8,562 research outputs found
The Mid-Infrared Spectral Energy Distribution, Surface Brightness and Color Profiles in Elliptical Galaxies
We describe photometry at mid-infrared passbands (1.2 - 24 microns) for a
sample of 18 elliptical galaxies. All surface brightness distributions resemble
de Vaucouleurs profiles, indicating that most of the emission arises from the
photospheres or circumstellar regions of red giant stars. The spectral energy
distribution peaks near 1.6 microns, but the half-light or effective radius has
a pronounced minimum near the K band (2.15 microns). Apart from the 24 micron
passband, all sample-averaged radial color profiles have measurable slopes
within about twice the (K band) effective radius. Evidently this variation
arises because of an increase in stellar metallicity toward the galactic cores.
For example, the sampled-averaged color profile (K - 5.8 microns) has a
positive slope although no obvious absorption feature is observed in spectra of
elliptical galaxies near 5.8 microns. This, and the minimum in the effective
radius, suggests that the K band may be anomalously luminous in metal-rich
stars in galaxy cores. Unusual radial color profiles involving the 24 micron
passband may suggest that some 24 micron emission comes from interstellar not
circumstellar dust grains.Comment: 18 pages. Accepted by Ap
The universal expression for the amplitude square in quantum electrodynamics
The universal expression for the amplitude square |u_f M u_i|^2 for any
matrix of interaction M is derived. It has obvious covariant form. It allows
the avoidance of calculation of products of the Dirac's matrices traces and
allows easy calculation of cross-sections of any different processes with
polarized and unpolarized particles.Comment: 4 page
Determination of continuous variable entanglement by purity measurements
We classify the entanglement of two--mode Gaussian states according to their
degree of total and partial mixedness. We derive exact bounds that determine
maximally and minimally entangled states for fixed global and marginal
purities. This characterization allows for an experimentally reliable estimate
of continuous variable entanglement based on measurements of purity.Comment: 4 pages, 3 EPS figures. Final versio
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