852 research outputs found
Dynamical Generation of CKM Mixings by Broken Horizontal Gauge Interactions
The fermion mass matrices are calculated in the framework of the dynamical
mass generation by the broken horizontal gauge interactions. The
non-proportional mass spectra between up- and down-sectors and CKM mixings are
obtained solely by radiative corrections due to the ordinary gauge
interactions.Comment: 20 pages + 1 uuencoded eps figure, PHYZZ
Measurement of Neutron Spallation Cross Sections of 12C, 27Al and 209Bi
開始ページ、終了ページ: 冊子体のページ付
Spatial correlation between submillimetre and Lyman-alpha galaxies in the SSA 22 protocluster
Lyman-alpha emitters are thought to be young, low-mass galaxies with ages of
~10^8 yr. An overdensity of them in one region of the sky (the SSA 22 field)
traces out a filamentary structure in the early Universe at a redshift of z =
3.1 (equivalent to 15 per cent of the age of the Universe) and is believed to
mark a forming protocluster. Galaxies that are bright at (sub)millimetre
wavelengths are undergoing violent episodes of star formation, and there is
evidence that they are preferentially associated with high-redshift radio
galaxies, so the question of whether they are also associated with the most
significant large-scale structure growing at high redshift (as outlined by
Lyman-alpha emitters) naturally arises. Here we report an imaging survey of
1,100-um emission in the SSA 22 region. We find an enhancement of submillimetre
galaxies near the core of the protocluster, and a large-scale correlation
between the submillimetre galaxies and the low-mass Lyman-alpha emitters,
suggesting synchronous formation of the two very different types of
star-forming galaxy within the same structure at high redshift. These results
are in general agreement with our understanding of the formation of cosmic
structure.Comment: Published in Nature (7th May 2009 issue). The astro-ph paper includes
the main text (10 pages, 2 figures, 1 table) and supplementary material (6
pages, 4 figures, 1 table
The K2K SciBar Detector
A new near detector, SciBar, for the K2K long-baseline neutrino oscillation
expe riment was installed to improve the measurement of neutrino energy
spectrum and to study neutrino interactions in the energy region around 1 GeV.
SciBar is a 'fully active' tracking detector with fine segmentation consisting
of plastic scintillator bars. The detector was constructed in summer 2003 and
is taking data since October 2003. The basic design and initial performance is
presented.Comment: 7 pages, 4figures, Contributed to Proceedings of the 10th Vienna
Conference on Instrumentation, Vienna, February 16-21, 200
Towards the prediction of molecular parameters from astronomical emission lines using Neural Networks
Molecular astronomy is a field that is blooming in the era of large observatories such as the Atacama Large Millimeter/Submillimeter Array (ALMA). With modern, sensitive, and high spectral resolution radio telescopes like ALMA and the Square Kilometer Array, the size of the data cubes is rapidly escalating, generating a need for powerful automatic analysis tools. This work introduces MolPred, a pilot study to perform predictions of molecular parameters such as excitation temperature (Tex) and column density (log(N)) from input spectra by the use of neural networks. We used as test cases the spectra of CO, HCO+, SiO and CH3CN between 80 and 400 GHz. Training spectra were generated with MADCUBA, a state-of-the-art spectral analysis tool. Our algorithm was designed to allow the generation of predictions for multiple molecules in parallel. Using neural networks, we can predict the column density and excitation temperature of these molecules with a mean absolute error of 8.5% for CO, 4.1% for HCO+, 1.5% for SiO and 1.6% for CH3CN. The prediction accuracy depends on the noise level, line saturation, and number of transitions. We performed predictions upon real ALMA data. The values predicted by our neural network for this real data differ by 13% from the MADCUBA values on average. Current limitations of our tool include not considering linewidth, source size, multiple velocity components, and line blending
Diffuse Gamma Rays: Galactic and Extragalactic Diffuse Emission
"Diffuse" gamma rays consist of several components: truly diffuse emission
from the interstellar medium, the extragalactic background, whose origin is not
firmly established yet, and the contribution from unresolved and faint Galactic
point sources. One approach to unravel these components is to study the diffuse
emission from the interstellar medium, which traces the interactions of high
energy particles with interstellar gas and radiation fields. Because of its
origin such emission is potentially able to reveal much about the sources and
propagation of cosmic rays. The extragalactic background, if reliably
determined, can be used in cosmological and blazar studies. Studying the
derived "average" spectrum of faint Galactic sources may be able to give a clue
to the nature of the emitting objects.Comment: 32 pages, 28 figures, kapproc.cls. Chapter to the book "Cosmic
Gamma-Ray Sources," to be published by Kluwer ASSL Series, Edited by K. S.
Cheng and G. E. Romero. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
Detection of an ultra-bright submillimeter galaxy in the Subaru/XMM-Newton Deep Field using AzTEC/ASTE
We report the detection of an extremely bright (37 mJy at 1100 m
and 91 mJy at 880 m) submillimeter galaxy (SMG),
AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi),
discovered in 1100 m observations of the Subaru/XMM-Newton Deep Field
using AzTEC on ASTE. Subsequent CARMA 1300 m and SMA 880 m
observations successfully pinpoint the location of Orochi and suggest that it
has two components, one extended (FWHM of 4) and one
compact (unresolved). Z-Spec on CSO has also been used to obtain a wide band
spectrum from 190 to 308 GHz, although no significant emission/absorption lines
are found. The derived upper limit to the line-to-continuum flux ratio is
0.1--0.3 (2 ) across the Z-Spec band.
Based on the analysis of the derived spectral energy distribution from
optical to radio wavelengths of possible counterparts near the SMA/CARMA peak
position, we suggest that Orochi is a lensed, optically dark SMG lying at behind a foreground, optically visible (but red) galaxy at . The deduced apparent (i.e., no correction for magnification) infrared
luminosity () and star formation rate (SFR) are
and 11000 yr, respectively, assuming that the
is dominated by star formation. These values suggest that Orochi
will consume its gas reservoir within a short time scale (
yr), which is indeed comparable to those in extreme starbursts like the centres
of local ULIRGs.Comment: 18 pages, 13 figure
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