RadioNet Software Forum - Archives and Virtual Observatories

PUBLISHING SINGLE DISH RADIO DATA

Visit of Jean-Michel Martin and Gilles Theureau to JBO on 12-13 Jan 2005

Introduction to Nancay observatory and related archives and discussions with JBO AstroGrid, MERLIN, RadioNet and PSR group representatives. Notes taken by Anita Richards.

1) The Nancay radiotelescope observes OH, HI and other spectral lines and radio continuum, such as for the the MIGALE project to study the universe at z=0-1 which is linked to Hyperleda. Galactic data include maser and pulsar observations. Database query and management uses the PleinPot package which offers visualisation and on-the-fly processing tools. Reduced data (and in some cases the raw 2D data) can be accessed via form or SQL queries. These include 1D velocity- or frequency-flux density data in an ascii-based format, displayed as line plots and 2D time-frequency-flux density data in proprietary format, displayed as pixel images.

2) At present only KLUN project data older than 2 years (~4000 HI profiles of spiral galaxies for Tully-Fisher applications) are publicly available. Many Nancay projects involve monitoring variability for many years. Nonetheless, some data could be made available and some of these could be in approximately science-ready form, i.e. in physical units, stacked, background subtracted etc., although (as with any VO data) very high-precision applications might need further processing. The PleinPot software can be downloaded.

3) The discussion on what software packages can be recommended to users should include single dish data processing. We have various kinds of data to consider (some interconvertible/overlapping) including:

• 1D frequency (or wavelength, velocity etc.) spectra
• 1D time series
• 2D position-velocity data
• 2D frequency (etc.)-time data
• 3D datacubes from which spectra can be extracted
• Polarization data

4) The steps involved in publishing radio spectra to VOs include

• Establishing science drivers e.g.
  • AGB to PNe transition (OH, CO etc.)
  • Low surface brightness galaxies (HI)
• Providing tools for viewing reduced, calibrated spectra
  • VOSpec (heterogenous data, simple BB etc. fits) - also available integrated into the AVO toolset - includes access to HyperLeda
  • SpecView (more detailed fits to spectra) available integrated into the AVO toolset
  • Consider wrapping dedicated radio analysis tools e.g. parts of PleinPot using the Common Execution Architecture (CEA) developed by AstroGrid, see links for implimentation.
• Publishing spectra
  1. static log of sources or observations
  2. as above with links to data (e.g. MERLIN archive log via Vizier)
  3. dynamic discovery of SSA-compliant archive
• 2. needs compliance with IVOA standards for SSA (Simple Spectral Access as used by VOSpec etc., see spectral links), data descriptions (Metadata, see Resource Registry) and other IVOA documents.
• Reduced spectra are on WCS in physical units - however frequency axis is often velocity. IVOA standards exist (Space-Time coordinate metadata) but VOSpec and SpecView cannot display this yet (although VOSpec can apply a redshift to spectra).
• Data need to be converted to standard VOTable or FITS - there are both interactive (ConVot, TopCat) tools and libraries which can be wrapped for batch jobs (e.g. the STIL library).

5) There are complementary VO methods for analysing data; the AVO toolset provides an interactive interface (which can also run scripts) whilst the AstroGrid portal enables the construction of complex asynchronous workflows. These are not exclusive; both tools and data can be shared. The simplest methods (e.g. 1) above) of publishing spectra allow limited AVO access to a static data set, and implementation of SSA would allow dynamic access via spectral tools. The PublishersAstrogridLibrary (PAL; link will be updated) is an installation providing a comprehensive range of web service tools from SSA to TomCat .

6) Discussion on publishing PSR data. See European Pulsar Network e.g. PSR browser. The archive contains metadata and time series in an ascii-based format. Contact Duncan Lorimer drljb.man.ac.uk or Michael Kramer mkramerjb.man.ac.uk for more information.

• Data formats like PSRFITS Hotan et al. were discussed with the conclusion that no data format is generally accepted
• Archives for the other types of data product (Times of Arrival, raw frequency/time cubes) do not yet exist
• Jodrell has a PPARC e-science students (Mike Keith) working on developing tools to make the Parkes Multibeam Pulsar Survey publically accessible via grid computing. That will serve as a prototype for tools to be included in AVO and astrogrid later.
• a prototype of individual (daily) profiles database in the framework of PLEINPOT (cf sect. 1) is under way at Nançay

7) Recomendations for RadioNet

1. The relevant work packages (ALMA, AlbusSupportAndUserRequirementsForum , ?) should consider single-dish as well as interferometry processing software.
2. Contact other providers of radio spectral data - could be done between RadioNet and IVOA:
   • Within RadioNet : Nancay, JBO, Onsala, Efflesberg, IRAM, JCMT (+??)
   • Internationally: ATCA, GBT, Nobeyama, Puschino etc.
3. Increase complementary use by advertising RadioNet facilities (proposal deadlines etc.) to all members
4. Liaise with SpectrumManagement group about setting up RFI data base to keep records of examples of damaged data
5. Pursue other points above in Archives and VOs group and draw up priorities.

-- AnitaRichards - 19 Jan 2005