32,314 research outputs found
Central Star Formation in Pseudobulges and Classical Bulges
I use Spitzer 3.6-8.0 \mu m color profiles to compare the radial structure of
star formation in pseudobulges and classical bulges. Pseudobulges are
``bulges'' which form through secular evolution, rather than mergers. In this
study, pseudobulges are identified using the presence of disk-like structure in
the center of the galaxy (nuclear spiral, nuclear bar, and/or high ellipticity
in bulge); classical bulges are those galaxy bulges with smooth isophotes which
are round compared to the outer disk, and show no disky structure in their
bulge. I show that galaxies structurally identified as having pseudobulges have
higher central star formation rates than those of classical bulges. Further, I
also show that galaxies identified as having classical bulges have remarkably
regular star formation profiles. The color profiles of galaxies with classical
bulges show a star forming outer disk with a sharp change, consistent with a
decline in star formation rates, toward the center of the galaxy. Classical
bulges have a nearly constant inner profile (r < 1.5 kpc) that is similar to
elliptical galaxies. Pseudobulges in general show no such transition in star
formation properties from the outer disk to the central pseudobulge. Thus I
conclude that pseudobulges and classical bulges do in fact form their stars via
different mechanisms. Further, this adds to the evidence that classical bulges
form most of their stars in fast episodic bursts, in a similar fashion to
elliptical galaxies; whereas, pseudobulges form stars from longer lasting
secular processes.Comment: accepted to ApJ Letter
Isospin fractionation and isoscaling in dynamical nuclear collisions
Isoscaling is found to hold for fragment yields in the antisymmetrized
molecular dynamics (AMD) simulations for collisions of calcium isotopes at 35
MeV/nucleon. This suggests the applicability of statistical considerations to
the dynamical fragment emission. The observed linear relationship between the
isoscaling parameters and the isospin asymmetry of fragments supports the above
suggestion. The slope of this linear function yields information about the
symmetry energy in low density region where multifragmentation occurs.Comment: 11 pages, 6 figure
Scaling for Interfacial Tensions near Critical Endpoints
Parametric scaling representations are obtained and studied for the
asymptotic behavior of interfacial tensions in the \textit{full} neighborhood
of a fluid (or Ising-type) critical endpoint, i.e., as a function \textit{both}
of temperature \textit{and} of density/order parameter \textit{or} chemical
potential/ordering field. Accurate \textit{nonclassical critical exponents} and
reliable estimates for the \textit{universal amplitude ratios} are included
naturally on the basis of the ``extended de Gennes-Fisher'' local-functional
theory. Serious defects in previous scaling treatments are rectified and
complete wetting behavior is represented; however, quantitatively small, but
unphysical residual nonanalyticities on the wetting side of the critical
isotherm are smoothed out ``manually.'' Comparisons with the limited available
observations are presented elsewhere but the theory invites new, searching
experiments and simulations, e.g., for the vapor-liquid interfacial tension on
the two sides of the critical endpoint isotherm for which an amplitude ratio
is predicted.Comment: 42 pages, 6 figures, to appear in Physical Review
Radial Redshift Space Distortions
The radial component of the peculiar velocities of galaxies cause
displacements in their positions in redshift space. We study the effect of the
peculiar velocities on the linear redshift space two point correlation
function. Our analysis takes into account the radial nature of the redshift
space distortions and it highlights the limitations of the plane parallel
approximation. We consider the problem of determining the value of \beta and
the real space two point correlation function from the linear redshift space
two point correlation function. The inversion method proposed here takes into
account the radial nature of the redshift space distortions and can be applied
to magnitude limited redshift surveys that have only partial sky coverage.Comment: 26 pages including 11 figures, to appear in Ap
Analysis of the effectiveness of industrial R and D
The criteria used by private industry in evaluating and selecting proposed research and development projects for implementation, and also in determining which R and D facilities are to be acquired were investigated. Conceptual and practical issues inherent in any quantitative analysis of the contribution of R and D to economic growth were identified in order to assist NASA in developing approaches for analzying the economic implication of its own R and D efforts
Lattice Models of Ionic Systems
A theoretical analysis of Coulomb systems on lattices in general dimensions
is presented. The thermodynamics is developed using Debye-Huckel theory with
ion-pairing and dipole-ion solvation, specific calculations being performed for
3D lattices. As for continuum electrolytes, low-density results for sc, bcc and
fcc lattices indicate the existence of gas-liquid phase separation. The
predicted critical densities have values comparable to those of continuum ionic
systems, while the critical temperatures are 60-70% higher. However, when the
possibility of sublattice ordering as well as Debye screening is taken into
account systematically, order-disorder transitions and a tricritical point are
found on sc and bcc lattices, and gas-liquid coexistence is suppressed. Our
results agree with recent Monte Carlo simulations of lattice electrolytes.Comment: 25 pages, 3 figures, ReVTeX 4, Submitted to J. Chem. Phy
Exploring Programmatic Issues which Affect Continuing Legal Education in Kansas
This mixed methods research study identified common mandatory continuing legal education (MCLE) practices by Kansas providers and evaluated these against established adult and continuing education best practices
Non-linear Constrained Realizations of the Large Scale Structure
The linear algorithm of the Wiener filter and constrained realizations (CRs)
of Gaussian random fields is extended here to perform non-linear CRs. The
procedure consists of: (1) Using low resolution data to constrain a high
resolution realization of the underlying field, as if the linear theory is
valid; (2) Taking the linear CR backwards in time, by the linear theory, to set
initial conditions for N-body simulations; (3) Forwarding the field in time by
an N-body code. An intermediate step is introduced to `linearize' the low
resolution data. The non-linear CR can be applied to any observational data set
that is quasi-linearly related to the underlying field. Here it is applied to
the IRAS 1.2Jy catalog using 846 data points within a sphere of 6000 km/s, to
reconstruct the full non-linear large scale structure of our `local' universe.
The method is tested against mock IRAS surveys, taken from random non-linear
realizations. A detaile analysis of the reconstructed non-linear structure is
presented.Comment: TeX file, 29 pages, 12 figures (included in the text), accepted in
ApJ main journa
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