The VPHAS+ DR4 H-alpha HiPS

The images of the VPHAS DR4 H-alpha ESO survey have been turned into a recently released new HiPS image survey, which can be explored with Aladin Desktop or Aladin Lite :

The original ESO images have been processed with the Montage IPAC library in order to correct the local sky background, and this greatly improves the overall survey aspect as can be seen below.

Mini tutorial : mystery object

This mini tutorial demonstrates the usage of SAMP, STMOCs and the IMCCE SkyBot service.

• Open the VPHAS+ DR4 Halpha filter survey in your favorite browser.

  

• Zoom and pan on RA=260.999789, DEC=-21.9102775. There is a very bright source saturating the image, but the SIMBAD pointer can't find a SIMBAD source around these coordinates. What is this mystery object ?

  

• Start Aladin Desktop on your machine, and make sure a SAMP hub is running (check the antenna icon at the bottom right of the application).

• A button should appear in the VPHAS+ DR4 Halpha filter web page, allowing you to broadcast the current HiPS to Aladin Desktop. Click the Send to Aladin Desktop button and confirm that you allow the browser to send information to the local Desktop application.

  

• Change the coordinates to J2000 in Aladin Lite, and right-click on the bright source to copy its coordinates to the clipboard.

  

• Paste these in the Location toolbar in Aladin Desktop to center the survey on the mystery source, and zoom in.

  

• Select the VPHAS HiPS plane, and load its STMOC coverage. This is the space-time coverage description of the VPHAS survey, describing when each image used in the HiPS was observed.

  

• With the "phot" tool, select the region around the mystery source, and convert this selection into a MOC with Coverage > Generate a spatial MOC based on... > The selected drawing object.

  

• In the properties of this new MOC (Moc reg), add a Time range corresponding to that of the VPHAS DR4 : 2011-12-29T00:00:00 - 2018-08-12T23:59:59.

  

• Compute the intersection of the two STMOCs from the menu Coverage > Logical operations..., select the two STMOCs and CREATE the intersection in space and time.

  

• The intersection spans only a few minutes of time, on 2017-07-26, between 02:52:50 and 02:58:23.

• We can use the IMCCE SkyBot tool (Ctrl+L > IMCCE SkyBot tab on the right), enter the median date and time and search for solar system objects around these coordinates at the time of the observations.

  

• Our mystery object was Saturn (and its moons) !

  

• Can you find the other location in the VPHAS DR4 survey where Saturn was also observed ? (with a different date and location, of course)