• 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: http://esavo.esac.esa.int/webstart/VOSpec.jnlp ) 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

Search for ULX sources and X-ray binaries in nearby (e.g. D<10 Mpc) galaxies (uses TOPCAT, Aladin).

ULXs (Ultra-Luminous X-ray sources) are X-ray sources that are less luminous than AGN but more luminous than any known stellar process (Lx > 10^39 erg/sec)

• tip: launch Aladin first, then TOPCAT; launch TOPCAT with a larger memory buffer; try java -Xmx512M -jar topcat-full.jar
• load the NED-1D galaxy catalogue (a .csv (coma-separated values) version of the catalogue can be found here:NED-1D.csv)
• the RA and Dec are in sexadecimals; convert RA, Dec to decimal: select Table Columns and then Add new sky coordinate column based on existing one; get rid of the multiple entries using the option match one
• optional: apply a filter in distance (e.g. D<10 Mpc) using TOPCAT (the stricter the criterion, the smaller the number of objects!) and send the filtered nearby galaxies catalogue to Aladin
• this catalogue does not contain any information about the size of the objets; load the hyperLeda catalogue in Aladin [(VII/237) from All VizieR (this might take a while as it contains about a million objects; place the cursor on the plane as it loads to get an idea of the number of objects still to be loaded); cross-match the two catalogues and send the match back to TOPCAT; add new column with radius in arcmin: pow(10.,$diameter_column)*0.1/2
• you can now delete the hyperLEDA plane in order to save memory; then load the 2XMMi catalogue (0.2-12 keV band) in Aladin (IX/40), which gives the calibrated fluxes for sources; send it to TOPCAT and cross-correlate (match two; "Sky with Errors"; "1&2"; "All Matches") the 2XMMi with the nearby galaxies catalogue using the new radius and the X-ray position uncertainty (ePOS) as errors
• add new column with the luminosity Lx for the point like sources from the calibrated flux and distance to each galaxy, i.e. Lx = 4*pi*D^2*fx = (do the math!) 50.078+2*log10($distance_column)+log10($fx_column)
• filter those sources with Lx >= 1e39 erg/s (our ULX candidates)
• plot Lx vs cross-correlation separation: most objects are at very low offsets, therefore X-ray emission most probably comes from the nucleus; some objects are clearly off; keep those above a given separation which you can select based on the separation distribution
• send the catalogue to Aladin keeping only the X-ray coordinates
• cross-match with X-ray binaries table(s) to find the non-matches
• cross-match with quasars and/or AGN catalogue(s)
• find images of the galaxies, plot the positions of the AGN and ULX candidates; verify their separation as well as from the galaxy centre
• find existing ULX catalogues to confirm candidates

-- MarkAllen - 15 Jun 2009