Searching for Data available for the bright galaxy M51

this tutoriel has been adapted from the version available here, originally developed by M. Allen.

Uses Aladin, Simbad, VizieR, TOPCAT and VOSpec.

The goal of this tutorial is to search for data available for the galaxy M51 (images at different wavelength, catalogs and spectra)

Step-by-step:

• launch Aladin (use the command line "java -Xmx512M -jar Aladin.jar" as the use case can be memory consuming) and search for images of the bright galaxy M51
• Search for M51 images from VO services
  • open the server selector ( icon or menu "File -> Open..." or CTRL+L)
  • Search for images in the Aladin image server
  • • select the 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 "Load" to upload the image in Aladin (you can close the "Data info frame")
  • in the server selector choose the 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
  • click "Submit" (fields should be already filled correctly)
  • switch back to 1 panel view
  • "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
  • 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 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 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 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, use the SAMP enabled interoperability of the two tools to send the Simbad catalogue to it:
  • start TOPCAT
  • right-click the Simbad plane in Aladin 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" ( icon, 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..." ( icon) and, left mouse button pressed, define a closed region on the plot
    • use menu "Subsets -> Finish Drawing Region..." (or re-click icon) to define the subset ("Add" it)
    • (alternatively use the "column data" display to select rows and define a subset)
    • 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 the synchronization between Aladin and TOPCAT point selection)
• search for more information about HII regions in M51
  • in the Aladin server selector choose now the 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
  • (don't discard this TOPCAT table as we will use it in the last point of this use case)
• start VOSpec and display some spectra
  • in the Aladin server selector choose , 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
• use TOPCAT to prepare a list of bright HII regions of M51 and query Vizier for more details on them
  • diplay 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("x" can be any column, i.e. RAJ2000)
  • (optionally) send the table to Aladin to see HII regions' positions in M51 (remember to select only the subset in the main TOPCAT window before broadcasting)
  • in the column metadata display (pay attention only the "bright" set is displayed) make visible only the RAJ2000 and DEJ2000 columns
  • from TOPCAT main window menu use "Save table" to write and ASCII table of the "bright" HII regions' positions defined above
  • open the saved file to remove the quotes from the positions (unless Vizier will not understand them)
  • open the Vizier service page: http://vizier.u-strasbg.fr/viz-bin/VizieR
  • enter "M51" in the "Words matching author's name, word(s) from title, description, etc." field (just under the "light green bar")
  • check the "Use LISTs of Targets" box on the right and click "Find Catalogues"
  • select one, some or "All" of the resulting catalogues and click "Query selected catalogues"
  • at the really bottom of the new page use the file input field to load your saved positions file and click "Submit Query"
  • have a look at the results