Virtual Astronomy in the Era of LSST

R J Hanisch (STScI VAO)
G B Berriman (IPAC Caltech VAO)
T J W Lazio (JPL VAO)
D C Tody (NRAO VAO)
M J Graham (Caltech VAO)
A H Rots (SAO VAO)

Virtual Astronomy in the Era of LSST

Virtual Astronomy - that is, the ability to discover, access, and integrate data from diverse observatories and instruments through utilization of the Internet - is already fundamental to advances in astronomical research. In the coming decade of increasingly large data sets and research challenges that are increasingly multi-wavelength, the capabilities of virtual astronomy will need to be developed and exploited at an even greater level than today. A substantial infrastructure for
virtual astronomy has been developed in the context of the Virtual Observatory, instantiated in the United States as the Virtual Astronomical Observatory program, and deployed on a world-wide level through the International Virtual Observatory Alliance.

Of particular interest to radio astronomy is the current development of the protocols for the discovery, access, and inter-comparison of data cubes. Data cubes are used to represent flux density as a function of two spatial coordinates and a spectral coordinate, and for instruments such as the VLA and ALMA, these can be of terabyte-scale. The VO data access protocol for data cubes thus must incorporate the concepts of dynamic data subsetting, slicing, and averaging, and must embody a distributed client-server architecture for obtaining data from a remote, scalable cluster.

Data cube structures are increasingly important for optical and infrared data, such as originate with integral field unit (IFU) spectroscopy, and since many science objectives involve comparison between radio, mm, IR, and optical data, interoperability of data cubes is essential. Data cubes can be generalized to hyper-cubes by bringing in a fourth dimension of time; LSST will produce multi-band time series images that map naturally into a hyper-cube representation. Even high energy data can be described in terms of a sparse hyper-cube, with two spatial coordinates, an energy coordinate, and a photon arrival time.

Other aspects of the VO infrastructure relevant to the radio/LSST interface include a scalable protocol for the dissemination of transient event notices: VOEvent.

We will describe the capabilities and development status for these initiatives, illustrated by several science use cases.

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