2,767 research outputs found
Infrared astronomy research and high altitude observations
Highlights are presented of studies of the emission mechanisms in the 4 to 8 micron region of the spectrum using a circular variable filter wheel spectrometer with a PbSnTe photovoltaic detector. Investigations covered include the spectroscopy of planets, stellar atmospheres, highly obscured objects in molecular clouds, planetary nebulae, H2 regions, and extragalactic objects
Selection and Mid-infrared Spectroscopy of Ultraluminous Star-Forming Galaxies at z~2
Starting from a sample of 24 \micron\ sources in the Extended Groth Strip, we
use 3.6 to 8 \micron\ color criteria to select ultraluminous infrared galaxies
(ULIRGs) at . Spectroscopy from 20-38 \micron\ of 14 objects verifies
their nature and gives their redshifts. Multi-wavelength data for these objects
imply stellar masses \Msun\ and star formation rates 410
\Msun yr. Four objects of this sample observed at 1.6 \micron\
(rest-frame visible) with {\it HST}/WFC3 show diverse morphologies, suggesting
that multiple formation processes create ULIRGs. Four of the 14 objects show
signs of active galactic nuclei, but the luminosity appears to be dominated by
star formation in all cases.Comment: 33 pages, 13 figures, accepted by Ap
Structural contacts in subduction complexes and their tectonic significance: the Late Palaeozoic coastal accretionary wedge of central Chile
Understanding the contact between the very low-grade metagreywacke of the Eastern Series and
high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of
central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show
the progressive development of structures and finite strain from the least deformed rocks in the eastern part of
the Eastern Series of the accretionary wedge to high-pressure schist of the Western Series at the Pacific coast.
Upright chevron folds of sedimentary layering are associated with an axial-plane foliation, S1. As the F1 folds
became slightly overturned to the west, S1 was folded about west-vergent open F2 folds and an S2 axial-plane
foliation developed. Near the contact between the Western and Eastern Series S2 represents a penetrative
subhorizontal transposition foliation. Towards the structurally deepest units in the west the transposition
foliation becomes progressively flattened. Finite-strain data as obtained by Rf /Ï• analysis in metagreywacke
and X-ray texture goniometry in phyllosilicate-rich rocks show a smooth and gradual increase in strain
magnitude from east to west. Overturned folds and other shear-sense indicators show a uniform top-to-the-west
shear sense in moderately deformed rocks, whereas the shear sense is alternating top-to-the-west and top-tothe-
east in the strongly flattened high-pressure rocks of the Western Series near the Pacific coast. We interpret
the progressive structural and strain evolution across the contact between the two series to reflect a continuous
change in the mode of accretion in the subduction wedge. Initially, the rocks of the Eastern Series were
frontally accreted to the pre-Andean margin before c. 300 Ma. Frontal accretion caused horizontal shortening,
and upright folds and subvertical axial-plane foliations developed. At c. 300 Ma the mode of accretion
changed and the rocks of the Western Series were underplated below the Andean margin. This basal accretion
caused a major change in the flow field within the wedge and gave rise to vertical shortening and the
development of the penetrative subhorizontal transposition foliation. Subsequent differential exhumation was
resolved gradually over a wide region, implying that exhumation was not tectonically controlled.researc
Structural contacts in the Late Paleozoic accretionary wedge of central Chile and their tectonic significance for the evolution of the accretionary complex
The Chilean accretionary wedge is part
of a Late Paleozoic subduction complex
that developed during subduction of the
Pacific plate underneath South America.
The wedge is commonly subdivided
into a structurally lower Western Series
and an upper Eastern Series. Understanding
the contact between both series
has been a long standing problem
and is fundamental for the understanding
of the evolution of the wedge system.
We show the progressive development
of structures and finite strain from
the least-deformed rocks in the eastern
part of the Eastern Series of the accretionary
wedge to higher grade schist of
the Western Series at the Pacific coast...conferenc
Mode-division-multiplexing of multiple Bessel-Gaussian beams carrying orbital-angular-momentum for obstruction-tolerant free-space optical and millimetre-wave communication links
We experimentally investigate the potential of using ‘self-healing’ Bessel-Gaussian beams carrying orbital-angular-momentum to overcome limitations in obstructed free-space optical and 28-GHz millimetre-wave communication links. We multiplex and transmit two beams (l = +1 and +3) over 1.4 metres in both the optical and millimetre-wave domains. Each optical beam carried 50-Gbaud quadrature-phase-shift-keyed data, and each millimetre-wave beam carried 1-Gbaud 16-quadrature-amplitude-modulated data. In both types of links, opaque disks of different sizes are used to obstruct the beams at different transverse positions. We observe self-healing after the obstructions, and assess crosstalk and power penalty when data is transmitted. Moreover, we show that Bessel-Gaussian orbital-angular-momentum beams are more tolerant to obstructions than non-Bessel orbital-angular-momentum beams. For example, when obstructions that are 1 and 0.44 the size of the l = +1 beam, are placed at beam centre, optical and millimetre-wave Bessel-Gaussian beams show ~6 dB and ~8 dB reduction in crosstalk, respectively
- …