Multicolor CCD photometry of supergiants in the disk of NGC 628

Young Jong Sohn, T. J. Davidge

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Abstract

We use VRI CCD images with sub-arcsec spatial resolution to investigate the photometric properties of red and blue supergiants in the nearby spiral galaxy NGC 628. Existing photometric surveys are used to identify H II regions, the majority of which have non-stellar colors. After removing these objects from our sample we are left with ∼ 310 stars. The (V-R,R-I) two-color diagram of these objects suggests that the majority have spectral types F, G, and K, indicating that residual contamination from non-stellar objects is negligible. Comparisons with theoretical evolutionary tracks indicate that the majority of supergiants in our field have progenitor masses below 25 M. The luminosity functions in all three bandpasses follow power laws, with the exponent in V=0.80±0.12, in good agreement with what is seen in other galaxies. The brightest RSGs occur at V∼ 21.0, from which we derive a distance modulus of 29.3.

Original languageEnglish
Pages (from-to)2280-2292
Number of pages13
JournalAstronomical Journal
Volume111
Issue number6
DOIs
Publication statusPublished - 1996 Jun 1

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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