21,331 research outputs found
Retrieving Bulge and Disk Parameters and Asymptotic Magnitudes from the Growth Curves of Galaxies
We show that the growth curves of galaxies can be used to determine their
bulge and disk parameters and bulge-to-total luminosity ratios, in addition to
their conventional asymptotic magnitudes, provided that the point spread
function is accurately known and signal-to-noise ratio is modest
(S/N). The growth curve is a fundamental quantity that most future
large galaxy imaging surveys will measure. Bulge and disk parameters retrieved
from the growth curve will enable us to perform statistical studies of
luminosity structure for a large number of galaxies.Comment: 28 pages including 13 PS figures; accepted for publication in PAS
Spectrum of an oscillator with jumping frequency and the interference of partial susceptibilities
We study an underdamped oscillator with shot-noise frequency fluctuations.
The oscillator spectrum is determined by the interference of the
susceptibilities for different eigenfrequencies. Depending on the parameters,
it has a fine structure or displays a single asymmetric peak. For
nano-mechanical resonators with a fluctuating number of attached molecules, the
spectrum is found in a simple analytical form. The results bear on various
types of systems where the reciprocal correlation time of frequency
fluctuations can be comparable to the typical frequency jumps
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Discontinuous Galerkin finite element method for dynamic viscoelasticity models of power-law type
Dat Availability Statement: All codes and scripts to reproduce can be found at Jang’s GitHub https://github.com/Yongseok7717/visco_frac_dg and Zenodo (https://doi.org/10.5281/zenodo.10973154).A preprint version is available at HAL open science: https://hal.science/hal-04315693/ . It has not been certified by peer review.Linear viscoelasticity can be characterized by a stress relaxation function. We consider a power-law type stress relaxation to yield a fractional order viscoelasticity model. The governing equation is a Volterra integral problem of the second kind with a weakly singular kernel. We employ spatially discontinuous Galerkin methods, symmetric interior penalty Galerkin method (SIPG) for spatial discretization, and the implicit finite difference schemes in time, Crank-Nicolson method. Further, in order to manage the weak singularity in the Volterra kernel, we use a linear interpolation technique. We present a priori stability and error analyses without relying on Grönwall's inequality, and so provide high quality bounds that do not increase exponentially in time. This indicates that our numerical scheme is well-suited for long-time simulations. Despite the limited regularity in time, we establish suboptimal fractional order accuracy in time as well as optimal convergence of SIPG. We carry out numerical experiments with varying regularity of exact solutions to validate our error estimates. Finally, we present numerical simulations based on real material data.This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors
NMA CO (J=1-0) Observations of the Halpha/Radio Lobe Galaxy NGC 3079: Gas Dynamics in a Weak Bar Potential and Central Massive Core
within 24 lines with 80 characters) We present ^12CO (1-0) observations in
the central 4.5 kpc (1 arcmin) of the Halpha/Radio lobe galaxy NGC 3079 with
the Nobeyama Millimeter Array. The molecular gas shows four components: a main
disk, spiral arms, a nuclear disk, and a nuclear core. The main disk extends
beyond our spatial coverage. The spiral arms are superimposed on the main disk.
The nuclear disk with about 600 pc radius has an intense concentration of
molecular gas. Its appearance on PV diagrams is indicative of oval motions of
the gas, rather than circular. The nuclear core is more compact than our
resolution. Though it is unresolved, the nuclear core shows a very high
velocity about 200 km/s even at the radius of about 100 pc on the PV diagram.
We propose a model that NGC 3079 contains a weak bar. This model explains the
observed features: the main disk and spiral arms result from gaseous x1-orbits
and associated crowding respectively. The nuclear disk arises from gaseous
x2-orbits. From the appearance of the spiral arms on the PV diagram, the
pattern speed of the bar is estimated to be 55+-10 km/s/kpc. The high velocity
of the nuclear core cannot be explained by our model for a bar. Thus we
attribute it to a central massive core with a dynamical mass of 10^9 Msun
within the central 100 pc. This mass is three orders of magnitude more massive
than that of a central black hole in this galaxy.Comment: 43 pages, 17 figures; ApJ, 573, 105, 200
B\"{a}cklund transformations for the KP and mKP hierarchies with self-consistent sources
Using gauge transformations for the corresponding generating
pseudo-differential operators in terms of eigenfunctions and adjoint
eigenfunctions, we construct several types of auto-B\"{a}cklund transformations
for the KP hierarchy with self-consistent sources (KPHSCS) and mKP hierarchy
with self-consistent sources (mKPHSCS) respectively. The B\"{a}cklund
transformations from the KPHSCS to mKPHSCS are also constructed in this way.Comment: 22 pages. to appear in J.Phys.
The Distribution of High and Low Redshift Type Ia Supernovae
The distribution of high redshift Type Ia supernovae (SNe Ia) with respect to
projected distance from the center of the host galaxy is studied and compared
to the distribution of local SNe. The distribution of high-z SNe Ia is found to
be similar to the local sample of SNe Ia discovered with CCDs, but different
than the sample discovered photographically. This is shown to be due to the
Shaw effect. These results have implications for the use of SNe Ia to determine
cosmological parameters if the local sample of supernovae used to calibrate the
light curve decline relationships is drawn from a sample discovered
photographically. A K-S test shows that the probability that the high redshift
SNe of the Supernova Cosmology Project are drawn from the same distribution as
the low redshift calibrators of Riess et al. is 0.1%. This is a potential
problem because photographically discovered SNe are preferentially discovered
farther away from the galaxy nucleus, where SNe show a lower scatter in
absolute magnitude, and are on average 0.3 magnitudes fainter than SNe located
closer to the center of their host galaxy. This raises questions about whether
or not the calibration SNe sample the full range of parameters potentially
present in high redshift SNe Ia. The limited data available suggest that the
calibration process is adequate; however, it would be preferable if high
redshift SNe and the low redshift SNe used to calibrate them were drawn from
the same sample, as subtle differences may be important. Data are also
presented which suggest that the seeming anti-Malmquist trend noticed by
Tammann et al.(1996, 1998) for SNe Ia in galaxies with Cepheid distances may be
due to the location of the SNe in their host galaxies.Comment: 16 pages, 2 figures Accepted for publication in the Astrophysical
Journa
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