130,658 research outputs found
An Advanced, Three-Dimensional Plotting Library for Astronomy
We present a new, three-dimensional (3D) plotting library with advanced
features, and support for standard and enhanced display devices. The library -
S2PLOT - is written in C and can be used by C, C++ and FORTRAN programs on
GNU/Linux and Apple/OSX systems. S2PLOT draws objects in a 3D (x,y,z) Cartesian
space and the user interactively controls how this space is rendered at run
time. With a PGPLOT inspired interface, S2PLOT provides astronomers with
elegant techniques for displaying and exploring 3D data sets directly from
their program code, and the potential to use stereoscopic and dome display
devices. The S2PLOT architecture supports dynamic geometry and can be used to
plot time-evolving data sets, such as might be produced by simulation codes. In
this paper, we introduce S2PLOT to the astronomical community, describe its
potential applications, and present some example uses of the library.Comment: 12 pages, 10 eps figures (higher resolution versions available from
http://astronomy.swin.edu.au/s2plot/paperfigures). The S2PLOT library is
available for download from http://astronomy.swin.edu.au/s2plo
Overcoming the Challenges Associated with Image-based Mapping of Small Bodies in Preparation for the OSIRIS-REx Mission to (101955) Bennu
The OSIRIS-REx Asteroid Sample Return Mission is the third mission in NASA's
New Frontiers Program and is the first U.S. mission to return samples from an
asteroid to Earth. The most important decision ahead of the OSIRIS-REx team is
the selection of a prime sample-site on the surface of asteroid (101955) Bennu.
Mission success hinges on identifying a site that is safe and has regolith that
can readily be ingested by the spacecraft's sampling mechanism. To inform this
mission-critical decision, the surface of Bennu is mapped using the OSIRIS-REx
Camera Suite and the images are used to develop several foundational data
products. Acquiring the necessary inputs to these data products requires
observational strategies that are defined specifically to overcome the
challenges associated with mapping a small irregular body. We present these
strategies in the context of assessing candidate sample-sites at Bennu
according to a framework of decisions regarding the relative safety,
sampleability, and scientific value across the asteroid's surface. To create
data products that aid these assessments, we describe the best practices
developed by the OSIRIS-REx team for image-based mapping of irregular small
bodies. We emphasize the importance of using 3D shape models and the ability to
work in body-fixed rectangular coordinates when dealing with planetary surfaces
that cannot be uniquely addressed by body-fixed latitude and longitude.Comment: 31 pages, 10 figures, 2 table
Catalogs of Hot White Dwarfs in the Milky Way from GALEX's Ultraviolet Sky Surveys. Constraining Stellar Evolution
We present comprehensive catalogs of hot star candidates in the Milky Way,
selected from GALEX far-UV (FUV, 1344-1786 AA) and near-UV (NUV, 1771-2831 AA)
imaging. The FUV and NUV photometry allows us to extract the hottest stellar
objects, in particular hot white dwarfs (WD), which are elusive at other
wavelengths because of their high temperatures and faint optical luminosities.
We generated catalogs of UV sources from two GALEX's surveys: AIS (All-Sky
Imaging Survey, depth ABmag~19.9/20.8 in FUV/NUV) and MIS (Medium-depth Imaging
Survey, depth ~22.6/22.7mag). The two catalogs (from GALEX fifth data release)
contain 65.3/12.6 million (AIS/MIS) unique UV sources with error(NUV)<0.5mag,
over 21,435/1,579 square degrees. We also constructed subcatalogs of the UV
sources with matched optical photometry from SDSS (7th data release): these
contain 0.6/0.9million (AIS/MIS) sources with errors <0.3mag in both FUV and
NUV, excluding sources with multiple optical counterparts, over an area of
7,325/1,103 square degrees. All catalogs are available online. We then selected
28,319(AIS)/9,028(MIS) matched sources with FUV-NUV<-0.13; this color cut
corresponds to stellar Teff hotter than ~18,000 K. An additional color cut of
NUV-r>0.1 isolates binaries with largely differing Teff's, and some intruding
QSOs. Available spectroscopy for a subsample indicates that hot-star candidates
with NUV-r<0.1 have negligible contamination by non-stellar objects. We discuss
the distribution of sources in the catalogs, and the effects of error and color
cuts on the samples. The density of hot-star candidates increases from high to
low Galactic latitudes, but drops on the MW plane due to dust extinction. Our
hot-star counts at all latitudes are better matched by Milky Way models
computed with an initial-final mass relation that favours lower final masses.
(ABRIDGED)Comment: To appear in MNRAS. Better printed in colou
Multiple rooks of chess - a generic integral field unit deployment technique
A new field re-configuration technique, Multiple Rooks of Chess (MRC), for
multiple deployable Integral Field Spectrographs has been developed. The method
involves mechanical geometry as well as an optimized deployment algorithm. The
geometry is found to be simple for mechanical implementation. The algorithm
initially assigns the IFUs to the target objects and then devises the movement
sequence based on the current and the desired IFU positions. The
reconfiguration time using the suitable actuators which runs at 20 cm/s is
found to be a maximum of 25 seconds for the circular DOTIFS focal plane (180 mm
diameter). The Geometry Algorithm Combination (GAC) has been tested on several
million mock target configurations with object-to-IFU ({\tau} ) ratio varying
from 0.25 to 16. The MRC method is found to-be efficient in target acquisition
in terms of field revisit and deployment time without any collision or
entanglement of the fiber bundles. The efficiency of the technique does not get
affected by the increase in number density of target objects. The technique is
compared with other available methods based on sky coverage, flexibility and
overhead time. The proposed geometry and algorithm combination is found to have
an advantage in all of the aspects.Comment: 18 Pages, 13 Figures, 1 Tabl
Stanilov-Tsankov-Videv Theory
We survey some recent results concerning Stanilov-Tsankov-Videv theory,
conformal Osserman geometry, and Walker geometry which relate algebraic
properties of the curvature operator to the underlying geometry of the
manifold.Comment: This is a contribution to the Proceedings of the 2007 Midwest
Geometry Conference in honor of Thomas P. Branson, published in SIGMA
(Symmetry, Integrability and Geometry: Methods and Applications) at
http://www.emis.de/journals/SIGMA
Halo based reconstruction of the cosmic mass density field
We present the implementation of a halo based method for the reconstruction
of the cosmic mass density field. The method employs the mass density
distribution of dark matter haloes and its environments computed from
cosmological N-body simulations and convolves it with a halo catalog to
reconstruct the dark matter density field determined by the distribution of
haloes. We applied the method to the group catalog of Yang etal (2007) built
from the SDSS Data Release 4. As result we obtain reconstructions of the cosmic
mass density field that are independent on any explicit assumption of bias. We
describe in detail the implementation of the method, present a detailed
characterization of the reconstructed density field (mean mass density
distribution, correlation function and counts in cells) and the results of the
classification of large scale environments (filaments, voids, peaks and sheets)
in our reconstruction. Applications of the method include morphological studies
of the galaxy population on large scales and the realization of constrained
simulations.Comment: Accepted for publication in MNRA
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