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Extragalactic 2

Baldi (Linux), Bonchi (Windows), Cassara' (Windows), Chon (Mac OS X), Finet (Windows/Linux), Fritz (Mac OS X), Guelbenzu (Linux), Leitet (Mac OS X), Messias (Mac OS X), Tepper-Garcia (Mac OS X), Vulcani (Mac OS X)

Schedule Tues March 31.

0900 - 1015

Intrduction: Use cases and participants' (group) projects

Extragalactic 2: use case 3: Searching for Data available for the bright galaxy M51. (Aladin, SIMBAD, VizieR , Topcat, VOSpec)

1045 - 1230


1400 - 1530

Extragalactic 1: use case 1: Confirming a supernova candidate (Aladin, Topcat)

option: Extragalactic 1: use case 2: Search for ULX sources and X-ray binaries in nearby (e.g. D<10 Mpc) galaxies (uses TOPCAT, Aladin).

1600 - 1730

CDS Training Materials







AstroGrid Python Scripting Information and worked examples


Use Case 1

_Based on Eduardo Gonzalez Solare case from the VO Info Day in Lisbon

Use Case 2

Finet Francois

  • search for existing quasars (ra. and decl., z, mag., etc.) in the narrow (+- 30')strip of sky visible at zenith from the Devasthal observatory (lat. +2922') in order to calibrate astrometrically all objects that will be detected with the International Liquid Mirror Telescope.
  • search for photometric standards in the r', g', i' systems in that same narrow strip of sky
  • identification of high proper motion objects and stars with known trigonometric parallaxes in that band of sky
  • production of long images at different wavelengths of that strip of sky based upon existing space and ground based observations

Use Case3: Searching for Data available for the bright galaxy M51. (Aladin, SIMBAD, VizieR , Topcat, VOSpec)

Mark Allen

  • Search for images of the bright galaxy M51 in Aladin.
  • Try the various image servers: The Aladin image server, Skyview and Sloan Digitial Sky Survey
  • Try the 'all VO' access (selecting image servers) - Note the method for selecting images at a given sky location. Clicking in the image puts a tick in the selection boxes of the available data.
  • Make a colour composite image using the RGB tool.
  • Use the multi-view windows to manage the various images you have in the 'stack'
  • Try the 'match' button at the bottom of the image window to align the image for synchronized zooming
  • Try the transparency control for viewing images overlaid on each other
  • Overlay as SIMBAD identifications using the SIMBAD link in the Server selector window

- Try 'with no filter' for a simple listsing of the IDs
- Try with 'Simbad filter' (colorized) to see how the same info can be presented in detail
(optional - open the 'properties' window for the Simbad plane to see or edit the filter)

  • Filtering of sources can also be done interactively with Topcat. Start Topcat, and send the SIMBAD plane to Topcat (right-click on the plane in the stack, and 'Broadcast selected tables to..'
  • View the table values in Topcat. Make a plot of the positions and try the area selection tools to select a number of points in the plot. Note how the selected subset may be transmitted back to Aladin to highlight sources from the original Simbad plane.
  • Make a subset of the brightest HII regions, and send the table back to Aladin using the Topcat 'Interop' menu
  • Search for spectra available in the VO with the 'all VO' button in the server selector window.
  • Find spectra available from the Hubble Space Telescope, and view the positions of the spectra (and sometimes thespectral slit aperture) on the image. Make a plane containing all the spectra positions, and cross match these with the positions of the HII regions.
  • Start VOSpec ( Web Start: ) and display some of the spectra, by clicking on the spectra in the server selector window, and 'Load in -> VOSpec'.
  • Check VizieR for more detailed catalogues of HII emitting regions in M51. This can be done via Aladinor via the more detailed VizieR interface.
  • (Advanced - compile a list of bright HII regions in M51 and query VizieR with this list

Use Case4

Elisabet Leitet

Search for galaxies with specific properties, example:

  • Redshift range z=0.3-0.4
  • EW(Halpha) = 20 - 200 , to ensure star formation
  • FWHM(Halpha) < 300 km/s to deselect active galaxies
  • [OIII]/Hbeta > 1.5 to ensure a young stellar population
  • Colours: u-g < 0.5 and g-r < 0.3 (after correction for both Galactic (Schlegel et al. 1998, ApJ 500, 525)
    and internal extinction (based on the Halpha /Hbeta ratio and assuming a Galactic extinction law)
  • Use the log([OIII]/H ))/log([NII]/H ) plot to deselect active galaxies
  • Crosscorrelate with GALEX for uv data

Name LastName

Problems encountered

Please list here any problems, big or small that you found with the VO tools used.

- Aladin: querying for images with the All-VO capability of aladin, the DSS images selected from the aladin image server entries in the returned list do not load, and report an error about RA and DEC rows.

- aladin filters - it is not obvious that one needs to 'apply' a filter before exporting the results to a plane

- topcat - how can one give a table a name so that it shows up with that name in the aladin stack when broadcast there?

-- PaoloPadovani - 02 Mar 2009

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