ESAC VO School

19 - 20 October 2010

European Space Astronomy Centre (ESAC)
ESA, Villafranca del Castillo, Madrid, Spain

ESAVO Portal

Use Case 1: Searching for Data available for the bright galaxy M51

Uses Aladin, TOPCAT, VOSpec and VODesktop.

Searching for available data for the bright galaxy M51

  • launch Aladin (use the command line "java -Xmx2048M -jar Aladin.jar" as the use case can be memory consuming) and search for images of the bright galaxy M51
  • open the server selector ("open" icon, menu "File -> Open..." or CTRL+L) to search M51 images from VO services
  • select the "Aladin images" tab in the "Image servers" tab column on the left
    • e.g. input: "Target" M51, "Radius" 10 arcmin, "default image format" FITS
    • click "Submit" and wait for the results
    • select a result (e.g. POSSII F-DSS2 image at 0.658um with OBS_ID=270) clicking on it, the "Data info frame" window should pop-up with image metadata content
    • click "Submit" to upload the image in Aladin (you can close the "Data info frame")
  • in the server selector choose the "SkyView" tab to search other M51 images
    • fields should be already filled up, try to "Submit" for 3 images changing only the "Surveys" field to: VLA First 1.4GHz, H-ALPHA COMP and VLSS
  • change to "4 panels" view to manage all the downloaded images
    • menu "View -> 4 panels" or click on the split icons at the bottom of the image display
    • click one after the other the image planes in the Aladin planes stack to display the images or simply drag and drop the planes on the four panels
    • try the "match" icon (at image display bottom near split icons) to zoom and/or pan simultaneously the four images (tip: clicking twice will make the icon red and automatically synchronize also the image orientation)
  • again in the server selector change tab to "Sloan"
    • click "Submit" (fields should be already filled correctly)
    • "mouse over" the results for the five (u,g,r,i,z) filter subsets to show the footprint of the retrieved results over the already loaded images (switch back to 1 panel view if you prefer)
    • select, by ticking the box on the left of the desired image, the 5 images (1 per filter) that better overlap the galaxy
    • submit to load them
  • select the "all VO" tab in the upper "Others" tab list of the server selector
    • untick "catalogues" and "spectra" server options
    • check the form fields, submit and wait for answers
    • "mouse over" the results to see the footprint overlap
    • click on the image (better in 1 panel view) to see the boxes of the results being selected/unselected if clicked point is contained in them (tip: easier to see in the SDSS results that are the same of the Sloan images already downloaded)
  • make a colour composite image using the Aladin RGB tool
    • click the "rgb" icon in the vertical toolbar between image display and planes' stack (or menu "Image -> RGB image builder...")
    • select from the drop down menus the images for the red, green and blue components and click "Create"
  • (optionally) use the multi-panel view to display the false color image along with its components or other images and try again the match tool for panning and zooming simultaneously the images
  • try the transparency tool dragging the slider to see image overlay (at the bottom side of each image plane there's a sliding little rectangular cursor, drag it)
  • get back to server selector and choose the "Simbad" tab in the "Catalog servers" tab column on the right
    • given the fields are already filled, select "- no filter -" for "Display filter"
    • submit to load the catalog in a new Aladin plane
    • right-click the newly created plane and click "Properties..."
      • switch through "dedicated filters" to see the various objects superposed to the image
      • try clicking "This filter on the stack plane for editing" to create a "filter" plane on the stack and see how to handle multiple information on the same image (have a look at the script in the "Advanced Mode" tab)
  • source filtering can also be done interactively in TOPCAT (start it), use the SAMP enabled interoperability of the two tools to send the Simbad catalogue to it
    • right-click the Simbad plane and "Broadcast selected tables to..." topcat (also possible through the "Interop" menu)
    • in TOPCAT (should have received the table) click the "Display table cell data" (4th icon from left, or menu "Views -> Table Data") to view table values
    • plot catalogue positions and try to define a subset to be sent back to Aladin
      • click "Scatter plot" (or menu "Graphics -> Plot")
      • use menu "Subsets -> Draw Subsets Region..." (or 9th icon in the icons' bar) and, left mouse button pressed, define a closed region on the plot
      • use menu "Subsets -> Finish Drawing Region..." (or re-click 9th, 'ticked' icon) to define the subset ("Add" it)
      • alternatively, use the "column data" display to select rows and define a subset (Subsets -> Subset From Selected Rows). Notice how in the scatter plot these subsets are also displayed
      • in the main TOPCAT window select the newly created subset using the "Row subset" dropdown menu and send it back to Aladin using "Interop -> Send table to... -> aladin"
      • get back to Aladin to view the new plane and display its points, if the "table view" in TOPCAT is open see how SAMP allows row automatic selection and highlighting when clicking on a catalogue point in the Aladin display
      • (if not the table view keep the TOPCAT scatter plot opened and look at the synchronization between the Aladin and TOPCAT point selection)
  • search for more information about HII regions in M51:
    • in Aladin: in the Aladin server selector choose the "All Vizier" tab, enter "HII" in the "Author, free text..." field and submit
      • submit one or more catalogues from the results window (e.g. J/ApJ/633/871)
      • send the table to TOPCAT to view the full table and/or click the catalog points in Aladin to see full details
    • in TOPCAT: select VO -> VizieR Catalogue Service. Type "M51" in the target and click resolve to obtain the coordinates
      • Choose a suitable radius and in the Catalogue Selection choose the "By Keyword" tab and type "HII" in the Keywords field.
      • Click "Search Catalogues", select each catalogue to be loaded and click "OK"
    • in VODesktop: in the VO Explorer window click New Smart List (File -> New Smart List)
      • Give the list a name, and in the Any main field contains type "M51"
      • when the query is over, i.e. the red moving status bar at the bottom of the page becomes green, press "Create"
      • explore VODesktop: check the various capabilities of each resources; check the "Information" and "Table Metadata" tabs at the bottom of the main window; see how the available "Actions" (left column of the main window) change with the selected resource
      • send tables to TOPCAT by clicking "Send tables to Topcat" in the Actions section (lower left part of the VODesktop main window)
  • start VOSpec and display some spectra
    • in the Aladin server selector choose "all VO" tick only the "spectra" server option and submit
    • mouse over collapsed server results looking at Aladin image display to see what positions the spectra refer to (one or more "S"s should appear there)
    • click over a result and, from the "Data info frame" click "Load in..." VOSpec to display the spectrum there
    • In addition, spectra can be searched for directly in VOSpec, type "M51" in the Target field of the main VOSpec window, select a suitable search radius in the Size field (in degrees) and click "Query"
    • the Server Selector will open. View the available VO Spectra Services (SSA) and Theoretical Spectral Services by clicking on each. Either select some of the services, or check the "Select all SSA" box to choose all SSA Services and click "Query"
    • all results will be listed, by service, within the Spectra List region in the main VOSpec window.
    • select spectra from any (more than one is possible) resource and click on "Retrieve"; all selected spectra will be displayed
    • by clicking the Tree/Table view (icon on the right of the upper tool bar) the returned SSAP servers can be displayed in a table or a tree view
  • use TOPCAT to prepare a list of bright HII regions of M51 and query the VO for each object in the list
    • display the table data for the Vizier table (sent before from Aladin)
    • display the column metadata to identify the luminosity of your choice for the brightness
    • use a scatter plot to draw a region in a "x" versus luminosity plot to define the wanted "bright" subset
    • select VO -> Multicone, type "M51" in the Keywords field and click "Submit Query"
    • choose a catalogue (e.g. J/ApJ/601/735) and the correct input table (remember to select only the subset in the main TOPCAT window)
    • Choose the correct RA and DEC columns, input the search radius, select Verbosity as 3 (to retrieve the maximum number of columns), the Output Mode as "New joined table with best matches" and click "Go"
    • have a look at the results and do the same for more catalogues in the VO