1,418 research outputs found
Exploiting Cross Correlations and Joint Analyses
In this report, we present a wide variety of ways in which information from
multiple probes of dark energy may be combined to obtain additional information
not accessible when they are considered separately. Fundamentally, because all
major probes are affected by the underlying distribution of matter in the
regions studied, there exist covariances between them that can provide
information on cosmology. Combining multiple probes allows for more accurate
(less contaminated by systematics) and more precise (since there is
cosmological information encoded in cross-correlation statistics) measurements
of dark energy. The potential of cross-correlation methods is only beginning to
be realized. By bringing in information from other wavelengths, the
capabilities of the existing probes of dark energy can be enhanced and
systematic effects can be mitigated further. We present a mixture of work in
progress and suggestions for future scientific efforts. Given the scope of
future dark energy experiments, the greatest gains may only be realized with
more coordination and cooperation between multiple project teams; we recommend
that this interchange should begin sooner, rather than later, to maximize
scientific gains.Comment: Report from the "Dark Energy and CMB" working group for the American
Physical Society's Division of Particles and Fields long-term planning
exercise ("Snowmass"
Perception-aware Path Planning
In this paper, we give a double twist to the problem of planning under
uncertainty. State-of-the-art planners seek to minimize the localization
uncertainty by only considering the geometric structure of the scene. In this
paper, we argue that motion planning for vision-controlled robots should be
perception aware in that the robot should also favor texture-rich areas to
minimize the localization uncertainty during a goal-reaching task. Thus, we
describe how to optimally incorporate the photometric information (i.e.,
texture) of the scene, in addition to the the geometric one, to compute the
uncertainty of vision-based localization during path planning. To avoid the
caveats of feature-based localization systems (i.e., dependence on feature type
and user-defined thresholds), we use dense, direct methods. This allows us to
compute the localization uncertainty directly from the intensity values of
every pixel in the image. We also describe how to compute trajectories online,
considering also scenarios with no prior knowledge about the map. The proposed
framework is general and can easily be adapted to different robotic platforms
and scenarios. The effectiveness of our approach is demonstrated with extensive
experiments in both simulated and real-world environments using a
vision-controlled micro aerial vehicle.Comment: 16 pages, 20 figures, revised version. Conditionally accepted for
IEEE Transactions on Robotic
Informative Path Planning for Active Field Mapping under Localization Uncertainty
Information gathering algorithms play a key role in unlocking the potential
of robots for efficient data collection in a wide range of applications.
However, most existing strategies neglect the fundamental problem of the robot
pose uncertainty, which is an implicit requirement for creating robust,
high-quality maps. To address this issue, we introduce an informative planning
framework for active mapping that explicitly accounts for the pose uncertainty
in both the mapping and planning tasks. Our strategy exploits a Gaussian
Process (GP) model to capture a target environmental field given the
uncertainty on its inputs. For planning, we formulate a new utility function
that couples the localization and field mapping objectives in GP-based mapping
scenarios in a principled way, without relying on any manually tuned
parameters. Extensive simulations show that our approach outperforms existing
strategies, with reductions in mean pose uncertainty and map error. We also
present a proof of concept in an indoor temperature mapping scenario.Comment: 8 pages, 7 figures, submission (revised) to Robotics & Automation
Letters (and IEEE International Conference on Robotics and Automation
The Transit Light Curve Project. X. A Christmas Transit of HD 17156b
Photometry is presented of the Dec. 25, 2007 transit of HD 17156b, which has
the longest orbital period and highest orbital eccentricity of all the known
transiting exoplanets. New measurements of the stellar radial velocity are also
presented. All the data are combined and integrated with stellar-evolutionary
modeling to derive refined system parameters. The planet's mass and radius are
found to be 3.212_{-0.082}^{+0.069} Jupiter masses and 1.023_{-0.055}^{+0.070}
Jupiter radii. The corresponding stellar properties are 1.263_{-0.047}^{+0.035}
solar masses and 1.446_{-0.067}^{+0.099} solar radii. The planet is smaller by
1 sigma than a theoretical solar-composition gas giant with the same mass and
equilibrium temperature, a possible indication of heavy-element enrichment. The
midtransit time is measured to within 1 min, and shows no deviation from a
linear ephemeris (and therefore no evidence for orbital perturbations from
other planets). We provide ephemerides for future transits and superior
conjunctions. There is an 18% chance that the orbital plane is oriented close
enough to edge-on for secondary eclipses to occur at superior conjunction.
Observations of secondary eclipses would reveal the thermal emission spectrum
of a planet that experiences unusually large tidal heating and insolation
variations.Comment: To appear in ApJ [26 pages
The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools
[Abridged] When WFC3 is installed on HST, the community will have powerful
new tools for investigating resolved stellar populations. The WFC3 Galactic
Bulge Treasury program will obtain deep imaging on 4 low-extinction fields.
These non-proprietary data will enable a variety of science investigations not
possible with previous data sets. To aid in planning for the use of these data
and for future proposals, we provide an introduction to the program, its
photometric system, and the associated calibration effort.
The observing strategy is based upon a new 5-band photometric system spanning
the UV, optical, and near-infrared. With these broad bands, one can construct
reddening-free indices of Teff and [Fe/H]. Besides the 4 bulge fields, the
program will target 6 fields in well-studied star clusters, spanning a wide
range of [Fe/H]. The cluster data serve to calibrate the indices, provide
population templates, and correct the transformation of isochrones into the
WFC3 photometric system. The bulge data will shed light on the bulge formation
history, and will also serve as population templates for other studies. One of
the fields includes 12 candidate hosts of extrasolar planets.
CMDs are the most popular tool for analyzing resolved stellar populations.
However, due to degeneracies among Teff, [Fe/H], and reddening in traditional
CMDs, it can be difficult to draw robust conclusions from the data. The 5-band
system used for the bulge Treasury observations will provide indices that are
roughly orthogonal in Teff and [Fe/H], and we argue that model fitting in an
index-index diagram will make better use of the information than fitting
separate CMDs. We provide simulations to show the expected data quality and the
potential for differentiating between different star-formation histories.Comment: Accepted for publication in The Astronomical Journal. 9 pages, 8
figures, latex, AJ forma
Report by the ESA-ESO Working Group on Fundamental Cosmology
ESO and ESA agreed to establish a number of Working Groups to explore
possible synergies between these two major European astronomical institutions.
This Working Group's mandate was to concentrate on fundamental questions in
cosmology, and the scope for tackling these in Europe over the next ~15 years.
One major resulting recommendation concerns the provision of new generations of
imaging survey, where the image quality and near-IR sensitivity that can be
attained only in space are naturally matched by ground-based imaging and
spectroscopy to yield massive datasets with well-understood photometric
redshifts (photo-z's). Such information is essential for a range of new
cosmological tests using gravitational lensing, large-scale structure, clusters
of galaxies, and supernovae. Great scope in future cosmology also exists for
ELT studies of the intergalactic medium and space-based studies of the CMB and
gravitational waves; here the synergy is less direct, but these areas will
remain of the highest mutual interest to the agencies. All these recommended
facilities will produce vast datasets of general applicability, which will have
a tremendous impact on broad areas of astronomy.Comment: ESA-ESO Working Groups Report No. 3, 125 pages, 28 figures. A PDF
version including the cover is available from
http://www.stecf.org/coordination/esa_eso/cosmology/report_cover.pdf and a
printed version (A5 booklet) is available in limited numbers from the Space
Telescope-European Coordinating Facility (ST-ECF): [email protected]
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