546 research outputs found
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
Optical Alignment System for the PHENIX Muon Tracking Chambers
A micron-precision optical alignment system (OASys) for the PHENIX muon
tracking chambers is developed. To ensure the required mass resolution of
vector meson detection, the relative alignment between three tracking station
chambers must be monitored with a precision of 25m. The OASys is a
straightness monitoring system comprised of a light source, lens and CCD
camera, used for determining the initial placement as well as for monitoring
the time dependent movement of the chambers on a micron scale.Comment: Accepted for the publication in Nucl.Instr.Meth.
Capacitar profissionais para trabalhar/difundir a segurança alimentar e nutricional da comunidade
Trabalho apresentado no II Congresso Nacional do PROJETO RONDON, realizado em Florianópolis, SC, no período de 23 a 25 de setembro de 2015 - Universidade Federal de Santa Catarina.O conceito de Segurança alimentar e Nutricional (SAN) é muito amplo, define-se como o direito de todos ao acesso a alimentos de qualidade e em quantidade, sem comprometer o acesso a outras necessidades essenciais. Além disso, a SAN constitui a prática de uma alimentação adequada com alimentos saudáveis, e consumir nutrientes necessários para as atividades diárias de cada cidadão. Sendo assim, foi desenvolvida durante a Operação Bororos - julho/2015, no Conjunto A de atividades no município de Nortelândia/MT, uma oficina que objetivou o esclarecimento dos direitos supracitados a toda população, além de promover o conhecimento sobre os alimentos que estão disponíveis para o consumo, e quais os benefícios que estes podem trazer para a saúde, sua quantidade e variedade adequada. Além de direcionar formas de promoção à alimentação saudável e de auto produção e consumo. Esta oficina foi desenvolvida na Escola Municipal Júlio Praxe de Duarte com auxílio de recursos audiovisuais para 47 pessoas que incluíam profissionais da área da saúde, merendeiras e comunidade em geral. Foram dois dias de atividade no período integral (manhã e tarde), onde no primeiro dia foram desenvolvidas atividades teóricas sobre conceitos de SAN, componentes dos alimentos, grupos alimentares, e aspectos de higiene alimentar. No segundo dia foram desenvolvidas atividades práticas, sendo construída, no período matutino uma horta comunitária no pátio da escola e no período vespertino praticado o monitoramento da SAN para a população, como exemplo, a realização do cálculo do Índice de Massa Corporal (IMC). Foi verificado que houve impacto das informações sobre a população, que se sentiu esclarecida, sendo ouvidos muitos relatos que deixou exposto que o ato de alimentar-se não expressava tanta preocupação com relação a qualidade e propósito dos alimentos. Também constatou-se que o conhecimento sobre como alimentar-se, e o que ingerir, e o porquê consumir tais alimentos apresentaram conceitos novos. Conclui-se desta forma que a atividade promoveu um impacto sobre a comunidade implicando em sua qualidade de vida, e que poderá ser replicada mesmo após a conclusão do trabalho dos rondonistas
Rotational and Cyclical Variability in gamma Cassiopeia
We report results of a nine-year monitoring effort on the unusual classical
Be with a robotic ground-based (APT) B,V-filtered telescope as well as
simultaneous observations in 2004 November with this instrument and the RXTE
(X-ray) telescope. Our observations disclosed no correlated optical response to
the rapid X-ray flares in this star, nor did the star show any sustained flux
changes during the course of either of the two monitored nights in either
wavelength regime. Our optical light curves reveal that gamma Cas undergoes
\~3%-amplitude cycles with lengths of 60--90 days. Over the nine days we
monitored the star with the RXTE, the X-ray flux varied in phase with its
optical cycle and with an amplitude predicted from correlated optical/X-ray
data from an earlier paper. The amplitudes of the V magnitude cycles are
30--40% larger than the B amplitudes, suggesting the seat of the cycles is
circumstellar. The cycle lengths constantly change and can damp or grow on
timescales as short as 13 days. We have also discovered a coherent period of
1.21581 +/-0.00002 days in all our data, which is consistent only with
rotation. The full amplitude of this variation is 0.0060 in both filters. The
derived waveform, somewhat surprisingly, is almost sawtooth in shape. This
variation probably originates on the star's surface. This circumstance hints at
the existence of a strong magnetic field with a complex topology and an
associated heterogeneous surface composition.Comment: 31 pages, 7 figures. Submitted to The Astrophysical Journa
X-ray and Optical Variations in the Classical Be Star gamma Cas
gamma Cas (B0.5e) is known to be a unique X-ray source because ot its
moderate L_x, hard X-ray spectrum, and light curve punctuated by ubiquitous
flares and slow undulations. Its X-ray peculiarities have led to a controversy
concerning their origin: either from wind infall onto a putative degenerate
companion, as for typical Be/X-ray binaries, or from the Be star per se. Recent
progress has been made to address this: (1) the discovery that gamma Cas is an
eccentric binary system (P = 203.59 d) with unknown secondary type, (2) the
accumulation of RXTE data at 9 epochs in 1996-2000, and (3) the collation of
robotic telescope B, V-band photometric observations over 4 seasons. The latter
show a 3%, cyclical flux variation with cycle lengths 55-93 days. We find that
X-ray fluxes at all 9 epochs show random variations with orbital phase. This
contradicts the binary accretion model, which predicts a substantial
modulation. However,these fluxes correlate well with the cyclical optical
variations. Also, the 6 flux measurements in 2000 closely track the
interpolated optical variations between the 2000 and 2001 observing seasons.
Since the optical variations represent a far greater energy than that emitted
as X-rays, the optical variability cannot arise from X-ray reprocessing.
However, the strong correlation between the two suggests that they are driven
by a common mechanism. We propose that this mechanism is a cyclical magnetic
dynamo excited by a Balbus-Hawley instability located within the inner part of
the circumstellar disk. In our model, variations in the field strength directly
produce the changes in the magnetically related X-ray activity. Turbulence
associated with the dynamo results in changes to the density distribution
within the disk and creates the observed optical variations.Comment: 30 dbl-spaced pages, Latex, plus 11 figures. Accepted by Ap
The X-ray emission of the gamma Cassiopeiae stars
Long considered as the "odd man out" among X-ray emitting Be stars, \gamma
Cas (B0.5e IV) is now recognized as the prototype of a class of stars that emit
hard thermal X-rays. Our classification differs from the historical use of the
term "gamma Cas stars" defined from optical properties alone. The luminosity
output of this class contributes significantly to the hard X-ray production in
massive stars in the Galaxy. The gamma Cas stars have light curves showing
variability on a few broadly-defined timescales and spectra indicative of an
optically thin plasma consisting of one or more hot thermal components. By now
9--13 Galactic \approx B0-1.5e main sequence stars are judged to be members or
candidate members of the \gamma Cas class. Conservative criteria for this
designation are for a \approxB0-1.5e III-V star to have an X-ray luminosity of
10^{32}--10^{33} ergs s^{-1}, a hot thermal spectrum containing the short
wavelength Ly \alpha FeXXV and FeXXVI lines and the fluorescence FeK feature
all in emission. If thermality cannot be demonstrated, for example from either
the presence of these Ly \alpha lines or curvature of the hard continuum; these
are the gamma Cas candidates. We discuss the history of the discovery of the
complicated characteristics of the variability in the optical, UV, and X-ray
domains, leading to suggestions for the physical cause of the production of
hard X-rays. These include scenarios in which matter from the Be star accretes
onto a degenerate secondary star and interactions between magnetic fields on
the Be star and its decretion disk. The greatest aid to the choice of the
causal mechanism is the temporal correlations of X-ray light curves and spectra
with diagnostics in the optical and UV wavebands. We show why the magnetic
star-disk interaction scenario is the most tenable explanation for the creation
of hard X-rays on these stars.Comment: Review paper for "X-ray Emissions from Hot Stars and their Winds"
compendium to be published by Advances in Space Research in mid-2016. Paper
is comprised of 66 pages, 15 figure
Cross sections and double-helicity asymmetries of midrapidity inclusive charged hadrons in p+p collisions at sqrt(s)=62.4 GeV
Unpolarized cross sections and double-helicity asymmetries of
single-inclusive positive and negative charged hadrons at midrapidity from p+p
collisions at sqrt(s)=62.4 GeV are presented. The PHENIX measurements for 1.0 <
p_T < 4.5 GeV/c are consistent with perturbative QCD calculations at
next-to-leading order in the strong coupling constant, alpha_s. Resummed pQCD
calculations including terms with next-to-leading-log accuracy, yielding
reduced theoretical uncertainties, also agree with the data. The
double-helicity asymmetry, sensitive at leading order to the gluon polarization
in a momentum-fraction range of 0.05 ~< x_gluon ~< 0.2, is consistent with
recent global parameterizations disfavoring large gluon polarization.Comment: PHENIX Collaboration. 447 authors, 12 pages, 5 figures, 5 tables.
Submitted to Physical Review
Inclusive cross section and double helicity asymmetry for pi^0 production in p+p collisions at sqrt(s) = 62.4 GeV
The PHENIX experiment presents results from the RHIC 2006 run with polarized
proton collisions at sqrt(s) = 62.4 GeV for inclusive pi^0 production at
mid-rapidity. Unpolarized cross section results are measured for transverse
momenta p_T = 0.5 to 7 GeV/c. Next-to-leading order perturbative quantum
chromodynamics calculations are compared with the data, and while the
calculations are consistent with the measurements, next-to-leading logarithmic
corrections improve the agreement. Double helicity asymmetries A_LL are
presented for p_T = 1 to 4 GeV/c and probe the higher range of Bjorken_x of the
gluon (x_g) with better statistical precision than our previous measurements at
sqrt(s)=200 GeV. These measurements are sensitive to the gluon polarization in
the proton for 0.06 < x_g < 0.4.Comment: 387 authors from 63 institutions, 10 pages, 6 figures, 1 table.
Submitted to Physical Review D. Plain text data tables for the points plotted
in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Inclusive cross section and single-transverse-spin asymmetry for very forward neutron production in polarized p+p collisions at sqrt(s)=200 GeV
The energy dependence of the single-transverse-spin asymmetry, A_N, and the
cross section for neutron production at very forward angles were measured in
the PHENIX experiment at RHIC for polarized p+p collisions at sqrt(s)=200 GeV.
The neutrons were observed in forward detectors covering an angular range of up
to 2.2 mrad. We report results for neutrons with momentum fraction of x_F=0.45
to 1.0. The energy dependence of the measured cross sections were consistent
with x_F scaling, compared to measurements by an ISR experiment which measured
neutron production in unpolarized p+p collisions at sqrt(s)=30.6--62.7 GeV. The
cross sections for large x_F neutron production for p+p collisions, as well as
those in e+p collisions measured at HERA, are described by a pion exchange
mechanism. The observed forward neutron asymmetries were large, reaching
A_N=-0.08+/-0.02 for x_F=0.8; the measured backward asymmetries, for negative
x_F, were consistent with zero. The observed asymmetry for forward neutron
production is discussed within the pion exchange framework, with interference
between the spin-flip amplitude due to the pion exchange and nonflip amplitudes
from all Reggeon exchanges. Within the pion exchange description, the measured
neutron asymmetry is sensitive to the contribution of other Reggeon exchanges
even for small amplitudes.Comment: 383 authors, 16 pages, 18 figures, 6 tables. Submitted to Phys. Rev.
D. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Centrality dependence of charged hadron production in deuteron+gold and nucleon+gold collisions at sqrt(s_NN)=200 GeV
We present transverse momentum (p_T) spectra of charged hadrons measured in
deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four
centrality classes. Nucleon-gold collisions were selected by tagging events in
which a spectator nucleon was observed in one of two forward rapidity
detectors. The spectra and yields were investigated as a function of the number
of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A
comparison of charged particle yields to those in p+p collisions show that the
yield per nucleon-nucleon collision saturates with \nu for high momentum
particles. We also present the charged hadron to neutral pion ratios as a
function of p_T.Comment: 330 authors, 15 pages text, 16 figures, 3 tables. Submitted to Phys.
Rev. Lett. v2 has minor changes to reflect revisions during review process.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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