702 research outputs found
Running a distributed virtual observatory: US Virtual Astronomical Observatory operations
Operation of the US Virtual Astronomical Observatory shares some issues with
modern physical observatories, e.g., intimidating data volumes and rapid
technological change, and must also address unique concerns like the lack of
direct control of the underlying and scattered data resources, and the
distributed nature of the observatory itself. In this paper we discuss how the
VAO has addressed these challenges to provide the astronomical community with a
coherent set of science-enabling tools and services. The distributed nature of
our virtual observatory-with data and personnel spanning geographic,
institutional and regime boundaries-is simultaneously a major operational
headache and the primary science motivation for the VAO. Most astronomy today
uses data from many resources. Facilitation of matching heterogeneous datasets
is a fundamental reason for the virtual observatory. Key aspects of our
approach include continuous monitoring and validation of VAO and VO services
and the datasets provided by the community, monitoring of user requests to
optimize access, caching for large datasets, and providing distributed storage
services that allow user to collect results near large data repositories. Some
elements are now fully implemented, while others are planned for subsequent
years. The distributed nature of the VAO requires careful attention to what can
be a straightforward operation at a conventional observatory, e.g., the
organization of the web site or the collection and combined analysis of logs.
Many of these strategies use and extend protocols developed by the
international virtual observatory community.Comment: 7 pages with 2 figures included within PD
A Cross-Match of 2MASS and SDSS: Newly-Found L and T Dwarfs and an Estimate of the Space Densitfy of T Dwarfs
We report new L and T dwarfs found in a cross-match of the SDSS Data Release
1 and 2MASS. Our simultaneous search of the two databases effectively allows us
to relax the criteria for object detection in either survey and to explore the
combined databases to a greater completeness level. We find two new T dwarfs in
addition to the 13 already known in the SDSS DR1 footprint. We also identify 22
new candidate and bona-fide L dwarfs, including a new young L2 dwarf and a
peculiar L2 dwarf with unusually blue near-IR colors: potentially the result of
mildly sub-solar metallicity. These discoveries underscore the utility of
simultaneous database cross-correlation in searching for rare objects. Our
cross-match completes the census of T dwarfs within the joint SDSS and 2MASS
flux limits to the 97% level. Hence, we are able to accurately infer the space
density of T dwarfs. We employ Monte Carlo tools to simulate the observed
population of SDSS DR1 T dwarfs with 2MASS counterparts and find that the space
density of T0-T8 dwarf systems is 0.0070 (-0.0030; +0.0032) per cubic parsec
(95% confidence interval), i.e., about one per 140 cubic parsecs. Compared to
predictions for the T dwarf space density that depend on various assumptions
for the sub-stellar mass function, this result is most consistent with models
that assume a flat sub-stellar mass function dN/dM ~ M^0. No >T8 dwarfs were
discovered in the present cross-match, though less than one was expected in the
limited area (2099 sq. degrees) of SDSS DR1.Comment: To appear in ApJ, Feb 10, 2008 issue. 37 pages, including 12 figures
and 14 table
BamView: visualizing and interpretation of next-generation sequencing read alignments.
So-called next-generation sequencing (NGS) has provided the ability to sequence on a massive scale at low cost, enabling biologists to perform powerful experiments and gain insight into biological processes. BamView has been developed to visualize and analyse sequence reads from NGS platforms, which have been aligned to a reference sequence. It is a desktop application for browsing the aligned or mapped reads [Ruffalo, M, LaFramboise, T, KoyutĂŒrk, M. Comparative analysis of algorithms for next-generation sequencing read alignment. Bioinformatics 2011;27:2790-6] at different levels of magnification, from nucleotide level, where the base qualities can be seen, to genome or chromosome level where overall coverage is shown. To enable in-depth investigation of NGS data, various views are provided that can be configured to highlight interesting aspects of the data. Multiple read alignment files can be overlaid to compare results from different experiments, and filters can be applied to facilitate the interpretation of the aligned reads. As well as being a standalone application it can be used as an integrated part of the Artemis genome browser, BamView allows the user to study NGS data in the context of the sequence and annotation of the reference genome. Single nucleotide polymorphism (SNP) density and candidate SNP sites can be highlighted and investigated, and read-pair information can be used to discover large structural insertions and deletions. The application will also calculate simple analyses of the read mapping, including reporting the read counts and reads per kilobase per million mapped reads (RPKM) for genes selected by the user
HST Fine Guidance Sensor Astrometric Parallaxes for Three Dwarf Novae: SS Aurigae, SS Cygni, and U Geminorum
We report astrometric parallaxes for three well known dwarf novae obtained
using the Fine Guidance Sensors on the Hubble Space Telescope. We found a
parallax for SS Aurigae of Pi = 5.00 +/- 0.64 mas, for SS Cygni we found Pi =
6.02 +/- 0.46 mas, and for U Geminorum we obtained Pi = 10.37 +/- 0.50 mas.
These represent the first true trigonometric parallaxes of any dwarf novae. We
briefly compare these results with previous distance estimates. This program
demonstrates that with a very modest amount of HST observing time, the Fine
Guidance Sensors can deliver parallaxes of unrivaled precision.Comment: 15 pages, 2 Table
Parallax and Distance Estimates for Fourteen Cataclysmic Variable Stars
I used the 2.4 m Hiltner telescope at MDM Observatory in an attempt to
measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques
are described in detail. In the best cases the parallax uncertainties are below
1 mas, and significant parallaxes are found for most of the program stars. A
Bayesian method which combines the parallaxes together with proper motions and
absolute magnitude constraints is developed and used to derive distance
estimates and confidence intervals. The most precise distance derived here is
for WZ Sge, for which I find 43.3 (+1.6, -1.5) pc. Six Luyten Half-Second stars
with previous precise parallax measurements were re-measured to test the
techniques, and good agreement is found.Comment: 33 pages, 3 figures. Astronomical Journal, accepte
5-micron photometry of late-type dwarfs
We present narrowband-M photometry of nine low-mass dwarfs with spectral
types ranging from M2.5 to L0.5. Combining the (L'-M') colours derived from our
observations with data from the literature, we find colours consistent with a
Rayleigh-Jeans flux distribution for spectral types earlier than M5, but
enhanced F_3.8/F_4.7 flux ratios (negative (L'-M') colours) at later spectral
types. This probably reflects increased absorption at M' due to the CO
fundamental band. We compare our results against recent model predictions and
briefly discuss the implications.Comment: accepted for the Astronomical Journa
The Design and Operation of The Keck Observatory Archive
The Infrared Processing and Analysis Center (IPAC) and the W. M. Keck
Observatory (WMKO) operate an archive for the Keck Observatory. At the end of
2013, KOA completed the ingestion of data from all eight active observatory
instruments. KOA will continue to ingest all newly obtained observations, at an
anticipated volume of 4 TB per year. The data are transmitted electronically
from WMKO to IPAC for storage and curation. Access to data is governed by a
data use policy, and approximately two-thirds of the data in the archive are
public.Comment: 12 pages, 4 figs, 4 tables. Presented at Software and
Cyberinfrastructure for Astronomy III, SPIE Astronomical Telescopes +
Instrumentation 2014. June 2014, Montreal, Canad
The First Data Release of the KODIAQ Survey
We present and make publicly available the first data release (DR1) of the
Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey.
The KODIAQ survey is aimed at studying galactic and circumgalactic gas in
absorption at high-redshift, with a focus on highly-ionized gas traced by OVI,
using the HIRES spectrograph on the Keck-I telescope. KODIAQ DR1 consists of a
fully-reduced sample of 170 quasars at 0.29 < z_em < 5.29 observed with HIRES
at high resolution (36,000 <= R <= 103,000) between 2004 and 2012. DR1 contains
247 spectra available in continuum normalized form, representing a sum total
exposure time of ~1.6 megaseconds. These co-added spectra arise from a total of
567 individual exposures of quasars taken from the Keck Observatory Archive
(KOA) in raw form and uniformly processed using a HIRES data reduction package
made available through the XIDL distribution. DR1 is publicly available to the
community, housed as a higher level science product at the KOA. We will provide
future data releases that make further QSOs, including those with pre-2004
observations taken with the previous-generation HIRES detectors.Comment: 14 pages, 9 figures, Submitted to AJ. All data products available at
the Keck Observatory Archive beginning May 15, 2015. URL:
https://koa.ipac.caltech.edu/applications/KODIA
Artemis: an integrated platform for visualization and analysis of high-throughput sequence-based experimental data.
MOTIVATION: High-throughput sequencing (HTS) technologies have made low-cost sequencing of large numbers of samples commonplace. An explosion in the type, not just number, of sequencing experiments has also taken place including genome re-sequencing, population-scale variation detection, whole transcriptome sequencing and genome-wide analysis of protein-bound nucleic acids. RESULTS: We present Artemis as a tool for integrated visualization and computational analysis of different types of HTS datasets in the context of a reference genome and its corresponding annotation. AVAILABILITY: Artemis is freely available (under a GPL licence) for download (for MacOSX, UNIX and Windows) at the Wellcome Trust Sanger Institute websites: http://www.sanger.ac.uk/resources/software/artemis/
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