| Title | Giant ringlike H II regions and the distance to M101 |
| Authors | Lawrie, D. G.; Kwitter, K. B. |
| Bibcode | 1982ApJ...255L..29L Search ADS ↗ |
| Abstract | A new determination of galaxy M101's distance modulus is presented based on the linear diameter of its largest ringlike H II region. Only well-defined rings whose diameters are independent of the filter used were selected. The photographic material shows a mean forbidden S II/H alpha intensity ratio of 0.42; this high value was confirmed and suggests that the gas may be excited by a shock due to supernova or stellar wind. A ringlike H II region was chosen because its diameters are easy to define objectively. The diameter is correlated with the parent galaxy's corrected face-on absolute magnitude and combined with the corrected face-on B-band apparent magnitude and the corrected face-on angular diameter of the galaxy to produce the distance modulus. |
| Objects | 2 Objects Search NED ↙ |
