3,732 research outputs found
Demonstrating the negligible contribution of optical ACS/HST galaxies to source-subtracted cosmic infrared background fluctuations in deep IRAC/Spitzer images
We study the possible contribution of optical galaxies detected with the {\it
Hubble} ACS instrument to the near-IR cosmic infrared (CIB) fluctuations in
deep {\it Spitzer} images. The {\it Spitzer} data used in this analysis are
obtained in the course of the GOODS project from which we select four
independent regions observed at both 3.6 and 4.5
\um. ACS source catalogs for all of these areas are used to construct maps
containing only their emissions in the ACS -bands. We find that
deep Spitzer data exhibit CIB fluctuations remaining after removal of
foreground galaxies of a very different clustering pattern at both 3.6 and 4.5
\um than the ACS galaxies could contribute. We also find that there are very
good correlations between the ACS galaxies and the {\it removed} galaxies in
the Spitzer maps, but practically no correlations remain with the residual
Spitzer maps used to identify the CIB fluctuations. These contributions become
negligible on larger scales used to probe the CIB fluctuations arising from
clustering. This means that the ACS galaxies cannot contribute to the
large-scale CIB fluctuations found in the residual Spitzer data. The absence of
their contributions also means that the CIB fluctuations arise at z\gsim 7.5
as the Lyman break of their sources must be redshifted past the longest ACS
band, or the fluctuations have to originate in the more local but extremely low
luminosity galaxies.Comment: Ap.J.Letters, in press. Minor revisions to mathc the accepted versio
New measurements of cosmic infrared background fluctuations from early epochs
Cosmic infrared background fluctuations may contain measurable contribution
from objects inaccessible to current telescopic studies, such as the first
stars and other luminous objects in the first Gyr of the Universe's evolution.
In an attempt to uncover this contribution we have analyzed the GOODS data
obtained with the Spitzer IRAC instrument, which are deeper and cover larger
scales than the Spitzer data we have previously analyzed. Here we report these
new measurements of the cosmic infrared background (CIB) fluctuations remaining
after removing cosmic sources to fainter levels than before. The remaining
anisotropies on scales > 0.5 arcmin have a significant clustering component
with a low shot-noise contribution. We show that these fluctuations cannot be
accounted for by instrumental effects, nor by the Solar system and Galactic
foreground emissions and must arise from extragalactic sources.Comment: Ap.J.Letters, in pres
Cosmic Infrared Background Fluctuations and Zodiacal Light
We have performed a specific observational test to measure the effect that
the zodiacal light can have on measurements of the spatial fluctuations of the
near-IR background. Previous estimates of possible fluctuations caused by
zodiacal light have often been extrapolated from observations of the thermal
emission at longer wavelengths and low angular resolution, or from IRAC
observations of high latitude fields where zodiacal light is faint and not
strongly varying with time. The new observations analyzed here target the
COSMOS field, at low ecliptic latitude where the zodiacal light intensity
varies by factors of over the range of solar elongations at which the
field can be observed. We find that the white noise component of the spatial
power spectrum of the background is correlated with the modeled zodiacal light
intensity. Roughly half of the measured white noise is correlated with the
zodiacal light, but a more detailed interpretation of the white noise is
hampered by systematic uncertainties that are evident in the zodiacal light
model. At large angular scales () where excess power above the
white noise is observed, we find no correlation of the power with the modeled
intensity of the zodiacal light. This test clearly indicates that the large
scale power in the infrared background is not being caused by the zodiacal
light.Comment: 17 pp. Accepted for publication in the Ap
Reconstructing emission from pre-reionization sources with cosmic infrared background fluctuation measurements by the JWST
We present new methodology to use cosmic infrared background (CIB)
fluctuations to probe sources at 10<z<30 from a JWST/NIRCam configuration that
will isolate known galaxies to 28 AB mag at 0.5--5 micron. At present
significant mutually consistent source-subtracted CIB fluctuations have been
identified in the Spitzer and Akari data at 2--5 micron, but we demonstrate
internal inconsistencies at shorter wavelengths in the recent CIBER data. We
evaluate CIB contributions from remaining galaxies and show that the bulk of
the high-z sources will be in the confusion noise of the NIRCam beam, requiring
CIB studies. The accurate measurement of the angular spectrum of the
fluctuations and probing the dependence of its clustering component on the
remaining shot noise power would discriminate between the various currently
proposed models for their origin and probe the flux distribution of its
sources. We show that the contribution to CIB fluctuations from remaining
galaxies is large at visible wavelengths for the current instruments precluding
probing the putative Lyman-break of the CIB fluctuations. We demonstrate that
with the proposed JWST configuration such measurements will enable probing the
Lyman break. We develop a Lyman-break tomography method to use the NIRCam
wavelength coverage to identify or constrain, via the adjacent two-band
subtraction, the history of emissions over 10<z<30 as the Universe comes out of
the 'Dark Ages'. We apply the proposed tomography to the current Spitzer/IRAC
measurements at 3.6 and 4.5 micron, to find that it already leads to
interestingly low upper limit on emissions at z>30.Comment: ApJ, in press. Minor revisions/additions to match the version in
proof
The 1/N Expansion in Noncommutative Quantum Mechanics
We study the 1/N expansion in noncommutative quantum mechanics for the
anharmonic and Coulombian potentials. The expansion for the anharmonic
oscillator presented good convergence properties, but for the Coulombian
potential, we found a divergent large N expansion when using the usual
noncommutative generalization of the potential. We proposed a modified version
of the noncommutative Coulombian potential which provides a well-behaved 1/N
expansion.Comment: v2: resided version, to appear in PRD, 18 pages, 4 figure
Context-aware support for cardiac health monitoring using federated machine learning
Context-awareness provides a platform for healthcare professionals to assess the health status of patients in their care using multiple relevant parameters such as heart rate, electrocardiogram (ECG) signals and activity data. It involves the use of digital technologies to monitor the health condition of a patient in an intelligent environment. Feedback gathered from relevant professionals at earlier stages of the project indicates that physical activity recognition is an essential part of cardiac condition monitoring. However, the traditional machine learning method f developing a model for activity recognition suffers two significant challenges; model overfitting and privacy infringements. This research proposes an intelligent and privacy-oriented context-aware decision support system for cardiac health monitoring using the physiological and the activity data of the patient. The system makes use of a federated machine learning approach to develop a model for physical activity recognition. Experimental analysis shows that the federated approach has advantages over the centralized approach in terms of model generalization whilst maintaining the privacy of the user
Context-aware system for cardiac condition monitoring and management: a survey
Health monitoring assists physicians in the decision-making process, which in turn, improves quality of life. As technology advances, the usage and applications of context-aware systems continue to spread across different areas in patient monitoring and disease management. It provides a platform for healthcare professionals to assess the health status of patients in their care using multiple relevant parameters.
In this survey, we consider context-aware systems proposed by researchers for health monitoring and management. More specifically, we investigate different technologies and techniques used for cardiac condition monitoring and management. This paper also propose "mCardiac", an enhanced context-aware decision support system for cardiac condition monitoring and management during rehabilitation
Context-aware approach for cardiac rehabilitation monitoring
As technology advances, the usage and applications of context-aware systems continue to spread across different areas in patient monitoring and disease management. It provides a platform for healthcare professionals to assess the health status of patients in their care using multiple relevant parameters. Existing technologies for cardiac patient monitoring are generally based on the physiological information, mostly the heart rate or Electrocardiogram(ECG) Signals. Other important factors such as physical activities and time of the day are usually ignored. We propose a context-aware solution for cardiac rehabilitation monitoring using multiple vital signs from the physiological and activity data of the patient. This research considers the activity of the patient alongside the time of the activity to facilitate physicians decision-making process. We provide a personalised physical activity recognition processing by generating a personalised model for each user. A prototype is presented to illustrate our proposed approach
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