1,013 research outputs found
The design of aircraft using the decision support problem technique
The Decision Support Problem Technique for unified design, manufacturing and maintenance is being developed at the Systems Design Laboratory at the University of Houston. This involves the development of a domain-independent method (and the associated software) that can be used to process domain-dependent information and thereby provide support for human judgment. In a computer assisted environment, this support is provided in the form of optimal solutions to Decision Support Problems
SPIRE Map-Making Test Report
The photometer section of SPIRE is one of the key instruments on board of
Herschel. Its legacy depends very much on how well the scanmap observations
that it carried out during the Herschel mission can be converted to high
quality maps. In order to have a comprehensive assessment on the current status
of SPIRE map-making, as well as to provide guidance for future development of
the SPIRE scan-map data reduction pipeline, we carried out a test campaign on
SPIRE map-making. In this report, we present results of the tests in this
campaign.Comment: This document has an executive summary, 6 chapters, and 102 pages.
More information can be found at:
https://nhscsci.ipac.caltech.edu/sc/index.php/Spire/SPIREMap-MakingTest201
The spatial clustering of ultraluminous infrared galaxies over 1.5 < z < 3
We present measurements of the spatial clustering of galaxies with stellar masses 1011 M, infrared luminosities 1012 L, and star formation rates 200 M yr-1 in two redshift intervals: 1.5 < z < 2.0 and 2 < z < 3. Both samples cluster moderately strongly, with spatial correlation lengths of r0 = 6.14 B1 0.84 h-1 Mpc for the 2 < z < 3 sample and r0 = 5.36 B1 1.28 h-1 Mpc for the 1.5 < z < 2.0 sample. These clustering amplitudes are consistent with both populations residing in dark matter halos with masses of 7 C 1012 M, which is comparable to that seen for optical QSOs at the same epochs. We infer that a minimum dark matter halo mass is an important factor for all forms of luminous, obscured activity in galaxies at z > 1, both starbursts and active galactic nuclei. Adopting plausible models for the growth of dark matter halos with redshift, the halos hosting the 2 < z < 3 sample will likely host poor to rich clusters of galaxies at z = 0, whereas the halos hosting the 1.5 < z < 2.0 sample will likely host L* elliptical galaxies or poor clusters at z = 0. We conclude that ultraluminous infrared galaxies (ULIRGs) at z 2.5 likely signpost stellar buildup in galaxies that will reside in clusters at z = 0 and that ULIRGs at z 1.7 signpost stellar buildup in sources that will either become L* elliptical galaxies or reside in poor clusters at z = 0
Census of the Local Universe (CLU) Narrow-Band Survey I: Galaxy Catalogs from Preliminary Fields
We present the Census of the Local Universe (CLU) narrow-band survey to
search for emission-line (\ha) galaxies. CLU-\ha~has imaged 3 of
the sky (26,470~deg) with 4 narrow-band filters that probe a distance out
to 200~Mpc. We have obtained spectroscopic follow-up for galaxy candidates in
14 preliminary fields (101.6~deg) to characterize the limits and
completeness of the survey. In these preliminary fields, CLU can identify
emission lines down to an \ha~flux limit of
~ at 90\% completeness, and recovers 83\%
(67\%) of the \ha~flux from catalogued galaxies in our search volume at the
=2.5 (=5) color excess levels. The contamination from galaxies
with no emission lines is 61\% (12\%) for =2.5 (=5). Also, in
the regions of overlap between our preliminary fields and previous
emission-line surveys, we recover the majority of the galaxies found in
previous surveys and identify an additional 300 galaxies. In total, we
find 90 galaxies with no previous distance information, several of which are
interesting objects: 7 blue compact dwarfs, 1 green pea, and a Seyfert galaxy;
we also identified a known planetary nebula. These objects show that the
CLU-\ha~survey can be a discovery machine for objects in our own Galaxy and
extreme galaxies out to intermediate redshifts. However, the majority of the
CLU-\ha~galaxies identified in this work show properties consistent with normal
star-forming galaxies. CLU-\ha~galaxies with new redshifts will be added to
existing galaxy catalogs to focus the search for the electromagnetic
counterpart to gravitational wave events.Comment: 28 pages, 22 figures, 4 tables (Accepted to ApJ
More Flexibility in Representing Geometric Distortion in Astronomical Images
A number of popular software tools in the public domain are used by astronomers, professional and amateur alike, but some of the tools that have similar purposes cannot be easily interchanged, owing to the lack of a common standard. For the case of image distortion, SCAMP and SExtractor, available from Astromatic.net, perform astrometric calibration and source-object extraction on image data, and image-data geometric distortion is computed in celestial coordinates with polynomial coefficients stored in the FITS header with the PV i_j keywords. Another widely-used astrometric-calibration service, Astrometry.net, solves for distortion in pixel coordinates using the SIP convention that was introduced by the Spitzer Science Center. Up until now, due to the complexity of these distortion representations, it was very difficult to use the output of one of these packages as input to the other. New Python software, along with faster-computing C-language translations, have been developed at the Infrared Processing and Analysis Center (IPAC) to convert FITS-image headers from PV to SIP and vice versa. It is now possible to straightforwardly use Astrometry.net for astrometric calibration and then SExtractor for source-object extraction. The new software also enables astrometric calibration by SCAMP followed by image visualization with tools that support SIP distortion, but not PV . The software has been incorporated into the image-processing pipelines of the Palomar Transient Factory (PTF), which generate FITS images with headers containing both distortion representations. The software permits the conversion of archived images, such as from the Spitzer Heritage Archive and NASA/IPAC Infrared Science Archive, from SIP to PV or vice versa. This new capability renders unnecessary any new representation, such as the proposed TPV distortion convention
Identification of Stellar Flares Using Differential Evolution Template Optimization
We explore methods for the identification of stellar flare events in
irregularly sampled data of ground-based time domain surveys. In particular, we
describe a new technique for identifying flaring stars, which we have
implemented in a publicly available Python module called "PyVAN". The approach
uses the Differential Evolution algorithm to optimize parameters of empirically
derived light-curve templates for different types of stars to fit a candidate
light-curve. The difference of the likelihoods that these best-fit templates
produced the observed data is then used to delineate targets that are well
explained by a flare template but simultaneously poorly explained by templates
of common contaminants. By testing on light-curves of known identity and
morphology, we show that our technique is capable of recovering flaring status
in of all light-curves containing a flare event above thresholds drawn
to include of any contaminant population. By applying to Palomar
Transient Factory data, we show consistency with prior samples of flaring
stars, and identify a small selection of candidate flaring G-type stars for
possible follow-up.Comment: 15 figures, 24 page
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