THE ASTRONOMICAL JOURNAL    VOLUME 108, NUMBER 4, PAGE 1276        OCTOBER 1994

 EMBEDDED CLUSTERS IN GIANT EXTRAGALACTIC H II REGIONS. I. BVRHalpha PHOTOMETRY

                                  Y. D. MAYYA

          Indian Institute of Astrophysics, Bangalore 560 034, India
                   Electronic mail: ydm@tifrvax.tifr.res.in


                                   ABSTRACT

    Photometry in BVR continuum bands and in the emission line of Halpha+
    [N II] are presented for a sample of H II complexes in disk, spiral arm
    and nuclear regions of galaxies NGC 1365, 1566, 2366, 2903, 2997, 3351,
    4303, 4449, and 5253.  Main sources of errors on H II region photometry
    are discussed.  Errors due to background subtraction are parametrized
    in terms of background nonuniformity and fractional background
    contribution and are described separately in the Appendix.  Our
    photometric data are compared with the existing data in the literature.
    Photometric properties of the sample regions are analyzed statistically
    and its implications on star formation are briefly discussed.  Colors
    and Halpha+[N II] equivalent widths of nuclear H II regions are found
    to be distinctly different from disk H II regions, suggesting different
    star formation histories.  We have identified a few high Halpha+[N II]
    equivalent width regions, which are fainter than average in both
    emission line and continuum fluxes, thus accounting for the low
    frequency of occurence of such regions in flux limited samples.