Look at page 3:
"We created a workflow, i.e. an automatic data retrieval and analysis system to search for cE galaxies in large data collections provided by the Virtual Observatory (VO, (12)). It comprised the following steps. (i) Identify nearby galaxy clusters at redshifts z < 0.055 using the Vizier Service (13) at the Centre de Donn´ees Astronomiques de Strasbourg. Without this condition our potential candidate cE galaxies would have been too faint for spectroscopic follow-up. (ii)
Once the sources were identified, gather more precise measurements using other VO services including the NASA/IPAC Extragalactic Database (NED, (14)). (iii) Use the IVOA Simple Image access Protocol to find and fetch the HST images of selected galaxy clusters from the Hubble Legacy Archive (HLA, (15)). (iv) For each image, run the SExtractor source identification software (16) to obtain half-light radii, total luminosities and approximate light profiles for all galaxies in each frame. (v) Apply color corrections to homogenize the results for all photometric bands and use the surface brightness – half-light radius criteria to find cE candidates. (vi) Finally, query NED, Vizier and a database of Sloan Digital Sky Survey Data Release 7 (17) to find additional information for candidate objects, such as published redshifts and integrated photometry."
A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory
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