The Application of the Montage Image Mosaic Engine To The Visualization Of Astronomical Images

The Montage Image Mosaic Engine was designed as a scalable toolkit, written in C for performance and portability across *nix platforms, that assembles FITS images into mosaics. The code is freely available and has been widely used in the astronomy and IT communities for research, product generation and for developing next-generation cyber-infrastructure. Recently, it has begun to finding applicability in the field of visualization. This has come about because the toolkit design allows easy integration into scalable systems that process data for subsequent visualization in a browser or client. And it includes a visualization tool suitable for automation and for integration into Python: mViewer creates, with a single command, complex multi-color images overlaid with coordinate displays, labels, and observation footprints, and includes an adaptive image histogram equalization method that preserves the structure of a stretched image over its dynamic range. The Montage toolkit contains functionality originally developed to support the creation and management of mosaics but which also offers value to visualization: a background rectification algorithm that reveals the faint structure in an image; and tools for creating cutout and down-sampled versions of large images. Version 5 of Montage offers support for visualizing data written in HEALPix sky-tessellation scheme, and functionality for processing and organizing images to comply with the TOAST sky-tessellation scheme required for consumption by the World Wide Telescope (WWT). Four online tutorials enable readers to reproduce and extend all the visualizations presented in this paper.Comment: 16 pages, 9 figures; accepted for publication in the PASP Special Focus Issue: Techniques and Methods for Astrophysical Data Visualizatio

The Montage Image Mosaic Service: Custom Image Mosaics On-Demand

The Montage software suite has proven extremely useful as a general engine for reprojecting, background matching, and mosaicking astronomical image data from a wide variety of sources. The processing algorithms support all common World Coordinate System (WCS) projections and have been shown to be both astrometrically accurate and flux conserving. The background ‘matching’ algorithm does not remove background flux but rather finds the best compromise background based on all the input and matches the individual images to that. The Infrared Science Archive (IRSA), part of the Infrared Processing and Analysis Center (IPAC) at Caltech, has now wrapped the Montage software as a CGI service and provided a compute and request management infrastructure capable of producing approximately 2 TBytes / day of image mosaic output (e.g. from 2MASS and SDSS data). Besides the basic Montage engine, this service makes use of a 16-node LINUX cluster (dual processor, dual core) and the ROME request management software developed by the National Virtual Observatory (NVO). ROME uses EJB/database technology to manage user requests, queue processing and load balance between users, and managing job monitoring and user notification. The Montage service will be extended to process userdefined data collections, including private data uploads

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

A Cost-Benefit Study of Doing Astrophysics On The Cloud: Production of Image Mosaics

Utility grids such as the Amazon EC2 and Amazon S3 clouds offer computational and storage resources that can be used on-demand for a fee by compute- and data-intensive applications. The cost of running an application on such a cloud depends on the compute, storage and communication resources it will provision and consume. Different execution plans of the same application may result in significantly different costs. We studied via simulation the cost performance trade-offs of different execution and resource provisioning plans by creating, under the Amazon cloud fee structure, mosaics with the Montage image mosaic engine, a widely used data- and compute-intensive application. Specifically, we studied the cost of building mosaics of 2MASS data that have sizes of 1, 2 and 4 square degrees, and a 2MASS all-sky mosaic. These are examples of mosaics commonly generated by astronomers. We also study these trade-offs in the context of the storage and communication fees of Amazon S3 when used for long-term application data archiving. Our results show that by provisioning the right amount of storage and compute resources cost can be significantly reduced with no significant impact on application performance

Nitroheterocyclic drug resistance mechanisms in <i>Trypanosoma brucei</i>

OBJECTIVES: The objective of this study was to identify the mechanisms of resistance to nifurtimox and fexinidazole in African trypanosomes. METHODS: Bloodstream-form Trypanosoma brucei were selected for resistance to nifurtimox and fexinidazole by stepwise exposure to increasing drug concentrations. Clones were subjected to WGS to identify putative resistance genes. Transgenic parasites modulating expression of genes of interest were generated and drug susceptibility phenotypes determined. RESULTS: Nifurtimox-resistant (NfxR) and fexinidazole-resistant (FxR) parasites shared reciprocal cross-resistance suggestive of a common mechanism of action. Previously, a type I nitroreductase (NTR) has been implicated in nitro drug activation. WGS of resistant clones revealed that NfxR parasites had lost >100 kb from one copy of chromosome 7, rendering them hemizygous for NTR as well as over 30 other genes. FxR parasites retained both copies of NTR, but lost >70 kb downstream of one NTR allele, decreasing NTR transcription by half. A single knockout line of NTR displayed 1.6- and 1.9-fold resistance to nifurtimox and fexinidazole, respectively. Since NfxR and FxR parasites are ∼6- and 20-fold resistant to nifurtimox and fexinidazole, respectively, additional factors must be involved. Overexpression and knockout studies ruled out a role for a putative oxidoreductase (Tb927.7.7410) and a hypothetical gene (Tb927.1.1050), previously identified in a genome-scale RNAi screen. CONCLUSIONS: NTR was confirmed as a key resistance determinant, either by loss of one gene copy or loss of gene expression. Further work is required to identify which of the many dozens of SNPs identified in the drug-resistant cell lines contribute to the overall resistance phenotype

The organization and management of the Virtual Astronomical Observatory

The U.S. Virtual Astronomical Observatory (VAO; http://www.us-vao.org/) has been in operation since May 2010. Its goal is to enable new science through efficient integration of distributed multi-wavelength data. This paper describes the management and organization of the VAO, and emphasizes the techniques used to ensure efficiency in a distributed organization. Management methods include using an annual program plan as the basis for establishing contracts with member organizations, regular communication, and monitoring of processes.Comment: 9 pages, 3 figures. SPIE Conference 8449: Modeling, Systems Engineering, and Project Management for Astronomy

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