5,599 research outputs found
The inner structure of very massive elliptical galaxies: implications for the inside-out formation mechanism of z~2 galaxies
We analyze a sample of 23 supermassive elliptical galaxies (central velocity
dispersion larger than 330 km s-1), drawn from the SDSS. For each object, we
estimate the dynamical mass from the light profile and central velocity
dispersion, and compare it with the stellar mass derived from stellar
population models. We show that these galaxies are dominated by luminous matter
within the radius for which the velocity dispersion is measured. We find that
the sizes and stellar masses are tightly correlated, with Re ~ M*^{1.1}$,
making the mean density within the de Vaucouleurs radius a steeply declining
function of M*: rho_e ~ M*^{-2.2}. These scalings are easily derived from the
virial theorem if one recalls that this sample has essentially fixed (but
large) sigma_0. In contrast, the mean density within 1 kpc is almost
independent of M*, at a value that is in good agreement with recent studies of
z ~ 2 galaxies. The fact that the mass within 1 kpc has remained approximately
unchanged suggests assembly histories that were dominated by minor mergers --
but we discuss why this is not the unique way to achieve this. Moreover, the
total stellar mass of the objects in our sample is typically a factor of ~ 5
larger than that in the high redshift (z ~ 2) sample, an amount which seems
difficult to achieve. If our galaxies are the evolved objects of the recent
high redshift studies, then we suggest that major mergers were required at z >
1.5, and that minor mergers become the dominant growth mechanism for massive
galaxies at z < 1.5.Comment: 11 pages, 8 figures, accepted in MNRA
A KAT-7 view of a low-mass sample of galaxy clusters
Radio observations over the last two decades have provided evidence that
diffuse synchrotron emission in the form of megaparsec-scale radio halos in
galaxy clusters is likely tracing regions of the intracluster medium where
relativistic particles are accelerated during cluster mergers. In this paper we
present results of a survey of 14 galaxy clusters carried out with the
7-element Karoo Array Telescope at 1.86 GHz, aimed to extend the current
studies of radio halo occurrence to systems with lower masses (M M). We found upper limits at the Watt Hz level for of the sample, confirming that
bright radio halos in less massive galaxy clusters are statistically rare.Comment: 7 pages, 4 figures. Conference proceeding of "The many facets of
extragalactic radio surveys: towards new scientific challenges", 20-23
October 2105, Bologna, Ital
Adubação de pastagens
Análise de solo; Recomendação de correção do solo e adubação; Sistemas de produção e estratégicas de adubação
Teores de enxofre em solos dos Estados do Rio de Janeiro e Espírito Santo.
bitstream/CNPS-2009-09/11269/1/comtec19_2003_teores_enxofre.pd
Generating Diverse and Meaningful Captions
Image Captioning is a task that requires models to acquire a multi-modal
understanding of the world and to express this understanding in natural
language text. While the state-of-the-art for this task has rapidly improved in
terms of n-gram metrics, these models tend to output the same generic captions
for similar images. In this work, we address this limitation and train a model
that generates more diverse and specific captions through an unsupervised
training approach that incorporates a learning signal from an Image Retrieval
model. We summarize previous results and improve the state-of-the-art on
caption diversity and novelty. We make our source code publicly available
online.Comment: Accepted for presentation at The 27th International Conference on
Artificial Neural Networks (ICANN 2018
A penalized regression model for spatial functional data with application to the analysis of the production of waste in Venice province
We propose a method for the analysis of functional data with complex dependencies, such as spatially dependent curves or time dependent surfaces, over highly textured domains. The models are based on the idea of regression with partial differential regularizations. In particular, we consider here two roughness penalties that account separately for the regularity of the field in space and in time. Among the various modelling features, the proposed method is able to deal with spatial domains featuring peninsulas, islands and other complex geometries. Space-time varying covariate information is included in the model via a semi-parametric framework. The proposed method is compared via simulation studies to other spatiotemporal techniques and it is applied to the analysis of the annual production of waste in the towns of Venice province
Discovery of the heavily obscured supernova 2002cv
On the 13th of May 2002, supernova 2002cv was discovered using a
near-infrared camera working at the AZT-24 1.1m telescope at Campo Imperatore
(AQ-Italy). After the infrared detection a simultaneous photometric follow-up
was started at optical wavelengths. The preliminary results confirm a heavily
obscured object with a V-K color not lower than 6 magnitudes, making SN 2002cv
the most reddened supernova ever observed. This finding, along with the recent
discovery of another obscured supernova, suggests a critical revision of the
rates known to date. The estimate of the visual extinction and the light curves
are provided here. These latter indicate that our SN 2002cv observations are
the earliest available for a type-Ia supernova at IR wavelengths.Comment: 4 page
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