821 research outputs found
Micro Fourier Transform Profilometry (FTP): 3D shape measurement at 10,000 frames per second
Recent advances in imaging sensors and digital light projection technology
have facilitated a rapid progress in 3D optical sensing, enabling 3D surfaces
of complex-shaped objects to be captured with improved resolution and accuracy.
However, due to the large number of projection patterns required for phase
recovery and disambiguation, the maximum fame rates of current 3D shape
measurement techniques are still limited to the range of hundreds of frames per
second (fps). Here, we demonstrate a new 3D dynamic imaging technique, Micro
Fourier Transform Profilometry (FTP), which can capture 3D surfaces of
transient events at up to 10,000 fps based on our newly developed high-speed
fringe projection system. Compared with existing techniques, FTP has the
prominent advantage of recovering an accurate, unambiguous, and dense 3D point
cloud with only two projected patterns. Furthermore, the phase information is
encoded within a single high-frequency fringe image, thereby allowing
motion-artifact-free reconstruction of transient events with temporal
resolution of 50 microseconds. To show FTP's broad utility, we use it to
reconstruct 3D videos of 4 transient scenes: vibrating cantilevers, rotating
fan blades, bullet fired from a toy gun, and balloon's explosion triggered by a
flying dart, which were previously difficult or even unable to be captured with
conventional approaches.Comment: This manuscript was originally submitted on 30th January 1
The Calar Alto Legacy Integral Field Area Survey: extended and remastered data release
This paper describes the extended data release of the Calar Alto Legacy
Integral Field Area (CALIFA) survey (eDR). It comprises science-grade quality
data for 895 galaxies obtained with the PMAS/PPak instrument at the 3.5 m
telescope at the Calar Alto Observatory along the last 12 years, using the V500
setup (3700-7500{\AA}, 6{\AA}/FWHM) and the CALIFA observing strategy. It
includes galaxies of any morphological type, star-formation stage, a wide range
of stellar masses (10 10 Msun ), at an average redshift of
0.015 (90\% within 0.005z0.05). Primarily selected based on the
projected size and apparent magnitude, we demonstrate that it can be volume
corrected resulting in a statistically limited but representative sample of the
population of galaxies in the nearby Universe. All the data were homogeneous
re-reduced, introducing a set of modifications to the previous reduction. The
most relevant is the development and implementation of a new
cube-reconstruction algorithm that provides with an (almost) seeing-limited
spatial resolution (FWHM PSF 1.0").To illustrate the usability and
quality of the data, we extracted two aperture spectra for each galaxy (central
1.5" and fully integrated), and analyze them using pyFIT3D. We obtain a set of
observational and physical properties of both the stellar populations and the
ionized gas, that have been compared for the two apertures, exploring their
distributions as a function of the stellar masses and morphologies of the
galaxies, comparing with recent results in the literature. DATA RELEASE:
http://ifs.astroscu. unam.mx/CALIFA_WEB/public_html/Comment: 30 pages, 26 figures, accepted for publishing in the MNRA
Designing Future Dark Energy Space Missions: II. Photometric Redshift of Space Weak Lensing Optimized Survey
Accurate weak-lensing analysis requires not only accurate measurement of
galaxy shapes but also precise and unbiased measurement of galaxy redshifts.
The photometric redshift technique appears as the only possibility to determine
the redshift of the background galaxies used in the weak-lensing analysis.
Using the photometric redshift quality, simple shape measurement requirements,
and a proper sky model, we explore what could be an optimal weak-lensing dark
energy mission based on FoM calculation. We found that photometric redshifts
reach their best accuracy for the bulk of the faint galaxy population when
filters have a resolution R~3.2. We show that an optimal mission would survey
the sky through 8 filters using 2 cameras (visible and near infrared). Assuming
a 5-year mission duration, a mirror size of 1.5m, a 0.5deg2 FOV with a visible
pixel scale of 0.15", we found that a homogeneous survey reaching IAB=25.6
(10sigma) with a sky coverage of ~11000deg2 maximizes the Weak Lensing FoM. The
effective number density of galaxies then used for WL is ~45gal/arcmin2, at
least a factor of two better than ground based survey. This work demonstrates
that a full account of the observational strategy is required to properly
optimize the instrument parameters to maximize the FoM of the future
weak-lensing space dark energy mission.Comment: 25 pages, 39 figures, accepted in A&
Innovations in the Analysis of Chandra-ACIS Observations
As members of the instrument team for the Advanced CCD Imaging Spectrometer
(ACIS) on NASA's Chandra X-ray Observatory and as Chandra General Observers, we
have developed a wide variety of data analysis methods that we believe are
useful to the Chandra community, and have constructed a significant body of
publicly-available software (the ACIS Extract package) addressing important
ACIS data and science analysis tasks. This paper seeks to describe these data
analysis methods for two purposes: to document the data analysis work performed
in our own science projects, and to help other ACIS observers judge whether
these methods may be useful in their own projects (regardless of what tools and
procedures they choose to implement those methods).
The ACIS data analysis recommendations we offer here address much of the
workflow in a typical ACIS project, including data preparation, point source
detection via both wavelet decomposition and image reconstruction, masking
point sources, identification of diffuse structures, event extraction for both
point and diffuse sources, merging extractions from multiple observations,
nonparametric broad-band photometry, analysis of low-count spectra, and
automation of these tasks. Many of the innovations presented here arise from
several, often interwoven, complications that are found in many Chandra
projects: large numbers of point sources (hundreds to several thousand), faint
point sources, misaligned multiple observations of an astronomical field, point
source crowding, and scientifically relevant diffuse emission.Comment: Accepted by the ApJ, 2010 Mar 10 (\#343576) 39 pages, 16 figure
The non-evolving internal structure of early-type galaxies: the case study SDSS J0728+3835 at z = 0.206
We study the internal dynamical structure of the early-type lens galaxy SDSS
J0728+3835 at z = 0.206. The analysis is based on two-dimensional kinematic
maps extending out to 1.7 effective radii obtained from Keck spectroscopy, on
lensing geometry and on stellar mass estimates obtained from multiband Hubble
Space Telescope imaging. The data are modelled under the assumptions of axial
symmetry supported by a two-integral distribution function (DF), by applying
the combined gravitational lensing and stellar dynamics code CAULDRON, and
yielding high-quality constraints for an early-type galaxy at cosmological
redshifts. Modelling the total density profile as a power-law of the form
rho_tot ~ 1/r^{gamma}, we find that it is nearly isothermal (logarithmic slope
gamma = 2.08^{+0.04}_{-0.02}), and quite flattened (axial ratio q =
0.60^{+0.08}_{-0.03}). The galaxy is mildly anisotropic (delta = 0.08 +/- 0.02)
and shows a fair amount of rotational support, in particular towards the outer
regions. We determine a dark matter fraction lower limit of 28 per cent within
the effective radius. The stellar contribution to the total mass distribution
is close to maximal for a Chabrier initial mass function (IMF), whereas for a
Salpeter IMF the stellar mass exceeds the total mass within the galaxy inner
regions. We find that the combination of a NFW dark matter halo with the
maximally rescaled luminous profile provides a remarkably good fit to the total
mass distribution over a broad radial range. Our results confirm and expand the
findings of the SLACS survey for early-type galaxies of comparable velocity
dispersion (sigma_SDSS = 214 +/- 11 km/s). The internal structure of J0728 is
consistent with that of local early-type galaxies of comparable velocity
dispersion as measured by the SAURON project, suggesting lack of evolution in
the past two billion years.Comment: 13 pages, 10 figures. MNRAS in press. Revised to match accepted
versio
- …