1,270 research outputs found
Double quantum dots as a high sensitive submillimeter-wave detector
A single electron transistor (SET) consisting of parallel double quantum dots
fabricated in a GaAs/AlGaAs heterostructure crystal is
demonstrated to serve as an extremely high sensitive detector of submillimeter
waves (SMMW). One of the double dots is ionized by SMMW via Kohn-mode plasma
excitation, which affects the SET conductance through the other quantum dot
yielding the photoresponse. Noise equivalent power of the detector for
wavelengths about 0.6 mm is estimated to reach the order of
W/ at 70 mK.Comment: 3 pages, 4 figures, REVTeX, submitted to Appl.Phys.Let
Newcomers Meet the Intracluster Medium in the Coma Cluster
A main topic at this meeting is how galaxies are affected when they enter for
the first time the cluster environment from the outskirts. Most of the times we
are forced to infer the environmental effects indirectly, relying on systematic
variations of galaxy properties with environment, but there aren't many
examples of direct observations able to unveil ongoing transformations taking
place, and the corresponding mechanism producing it. We present a case in which
it is possible to identify the cluster environment, and in particular the
intracluster medium and the recent infall history of galaxies onto the cluster,
as the cause for a recent, abrupt change in the evolutionary history of
galaxies.Comment: 5 pages, 1 postscript figure -- to appear in "Outskirts of Galaxy
Clusters: intense life in the suburbs", IAU Colloquium N. 195, 2004, ed. A
Diaferi
CSIP - a Novel Photon-Counting Detector Applicable for the SPICA Far-Infrared Instrument
We describe a novel GaAs/AlGaAs double-quantum-well device for the infrared
photon detection, called Charge-Sensitive Infrared Phototransistor (CSIP). The
principle of CSIP detector is the photo-excitation of an intersubband
transition in a QW as an charge integrating gate and the signal amplification
by another QW as a channel with very high gain, which provides us with
extremely high responsivity (10^4 -- 10^6 A/W). It has been demonstrated that
the CSIP designed for the mid-infrared wavelength (14.7 um) has an excellent
sensitivity; the noise equivalent power (NEP) of 7x10^-19 W/rHz with the
quantum efficiency of ~2%. Advantages of the CSIP against the other highly
sensitive detectors are, huge dynamic range of >10^6, low output impedance of
10^3 -- 10^4 Ohms, and relatively high operation temperature (>2K). We discuss
possible applications of the CSIP to FIR photon detection covering 35 -- 60 um
waveband, which is a gap uncovered with presently available photoconductors.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Dynamic Nuclear Polarization in a Quantum Hall Corbino Disk
Electrical polarization of nuclear spins is studied in a Corbino disk under a
breakdown regime of the quantum Hall effect (QHE). Since the edge channels are
completely absent in the Corbino disk, we conclude that the electric current
flowing in the bulk channel of a quantum Hall conductor is relevant to dynamic
nuclear polarization (DNP). A pump and probe measurement demonstrates that DNP
emerges near the critical voltage of the QHE breakdown. The agreement of the
onset voltage of DNP with that of the QHE breakdown indicates that the
underlying origin of DNP is closely related to that of the QHE breakdown.Comment: 3 pages, 4 figure
Probing the evolution of early-type galaxies using multi-colour number counts and redshift distributions
We investigate pure luminosity evolution models for early-type (elliptical
and S0) galaxies (i.e., no number density change or morphology transition), and
examine whether these models are consistent with observed number counts in the
B, I and K bands and redshift distributions of two samples of faint galaxies
selected in the I and K bands. The models are characterized by the star
formation time scale and the time when galactic wind blows
in addition to several other conventional parameters. We find the single-burst
model (=0.1 Gyr and =0.353 Gyr), which is known to reproduce
the photometric properties of early-type galaxies in clusters, is inconsistent
with redshift distributions of early-type galaxies in the field environment due
to overpredictions of galaxies at z\gsim1.4 even with strong extinction which
is at work until . In order for dust extinction to be more effective,
we change and as free parameters, and find that models
with \tau_{SF}\gsim0.5 Gyr and Gyr can be made consistent with
both the observed redshift distributions and number counts, if we introduce
strong extinction as a peak value). These results suggest that
early-type galaxies in the field environment do not have the same evolutionary
history as described by the single-burst model.Comment: 6 pages including 4 PS figures; accepted for publication in MNRA
The HST Cosmos Project: Contribution from the Subaru Telescope
The Cosmic Evolution Survey (COSMOS) is a Hubble Space Telescope (HST)
treasury project.The COSMOS aims to perform a 2 square degree imaging survey of
an equatorial field in (F814W) band, using the Advanced Camera for Surveys
(ACS). Such a wide field survey, combined with ground-based photometric and
spectroscopic data, is essential to understand the interplay between large
scale structure, evolution and formation of galaxies and dark matter. In 2004,
we have obtained high-quality, broad band images of the COSMOS field ( and ) using Suprime-Cam on the Subaru
Telescope, and we have started our new optical multi-band program, COSMOS-21 in
2005. Here, we present a brief summary of the current status of the COSMOS
project together with contributions from the Subaru Telescope. Our future
Subaru program, COSMOS-21, is also discussed briefly.Comment: 4 pages, 3 figures, to appear in the Proceedings of the 6th East
Asian Meeting on Astronomy, JKAS, 39, in pres
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