We present surface photometry for the central regions of a sample of 48 spiral galaxies (mostly unbarred and barred of types Sbc or Sc) observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Surface brightness profiles were derived and modeled with a Nuker law. We also analyzed archival Wide Field Planetary Camera 2 images with a larger field of view, available for 18 galaxies in our sample. We modeled the extracted bulge surface brightness profiles with an exponential, an r1/4, or an rn profile. In agreement with previous studies, we find that bulges of Sbc galaxies fall into two categories: bulges well described by an exponential profile and those well described by an r1/4 profile. Only one galaxy requires the use of a more general Sersic profile to properly describe the bulge. Nuclear photometrically distinct components are found in ∼ 55% of the galaxies. For those that we classify as star clusters based on their resolved extent we find absolute magnitudes that are brighter on average than those previously identified in spiral galaxies. This might be due to a bias in our sample toward star forming galaxies, combined with a trend for star forming galaxies to host brighter central clusters. (Refer to PDF file for exact formulas).

Publication Date



This is the pre-print of an article published by The American Astronomical Society. © 2004 The American Astronomical Society. The final, published version is available here: https://doi.org/10.1086/423036

Also archived in: arXiv:astro-ph/0408435 v1 24 Aug 2004

This work was funded by NASA grants for program GO-08228 from the Space Telescope Science Institute (operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555). We made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

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Document Type


Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus