experimental results of temperature dependence of the NMR relaxation rate
.Comment: REVTeX, 10 pages, 8 figures, accepted for Phys. Rev.
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