4,709 research outputs found
Integral Field Spectroscopy of two radio galaxies at z~2.3
In this article we study the morphology, kinematics and ionization properties
of the giant ionized gas nebulae surrounding two high redshift radio galaxies,
4C40.36 (z=2.27) and 4C48.48 (z=2.34).}{Integral Field Spectroscopy
observations were taken using the PPAK bundle of the PMAS spectrograph, mounted
on the 3.5m on the Calar Alto Observatory, in order to cover a field-of-view of
64" X 72" centered in each radio galaxy. The observations spanned over 5
nights, using two different spectral resolutions (with FWHM~4 AA and ~8 AA
respectively), covering the optical wavelength range from ~3700 AA to ~7100 AA,
which corresponds to the rest-frame ultraviolet range from ~1100 AA to ~2000 AA
>. Various emission lines are detected within this wavelength range, including
Lyalpha (1216 AA), NV (1240 AA), CIV (1549 AA), HeII (1640 AA), OIII] (1663 AA)
and CIII] (1909\AA). The dataset was used to derive the spatial distribution of
the flux intensity of each of these lines and the gas kinematics. The
properties of the emission lines in the nuclear regions were studied in
detail.In agreement with previous studies, we find that both objects are
embedded in a large ionized gas nebula, where Ly alpha emission is extended
across ~100 kpc or more. The CIV and HeII emission lines are also spatially
extended. The nebulae are generally aligned with the radio axis, although we
detect emission far from it. In 4C+48.48, there is a band of low Ly-alpha/CIV
running perpendicular to the radio axis, at the location of the active nucleus.
This feature might be the observational signature of an edge-on disk of neutral
gas. The kinematics of both nebulae are inconsistent with stable rotation,
although they are not inconsistent with infall or outflow.Comment: 14 pages, 5 figures, accepted for publishing in Astronomy &
Astrophysic
Local and average fields inside surface-disordered waveguides: Resonances in the one-dimensional Anderson localization regime
We investigate the one-dimensional propagation of waves in the Anderson
localization regime, for a single-mode, surface disordered waveguide. We make
use of both an analytical formulation and rigorous numerical simulation
calculations. The occurrence of anomalously large transmission coefficients for
given realizations and/or frequencies is studied, revealing huge field
intensity concentration inside the disordered waveguide. The analytically
predicted s-like dependence of the average intensity, being in good agreement
with the numerical results for moderately long systems, fails to explain the
intensity distribution observed deep in the localized regime. The average
contribution to the field intensity from the resonances that are above a
threshold transmission coefficient is a broad distribution with a large
maximum at/near mid-waveguide, depending universally (for given ) on the
ratio of the length of the disorder segment to the localization length,
. The same universality is observed in the spatial distribution of the
intensity inside typical (non-resonant with respect to the transmission
coefficient) realizations, presenting a s-like shape similar to that of the
total average intensity for close to 1, which decays faster the lower
is . Evidence is given of the self-averaging nature of the random
quantity . Higher-order moments of the intensity are
also shown.Comment: 9 pages, 9 figure
Magnetic Field Effects on the Transport Properties of One-sided Rough Wires
We present a detailed numerical analysis of the effect of a magnetic field on
the transport properties of a `small-' one-sided surface disordered wire.
When time reversal symmetry is broken due to a magnetic field , we find a
strong increase with not only of the localization length but also of
the mean free path caused by boundary states. Despite this, the
universal relationship between and does hold. We also analyze the
conductance distribution at the metal-insulator crossover, finding a very good
agreement with Random Matrix Theory with two fluctuating channels within the
Circular Orthogonal(Unitary) Ensemble in absence(presence) of Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Universal Conductance Distributions in the Crossover between Diffusive and Localization Regimes
The full distribution of the conductance in quasi-one-dimensional
wires with rough surfaces is analyzed from the diffusive to the localization
regime. In the crossover region, where the statistics is dominated by only one
or two eigenchannels, the numerically obtained P(G) is found to be independent
of the details of the system with the average conductance as the only
scaling parameter. For < e^2/h, P(G) is given by an essentially
``one-sided'' log-normal distribution. In contrast, for e^2/h <= 2e^2/h,
the shape of P(G) remarkable agrees with those predicted by random matrix
theory for two fluctuating transmission eigenchannels.Comment: Accepted for publication in Phys. Rev. Let
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