2,944 research outputs found
Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
For the first time accurate pulsation properties of the ancient variable
stars of the Fornax dwarf spheroidal galaxy (dSph) are discussed in the broad
context of galaxy formation and evolution. Homogeneous multi-band optical
photometry of spanning {\it twenty} years has allowed us to identify and
characterize more than 1400 RR Lyrae stars (RRLs) in this galaxy. Roughly 70\%
are new discoveries. We investigate the period-amplitude distribution and find
that Fornax shows a lack of High Amplitude (A_V\gsim0.75 mag) Short Period
fundamental-mode RRLs (P\lsim0.48 d, HASPs). These objects occur in stellar
populations more metal-rich than [Fe/H]-1.5 and they are common in the
Galactic halo (Halo) and in globulars. This evidence suggests that old (age
older than 10 Gyr) Fornax stars are relatively metal-poor.
A detailed statistical analysis of the role of the present-day Fornax dSph in
reproducing the Halo period distribution shows that it can account for only a
few to 20\% of the Halo when combined with RRLs in massive dwarf galaxies
(Sagittarius dSph, Large Magellanic Cloud). This finding indicates that
Fornax-like systems played a minor role in building up the Halo when compared
with massive dwarfs. We also discuss the occurrence of HASPs in connection with
the luminosity and the early chemical composition of nearby dwarf galaxies. We
find that, independently of their individual star formation histories, bright
(M_V\lsim-13.5 mag) galaxies have HASPs, whereas faint ones (M_V\gsim-11
mag) do not. Interestingly enough, Fornax belongs to a luminosity range
(--11M--13.5 mag) in which the occurrence of HASPs appears to be
correlated with the early star formation and chemical enrichment of the host
galaxy.Comment: 7 pages, 5 figures, A&A, accepte
Glueball Regge trajectories from gauge/string duality and the Pomeron
The spectrum of light baryons and mesons has been reproduced recently by
Brodsky and Teramond from a holographic dual to QCD inspired in the AdS/CFT
correspondence. They associate fluctuations about the AdS geometry with four
dimensional angular momenta of the dual QCD states. We use a similar approach
to estimate masses of glueball states with different spins and their
excitations. We consider Dirichlet and Neumann boundary conditions and find
approximate linear Regge trajectories for these glueballs. In particular the
Neumann case is consistent with the Pomeron trajectory.Comment: In this revised version we made some additional remarks on the text.
We also included 2 more references. The glueball spectrum and Regge
trajectories are unchanged. 10 pages, 2 eps figure
Impact of distance determinations on Galactic structure. II. Old tracers
Here we review the efforts of a number of recent results that use old tracers
to understand the build up of the Galaxy. Details that lead directly to using
these old tracers to measure distances are discussed. We concentrate on the
following: (1) the structure and evolution of the Galactic bulge and inner
Galaxy constrained from the dynamics of individual stars residing therein; (2)
the spatial structure of the old Galactic bulge through photometric
observations of RR Lyrae-type stars; (3) the three\--dimensional structure,
stellar density, mass, chemical composition, and age of the Milky Way bulge as
traced by its old stellar populations; (4) an overview of RR Lyrae stars known
in the ultra-faint dwarfs and their relation to the Galactic halo; and (5)
different approaches for estimating absolute and relative cluster ages.Comment: Review article, 80 pages (25 figures); Space Science Reviews, in
press (chapter of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
An analysis of rainfall based on entropy theory
The principle of maximum entropy can provide consistent basis for analyzing rainfall and for geophysical processes in general. The daily rainfall data was assessed using the Shannon entropy for a 10-years period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and isoentropy maps were then constructed for delineating annual and seasonal characteristics of rainfall. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy for two sample stations. The marginal entropy values of rainfall were higher for locations and periods with highest amount of rainfall. The results also showed that the marginal entropy decreased exponentially with increasing coefficient of variation. The Shannon theory produced spatial patterns which led to a better understanding of rainfall characteristics throughout the northeastern region of Brazil. Trend analysis indicated that most time series did not have any significant trends
Avaliação da qualidade protéica do milho carunchado através de ensaio metabólico com ratas.
Um experimento foi realizado com o objetivo de avaliar a qualidade proteica do milho carunchado atraves de ensaios metabolicos com ratas. 36 ratas de peso medio inicial de 53,9 g foram distribuidas em um delineamento inteiramente casualizado para seis tratamentos com seis repeticoes. Os tratamentos consistiram de racoes com milho 1,79; 10,27; 17,49; 38,15% carunchado, uma racao a base de caseina e outra aproteica. Observou-se que a proteina do milho carunchado apresentou uma razao proteica liquida de 57,95% da caseina e pior digestibilidade e desempenho do que a caseina
Efeito de diferentes proporções de sulfato/cloreto de potássio no potencial produtivo do morangueiro.
O objetivo do trabalho foi avaliar o efeito de duas fontes de fertilizante potássico aplicadas em diferentes proporções, nas variáveis agronòmicas do morangueiro.Suplemento. Trabalho apresentado no 52. Congresso Brasileiro de Olericultura, Salvador, 2012
Anti-de Sitter boundary in Poincare coordinates
We study the space-time boundary of a Poincare patch of Anti-de Sitter (AdS)
space. We map the Poincare AdS boundary to the global coordinate chart and show
why this boundary is not equivalent to the global AdS boundary. The Poincare
AdS boundary is shown to contain points of the bulk of the entire AdS space.
The Euclidean AdS space is also discussed. In this case one can define a
semi-global chart that divides the AdS space in the same way as the
corresponding Euclidean Poincare chart.Comment: In this revised version we add a discussion of the physical
consequences of the choice of a coordinate system for AdS space. We changed
figure 1 and added more references. Version to be published in Gen. Relat.
Grav
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