Virtual Observatories

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Virtual Observatories

• ...or how to do your research from a beach in the
  Bahamas rather than stuck up a cold mountain in
  the middle of the night...

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Who I am

• John Taylor jdt_at_roe.ac.uk
• Work on the AstroGrid and VOTech Virtual
  Observatory projects
• Member of Edinburgh's Wide Field Astronomy Unit
  curates catalogue and image data from SuperCOSMOS
  and (soon) WFCAM and (less soon) VISTA
• Software engineer NOT Astronomer

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Outline

• The data deluge
• Why science is changing
• The scale of the problem and technical issues
• Catalogues
• How to use them
• VOTables, FITS files
• Visualisation tools
• The Virtual Observatory
• AstroGrid Demonstration

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I The astronomer's world is changing...

• Previously an Astronomer was a radio astronomer
  or a x-ray astronomer. Now you need to be an
  expert in all wavelengths.
• The move towards Survey Astronomy
• Federating data from different instruments.
• Vast quantities of auto-generated data
• See http//grist.caltech.edu/sc4devo/What_is_the_
  VO.pdf

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Dust shows in the IR
Shocks seen in the X-ray Chandra image
Supernova Remnant Cassiopeia-A a 300 year old
Supernova
Heavy elements seen in the optical
Mapping es in the magnetic field as revealed
by Radio data
Images from Chandra Science Centre Slide Nic
Walton, AstroGrid Project Scientist
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Data Deluge

• SuperCOSMOS 2.5 Tb
• WFCAM 14Tb per year
• VISTA 4Tb per week
• Physicists, Astronomers, Biologists all facing
  the same problem
• Steve Lloyd http//www.gridpp.ac.uk/talks/Data_De
  luge_Brunel_2005.ppt

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Nearby Spiral Galaxy
x-ray
optical
radio
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II Catalogue and Image Servers

• Cone searches
• Data formats FITS and VOTables
• Visualising the data Topcat and Aladin
• More sophisticated searches using SQL
• Demo of the SuperCOSMOS Science Archive

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Example SuperCosmos Science Archive

• Scans of the UK Schmidt telescope plates
• Catalogue data Image data
• 3 wavebands, 2 epochs
• Over 1 billion objects
• 2.5 terabytes in size

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Data Formats

• FITS the astronomer's jpeg
• images/spectra/tables
• Includes metadata
• VOTable
• xml format for tables
• The VO standard
• UCDs
• describe what a quantity is

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Visualising the data

• TOPCAT
• For viewing and manipulating tables, especially
  VOTables
• Create new columns
• Filter the sources
• Output the table in different formats

• Aladin
• Good for viewing image files
• Overlay catalogue tables
• Create RGB images
• Access data archives such as Vizier
• Aims to be a general Virtual Observatory portal

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Complex queries SQL

• SQL is a general language for querying databases
• select ra,dec,mag FROM sources where ragt0 and
  ralt1 and decgt-45 and declt-44 and maggt23

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SQL II

• Plenty of resources on the web for learning SQL
  e.g. http//www.w3schools.com/sql/default.asp
• There is an astronomy variant of SQL called ADQL
  (astronomy data query language)
• It's basically SQL with a few extra bits thrown
  in (a CIRCLE keyword for doing cone searches, and
  an XMATCH keyword for cross-matching data between
  databases)
• Cross Matching Taking two or more different
  database tables from (maybe) different sources
  and joining them together based on their RA and
  DEC

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Some databases

• SIMBAD - Basic data on objectshttp//simbad.u-stra
  sbg.fr/Simbad
• SuperCOSMOS Science Archive http//surveys.roe.ac.
  uk/ssa/
• SDSS (Sloan Digital Sky Survey)
  http//www.sdss.org/
• 2mass (2 micron all sky survey)
  http//www.ipac.caltech.edu/2mass/
• XMM http//xmm.vilspa.esa.es/external/xmm_data_acc
  /xsa/index.shtml

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Databases of databases

• Vizier http//vizier.u-strasbg.fr/viz-bin/VizieR
• Datascope http//heasarc.gsfc.nasa.gov/cgi-bin/vo/
  datascope/init.pl
• NED (Nasa Extragalactic Database)
  http//nedwww.ipac.caltech.edu/
• OpenSkyQuery http//openskyquery.net/Sky/skysite/

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This presentation will be available at

• http//wiki.astrogrid.org/pub/Main/JohnTaylor/neon
  .sxi

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A recap on yesterday

• Is the SSA now behaving?
• Last night's observing group how to use SQL to
  get your list of galaxies from SDSS
• select g.ra,g.dec,g.objId, s.z from Galaxy g,
  ELRedShift s where g.specObjIDs.specObjID and
  s.zgt0 and s.zlt0.01 and g.rlt10 and g.ragt0 and
  .........

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III Virtual Observatories

• What's a virtual observatory?
• What do you need to make one?
• AstroGrid glue for the Euro-VO
• Demo

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The International Virtual Observatory
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Virtual Observatory

• The VO vision can be summed up as the desire to
  make all archives speak the same language - all
  searchable and analysable by the same tools, all
  data sources accessible through a common
  interface, all data held in distributed databases
  that appear as one.Andy Lawrence, 09/2003
• Take all the world's Astronomical data, and all
  the world's applications and computing power and
  make it appear that they reside on the user's
  desktop.

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Science Cases Brown Dwarf Location

• Brown Dwarfs are cool, faint and (if can see
  them) close
• Roughly speaking
• Query optical and infrared catalogues for objects
  that are bright in the infra red, but not in
  the optical and have large proper motions.
• Requires use of more than one catalogue
• More The AstroGrid 10 http//wiki.astrogrid.org
  /bin/view/Astrogrid/ScienceProblems

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AstroGrid Components
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Example workflow calculating photometric
redshifts
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AstroGrid Components
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Demo
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Contacts and info

• Contacts
• John Taylor jdt_at_roe.ac.uk Institute for
  Astronomy, Royal Observatoy of Edinburgh
• Background Info on AstroGrid
• http//www.astrogrid.org
• Download the Euro-VO AstroGrid software from
• http//software.astrogrid.org

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What now?

• AstroGrid Release 1 is up and running now

http//www.astrogrid.org/release
http//wiki.astrogrid.org/bin/view/Astrogrid/Relea
seV1Pages
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Locating data and applications

• IVO-standard registry
• Registries harvest from each other
• Xml-based query language ADQL

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Workflow

• Orchestrate services
• Queries and workflows are designed using the
  portal other clients on the way
• Work is run remotely and asynchronously
• Archives searched and results manipulated
• Results are stored in a virtual file system
• Queries and workflows can be re-used and shared

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AstroGrid Intro Demo

• John Taylor
• Institute for Astronomy, Edinburgh

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Building a VO - Layer Diagram