Confirmation of a Supernova candidate

(based on the EuroVO-AIDA WP5 case, developed by G. Iafrate and M. Ramella, expanded by E. Hatziminaoglou. The original version can be found here)

Uses Aladin and TOPCAT.

The goal of this tutorial is to look for a supernova candidate on an image taken by the Col Druscie Remote Observatory Supernovae Search (CROSS) programme and look for other Supernovae in the field.


  • launch Aladin and TOPCAT
  • load the local image of NGC6946 ( taken by the Col Druscie Remote Observatory Supernovae Search (CROSS) programme
  • to make the image clearer, modify the pixel distribution (pixel_button.png button, 3rd from the bottom in the vertical tool bar, right next to the image window) by changing the Contrast
    • you can also change the colour map

Astrometric Calibration of an image

  • the image has no astrometric calibration; the calibration can be done from within Aladin
    • open the Server Selector by clicking on the Load button(load_button.png)
    • select allVO ( AllVO_button.png ); explore allVO for NGC6946
      • tick off catalogs_button.png and Spectra_button.png and open the Server list (click on detailed_list.png)
      • the button marked question_mark.png next to each Registry will give information about the Registry
      • you can Filter the resources
      • select a few resources (e.g. Aladin image server) and fire the query ( submit_button.png)
      • the response will appear in the form of a tree in the Server selector window
      • Images from the Aladin image server can also be found through the "Aladin image" tab of the server selector
      • pick the image of your choice (e.g, POSSI E-DSS1 14.2' cutout, tip: do not select large images!)
    • select a reference catalogue from the Catalogue Servers (e.g. 2MASS, USNO) either from the AllVO menu or from the Surveys tab
    • place both images (calibrated and non-calibrated) side by side by splitting the display window in two panels (click on the corresponding option at the bottom left of the display window - multiview) Aladin_m51_fig1.png
    • highlight the non-calibrated image plane and select the properties button pro_button.png(or right-click on the image and select "Properties ...")
    • in the Astrometric Reduction section select New and select by matching stars
    • activate the cells under "x y" position (by clicking on them) and click on a few (3-4) stars on the uncalibrated image; then select the corresponding stars on the calibrated image after activating the cells under hh mm ss +dd mm ss and then click Create
    • Aladin_m51_fig2.png

Identifying the supernova candidate

  • the local image is now calibrated and can be superposed on the POSSI (or other) image, in order to identify the Supernova:
    • go back to single view mode (showing one single image in the main Aladin window)
    • change the transparency of the POSSI image by sliding bar appearing on the image logo to the right
    • OR associate the two images (this can be done by clicking on the assoc_button.png icon)
    • "tag" the supernova(tag_button.png icon)

Further steps:

  • measure the distance from the centre of the galaxy
    • click on the dist_button.png icon
    • then click on the centre of the galaxy and without releasing the mouse button, drag the pointer all the way to the supernova
    • the distance is displayed on the main window
  • check for more SNe and other interesting objects in the same galaxy:
    • load simbad_tab.pngfrom the Server Selector
    • clicking on either of the object, the available information will appear in tabular form at the bottom of the Aladin window, linking directly to the Simbad query results on your browser- Try it!
    • to see immediately the SNe, highlight the Simbad plane and click on the column named OTYPE
    • the corresponding histogram (objects grouped per type) will appear in the little graphic window below the stacks; move the mouse over each bar to see the corresponding objects highlighted in the main Aladin window Aladin_m51_fig3.png
  • interact between TOPCAT and Aladin:
    • send the Simbad plane to TOPCAT
      • right click on the SIMBAD plane
      • select Broadcast selected table to... topcat
    • in TOPCAT, view the Simbad table by selecting in the Menu Views -> Table Data or by pressing on the topcat_tabledata.png button
    • view the column metadata selecting Views -> Column Info or by pressing the topcat_columninfo.png button
    • in Aladin, place the cursor on any Simbad identification on the main Aladin window and see how the relevant column is highlighted in the TOPCAT Table Data
    • in TOPCAT, create the SN sub-sample as follows:
      • click on Display row subset (topcat_displaysub.png) -> Define new subset using algebraic expression (topcat_definesub.png) with the expression: equals(OTYPE,"SN") topcat_m51_fig1.png
      • OR (if you don't know the syntax for the algebraic expression) display the column metadata (topcat_columnmeta.png); highlight the OTYPE column; rank the table based on the selected column by clicking on one of the yellow arrows at the top of the column metadata window; display the table; select the rows with OTYPE=SN; define a new sub-set including the selected rows only by clicking on the upper left button of the display table window(topcat_definerowsub.png) topcat_m51_fig2.png
      • OR you can click on filter_button.png in Aladin (make sure the Simbad plane is highlighted), advanced mode and define: $[src.class]="SN" {draw red square} (the SNe will appear in red); Apply and/or Export; a new plane with the filtered source has now been created
      • OR in Aladin, you can search for SNe in VizieR catalogs (in the vizier_tab.png tab or using the AllVO_button.png button where you will also find other catalogs)
  • select other images taken in other wavebands and different epochs
    • look for e.g. X-ray (or other wavelengths) counterparts: in TOPCAT: Load (topcat_load.png) ->Cone Search(topcat_conesearch.png)
    • in the "Keywords" field type your constraints (e.g. x-ray, radio, gamma, supernovae) and select the resources to be queried
    • put the objects name (NGC6946) in the "Object Name" field and query
    • cross-correlate (topcat_xmatch.png) the resulting catalogues with the one(s) already loaded in TOPCAT, send them to Aladin with SAMP (topcat_sendsamp.png), check them against the images, improvise!
    • other things to try with Aladin:
      • draw contours (contour_button.png) on any of the image
      • activate the Simbad automatic pointer (from the "Tools" menu), place the pointer on any object of the image
      • try to create an RGB image (rgb_button.png) from three images of your choice

-- CarolineBot - 26 May 2010

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng Aladin_m51_fig1.png r1 manage 374.2 K 2010-05-26 - 11:46 UnknownUser fig1
PNGpng Aladin_m51_fig2.png r1 manage 61.5 K 2010-05-26 - 11:53 UnknownUser fig2
PNGpng Aladin_m51_fig3.png r3 r2 r1 manage 239.2 K 2010-05-26 - 12:57 UnknownUser fig3
PNGpng AllVO_button.png r1 manage 6.3 K 2010-05-26 - 12:14 UnknownUser allVObutton
PNGpng Spectra_button.png r2 r1 manage 5.5 K 2010-05-26 - 12:18 UnknownUser spectra button
PNGpng assoc_button.png r1 manage 4.5 K 2010-05-26 - 12:01 UnknownUser assoc button
PNGpng catalogs_button.png r2 r1 manage 5.3 K 2010-05-26 - 12:18 UnknownUser catalogs_button
PNGpng contour_button.png r1 manage 4.5 K 2010-05-26 - 13:49 UnknownUser contour button
PNGpng detailed_list.png r1 manage 6.1 K 2010-05-26 - 12:15 UnknownUser detailed_list_button
PNGpng dist_button.png r1 manage 4.5 K 2010-05-26 - 12:37 UnknownUser dist button
PNGpng filter_button.png r1 manage 4.4 K 2010-05-26 - 13:33 UnknownUser filter button
PNGpng load_button.png r1 manage 4.1 K 2010-05-26 - 12:09 UnknownUser load button
PNGpng pixel_button.png r1 manage 4.6 K 2010-05-26 - 12:06 UnknownUser pixel_button
PNGpng pro_button.png r1 manage 4.4 K 2010-05-26 - 12:03 UnknownUser prop button
PNGpng question_mark.png r1 manage 4.4 K 2010-05-26 - 12:15 UnknownUser question_mark
PNGpng rgb_button.png r1 manage 4.6 K 2010-05-26 - 13:50 UnknownUser RGB button
PNGpng simbad_tab.png r1 manage 5.4 K 2010-05-26 - 12:39 UnknownUser simbad tab
PNGpng submit_button.png r1 manage 6.0 K 2010-05-26 - 12:21 UnknownUser submit button
PNGpng tag_button.png r1 manage 4.5 K 2010-05-26 - 11:59 UnknownUser tag
PNGpng topcat_columninfo.png r1 manage 4.6 K 2010-05-26 - 13:04 UnknownUser topcat column info button
PNGpng topcat_columnmeta.png r2 r1 manage 4.6 K 2010-05-26 - 13:27 UnknownUser topcat column meta button
PNGpng topcat_conesearch.png r1 manage 4.8 K 2010-05-26 - 13:41 UnknownUser topcat cone search
PNGpng topcat_definerowsub.png r1 manage 4.5 K 2010-05-26 - 13:26 UnknownUser topcat define row subset button
PNGpng topcat_definesub.png r1 manage 4.6 K 2010-05-26 - 13:09 UnknownUser topcat define subset button
PNGpng topcat_displaysub.png r1 manage 4.6 K 2010-05-26 - 13:07 UnknownUser topcat display subset button
PNGpng topcat_load.png r1 manage 4.7 K 2010-05-26 - 13:41 UnknownUser topcat load button
PNGpng topcat_m51_fig1.png r1 manage 25.7 K 2010-05-26 - 13:12 UnknownUser topcat fig1
PNGpng topcat_m51_fig2.png r1 manage 80.7 K 2010-05-26 - 13:26 UnknownUser topcat fig2
PNGpng topcat_sendsamp.png r1 manage 4.7 K 2010-05-26 - 13:47 UnknownUser topcat send samp button
PNGpng topcat_tabledata.png r1 manage 4.5 K 2010-05-26 - 13:04 UnknownUser topcat table data button
PNGpng topcat_xmatch.png r1 manage 4.6 K 2010-05-26 - 13:45 UnknownUser topcat xmatch button
PNGpng vizier_tab.png r1 manage 5.9 K 2010-05-26 - 13:37 UnknownUser vizier tab
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Topic revision: r4 - 2010-06-02 - CarolineBot
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