1,797 research outputs found
From fields to a super-cluster: the role of the environment at z=0.84 with HiZELS
At z=0, clusters are primarily populated by red, elliptical and massive
galaxies, while blue, spiral and lower-mass galaxies are common in low-density
environments. Understanding how and when these differences were established is
of absolute importance for our understanding of galaxy formation and evolution,
but results at high-z remain contradictory. By taking advantage of the widest
and deepest H-alpha narrow-band survey at z=0.84 over the COSMOS and UKIDSS UDS
fields, probing a wide range of densities (from poor fields to rich groups and
clusters, including a confirmed super-cluster with a striking filamentary
structure), we show that the fraction of star-forming galaxies falls
continuously from ~40% in fields to approaching 0% in rich groups/clusters. We
also find that the median SFR increases with environmental density, at least up
to group densities - but only for low and medium mass galaxies, and thus such
enhancement is mass-dependent at z~1. The environment also plays a role in
setting the faint-end slope (alpha) of the H-alpha luminosity function. Our
findings provide a sharper view on galaxy formation and evolution and reconcile
previously contradictory results at z~1: stellar mass is the primary predictor
of star formation activity, but the environment also plays a major role.Comment: 5 pages, 4 figures, to appear in the proceedings of JENAM 2010 S2:
`Environment and the Formation of Galaxies: 30 years later', ASSP, Springe
Lyapunov exponent in the Vicsek model
The well-known Vicsek model describes the flock dynamics of self-propelled
agents. Surprisingly, a direct measure of the chaotic behavior of such systems
is missing. Here, we discuss the kinetic phase transition present in Vicsek
systems in light of the largest Lyapunov exponent, which is numerically
computed by following the dynamical evolution in tangent space. As
discontinuities in the neighbors weighting factor hinder the computations, we
propose a continuous form of the model. Our results about chaotic regime
reinforce the idea that the Lyapunov exponent is also a phase transition
indicator.Comment: 7 pages, 16 equations, 6 figure
Dentinogénese Imperfeita – A propósito de um caso clínico
Poster apresentado nas XXII Jornadas Internacionais de Medicina Dentária ISCSEM, Monte de Caparica, 28-29 Março 2014
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