5,310 research outputs found
First results from SAM-FP: Fabry-Perot observations with ground-layer adaptive optics - the structure and kinematics of the core of 30 Doradus
The aim of this paper is to present the first data set obtained with SOAR
Adaptive Module-Fabry-Parot (SAM-FP), a Fabry-Perot instrument mounted inside
the SOAR telescope Adaptive-Optics Module. This is the only existing imaging
Fabry-Perot interferometer using laser-assisted ground-layer adaptive optics.
SAM-FP was used to observe the ionized gas, traced by Halpha, in the centre of
the 30 Doradus starburst (the Tarantula Nebula) in the Large Magellanic Cloud,
with high spatial (~0.6" or 0.15 pc) and spectral (R=11200) resolution. Radial
velocity, velocity dispersion and monochromatic maps were derived. The region
displays a mix of narrow, sigma ~ 20 km/s profiles and multiple broader
profiles with sigma ~ 70-80 km/s, indicating the complex nature of the nebula
kinematics. A comparison with previously obtained VLT/FLAMES spectroscopy
demonstrates that the data agree well in the regions of overlap, but the
Fabry-Perot data are superior in spatial coverage. A preliminary analysis of
the observations finds a new expanding bubble south of R136, with a projected
radius of r=5.6 pc and an expansion velocity of 29 +/- 4 km/s. In addition, the
first-time detailed kinematic maps derived here for several complexes and
filaments of 30 Doradus allow identification of kinematically independent
structures. These data exemplify the power of the combination of a high-order
Fabry-Perot with a wide-field imager (3' x 3' GLAO-corrected field of view) for
high-resolution spatial and spectral studies. In particular, SAM-FP data cubes
are highly advantageous over multifibre or long-slit data sets for nebula
structure studies and to search for small-scale bubbles, given their greatly
improved spatial coverage. For reference, this paper also presents two
appendices with detailed descriptions of the usage of Fabry-Perot devices,
including formulae and explanations for understanding Fabry-Perot observations.Comment: 22 pages, 9 figures, 1 tabl
Adaptive smartphone-based sensor fusion for estimating competitive rowing kinematic metrics.
Competitive rowing highly values boat position and velocity data for real-time feedback during training, racing and post-training analysis. The ubiquity of smartphones with embedded position (GPS) and motion (accelerometer) sensors motivates their possible use in these tasks. In this paper, we investigate the use of two real-time digital filters to achieve highly accurate yet reasonably priced measurements of boat speed and distance traveled. Both filters combine acceleration and location data to estimate boat distance and speed; the first using a complementary frequency response-based filter technique, the second with a Kalman filter formalism that includes adaptive, real-time estimates of effective accelerometer bias. The estimates of distance and speed from both filters were validated and compared with accurate reference data from a differential GPS system with better than 1 cm precision and a 5 Hz update rate, in experiments using two subjects (an experienced club-level rower and an elite rower) in two different boats on a 300 m course. Compared with single channel (smartphone GPS only) measures of distance and speed, the complementary filter improved the accuracy and precision of boat speed, boat distance traveled, and distance per stroke by 44%, 42%, and 73%, respectively, while the Kalman filter improved the accuracy and precision of boat speed, boat distance traveled, and distance per stroke by 48%, 22%, and 82%, respectively. Both filters demonstrate promise as general purpose methods to substantially improve estimates of important rowing performance metrics
The Brazilian Tunable Filter Imager for the SOAR telescope
This paper presents a new Tunable Filter Instrument for the SOAR telescope.
The Brazilian Tunable Filter Imager (BTFI) is a versatile, new technology,
tunable optical imager to be used in seeing-limited mode and at higher spatial
fidelity using the SAM Ground-Layer Adaptive Optics facility at the SOAR
telescope. The instrument opens important new science capabilities for the SOAR
community, from studies of the centers of nearby galaxies and the insterstellar
medium to statistical cosmological investigations. The BTFI takes advantage of
three new technologies. The imaging Bragg Tunable Filter concept utilizes
Volume Phase Holographic Gratings in a double-pass configuration, as a tunable
filter, while a new Fabry-Perot (FP) concept involves technologies which allow
a single FP etalon to act over a large range of interference orders and
spectral resolutions. Both technologies will be in the same instrument.
Spectral resolutions spanning the range between 25 and 30,000 can be achieved
through the use of iBTF at low resolution and scanning FPs beyond R ~2,000. The
third new technologies in BTFI is the use of EMCCDs for rapid and cyclically
wavelength scanning thus mitigating the damaging effect of atmospheric
variability through data acquisition. An additional important feature of the
instrument is that it has two optical channels which allow for the simultaneous
recording of the narrow-band, filtered image with the remaining (complementary)
broad-band light. This avoids the uncertainties inherent in tunable filter
imaging using a single detector. The system was designed to supply tunable
filter imaging with a field-of-view of 3 arcmin on a side, sampled at 0.12" for
direct Nasmyth seeing-limited area spectroscopy and for SAM's visitor
instrument port for GLAO-fed area spectroscopy. The instrument has seen first
light, as a SOAR visitor instrument. It is now in comissioning phase.Comment: accepted in PAS
The circumstellar environment of T Tau S at high spatial and spectral resolution
We have obtained the first high spatial (0.05'') and spectral (R~35000)
resolution 2 micron spectrum of the T Tau S tight binary system using adaptive
optics on the Keck II telescope. We have also obtained the first 3.8 and 4.7
micron images that resolve the three components of the T Tau multiple system,
as well as new 1.6 and 2.2 micron images. Together with its very red
near-infrared colors, the spectrum of T Tau Sb shows that this T Tauri star is
extincted by a roughly constant extinction of Av~15 mag, which is probably the
0.7''x0.5'' circumbinary structure recently observed in absorption in the
ultraviolet. T Tau Sa, which is also observed through this screen and is
actively accreting, further possesses a small edge-on disk that is evidenced by
warm (390 K), narrow overtone CO rovibrational absorption features in our
spectrum. We find that T Tau Sa is most likely an intermediate-mass star
surrounded by a semi-transparent 2-3 AU-radius disk whose asymmetries and short
Keplerian rotation explain the large photometric variability of the source on
relatively short timescales. We also show that molecular hydrogen emission
exclusively arises from the gas that surrounds T Tau S and that its spatial and
kinematic structure, while providing suggestive evidence for a jet-like
structure, is highly complex.Comment: accepted for publication in the Astrophysical Journal; 41 pages, 10
figure
F-8C adaptive flight control extensions
An adaptive concept which combines gain-scheduled control laws with explicit maximum likelihood estimation (MLE) identification to provide the scheduling values is described. The MLE algorithm was improved by incorporating attitude data, estimating gust statistics for setting filter gains, and improving parameter tracking during changing flight conditions. A lateral MLE algorithm was designed to improve true air speed and angle of attack estimates during lateral maneuvers. Relationships between the pitch axis sensors inherent in the MLE design were examined and used for sensor failure detection. Design details and simulation performance are presented for each of the three areas investigated
Resolved Spectroscopy of Gravitationally-Lensed Galaxies: Recovering Coherent Velocity Fields in Sub-Luminous z~2-3 Galaxies
We present spatially-resolved dynamics for six strongly lensed star-forming
galaxies at z=1.7-3.1, each enlarged by a linear magnification factor ~8. Using
the Keck laser guide star AO system and the OSIRIS integral field unit
spectrograph we resolve kinematic and morphological detail in our sample with
an unprecedented fidelity, in some cases achieving spatial resolutions of ~100
pc. With one exception our sources have diameters ranging from 1-7 kpc, star
formation rates of 2-40 Msun/yr (uncorrected for extinction) and dynamical
masses of 10^(9.7-10.3) Msun. With this exquisite resolution we find that four
of the six galaxies display coherent velocity fields consistent with a simple
rotating disk model, which can only be recovered with the considerably improved
spatial resolution and sampling from the combination of adaptive optics and
strong gravitational lensing. Our model fits imply ratios for the systemic to
random motion, V sin(i)/sigma, ranging from 0.5-1.3 and Toomre disk parameters
Q<1. The large fraction of well-ordered velocity fields in our sample is
consistent with data analyzed for larger, more luminous sources at this
redshift. Our high resolution data further reveal that all six galaxies contain
multiple giant star-forming HII regions whose resolved diameters are in the
range 300 pc - 1.0 kpc, consistent with the Jeans length expected in the case
of dispersion support. The density of star formation in these regions is ~100
times higher than observed in local spirals; such high values are only seen in
the most luminous local starbursts. The global dynamics and demographics of
star formation in these HII regions suggest that vigorous star formation is
primarily governed by gravitational instability in primitive rotating disks.Comment: 18 pages, 8 figures, submitted to MNRA
Astrometry with the Wide-Field InfraRed Space Telescope
The Wide-Field InfraRed Space Telescope (WFIRST) will be capable of
delivering precise astrometry for faint sources over the enormous field of view
of its main camera, the Wide-Field Imager (WFI). This unprecedented combination
will be transformative for the many scientific questions that require precise
positions, distances, and velocities of stars. We describe the expectations for
the astrometric precision of the WFIRST WFI in different scenarios, illustrate
how a broad range of science cases will see significant advances with such
data, and identify aspects of WFIRST's design where small adjustments could
greatly improve its power as an astrometric instrument.Comment: version accepted to JATI
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