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.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science