748 research outputs found
Single-object Imaging and Spectroscopy to Enhance Dark Energy Science from LSST
Single-object imaging and spectroscopy on telescopes with apertures ranging
from ~4 m to 40 m have the potential to greatly enhance the cosmological
constraints that can be obtained from LSST. Two major cosmological probes will
benefit greatly from LSST follow-up: accurate spectrophotometry for nearby and
distant Type Ia supernovae will expand the cosmological distance lever arm by
unlocking the constraining power of high-z supernovae; and cosmology with time
delays of strongly-lensed supernovae and quasars will require additional
high-cadence imaging to supplement LSST, adaptive optics imaging or
spectroscopy for accurate lens and source positions, and IFU or slit
spectroscopy to measure detailed properties of lens systems. We highlight the
scientific impact of these two science drivers, and discuss how additional
resources will benefit them. For both science cases, LSST will deliver a large
sample of objects over both the wide and deep fields in the LSST survey, but
additional data to characterize both individual systems and overall systematics
will be key to ensuring robust cosmological inference to high redshifts.
Community access to large amounts of natural-seeing imaging on ~2-4 m
telescopes, adaptive optics imaging and spectroscopy on 8-40 m telescopes, and
high-throughput single-target spectroscopy on 4-40 m telescopes will be
necessary for LSST time domain cosmology to reach its full potential. In two
companion white papers we present the additional gains for LSST cosmology that
will come from deep and from wide-field multi-object spectroscopy.Comment: Submitted to the call for Astro2020 science white paper
Supergrowth and sub-wavelength object imaging
We further develop the concept of supergrowth [Jordan, Quantum Stud.: Math.
Found. , 285-292 (2020)], a phenomenon complementary to
superoscillation, defined as the local amplitude growth rate of a function
being higher than its largest wavenumber. We identify the superoscillating and
supergrowing regions of a canonical oscillatory function and find the maximum
values of local growth rate and wavenumber. Next, we provide a quantitative
comparison of lengths and relevant intensities between the superoscillating and
the supergrowing regions of a canonical oscillatory function. Our analysis
shows that the supergrowing regions contain intensities that are exponentially
larger in terms of the highest local wavenumber compared to the
superoscillating regions. Finally, we prescribe methods to reconstruct a
sub-wavelength object from the imaging data using both superoscillatory and
supergrowing point spread functions. Our investigation provides an
experimentally preferable alternative to the superoscillation based
superresolution schemes and is relevant to cutting-edge research in far-field
sub-wavelength imaging.Comment: 9 pages, 3 figure
Enhanced Thermal Object Imaging by Photon Addition or Subtraction
Long-baseline interferometry (LBI) is used to reconstruct the image of faint
thermal objects. The image quality, for a given exposure time, is in general
limited by a low signal-to-noise ratio (SNR). We show theoretically that a
significant increase of the SNR, in a LBI, is possible by adding or subtracting
photons to the thermal beam. At low photon counts, photon addition-subtraction
technology strongly enhances the image quality. We have experimentally realized
a nondeterministic physical protocol for photon subtraction. Our theoretical
predictions are supported by experimental results.Comment: 4 pages, 5 figure
J- and Ks-band Galaxy Counts and Color Distributions in the AKARI North Ecliptic Pole Field
We present the J- and Ks-band galaxy counts and galaxy colors covering 750
square arcminutes in the deep AKARI North Ecliptic Pole (NEP) field, using the
FLoridA Multi-object Imaging Near-ir Grism Observational Spectrometer
(FLAMINGOS) on the Kitt Peak National Observatory (KPNO) 2.1m telescope. The
limiting magnitudes with a signal-to-noise ratio of three in the deepest
regions are 21.85 and 20.15 in the J- and Ks-bands respectively in the Vega
magnitude system. The J- and Ks-band galaxy counts in the AKARI NEP field are
broadly in good agreement with those of other results in the literature,
however we find some indication of a change in the galaxy number count slope at
J~19.5 and over the magnitude range 18.0 < Ks < 19.5. We interpret this feature
as a change in the dominant population at these magnitudes because we also find
an associated change in the B - Ks color distribution at these magnitudes where
the number of blue samples in the magnitude range 18.5 < Ks < 19.5 is
significantly larger than that of Ks < 17.5
Integrated Sensing and Communications for 3D Object Imaging via Bilinear Inference
We consider an uplink integrated sensing and communications (ISAC) scenario
where the detection of data symbols from multiple user equipment (UEs) occurs
simultaneously with a three-dimensional (3D) estimation of the environment,
extracted from the scattering features present in the channel state information
(CSI) and utilizing the same physical layer communications air interface, as
opposed to radar technologies. By exploiting a discrete (voxelated)
representation of the environment, two novel ISAC schemes are derived with
purpose-built message passing (MP) rules for the joint estimation of data
symbols and status (filled/empty) of the discretized environment. The first
relies on a modular feedback structure in which the data symbols and the
environment are estimated alternately, whereas the second leverages a bilinear
inference framework to estimate both variables concurrently. Both contributed
methods are shown via simulations to outperform the state-of-the-art (SotA) in
accurately recovering the transmitted data as well as the 3D image of the
environment. An analysis of the computational complexities of the proposed
methods reveals distinct advantages of each scheme, namely, that the bilinear
solution exhibits a superior robustness to short pilots and channel blockages,
while the alternating solution offers lower complexity with large number of UEs
and superior performance in ideal conditions
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