Viewpoints: A high-performance high-dimensional exploratory data analysis tool

Scientific data sets continue to increase in both size and complexity. In the past, dedicated graphics systems at supercomputing centers were required to visualize large data sets, but as the price of commodity graphics hardware has dropped and its capability has increased, it is now possible, in principle, to view large complex data sets on a single workstation. To do this in practice, an investigator will need software that is written to take advantage of the relevant graphics hardware. The Viewpoints visualization package described herein is an example of such software. Viewpoints is an interactive tool for exploratory visual analysis of large, high-dimensional (multivariate) data. It leverages the capabilities of modern graphics boards (GPUs) to run on a single workstation or laptop. Viewpoints is minimalist: it attempts to do a small set of useful things very well (or at least very quickly) in comparison with similar packages today. Its basic feature set includes linked scatter plots with brushing, dynamic histograms, normalization and outlier detection/removal. Viewpoints was originally designed for astrophysicists, but it has since been used in a variety of fields that range from astronomy, quantum chemistry, fluid dynamics, machine learning, bioinformatics, and finance to information technology server log mining. In this article, we describe the Viewpoints package and show examples of its usage.Comment: 18 pages, 3 figures, PASP in press, this version corresponds more closely to that to be publishe

GAIA: Composition, Formation and Evolution of the Galaxy

The GAIA astrometric mission has recently been approved as one of the next two `cornerstones' of ESA's science programme, with a launch date target of not later than mid-2012. GAIA will provide positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars throughout our Galaxy (and into the Local Group), amounting to about 1 per cent of the Galactic stellar population. GAIA's main scientific goal is to clarify the origin and history of our Galaxy, from a quantitative census of the stellar populations. It will advance questions such as when the stars in our Galaxy formed, when and how it was assembled, and its distribution of dark matter. The survey aims for completeness to V=20 mag, with accuracies of about 10 microarcsec at 15 mag. Combined with astrophysical information for each star, provided by on-board multi-colour photometry and (limited) spectroscopy, these data will have the precision necessary to quantify the early formation, and subsequent dynamical, chemical and star formation evolution of our Galaxy. Additional products include detection and orbital classification of tens of thousands of extra-Solar planetary systems, and a comprehensive survey of some 10^5-10^6 minor bodies in our Solar System, through galaxies in the nearby Universe, to some 500,000 distant quasars. It will provide a number of stringent new tests of general relativity and cosmology. The complete satellite system was evaluated as part of a detailed technology study, including a detailed payload design, corresponding accuracy assesments, and results from a prototype data reduction development.Comment: Accepted by A&A: 25 pages, 8 figure

Comparing Tycho-2 Astrometry with UCAC1

The Tycho-2 Catalogue, released in February 2000, is based on the ESA Hipparcos space mission data and various ground-based catalogs for proper motions. An external comparison of the Tycho-2 astrometry is presented here using the first U.S. Naval Observatory CCD Astrograph Catalog (UCAC1). The UCAC1 data were obtained from observations performed at CTIO between February 1998 and November 1999, using the 206 mm aperture 5-element lens astrograph and a 4k x 4k CCD. Only small systematic differences in position between Tycho-2 and UCAC1 up to 15 milliarcseconds (mas) are found, mainly as a function of magnitude. The standard deviations of the distributions of the position differences are in the 35 to 140 mas range, depending on magnitude. The observed scatter in the position differences is about 30% larger than expected from the combined formal, internal errors, also depending on magnitude. The Tycho-2 Catalogue has the more precise positions for bright stars (V <= 10 mag) while the UCAC1 positions are significantly better at the faint end (11 mag <= V <= 12.5 mag) of the magnitude range in common. UCAC1 goes much fainter (to R=16) than Tycho-2; however complete sky coverage is not expected before mid 2003.Comment: LaTeX, 8 pages, 3 PS figures, accepted by AJ (Aug 2000) see also http://ad.usno.navy.mil/ad/ucac/ request for UCAC1 CD-ROM: e-mail to [email protected] request for Tycho-2 CD-ROM: e-mail to [email protected] or [email protected]

Optimization of the Agar-gel Method for Isolation of Migrating Ascaris suum Larvae From the Liver and Lungs of Pigs

Experiments on use of an agar-gel method for recovery of migrating Ascaris suum larvae from the liver and lungs of pigs were conducted to obtain fast standardized methods. Subsamples of blended tissues of pig liver and lungs were mixed with agar to a final concentration of 1% agar and the larvae allowed to migrate out of the agar-gel into 0.9% NaCl at 38°C. The results showed that within 3 h more than 88% of the recoverable larvae migrated out of the liver agar-gel and more than 83% of the obtained larvae migrated out of the lung agar-gel. The larvae were subsequently available in a very clean suspension which reduced the sample counting time. Blending the liver for 60 sec in a commercial blender showed significantly higher larvae recovery than blending for 30 sec. Addition of gentamycin to reduce bacterial growth during incubation, glucose to increase larval motility during migration or ice to increase sedimentation of migrated larvae did not influence larvae recovery significantly

The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS

USNO-B1.0 and 2MASS are the most widely used full-sky surveys. However, 2MASS has no proper motions at all, and USNO-B1.0 published only relative, not absolute (i.e. on ICRS) proper motions. We performed a new determination of mean positions and proper motions on the ICRS system by combining USNO-B1.0 and 2MASS astrometry. This catalog is called PPMXL {VO-access to the catalog is possible via http://vo.uni-hd.de/ppmxl}, and it aims to be complete from the brightest stars down to about $V \approx 20$ full-sky. PPMXL contains about 900 million objects, some 410 million with 2MASS photometry, and is the largest collection of ICRS proper motions at present. As representative for the ICRS we chose PPMX. The recently released UCAC3 could not be used because we found plate-dependent distortions in its proper motion system north of -20$^\circ$ declination. UCAC3 served as an intermediate system for $\delta \leq -20^\circ$. The resulting typical individual mean errors of the proper motions range from 4 mas/y to more than 10 mas/y depending on observational history. The mean errors of positions at epoch 2000.0 are 80 to 120 mas, if 2MASS astrometry could be used, 150 to 300 mas else. We also give correction tables to convert USNO-B1.0 observations of e.g. minor planets to the ICRS system.Comment: 9 pages, 9 figure

The Carlsberg Meridian Telescope CCD Drift Scan Survey

This paper contains the general data reduction methods used in processing the data from the Carlsberg Meridian Telescope CCD Drift Scan Survey. An efficient method to calibrate the fluctuations in the positions of the images caused by atmospheric turbulence is described. The external accuracy achieved is 36 mas in right ascension and declination. A description of the recently released catalogue is given.Comment: 13 pages 11 Figures (PS) Accepted for publication in A&A. The catalogue can be found at http://www.ast.cam.ac.uk/~dwe/SRF/cmc12

Kinematic Control of the Inertiality of the System of Tycho-2 and UCAC2 Stellar Proper Motions

Based on the Ogorodnikov-Milne model, we analyze the proper motions of Tycho-2 and UCAC2 stars. We have established that the model component that describes the rotation of all stars under consideration around the Galactic y axis differs significantly from zero at various magnitudes. We interpret this rotation found using the most distant stars as a residual rotation of the ICRS/Tycho-2 system relative to the inertial reference frame. For the most distant ($d\approx900$ pc) Tycho-2 and UCAC2 stars, the mean rotation around the Galactic y axis has been found to be $M_{13}=-0.37\pm0.04$ mas yr$^{-1}$. The proper motions of UCAC2 stars with magnitudes in the range $12-15^m$ are shown to be distorted appreciably by the magnitude equation in $\mu_\alpha\cos\delta$, which has the strongest effect for northern-sky stars with a coefficient of $-0.60\pm0.05$ mas yr$^{-1}$ mag$^{-1}$. We have detected no significant effect of the magnitude equation in the proper motions of UCAC2 stars brighter than $\approx11^m$.Comment: 15 pages, 6 figure

Clustering of photometric luminous red galaxies I : Growth of Structure and Baryon Acoustic Feature

The possibility of measuring redshift space (RSD) distortions using photometric data have been recently highlighted. This effect complements and significantly alters the detectability of baryon acoustic oscillations (BAO) in photometric surveys. In this paper we present measurements of the angular correlation function of luminous red galaxies (LRGs) in the photometric catalog of the final data release (DR7) of the Sloan Digital Sky Survey II (SDSS). The sample compromise ~ 1.5 x 10^6 LRGs distributed in 0.45 < z < 0.65, with a characteristic photometric error of ~ 0.05. Our measured correlation centered at z=0.55 is in very good agreement with predictions from standard LCDM in a broad range of angular scales, $0.5^\circ < \theta < 6^\circ$. We find that the growth of structure can indeed be robustly measured, with errors matching expectations. The velocity growth rate is recovered as $f \sigma_8 = 0.53 \pm 0.42$ when no prior is imposed on the growth factor and the background geometry follows a LCDM model with WMAP7+SNIa priors. This is compatible with the corresponding General Relativity (GR) prediction $f \sigma_8 = 0.45$ for our fiducial cosmology. If we adopt a parametrization such that $f=\Omega ^\gamma_m(z)$, with $\gamma \approx 0.55$ in GR, and combine our $f\sigma_8$ measurement with the corresponding ones from spectroscopic LRGs at lower redshifts we obtain $\gamma=0.54 \pm 0.17$. In addition we find evidence for the presence of the baryon acoustic feature matching the amplitude, location and shape of LCDM predictions. The photometric BAO feature is detected with 98 % confidence level at z=0.55.Comment: 16 pages, 19 figures, minor changes to text to match accepted version by MNRA

VLBI for Gravity Probe B. V. Proper Motion and Parallax of the Guide Star, IM Pegasi

We present the principal astrometric results of the very-long-baseline interferometry (VLBI) program undertaken in support of the Gravity Probe B (GP-B) relativity mission. VLBI observations of the GP-B guide star, the RS CVn binary IM Pegasi (HR 8703), yielded positions at 35 epochs between 1997 and 2005. We discuss the statistical assumptions behind these results and our methods for estimating the systematic errors. We find the proper motion of IM Peg in an extragalactic reference frame closely related to the International Celestial Reference Frame 2 (ICRF2) to be -20.83 +- 0.03 +- 0.09 mas/yr in right ascension and -27.27 +- 0.03 +- 0.09 mas/yr in declination. For each component the first uncertainty is the statistical standard error and the second is the total standard error (SE) including plausible systematic errors. We also obtain a parallax of 10.37 +- 0.07 mas (distance: 96.4 +- 0.7 pc), for which there is no evidence of any significant contribution of systematic error. Our parameter estimates for the ~25-day-period orbital motion of the stellar radio emission have SEs corresponding to ~0.10 mas on the sky in each coordinate. The total SE of our estimate of IM Peg's proper motion is ~30% smaller than the accuracy goal set by the GP-B project before launch: 0.14 mas/yr for each coordinate of IM Peg's proper motion. Our results ensure that the uncertainty in IM Peg's proper motion makes only a very small contribution to the uncertainty of the GP-B relativity tests.Comment: Accepted for publication in the Astrophysical Journal Supplement Serie

Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood

Debris discs - analogous to the Asteroid and Kuiper-Edgeworth belts in the Solar system - have so far mostly been identified and studied in thermal emission shortward of 100 um. The Herschel space observatory and the SCUBA-2 camera on the James Clerk Maxwell Telescope will allow efficient photometric surveying at 70 to 850 um, which allow for the detection of cooler discs not yet discovered, and the measurement of disc masses and temperatures when combined with shorter wavelength photometry. The SCUBA-2 Unbiased Nearby Stars (SUNS) survey and the DEBRIS Herschel Open Time Key Project are complimentary legacy surveys observing samples of ~500 nearby stellar systems. To maximise the legacy value of these surveys, great care has gone into the target selection process. This paper describes the target selection process and presents the target lists of these two surveys.Comment: 67 pages with full tables, 7 figures, accepted to MNRA