1,124 research outputs found
The Asiago-ESO/RASS QSO Survey II. The Southern Sample
This is the second paper of a series describing the Asiago-ESO/RASS QSO
survey, a project aimed at the construction of an all-sky statistically
well-defined sample of very bright QSOs (B_J < 15). Such a survey is required
to remove the present uncertainties about the properties of the local QSO
population and constitutes an homogeneous database for detailed evolutionary
studies of AGN. We present here the complete Southern Sample, which comprises
243 bright (12.60 < B_J < 15.13) QSO candidates at high galactic latitudes
(|b_{gal}| > 30^{\circ}). The area covered by the survey is 5660 sq. deg.
Spectroscopy for the 137 still unidentified objects has been obtained. The
total number of AGN turns out to be 111, 63 of which are new identifications.
The properties of the selection are discussed. The completeness and the success
rate for this survey at the final stage are 63% and 46%, respectively.Comment: 36 pages Latex, with 15 PostScript figures. Accepted for publication
in Astronomical Journa
The power spectrum of the flux distribution in the Lyman-alpha forest of a Large sample of UVES QSO Absorption Spectra (LUQAS)
The flux power spectra of the Lyman-alpha forest from a sample of 27 QSOs
taken with the high resolution echelle spectrograph UVES on VLT are presented.
We find a similar fluctuation amplitude at the peak of the ``3D'' flux power
spectrum at k ~ 0.03 (km/sec)^(-1) as the study by Croft et al. (2002), in the
same redshift range. The amplitude of the flux power spectrum increases with
decreasing redshift if corrected for the increase in the mean flux level as
expected if the evolution of the flux power spectrum is sensitive to the
gravitational growth of matter density fluctuations. This is in agreement with
the findings of McDonald et al. (2000) at larger redshift. The logarithmic
slope of the "3D" flux power spectrum, P_F(k), at large scales k < 0.03
(km/sec)^(-1), is 1.4 +- 0.3, i.e. 0.3 shallower than that found by Croft et
al. (2002) but consistent within the errors.Comment: 18 pages, 9 PS figures, 6 tables. Note that the k-values of the 1D
flux power spectrum had been erroneously shifted by half a bin size (in log
k) in the previous version. All the other results are unaffected. New tables
can be found at http://www.ast.cam.ac.uk/~rtnigm/luqas.ht
Dynamics and phase evolution of Bose-Einstein condensates in one-dimensional optical lattices
We report experimental results on the dynamics and phase evolution of
Bose-Einstein condensates in 1D optical lattices. The dynamical behaviour is
studied by adiabatically loading the condensate into the lattice and
subsequently switching off the magnetic trap. In this case, the condensate is
free to expand inside the periodic structure of the optical lattice. The phase
evolution of the condensate, on the other hand, can be studied by
non-adiabatically switching on the periodic potential. We observe decays and
revivals of the interference pattern after a time-of-flight.Comment: 6 pages, 5 figures; submitted to the Proceedings of the 11th Laser
Physics Workshop, Bratislava 200
Localization of Two-Component Bose-Einstein Condensates in Optical Lattices
We reveal underlying principles of nonlinear localization of a two-component
Bose-Einstein condensate loaded into a one-dimensional optical lattice. Our
theory shows that spin-dependent optical lattices can be used to manipulate
both the type and magnitude of nonlinear interaction between the ultracold
atomic species and to observe nontrivial two-componentnlocalized states of a
condensate in both bands and gaps of the matter-wave band-gap structure.Comment: 4 pages, 4 figure
Instabilities of a Bose-Einstein condensate in a periodic potential: an experimental investigation
By accelerating a Bose-Einstein condensate in a controlled way across the
edge of the Brillouin zone of a 1D optical lattice, we investigate the
stability of the condensate in the vicinity of the zone edge. Through an
analysis of the visibility of the interference pattern after a time-of-flight
and the widths of the interference peaks, we characterize the onset of
instability as the acceleration of the lattice is decreased. We briefly discuss
the significance of our results with respect to recent theoretical work.Comment: 7 pages, 3 figures; submitted to Optics Express (Focus Issue on Cold
Atomic Gases in Optical Lattices
Coherent Storage of Temporally Multimode Light Using a Spin-Wave Atomic Frequency Comb Memory
We report on coherent and multi-temporal mode storage of light using the full
atomic frequency comb memory scheme. The scheme involves the transfer of
optical atomic excitations in Pr3+:Y2SiO5 to spin-waves in the hyperfine levels
using strong single-frequency transfer pulses. Using this scheme, a total of 5
temporal modes are stored and recalled on-demand from the memory. The coherence
of the storage and retrieval is characterized using a time-bin interference
measurement resulting in visibilities higher than 80%, independent of the
storage time. This coherent and multimode spin-wave memory is promising as a
quantum memory for light.Comment: 17 pages, 5 figure
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