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T HE US N ATIONAL V IRTUAL O BSERVATORY. NVO Science Overview for the NVO Science Steering Committee. Alex Szalay, Dave De Young, Bob Hanisch US NVO Project. NVO: History and Motivation. History.

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NVO Science Overview

for the

NVO Science Steering Committee

Alex Szalay, Dave De Young, Bob Hanisch

US NVO Project


  • 1990s: NASA establishes wavelength-oriented science archive centers; multiple large ground-based digital sky survey projects initiated
  • April 1999: Decadal Survey Panel on Theory, Computation, and Data Discovery meets in Los Alamos
    • Szalay, Prince, and Alcock coin the name “National Virtual Observatory”
  • November 1999: NVO organizational workshop at JHU
  • February 2000: 2nd NVO workshop at NOAO-Tucson
  • June 2000:, conference held at Caltech, “Towards a Virtual Observatory”
  • June 2000: ad hoc Steering Committee formed
  • February 2001: AASC/NAS report released
  • April 2001: proposal submitted to NSF ITR - 17 collaborating institutions
  • September 2001: NSF announces proposal selection
  • April 2002: joint NASA/NSF Science Definition Team submits report
  • January 200:, first NVO science prototypes shown at Seattle AAS


decadal survey recommendation
Decadal Survey Recommendation
  • National Academy of Sciences Decadal Survey recommended NVO as highest priority small (<$100M) project

“ Several small initiatives recommended by the committee span both ground and space. The first among them—the National Virtual Observatory (NVO)—is the committee’s top priority among the small initiatives. The NVO will provide a “virtual sky” based on the enormous data sets being created now and the even larger ones proposed for the future. It will enable a new mode of research for professional astronomers and will provide to the public an unparalleled opportunity for education and discovery.”

—Astronomy and Astrophysics in the New Millennium, p. 14


what the virtual observatory is
What the Virtual Observatory is …
  • A set of international standards to share complex data
  • A modular set of tools to work with distributed data
  • An essential part of the research astronomer’s toolkit
  • A catalyst for world-wide access to astronomical archives
  • A vehicle for education and public outreach
  • NOT a replacement for building new telescopes and instruments
  • NOT a centralized repository for data
  • NOT a data quality enforcement organization


international vo alliance7
International VO Alliance
  • The IVOA brings together the astronomers, developers, and managers of the VO initiatives world-wide
    • Agreements on standards for data access (VOTable, catalog queries, image retrieval, resource descriptions, etc.)
    • Coordination of development activities
    • Sharing of software
    • Sharing of experience
  • 15 participating organizations: Astrogrid, AVO, US-NVO, VO-Australia, VO-Canada, VO-China, VO-France, VO-Germany (GAVO), VO-Hungary, VO-India, VO-Italy (DRACO), VO-Japan, VO-Korea, VO-Russia, Spanish VO


nvo science steering committee
NVO Science Steering Committee
  • Recommended by NVO Advisory Committee – December 2003
    • G. Gilmore, J.Huchra, S. Karin, R.Kennicutt, C. Lagoze,

P. Messina, E. Ostriker, S. Wolff (Chair)

  • “It is now time to actively engage the user community in order to ensure acceptance and success.” - NVO Advisory Committee Report
  • SSC Membership: D. De Young (Chair), G. Djorgovski, M. Donahue, M. Haynes (after 10/04), F. Hill, P. Pinto, J. Ulvestad, B. Wilkes


nvo science steering committee9
NVO Science Steering Committee
  • SSC Mandate:
    • Advise and assist the NVO in formulating science policies and objectives
      • Near term and long term
    • Advise the NVO on strategies to achieve these objectives
    • Monitor progress of implementation plans
  • Not a passive committee


nvo science steering committee10
NVO Science Steering Committee
  • Objectives of this meeting
    • Familiarization with current NVO status and capabilities
    • Review current Issues and problems faced
    • Focus on strategy for engagement of scientific community
    • Recommendations for near term efforts re: January AAS meeting
    • Other strategy recommendations – short and long term


science prototypes
Science Prototypes
  • Science prototypes guide and validate technical initiatives
  • NVO Year 1
    • Brown dwarf candidate search
    • Gamma-ray burst follow-up
    • Galaxy morphology measurement (utilizing computational grid)
  • Year 1.5
    • Data Inventory Service
  • Year 2
    • Data Inventory Service with registry-based resource selection
    • Access to theoretical simulation (globular cluster) and virtual observations
  • European VO project
    • Type 2 (obscured) quasars: 40 new candidates found; paper published in A&A
    • Galactic star formation regions
  • Year 3: First robust science applications


data inventory service
Data Inventory Service

Scientific Motivation: Rapid collection of multi-wavelength imaging, catalog and observation data following an interesting transient event is essential. This service can also be used as a general tool to quickly access all data available on any patch of sky for any science use.

Data Resources: Multi-wavelength data from any number of sites (currently 13 different sites) sampling energies from X-ray to radio, and including images, object lists, and catalogues of observations.

What the VO Brings: Integration and organization of a variety of data sources into an easily comprehensible information set. Scalability to an arbitrary number of data providers. Integrates data with multiple data visualization services.

Enabling Technologies: Standard protocols to remote services such as Cone Search and Simple Image Access, standardized VOTables for data retrieval transformation, and standardized semantics encoded as Uniform Content Descriptors (UCDs). Resource registry.

Future Prospects: Customization and quality control of resources searched; more sophisticated use of metadata.

Positions of HST and Chandra observations for GRB010222


data inventory service16
Data Inventory Service


brown dwarf candidate search
Brown Dwarf Candidate Search

Scientific Motivation: The search for brown dwarfs has been revolutionized by the latest deep sky surveys. A key attribute to discovering brown dwarfs is the federation of many surveys over different wavelengths. Such matching of catalogs is currently laborious and time consuming. This matching problem is generic to many areas of astrophysics.

Data Resources: Sloan Digital Sky Survey (SDSS) Early Data Release (15 million objects) 2-Micron All Sky Survey (2MASS) 2nd Incremental Point Source Catalog (162 million objects)

What the VO Brings: Today, doing datasets is user-intensive and is replicated by many different users. Also, the correlation of these two datasets can take years of CPU time if not done correctly. The NVO brings two key aspects to this problem. First, it removes the need for the user to download large data to their machine, making direct use of distributed data. Second, the matching algorithm used here is computationally efficient and designed to give answers in minutes rather than hours; results can be returned to the user in real-time.

Sloan z magnitudes vs. 2MASS J magnitudes, with brown dwarf candidates in red.  Data are from the SDSS Early Data Release and 2MASS 2nd Incremental Release.

Future Prospects: Catalog matching of large datasets is a generic problem in astrophysics. Therefore, making the matching facility available to any user for use on any dataset will greatly enhance the productivity of scientists. Standard I/O formats allow developers to create tools to use the matched data and easily integrate with existing visualization and analysis tools (anomaly detector). Bringing these data together on remote machines with enough CPU to perform analysis (Grid technology) will allow cross-comparisons of unprecedented scale.


As a T dwarf becomes cooler (i.e., methane and water absorptions increase) or more distant…
  • SDSS detects it only at z’ band
  • 2MASS detects it only at J band


demo leads to discovery
Demo Leads to Discovery!
  • New brown dwarf candidate confirmed spectroscopically with Keck Observatory


galaxy morphology in clusters
Galaxy Morphology in Clusters

Scientific Motivation: Investigate the dynamical state of galaxy clusters and galaxy evolution within the context of large-scale structure.  Use galaxy morphology as a probe of dynamical history by calculating, for each galaxy in a cluster:

• Surface brightness • Concentration index • Asymmetry index

These parameters are analyzed with other indicators such as magnitude, color, peculiar velocity, position in cluster, and cluster large-scale structure.

Data Resources: Computing Resources:

Chandra X-ray image (SAO/CXC) USC/ISI


DSS image (STScI/MAST) Fermilab

Galaxy cluster catalogs (NED)

CNOC1 cluster images and catalogs (CADC)

What the VO Brings: Distributed data access and Grid-based computing make possible for the first time effective integration of multiple datasets and real-time computing. Integration of data from diverse sources is enabled by standardized data objects and standardized remote computing services. Flexibility of access means that further NVO-compliant images and catalogs can be added easily. Users can select their visualization portal (Aladin, OASIS, DS9).

Enabling Technologies: VOTable, NVO-compliant catalog and image access, standard semantics, Grid computing infrastructure.

Future Prospects: Dynamic discovery and selection of image, catalog, and computing resources. User-selection of analysis tools and ability to publish data to the NVO framework.


globular cluster simulations
Globular Cluster Simulations


spectral database browser
Spectral Database Browser


  • The Montage project will deploy a portable, compute-intensive service that will deliver science-grade custom mosaics on demand, with requests made through existing portals. Science-grade in this context requires that terrestrial and instrumental features are removed from images in a way that can be described quantitatively; custom refers to user-specified parameters of projection, coordinates, size, rotation and spatial sampling.


  • The Atlasmaker project is using Grid technology in combination with NVO interoperability to create new knowledge resources in astronomy. The product is a multi-faceted, multi-dimensional, scientifically trusted image atlas of the sky, made by federating many different surveys at different wavelengths, times, resolutions, polarizations, etc. Atlasmaker does resampling and mosaicking of image collections, and is well-suited to operate with the Hyperatlas standard. Requests can be satisfied via on-demand computations or by accessing a data cache. Computed data is stored in a distributed virtual file system, such as the Storage Resource Broker (SRB). We expect these atlases to be a new and powerful paradigm for knowledge extraction in astronomy, as well as a way to build educational resources. The system is being incorporated into the data analysis pipeline of the Palomar-Quest synoptic survey, and is being used to generate all-sky atlases from the 2MASS, SDSS, and DPOSS surveys for joint object detection.


resource registry
Resource Registry


open sky query
Open Sky Query


nvo web site
NVO Web Site
  • Redesigned NVO web site with a focus on end-users
  • Software tools/applications and data access services are easier to locate
  • Application and service providers can provide their own documentation


vision of year3 applications
Vision of Year3 Applications
  • Take ~5 simple core applications representing daily tasks of research astronomers
  • Should be convincing for first time users
  • Easy-to-use, robust services with clear documentation
  • Focus on quality instead of ‘feature creep’
  • Should all be based on VO standards
  • Deploy in Q1 2005
  • Templates/prototypes/docs and training for community
  • Expect increasing number of community contributed tools


strawman list of year3 apps
Strawman List of Year3 Apps
  • Queryable VO Registry
  • Simple data access layer on most archives (SIAP,SSAP,Cone)
  • OpenSkyNode access with most archives participating
  • DIS service
  • OpenSkyQuery
  • Spectrum/bandpass service
  • Dynamic image-to-catalog tool
  • AtlasMaker

These exist in prototype formList short enough to be comprehensible, achievable