1,534 research outputs found
Systematic variations of central mass density slopes in early-type galaxies
We study the total density distribution in the central regions (≳1 effective radius, Re) of earlytype galaxies (ETGs), using data from SPIDER and ATLAS3D. Our analysis extends the range of galaxy stellar mass (M*) probed by gravitational lensing, down to ~1010M. We model each galaxy with two components (dark matter halo + stars), exploring different assumptions for the dark matter halo profile (i.e. NFW, NFW-contracted, and Burkert profiles), and leaving stellar mass-to-light (M*/L) ratios as free fitting parameters to the data. For all plausible halo models, the best-fitting M*/L, normalized to that for a Chabrier initial mass function, increases systematically with galaxy size and mass. For anNFWprofile, the slope of the total mass profile is non-universal, independently of several ingredients in the modelling (e.g. halo contraction, anisotropy, and rotation velocity in ETGs). For the most massive (M* ~ 1011.5M) or largest (Re ~ 15 kpc) ETGs, the profile is isothermal in the central regions (~Re/2), while for the low-mass (M* ~ 1010.2M) or smallest (Re ~ 0.5 kpc) systems, the profile is steeper than isothermal, with slopes similar to those for a constant-M/L profile. For a steeper concentration- mass relation than that expected from simulations, the correlation of density slope with galaxy mass tends to flatten, while correlations with Re and velocity dispersions are more robust. Our results clearly point to a 'non-homology' in the total mass distribution of ETGs, which simulations of galaxy formation suggest may be related to a varying role of dissipation with galaxy mass. 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Spatial and temporal analysis of stem bleeding disease in coconut palm in the state of sergipe, Brazil
Secular Evolution and the Formation of Pseudobulges in Disk Galaxies
We review internal processes of secular evolution in galaxy disks,
concentrating on the buildup of dense central features that look like
classical, merger-built bulges but that were made slowly out of disk gas. We
call these pseudobulges. As an existence proof, we review how bars rearrange
disk gas into outer rings, inner rings, and gas dumped into the center. In
simulations, this gas reaches high densities that plausibly feed star
formation. In the observations, many SB and oval galaxies show central
concentrations of gas and star formation. Star formation rates imply plausible
pseudobulge growth times of a few billion years. If secular processes built
dense central components that masquerade as bulges, can we distinguish them
from merger-built bulges? Observations show that pseudobulges retain a memory
of their disky origin. They have one or more characteristics of disks: (1)
flatter shapes than those of classical bulges, (2) large ratios of ordered to
random velocities indicative of disk dynamics, (3) small velocity dispersions,
(4) spiral structure or nuclear bars in the bulge part of the light profile,
(5) nearly exponential brightness profiles, and (6) starbursts. These
structures occur preferentially in barred and oval galaxies in which secular
evolution should be rapid. So the cleanest examples of pseudobulges are
recognizable. Thus a large variety of observational and theoretical results
contribute to a new picture of galaxy evolution that complements hierarchical
clustering and merging.Comment: 92 pages, 21 figures in 30 Postscript files; to appear in Annual
Review of Astronomy and Astrophysics, Vol. 42, 2004, in press; for a version
with full resolution figures, see
http://chandra.as.utexas.edu/~kormendy/ar3ss.htm
Técnica de Rosanov modificada na reconstrução do trato digestivo após gastrectomia total
A genetic algorithm for the one-dimensional cutting stock problem with setups
This paper investigates the one-dimensional cutting stock problem considering two conflicting objective functions: minimization of both the number of objects and the number of different cutting patterns used. A new heuristic method based on the concepts of genetic algorithms is proposed to solve the problem. This heuristic is empirically analyzed by solving randomly generated instances and also practical instances from a chemical-fiber company. The computational results show that the method is efficient and obtains positive results when compared to other methods from the literature. © 2014 Brazilian Operations Research Society
Diversity, community structure and conservation status of an Atlantic Forest fragment in Rio de Janeiro State, Brazil
Effect of light-activation with different light-curing units and time intervals on resin cement bond strength to intraradicular dentin
Polymerization shrinkage stress of composites photoactivated by different light sources
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