338 research outputs found
The science case for the Next Generation AO system at W. M. Keck Observatory
The W. M. Keck Observatory is designing a new adaptive optics system providing precision AO correction in the near infrared, good correction at visible wavelengths, and multiplexed spatially resolved spectroscopy. We discuss science cases for this Next Generation AO (NGAO), and show how the system requirements were derived from these science cases. Key science drivers include asteroid companions, planets around low-mass stars, general relativistic effects around the Galactic Center black hole, nearby active galactic nuclei, and high-redshift galaxies (including galaxies lensed by intervening galaxies or clusters). The multi-object AO-corrected integral field spectrograph will be optimized for high-redshift galaxy science
MEMS practice, from the lab to the telescope
Micro-electro-mechanical systems (MEMS) technology can provide for deformable
mirrors (DMs) with excellent performance within a favorable economy of scale.
Large MEMS-based astronomical adaptive optics (AO) systems such as the Gemini
Planet Imager are coming on-line soon. As MEMS DM end-users, we discuss our
decade of practice with the micromirrors, from inspecting and characterizing
devices to evaluating their performance in the lab. We also show MEMS wavefront
correction on-sky with the "Villages" AO system on a 1-m telescope, including
open-loop control and visible-light imaging. Our work demonstrates the maturity
of MEMS technology for astronomical adaptive optics.Comment: 14 pages, 15 figures, Invited Paper, SPIE Photonics West 201
Technology infrastructure for citizen science
Citizen science, the active participation of the public in scientific research projects, is a rapidly expanding field in open science and open innovation. It provides an integrated model of public knowledge production and engagement with science. As a growing worldwide phenomenon, it is invigorated by evolving new technologies that connect people easily and effectively with the scientific community. Catalysed by citizens’ wishes to be actively involved in scientific processes, as a result of recent societal trends, it also offers contributions to the rise in tertiary education. In addition, citizen science provides a valuable tool for citizens to play a more active role in sustainable development.
This book identifies and explains the role of citizen science within innovation in science and society, and as a vibrant and productive science-policy interface. The scope of this volume is global, geared towards identifying solutions and lessons to be applied across science, practice and policy. The chapters consider the role of citizen science in the context of the wider agenda of open science and open innovation, and discuss progress towards responsible research and innovation, two of the most critical aspects of science today
Characterizing the Adaptive Optics Off-Axis Point-Spread Function. II. Methods for Use in Laser Guide Star Observations
Most current astronomical adaptive optics (AO) systems rely on the
availability of a bright star to measure the distortion of the incoming
wavefront. Replacing the guide star with an artificial laser beacon alleviates
this dependency on bright stars and therefore increases sky coverage, but it
does not eliminate another serious problem for AO observations. This is the
issue of PSF variation with time and field position near the guide star. In
fact, because a natural guide star is still necessary for correction of the
low-order phase error, characterization of laser guide star (LGS) AO PSF
spatial variation is more complicated than for a natural guide star alone. We
discuss six methods for characterizing LGS AO PSF variation that can
potentially improve the determination of the PSF away from the laser spot, that
is, off-axis. Calibration images of dense star fields are used to determine the
change in PSF variation with field position. This is augmented by AO system
telemetry and simple computer simulations to determine a more accurate off-axis
PSF. We report on tests of the methods using the laser AO system on the Lick
Observatory Shane Telescope. [Abstract truncated.]Comment: 31 pages, 5 figures, accepted by PAS
Characterizing the Adaptive Optics Off-Axis Point-Spread Function - I: A Semi-Empirical Method for Use in Natural-Guide-Star Observations
Even though the technology of adaptive optics (AO) is rapidly maturing,
calibration of the resulting images remains a major challenge. The AO
point-spread function (PSF) changes quickly both in time and position on the
sky. In a typical observation the star used for guiding will be separated from
the scientific target by 10" to 30". This is sufficient separation to render
images of the guide star by themselves nearly useless in characterizing the PSF
at the off-axis target position. A semi-empirical technique is described that
improves the determination of the AO off-axis PSF. The method uses calibration
images of dense star fields to determine the change in PSF with field position.
It then uses this information to correct contemporaneous images of the guide
star to produce a PSF that is more accurate for both the target position and
the time of a scientific observation. We report on tests of the method using
natural-guide-star AO systems on the Canada-France-Hawaii Telescope and Lick
Observatory Shane Telescope, augmented by simple atmospheric computer
simulations. At 25" off-axis, predicting the PSF full width at half maximum
using only information about the guide star results in an error of 60%. Using
an image of a dense star field lowers this error to 33%, and our method, which
also folds in information about the on-axis PSF, further decreases the error to
19%.Comment: 29 pages, 9 figures, accepted for publication in the PAS
The science case for the Next Generation AO system at W. M. Keck Observatory
The W. M. Keck Observatory is designing a new adaptive optics system providing precision AO correction in the near infrared, good correction at visible wavelengths, and multiplexed spatially resolved spectroscopy. We discuss science cases for this Next Generation AO (NGAO), and show how the system requirements were derived from these science cases. Key science drivers include asteroid companions, planets around low-mass stars, general relativistic effects around the Galactic Center black hole, nearby active galactic nuclei, and high-redshift galaxies (including galaxies lensed by intervening galaxies or clusters). The multi-object AO-corrected integral field spectrograph will be optimized for high-redshift galaxy science
The LUMBA UVES stellar parameter pipeline
Context. The Gaia-ESO Survey has taken high-quality spectra of a subset of 100 000 stars observed with the Gaia spacecraft. The
goal for this subset is to derive chemical abundances for these stars that will complement the astrometric data collected by Gaia.
Deriving the chemical abundances requires that the stellar parameters be determined.
Aims. We present a pipeline for deriving stellar parameters from spectra observed with the FLAMES-UVES spectrograph in its
standard fibre-fed mode centred on 580 nm, as used in the Gaia-ESO Survey. We quantify the performance of the pipeline in terms of
systematic offsets and scatter. In doing so, we present a general method for benchmarking stellar parameter determination pipelines.
Methods. Assuming a general model of the errors in stellar parameter pipelines, together with a sample of spectra of stars whose stellar
parameters are known from fundamental measurements and relations, we use a Markov chain Monte Carlo method to quantitatively
test the pipeline.
Results. We find that the pipeline provides parameter estimates with systematic errors on effective temperature below 100 K, on
surface gravity below 0.1 dex, and on metallicity below 0.05 dex for the main spectral types of star observed in the Gaia-ESO Survey
and tested here. The performance on red giants is somewhat lower.
Conclusions. The pipeline performs well enough to fulfil its intended purpose within the Gaia-ESO Survey. It is also general enough
that it can be put to use on spectra from other surveys or other spectrographs similar to FLAMES-UVES.Parts of this research were conducted by the Australian Research
Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions
(ASTRO 3D), through project number CE170100013. PG thanks the European Science Foundation (ESF) for support in the framework of EuroGENESIS. KL acknowledges funds from the Alexander von Humboldt Foundation in
the framework of the Sofja Kovalevskaja Award endowed by the Federal
Ministry of Education and Research and funds from the Swedish Research
Council (Grant no. 2015-00415_3) and Marie Skłodowska Curie Actions
(Cofund Project INCA 600398). This research has made use of the SIMBAD
database, operated at CDS, Strasbourg, France
Stellar Companions to Stars with Planets
A combination of high-resolution and wide-field imaging reveals two binary
stars and one triple star system among the sample of the first 11 stars with
planets detected by radial velocity variations. High resolution speckle or
adaptive optics (AO) data probe subarcsecond scales down to the diffraction
limit of the Keck 10-m or Lick 3-m, and direct images or AO images are
sensitive to a wider field, extending to 10" or 38", depending upon the camera.
One of the binary systems -- HD 114762 -- was not previously known to be a
spatially resolved multiple system; additional data taken with the combination
of Keck adaptive optics and NIRSPEC are used to characterize the new companion.
The second binary system -- Tau Boo -- was a known multiple with two
conflicting orbital solutions; the current data will help constrain the
discrepant estimates of periastron time and separation. Another target -- 16
Cyg B -- was a known common proper motion binary, but the current data resolve
a new third component, close to the wide companion 16 Cyg A. Both the HD 114762
and 16 Cyg B systems harbor planets in eccentric orbits, while the Tau Boo
binary contains an extremely close planet in a tidally-circularized orbit.
Although the sample is currently small, the proportion of binary systems is
comparable to that measured in the field over a similar separation range.
Incorporating the null result from another companion search project lowers the
overall fraction of planets in binary systems, but the detections in our survey
reveal that planets can form in binaries separated by less than 50 AU.Comment: 5 Tables, 16 Figures. ApJ, accepte
- …