Nebulous Objects in Messier 31 Provisionally Identified as Globular Clusters
Abstract
One hundred and forty nebulous objects have been found in or close to the borders of Messier 3' which, from their numbers, their distribution, and the radial velocity of a typical example, are presumably associated with the spiral. From their forms, structure, colors, luminosities, and dimensions they are provisionally identified as globular clusters. Absolute photographic magnitudes range from -4 to -7, the mean being -5.3. The luminosity function has a double maximum, which suggests a mixture of two homogene- ous groups having most frequent magnitudes at -5.0 and -6.2. Diameters range from about 4 to i6 parsecs. The number of objects per unit area decreases with distance from the nucleus of M 31, and occasional objects are found as far as 3~5 from the nucleus. The diameter of the spiral as derived from the distribution of these objects is probably of the order of 30,000 parsecs. According to Shapley's distances and magnitudes for the clusters in our system, reduced to the conventional scale, the objects in M 31 are systematically fainter than the galactic globular clusters, by an amount varying from about 0.75 to 1.95 mag. ac- cording to the interpretation of the data. The ranges in absolute luminosity are of the same order, however, and the two groups overlap to a considerable extent. The known globular clusters in the Magellanic Clouds are comparable with the brighter objects in M 31. Objects apparently similar to those in M 31 are found in N.G.C. 6822, M 3~, M 8i, and ~f ioi
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1932
- DOI:
- 10.1086/143397
- Bibcode:
- 1932ApJ....76...44H