NEON Archive School, P. Padovani Astrophysical Virtual Observatory (AVO) demo tutorial (prototype available at http://www.euro-vo.org/twiki/bin/view/Avo/SwgDownload) Open cluster membership * fire up the AVO prototype portal as described on the installation page * click on Load, enter target "pleiades" and radius "30 arcmin", press Submit * click on Data Tree * moving the cursor on the data tree "branches" one sees the field of view of the various images * load, for example, J-band, POSSII image 6.4 x 6.4 deg * centre the image by clicking on "zoom" and then clicking over the cluster centre * we now need distance information on the stars; click on Load again, then on "Vizier Catalogs"; enter "parallax" in the "Author, free text ..." field click Submit * select "The Hipparcos and Tycho Catalogues", then go back to the "Load" window, add "/hip_main" to "I/239" (need to do that to avoid loading more than one table, which confuses the plotting package), put in a radius of "5 deg", then click "Submit" * the catalog is now loaded (see right, above the POSSII image) and the sources are overlaid on the image * select with the cursor the central region: the selected sources get highlighted and the catalog parameters appear in the window below the image; moving the cursor over a column gives the column name * we now want to plot an histogram of the Hipparcos parallaxes; we first select with the cursor all stars in the image, then click on "Plugins" and select "VOPlot". Select "Plx" for the x axis, then click on "Histogram". Parallax for this cluster has to be around 8 - 9 mas (real value is 8.46+/-0.22 mas) and there are many foreground stars and a few background ones * we now want to plot a colour-magnitude diagram; we want first to correct for reddening, using the relation (B-V)o = (B-V) - E(B-V) = (B-V) - 0.04 for this cluster. We need then to add a new column by "right clicking" on the catalogue plane and selecting "Add a new column". "Name" can be "(B-V)o". Click on "B-V" under "Pick up a column name", and then enter "-0.04" after the column name. Then click on "Add a new column". * scroll the bottom bar all the way to the left, and check that indeed a new column with the name "(B-V)o" has been added as the last column * now we plot Vmag vs. (B-V)o for the cluster; we go back to the VOplot window, click "Plot" and then select "Vmag" for the Y axis and "(B-V)o" for the x axis, then click "Plot" again. Then click the "Rev" button above "Vmag" to flip the Y axis. The Zero Age Mean Sequence (ZAMS) is clearly visible. Select sources in the top left corner by using the cursor: the corresponding sources get highlighted in the image. Note how they are mostly in the centre. Click on "out" (bottom right) to see all the selected sources. Notice how most of them have parallaxes ~ 8 - 9 mas * now select with VOPlot the outliers (bottom right); look at the image, now they appear to be mostly at the edge of the field. As before, look at their parallaxes: now they are mostly foreground sources, with a couple of background objects and some ~ 8 mas * now we want to look for data available for selected sources in various mission archives. We then select some sources in the image, for example in the center, and then go to the Load window, click on "Missions in VizieR" and select, for example, ESO, then hit Submit; do the same for HST and then IUE. The pointings for the three missions are overlaid in the image * select one IUE pointing, then click on the first column, which is highlighted. One gets the entry in the INES catalogue in the Web browser, with a link to a preview of the IUE spectrum * now select one HST pointing; an "Image" link means that there is a preview image available, a "Spectrum" link means that there is a preview spectrum (clicking on "Image" loads it in the tree.) By clicking on the "Dataset" column one is taken to the MAST archive, with information on the dataset. Clicking on the "Catalog search" link one can then request the dataset. Scrolling down and clicking on the highlighted "Proposal ID" number one gets to the proposal page, with abstract, link to published papers (if any), and a list of all the datasets belonging to that proposal. Looking for optical counterparts of X-ray sources * fire up the AVO prototype portal as described on the installation page * click on Load, enter target CDFS and radius = 30 arcmin, press Submit * click on Data Tree * load V-band WFI preview image of whole CDFS as background: find tree node GOODS-WFI, expand node V89, select item DEEP2C-FV-PREVIEW... and press submit * now we want to look for X-ray sources in the area; we go to Load, click on Vizier Catalogs, select X-ray and the submit; select Alexander et al. then add /cdfs then submit (MAKE SURE TO HAVE WFI IMAGE SELECTED BEFORE DOING THAT) * now overlay the FOV of GOODS-ACS-HST data and show how one can see which X-ray sources are or not in the GOODS area; then select a few sources on the image and show the catalog entries * then open e.g. ACS F850LP box, then open version1.0 (these are the 5-epoch, stacked images), close WFI * check box on sector 33, click submit and download the ACS image * click in the center of the field, open version 1.0 for other filters, see checked boxes in those as well * hit submit and download all checked boxes (typically 3 ACS images F435W, F775W, F850LP) * close ACS * make RGB of ACS images * zoom out, see sources are mostly blue, notice tiny size of ACS image compared to WFI * now look for sources with VLT/FORS spectra: click on Load, click on VOdemo, select "SSA server for VLT/FORS spectra", change radius to, say, 0.5 deg, hit Submit * this loads the spectra into the tree, and one can see them all with their position angles (needs cursor on top level "SSA server for VLT/FORS spectra" in the tree); zoom in a little to be able to see the slits on the objects in the ACS image * right click on same text in the tree to create a catalog plane for spectra (might need to change colour by using the "properties" button) * to get to the spectra one selects a region and then clicks on the "spectrum" link; this sends off a request to ESO, retrieves the FITS file and displays it using SpeCView AS OF VERSION 2.0 THE FOLLOWING PART IS OUT-OF-DATE, AS THE ACE PLUG-IN IS NOT PART OF THE PROTOTYPE ANYMORE BUT IS NOW A WEB SERVICE * now we want to create a catalog of ACS sources; select the ACS image, then call ACE (Astronomical Catalog Extractor) from Plugins, then Open the configuration file, F775W-v1-config.ace, which is important as it tells ACE which settings to use for SExtractor (this file is available from http://www.euro-vo.org/twiki/bin/view/Avo/ExtragalacticScenario/ demo_files.tar.gz) * click on Extract; this tells the CDS server in Strasbourg to send the image to ACE in Cambridge and then returns to the user the output catalog whose sources are automatically overlaid * now cross-correlate the optical and X-ray sources by using the Cross-match service under Plugins; this creates a plane with the cross-matches and a table which is a joint between the two input tables for the matching sources; can first check typical X-ray positional errors using VOPlot; use 1.25 arcsec * one could now create derived parameters, like X-ray-to-optical flux ratios using the "add a column" feature