288 research outputs found
Observational tests for oscillating expansion rate of the Universe
We investigate the observational constraints on the oscillating scalar field
model using data from type Ia supernovae, cosmic microwave background
anisotropies, and baryon acoustic oscillations. According to a Fourier
analysis, the galaxy number count from redshift data indicates that
galaxies have preferred periodic redshift spacings. We fix the mass of the
scalar field as such that the scalar
field model can account for the redshift spacings, and we constrain the other
basic parameters by comparing the model with accurate observational data. We
obtain the following constraints: (95% C.L.),
(95% C.L.) (in the range
). The best fit values of the energy density parameter of the scalar
field and the coupling constant are and ,
respectively. The value of is close to but not equal to .
Hence, in the scalar field model, the amplitude of the galaxy number count
cannot be large. However, because the best fit values of and
are not , the scalar field model has the possibility of accounting for
the periodic structure in the -- relation of galaxies. The variation of
the effective gravitational constant in the scalar field model is not
inconsistent with the bound from observation.Comment: 9 pages, 11 figures, 1 table, Accepted for publication in Physical
Review
Multi-label Ferns for Efficient Recognition of Musical Instruments in Recordings
In this paper we introduce multi-label ferns, and apply this technique for
automatic classification of musical instruments in audio recordings. We compare
the performance of our proposed method to a set of binary random ferns, using
jazz recordings as input data. Our main result is obtaining much faster
classification and higher F-score. We also achieve substantial reduction of the
model size
Rest-frame Optical Emission Lines in Far-Infrared Selected Galaxies at z<1.7 from the FMOS-COSMOS Survey
We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123
far-infrared selected galaxies in COSMOS and obtain the key rest-frame optical
emission lines. This is the largest sample of infrared galaxies with
near-infrared spectroscopy at these redshifts. The far-infrared selection
results in a sample of galaxies that are massive systems that span a range of
metallicities in comparison with previous optically selected surveys, and thus
has a higher AGN fraction and better samples the AGN branch. We establish the
presence of AGN and starbursts in this sample of (U)LIRGs selected as
Herschel-PACS and Spitzer-MIPS detections in two redshift bins (z~0.7 and
z~1.5) and test the redshift dependence of diagnostics used to separate AGN
from star-formation dominated galaxies. In addition, we construct a low
redshift (z~0.1) comparison sample of infrared selected galaxies and find that
the evolution from z~1.5 to today is consistent with an evolving AGN selection
line and a range of ISM conditions and metallicities from the models of Kewley
et al. (2013b). We find that a large fraction of (U)LIRGs are BPT-selected AGN
using their new, redshift-dependent classification line. We compare the
position of known X-ray detected AGN (67 in total) with the BPT selection and
find that the new classification line accurately selects most of these objects
(> 70%). Furthermore, we identify 35 new (likely obscured) AGN not selected as
such by their X-ray emission. Our results have direct implications for AGN
selection at higher redshift with either current (MOSFIRE, KMOS) or future
(PFS, MOONS) spectroscopic efforts with near-infrared spectral coverage.Comment: 7 pages, 3 figures, 2 tables. Accepted for publication in The
Astrophysical Journal Letter
Lagrangian drifter paths and length scales in the tropical Pacific warm pool from 1990 to 1991: with application of fractal techniques
International audienceThis paper presents an analysis of WOCE/TOGA surface drifter paths and its interpretation in conjunction with the west Pacific warm pool water motion. Our interest here lies in the existence of scale invariance in the observed data sets. The analysis proceeds by detecting scale invariance in the drifter paths data, and interpreting the invariance in terms of the statistical second order moment. The range of constant scaling exponent was found to be between 5 days and 10 days, and this range corresponded with the "long tail" of the temporal correlation function in the zonal direction. Velocity covariances in both the zonal and meridional directions were computed, and corresponding diffusivities were 8100 m2/sec meridionally and 41000 m2/sec zonally. Considering the existence of large scale mean flow, it is thought that self-similar energy cascade processes associated with constant scaling exponent may be responsible for the anomalous zonal diffusivity, while the meridional diffusivity may be approximated by ordinary Brownian processes. We suggest that the scale invariance of the WOCE/TOGA surface drifter paths may be a manifestation of energy cascade processes from large scale mean flow to smaller scale irregular flow that is represented by fractional Brownian motion in the zonal direction
The FMOS-COSMOS survey of star-forming galaxies at z ~ 1.6. I. H\alpha -based star formation rates and dust extinction
We present the first results from a near-IR spectroscopic survey of the
COSMOS field, using the Fiber Multi-Object Spectrograph on the Subaru
telescope, designed to characterize the star-forming galaxy population at
. The high-resolution mode is implemented to detect H in
emission between with erg cm s. Here, we specifically
focus on 271 sBzK-selected galaxies that yield a H detection thus
providing a redshift and emission line luminosity to establish the relation
between star formation rate and stellar mass. With further -band
spectroscopy for 89 of these, the level of dust extinction is assessed by
measuring the Balmer decrement using co-added spectra. We find that the
extinction () rises with stellar
mass and is elevated at high masses compared to low-redshift galaxies. Using
this subset of the spectroscopic sample, we further find that the differential
extinction between stellar and nebular emission
\hbox{} is 0.7--0.8, dissimilar to
that typically seen at low redshift. After correcting for extinction, we derive
an H-based main sequence with a slope () and normalization
similar to previous studies at these redshifts.Comment: 6 pages, 4 figures, and 1 table. Published in ApJ Letter
The FMOS-COSMOS survey of star-forming galaxies at z~1.6 III. Survey design, performance, and sample characteristics
We present a spectroscopic survey of galaxies in the COSMOS field using the
Fiber Multi-Object Spectrograph (FMOS), a near-infrared instrument on the
Subaru Telescope. Our survey is specifically designed to detect the Halpha
emission line that falls within the H-band (1.6-1.8 um) spectroscopic window
from star-forming galaxies with 1.4 ~10^10 Msolar. With
the high multiplex capability of FMOS, it is now feasible to construct samples
of over one thousand galaxies having spectroscopic redshifts at epochs that
were previously challenging. The high-resolution mode (R~2600) effectively
separates Halpha and [NII]6585 thus enabling studies of the gas-phase
metallicity and photoionization state of the interstellar medium. The primary
aim of our program is to establish how star formation depends on stellar mass
and environment, both recognized as drivers of galaxy evolution at lower
redshifts. In addition to the main galaxy sample, our target selection places
priority on those detected in the far-infrared by Herschel/PACS to assess the
level of obscured star formation and investigate, in detail, outliers from the
star formation rate - stellar mass relation. Galaxies with Halpha detections
are followed up with FMOS observations at shorter wavelengths using the J-long
(1.11-1.35 um) grating to detect Hbeta and [OIII]5008 that provides an
assessment of extinction required to measure star formation rates not hampered
by dust, and an indication of embedded Active Galactic Nuclei. With 460
redshifts measured from 1153 spectra, we assess the performance of the
instrument with respect to achieving our goals, discuss inherent biases in the
sample, and detail the emission-line properties. Our higher-level data
products, including catalogs and spectra, are available to the community.Comment: 26 pages, Updated version resubmitted to ApJSS; Data products and
catalogs are now available at http://member.ipmu.jp/fmos-cosmos
Adaptation to acidic soil is achieved by increased numbers of cis-acting elements regulating ALMT1 expression in Holcus lanatus
Yorkshire fog (Holcus lanatus), which belongs to the Poaceae family and is a close relative of the agronomic crop oat (Avena sativa), is a widely adaptable grass species that is able to grow on highly acidic soils with high levels of Al, but the mechanism underlying the high Al tolerance is unknown. Here, we characterized two accessions of H.lanatus collected from an acid plot (soil pH 3.6, HL-A) and a neutral plot (pH 7.1, HL-N) in terms of Al tolerance, organic acid anion secretion and related gene expression. In response to Al (pH 4.5), the HL-A roots secreted approximately twice as much malate as the HL-N roots, but there was no difference in citrate secretion. Cloning of the gene HlALMT1 responsible for malate secretion showed that the encoded amino acid sequence did not differ between two accessions, but the expression level in the outer cell layers of the HL-A roots was twice as high as in the HL-N roots. This difference was not due to the genomic copy number, but was due to the number of cis-acting elements for an Al-responsive transcription factor (HlART1) in the promoter region of HlALMT1, as demonstrated by both a yeast one-hybrid assay and a transient assay in tobacco protoplasts. Furthermore, introduction of HlALMT1 driven by the HL-A promoter into rice resulted in significantly more Al-induced malate secretion than introduction of HlALMT1 driven by the HL-N promoter. These findings indicate that the adaptation of H.lanatus to acidic soils may be achieved by increasing number of cis-acting elements for ART1 in the promoter region of the HlALMT1 gene, enhancing the expression of HlALMT1 and the secretion of malate
Structure and physical properties of Cs3+alpha C60 (alpha=0.0-1.0) under ambient and high pressures
The intermediate phases Cs3+alphaC60 (alpha=0.0-1.0), have been prepared, and their structure and physical properties are studied by x-ray powder diffraction, Raman, ESR, electric conductivity, and ac susceptibility measurements under ambient and high pressures. The x-ray powder diffraction pattern of Cs3+alphaC60 (alpha=0.0-1.0) can be indexed as a mixture of the body-centered-orthorhombic (bco) and cubic (A15) phases. The A15 phase diminishes above 30 kbar. The broad ESR peak due to the conduction electron (c-ESR) is observed only for the phases around alpha=0.0 in Cs3+alphaC60. The resistivity of the Cs3+alphaC60 (alphanot equal0) sample follows the granular metal theory and/or Sheng model even in the sample exhibiting a broad ESR peak. No superconducting transition is observed up to 10.6 kbar in Cs3+alphaC60 (alphanot equal0). These results present that bco phase of Cs3+alphaC60 (alpha=0) is a final candidate for a pressure-induced superconductor.</p
Spatial Periodicity of Galaxy Number Counts, CMB Anisotropy, and SNIa Hubble Diagram Based on the Universe Accompanied by a Non-Minimally Coupled Scalar Field
We have succeeded in establishing a cosmological model with a non-minimally
coupled scalar field that can account not only for the spatial
periodicity or the {\it picket-fence structure} exhibited by the galaxy -
relation of the 2dF survey but also for the spatial power spectrum of the
cosmic microwave background radiation (CMB) temperature anisotropy observed by
the WMAP satellite. The Hubble diagram of our model also compares well with the
observation of Type Ia supernovae. The scalar field of our model universe
starts from an extremely small value at around the nucleosynthesis epoch,
remains in that state for sufficiently long periods, allowing sufficient time
for the CMB temperature anisotropy to form, and then starts to grow in
magnitude at the redshift of , followed by a damping oscillation
which is required to reproduce the observed picket-fence structure of the
- relation. To realize such behavior of the scalar field, we have found
it necessary to introduce a new form of potential , with being a constant. Through this parameter ,
we can control the epoch at which the scalar field starts growing.Comment: 19 pages, 18 figures, Accepted for publication in Astrophysics &
Space Scienc
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