The observations are done through narrow band Hα and [SII] filters, and until now were mostly done on the 2m telescope at the National Astronomical Observatory (NAO) Rozhen, Bulgaria. We search for HII regions and supernova remnants. Supernova remnants are identified by their elevated [SII] /Hα > 0.4 ratios compared to HII regions.
Star formation rate in galaxies is usually derived based on their Hα fluxes, which should correlate with number of HII regions within the galaxy. By using [SII] /Hα criterion we found that supernova remnants can contaminate Hα flux of the observed galaxies to a few percents. By only observing in Hα line we cannot exclude these supernova remnants. Therefore, star formation rate based on just Hα observations are not very precise and it is important to correct them for supernova remnant contamination.
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