17,233 research outputs found
NIR Luminosity Function of Galaxies in Close Major-Merger Pairs and Mass Dependence of Merger Rate
A sample of close major-merger pairs (projected separation kpc, band magnitude difference mag) is selected from the matched 2MASS-2dFGRS catalog of Cole et al.
(2001). The pair primaries are brighter than mag. After
corrections for various biases, the comparison between counts in the paired
galaxy sample and counts in the parent sample shows that for the local `M*
galaxies' sampled by flux limited surveys, the fraction of galaxies in the
close major-merger pairs is 1.70. Using 38 paired galaxies in the
sample, a band luminosity function (LF) is calculated. This is the
first unbiased LF for a sample of objectively defined interacting/merging
galaxies in the local universe, while all previously determined LFs of paired
galaxies are biased by mistreating paired galaxies as singles. A stellar mass
function (MF) is translated from the LF. Compared to the LF/MF of 2MASS
galaxies, a differential pair fraction function is derived. The results suggest
a trend in the sense that less massive galaxies may have lower chance to be
involved in close major-merger pairs than more massive galaxies. The algorithm
presented in this paper can be easily applied to much larger samples of 2MASS
galaxies with redshifts in near future.Comment: Accepted by ApJL, 16 pages, 2 figure
The Mass-to-Light Ratio of Binary Galaxies
We report on the mass-to-light ratio determination based on a newly selected
binary galaxy sample, which includes a large number of pairs whose separations
exceed a few hundred kpc. The probability distributions of the projected
separation and the velocity difference have been calculated considering the
contamination of optical pairs, and the mass-to-light ratio has been determined
based on the maximum likelihood method. The best estimate of in the B
band for 57 pairs is found to be 28 36 depending on the orbital
parameters and the distribution of optical pairs (solar unit, km
s Mpc). The best estimate of for 30 pure spiral pairs is
found to be 12 16. These results are relatively smaller than those
obtained in previous studies, but consistent with each other within the errors.
Although the number of pairs with large separation is significantly increased
compared to previous samples, does not show any tendency of increase, but
found to be almost independent of the separation of pairs beyond 100 kpc. The
constancy of beyond 100 kpc may indicate that the typical halo size of
spiral galaxies is less than kpc.Comment: 18 pages + 8 figures, to appear in ApJ Vol. 516 (May 10
Melancia sem semente, alternativa cultural na campina de Idanha
A melancia sem semente é uma alternativa cultural e um fruto a incentivar para os
consumidores portugueses, mas a sua produção terá que ser de elevada qualidade e
rentável para os produtores. A campina de Idanha-a-Nova apresenta excelentes
caracterÃsticas para a produção de culturas regadas em particular a melancia com
semente, sendo já conhecida como uma região de excelência pela qualidade da
produção neste fruto. Este trabalho resulta de um ensaio de produção de melancia sem
semente ao ar livre, em camalhões, com cobertura de solo e rega gota a gota, utilizando
a cultivar Romalinda (cv. sem semente, triplóide) consociada em dois distintos
compassos de plantação com a cultivar Augusta (cv. polinizadora, diplóide). As
modalidades consistiram de 2 repetições para camalhões de 4 linhas em que na Mod. I.
a cv Romalinda e a cv Augusta se encontravam na proporção de 2:1 na linha (50 plantas
da cv. Romalinda e 25 plantas da cv. Augusta) e na Mod II. cada camalhão era
constituÃdo por uma linha da cv. Augusta intercalada com 2 linhas da cv. Romalinda (50
plantas da cv. Romalinda e 50 plantas da cv. Augusta) por camalhão. A análise da
produção foi realizada escalonadamente, em três datas de colheita de julho a agosto,
com 15 dias de intervalo. O ensaio foi realizado desde a sementeira à colheita e foram
analisados os seguintes parâmetros produtivos: número de frutos; produtividade; peso
dos frutos; espessura da casca; perÃmetro do fruto; altura e largura do fruto e grau brix;.
A adaptação da cv. sem semente foi excelente. Não se registaram diferenças
significativas entre os parâmetros analisados e os compassos de plantação das
modalidades ensaiadas. As plantas tiveram uma produção média de 3-4 frutos por
planta; pesos médios entre 3,70kg e 4,20kg. O teor em açúcar foi aumentando da
primeira para a última colheita atingindo valores médios de 11,53. Conclui-se que a cv.
Romalinda exibiu melhores caracterÃsticas de produção quantitativa e qualitativa do que
a cv. Augusta sendo promissora como uma alternativa de produção tardia na região
Float-polishing process and analysis of float-polished quartz
A fluid-mechanical model is developed for the float-polishing process. In this model laminar flow between the sample and the lap results in pressure gradients at the grooves that support the sample on a fluid layer. The laminar fluid motion also produces supersmooth, damage-free surfaces. Quartz substrates for applications in high-stress environments were float polished, and their surfaces were analyzed by optical scatterometry, photoacoustic spectroscopy, and atomic force microscopy. The removal of 100 µm of material by a lapping-polishing process, with final float polishing, left low levels of subsurface damage, with a surface roughness of approximately 0.2-nm rms
Image Subtraction Reduction of Open Clusters M35 & NGC 2158 In The K2 Campaign-0 Super-Stamp
Observations were made of the open clusters M35 and NGC 2158 during the
initial K2 campaign (C0). Reducing these data to high-precision photometric
time-series is challenging due to the wide point spread function (PSF) and the
blending of stellar light in such dense regions. We developed an
image-subtraction-based K2 reduction pipeline that is applicable to both
crowded and sparse stellar fields. We applied our pipeline to the data-rich C0
K2 super-stamp, containing the two open clusters, as well as to the neighboring
postage stamps. In this paper, we present our image subtraction reduction
pipeline and demonstrate that this technique achieves ultra-high photometric
precision for sources in the C0 super-stamp. We extract the raw light curves of
3960 stars taken from the UCAC4 and EPIC catalogs and de-trend them for
systematic effects. We compare our photometric results with the prior
reductions published in the literature. For detrended, TFA-corrected sources in
the 12--12.25 magnitude range, we achieve a best 6.5 hour window
running rms of 35 ppm falling to 100 ppm for fainter stars in the 14--14.25 magnitude range. For stars with , our detrended and
6.5 hour binned light curves achieve the highest photometric precision.
Moreover, all our TFA-corrected sources have higher precision on all time
scales investigated. This work represents the first published image subtraction
analysis of a K2 super-stamp. This method will be particularly useful for
analyzing the Galactic bulge observations carried out during K2 campaign 9. The
raw light curves and the final results of our detrending processes are publicly
available at \url{http://k2.hatsurveys.org/archive/}.Comment: Accepted for publication in PASP. 14 pages, 5 figures, 2 tables.
Light curves available from http://k2.hatsurveys.org/archive
Lobby index as a network centrality measure
We study the lobby index (l-index for short) as a local node centrality
measure for complex networks. The l-inde is compared with degree (a local
measure), betweenness and Eigenvector centralities (two global measures) in the
case of biological network (Yeast interaction protein-protein network) and a
linguistic network (Moby Thesaurus II). In both networks, the l-index has poor
correlation with betweenness but correlates with degree and Eigenvector. Being
a local measure, one can take advantage by using the l-index because it carries
more information about its neighbors when compared with degree centrality,
indeed it requires less time to compute when compared with Eigenvector
centrality. Results suggests that l-index produces better results than degree
and Eigenvector measures for ranking purposes, becoming suitable as a tool to
perform this task.Comment: 11 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1005.480
Rotation intrinsic spin coupling--the parallelism description
For the Dirac particle in the rotational system, the rotation induced inertia
effect is analogously treated as the modification of the "spin connection" on
the Dirac equation in the flat spacetime, which is determined by the equivalent
tetrad. From the point of view of parallelism description of spacetime, the
obtained torsion axial-vector is just the rotational angular velocity, which is
included in the "spin connection". Furthermore the axial-vector spin coupling
induced spin precession is just the rotation-spin(1/2) interaction predicted by
Mashhoon. Our derivation treatment is straightforward and simplified in the
geometrical meaning and physical conception, however the obtained conclusions
are consistent with that of the other previous work.Comment: 10 pages, no figur
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