8,755 research outputs found
A catalog of planetary nebulae in the elliptical galaxy NGC 4697
We present a catalog of 535 planetary nebulae discovered in the flattened
elliptical galaxy NGC 4697, using the FORS1 Cassegrain spectrograph of the Very
Large Telescope of the European Southern Observatory at Cerro Paranal, Chile.
The catalog provides positions (x, y coordinates relative to the center of
light of NGC 4697, as well as RA, Dec.), and, for almost all PNs, the magnitude
m(5007) and the heliocentric radial velocity in km/s.Comment: 16 pages, 5 figures, ApJS in pres
The structures underlying soliton solutions in integrable hierarchies
We point out that a common feature of integrable hierarchies presenting
soliton solutions is the existence of some special ``vacuum solutions'' such
that the Lax operators evaluated on them, lie in some abelian subalgebra of the
associated Kac-Moody algebra. The soliton solutions are constructed out of
those ``vacuum solitons'' by the dressing transformation procedure.Comment: Talk given at the I Latin American Symposium on High Energy Physics,
I SILAFAE, Merida, Mexico, November/96, 5 pages, LaTeX, needs aipproc.tex,
aipproc.sty, aipproc.cls, available from
ftp://ftp.aip.org/ems/tex/macros/proceedings/6x9
Face recognition system using fringe projection and moiré: characterization with fractal parameters
We show a new method for face recognition which combines the projection of structures with different characteristics (fringes, bars or grids, dots or speckle) over the face. These projections will then allow the creation of a computer-generated moiré pattern over which different kinds of fractal and complex geometry parameters are then measured. Such parameters will then be used as inputs for a neuro-symbolic hybrid system. Here, we analyze the incidence of some parameters on the efficience for the face recognition method
Planetary nebulae and stellar kinematics in the flattened elliptical galaxy NGC 1344
We present photometric and kinematic information obtained by measuring 197
planetary nebulae (PNs) discovered in the flattened Fornax elliptical galaxy
NGC 1344 (also known as NGC 1340) with an on-band, off-band, grism + on-band
filter technique. We build the PN luminosity function (PNLF) and use it to
derive a distance modulus m-M=31.4, slightly smaller than, but in good
agreement with, the surface brightness fluctuation distance. The PNLF also
provides an estimate of the specific PN formation rate: 6x10^-12 PNs per year
per solar luminosity. Combining the positional information from the on-band
image with PN positions measured on the grism + on-band image, we can measure
the radial velocities of 195 PNs, some of them distant more than 3 effective
radii from the center of NGC 1344. We complement this data set with stellar
kinematics derived from integrated spectra along the major and minor axes, and
parallel to the major axis of NGC 1344. The line-of-sight velocity dispersion
profile indicates the presence of a dark matter halo around this galaxy.Comment: 45 pages, 18 figures, accepted for publication in Ap
Vibrating soap films: An analog for quantum chaos on billiards
We present an experimental setup based on the normal modes of vibrating soap
films which shows quantum features of integrable and chaotic billiards. In
particular, we obtain the so-called scars -narrow linear regions with high
probability along classical periodic orbits- for the classically chaotic
billiards. We show that these scars are also visible at low frequencies.
Finally, we suggest some applications of our experimental setup in other
related two-dimensional wave phenomena.Comment: 5 pages, 7 figures. Better Postscript figures available on reques
More evidence for an intracluster planetary nebulae population in the Virgo cluster
We surveyed a 50 sq arcmin region in the Virgo cluster core to search for
intergalactic planetary nebulae, and found 11 candidates in the surveyed area.
The measured fluxes of these unresolved sources are consistent with these
objects being planetary nebulae from an intracluster population of stars. We
compute the cumulative luminosity function of these 11 planetary nebula
candidates. If we assume that they belong to the Virgo cluster, their
cumulative luminosity function is in good agreement with planetary nebula
luminosity function simulations. This comparison allows us to estimate the
surface mass density of the intracluster stellar population at the surveyed
field in the cluster core.Comment: ApJ Letters, in press. A .ps file is also available at:
http://www.usm.uni-muenchen.de:8001/people/mendez/preprints/preprints.htm
Toward better simulations of planetary nebulae luminosity functions
We describe a procedure for the numerical simulation of the planetary nebulae
luminosity function (PNLF), improving on previous work (Mendez & Soffner 1997).
Earlier PNLF simulations were based on an imitation of the observed
distribution of the intensities of [O III] 5007 relative to Hbeta, generated
predominantly using random numbers. We are now able to replace this by a
distribution derived from the predictions of hydrodynamical PN models
(Schoenberner et al. 2007), which are made to evolve as the central star moves
across the HR diagram, using proper initial and boundary conditions. In this
way we move one step closer to a physically consistent procedure for the
generation of a PNLF. As an example of these new simulations, we have been able
to reproduce the observed PNLF in the Small Magellanic Cloud.Comment: 23 pages, 9 figures, accepted for publication in Ap
Shot Noise Enhancement in Resonant Tunneling Structures in a Magnetic Field
We have observed that the shot noise of tunnel current, I, in
GaSb-AlSb-InAs-AlSb-GaSb double-barrier structure under a magnetic field can
exceed 2qI. The measurements were done at T=4K in fields up to 5T parallel to
the current. The noise enhancement occurred at each of the several
negative-differential conductance regions induced by the tunneling of holes
through Landau levels in the InAs quantum well. The amount of the enhancement
increased with the strength of the negative conductance and reached values up
to 8qI. These results are explained qualitatively by fluctuations of the
density of states in the well, but point out the need for a detailed theory of
shot noise enhancement in resonant tunneling devices.Comment: 4 pages, RevTex, 3 figure
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