544 research outputs found
Deficiency of `Thin' Stellar Bars in Seyfert Host Galaxies
Using all available major samples of Seyfert galaxies and their corresponding
control samples of closely matched non-active galaxies, we find that the bar
ellipticities (or axial ratios) in Seyfert galaxies are systematically
different from those in non-active galaxies. Overall, there is a deficiency of
bars with large ellipticities (i.e., `fat' or `weak' bars) in Seyferts,
compared to non-active galaxies. Accompanied with a large dispersion due to
small number statistics, this effect is strictly speaking at the `2sigma'
level. To obtain this result, the active galaxy samples of near-infrared
surface photometry were matched to those of normal galaxies in type, host
galaxy ellipticity, absolute magnitude, and, to some extent, in redshift. We
discuss possible theoretical explanations of this phenomenon within the
framework of galactic evolution, and, in particular, of radial gas
redistribution in barred galaxies. Our conclusions provide further evidence
that Seyfert hosts differ systematically from their non-active counterparts on
scales of a few kpc.Comment: Astrophysical Journal Letters, in press. Latex, 2 postscript figure
A monolithic collapse origin for the thin/thick disc structure of ESO 243-49
ESO 243-49 is a high-mass (circular velocity ) edge-on S0 galaxy in the Abell 2877 cluster at a distance of
. To elucidate the origin of its thick disc, we use MUSE
science verification data to study its kinematics and stellar populations. The
thick disc emits of the light at heights in excess of
(). The rotation velocities of its stars
lag by compared to those in the thin disc, which is
compatible with the asymmetric drift. The thick disc is found to be more
metal-poor than the thin disc, but both discs have old ages. We suggest an
internal origin for the thick disc stars in high-mass galaxies. We propose that
the thick disc formed either first in a turbulent phase with a high
star formation rate and that a thin disc formed shortly afterwards, or because of the dynamical heating of a thin pre-existing component. Either
way, the star formation in ESO 243-49 was quenched just a few Gyrs after the
galaxy was born and the formation of a thin and a thick disc must have occurred
before the galaxy stopped forming stars. The formation of the discs was so fast
that it could be described as a monolithic collapse where several generations
of stars formed in a rapid succession.Comment: Accepted for publication in A&A. The reduced data-cube as well as the
data necessary to build the kinematic and stellar population maps are
available at
https://etsin.avointiede.fi/dataset/urn-nbn-fi-csc-kata2016092414291163237
Thermal Modeling in Polymer Extrusion
In this paper we consider thermal effects of polymer flows through a cylindrical die. First, we derive a model for the oscillatory behavior of polymer flow in an extruder given a functional relation between the pressure and flow rate. A simple isothermal but temperature dependent model is constructed to find this relation. Unfortunately, the model is shown to be invalid in the physical regime of interest. We present several arguments to suggest that the isothermal assumption is reasonable but that a more detailed understanding of the small-scale molecular dynamics near the boundary may be required. Second, we show that a simplified model for thermoflow multiplicity in a cooled tube is inconsistent, when the stationary non-Newtonian flow is assumed to be incompressible without radial pressure gradients and without radial velocity. This inconsistency can be removed by allowing for weak compressibility effects in the down-steam area
A consistent treatment of link and writhe for open rods, and their relation to end rotation
We combine and extend the work of Alexander & Antman \cite{alexander.82} and
Fuller \cite{fuller.71,fuller.78} to give a framework within which precise
definitions can be given of topological and geometrical quantities
characterising the contortion of open rods undergoing large deformations under
end loading. We use these definitions to examine the extension of known results
for closed rods to open rods. In particular, we formulate the analogue of the
celebrated formula (link equals twist plus writhe) for open rods and
propose an end rotation, through which the applied end moment does work, in the
form of an integral over the length of the rod. The results serve to promote
the variational analysis of boundary-value problems for rods undergoing large
deformations.Comment: 17 pages, 4 figure
Influence of Seasonal Variations of Temperature and Light on the Growth Rate of Cultures and Natural Populations of Intertidal Diatoms
Influence of Seasonal Variations of Temperature and Light on the Growth Rate of Cultures and Natural Populations of Intertidal Diatoms
The Effect of Fiscal Rules on Public Investment if Budget Deficits Are Politically Motivated
Uncertainty about the future preferences of the government may induce policy makers to run excessive budget deficits. As a solution to this problem, economists have proposed to impose a binding debt rule. In this paper we argue that a binding debt rule does not eliminate the distortions due to strategic behaviour of politicians. Rather, strategic manipulation shifts from public debt to public investment. As an alternative, we examine the effects of a capital borrowing rule which permits the government to run a budget deficit equal to the amount of public investment. We show that this rule effectively eliminates strategic behaviour.fiscal rules and budget deficits and public investment
Quantification of coarse-graining error in Langevin and overdamped Langevin dynamics
In molecular dynamics and sampling of high dimensional Gibbs measures
coarse-graining is an important technique to reduce the dimensionality of the
problem. We will study and quantify the coarse-graining error between the
coarse-grained dynamics and an effective dynamics. The effective dynamics is a
Markov process on the coarse-grained state space obtained by a closure
procedure from the coarse-grained coefficients. We obtain error estimates both
in relative entropy and Wasserstein distance, for both Langevin and overdamped
Langevin dynamics. The approach allows for vectorial coarse-graining maps.
Hereby, the quality of the chosen coarse-graining is measured by certain
functional inequalities encoding the scale separation of the Gibbs measure. The
method is based on error estimates between solutions of (kinetic) Fokker-Planck
equations in terms of large-deviation rate functionals
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