Luminosity Function of the Elliptical Galaxies in the Virgo Cluster and the Hubble Constant.
Abstract
Photographic photometry has been completed for all elliptical galaxies brighter than m~~= 16.0 in the central 6.6X6.6 deg region of the Virgo cluster. individual magnitudes obtained for the brighter galaxies agree very well with those published by Holmberg (Medd. Lund Ser. II, No. 136, 1958). The overwhelming majority of the galaxies measured, especially the brighter ones, must be cluster members. The integrated luminosity function for the bright galaxies is found to rise exponentially with magnitude as 10O.8m, while for galaxies fainter than m = 10.0 the function changes rather abruptly to 10O.2m. The luminosity function for the Virgo ellipticals is thus an excellent match to the luminosity functions found for elliptical galaxies in several other clusters. However, the brightest Virgo elliptical is fainter by more than a magnitude than the brightest ellipticals in the Coma and Corona Borealis clusters. If the luminosity function for the Virgo galaxies is matched to that found for the Coma and Corona Borealis clusters, the difference in distance modulus between Virgo and Coma is 4.7 mag, and between Virgo and Corona Borealis is 7.2 mag. According to Sandage (Astrophys. J. Letters 152, L149, 1968) the distance modulus of M87 in the Virgo cluster is 31.1. If we adopt Sandage's value as appropriate to the cluster as a whole, we find the moduli of the Coma and Corona Borealis clusters to be 35.8 and 38.3, respectively. Combining these distances with the mean radial velocities of those clusters (6866 km/sec and 21 651 km/sec), we find a Hubble constant of 47 km/sec Mpc. If the adopted modulus for the Virgo cluster is correct, and if the procedure for fitting together the luminosity functions is valid,
- Publication:
-
The Astronomical Journal Supplement
- Pub Date:
- 1968
- Bibcode:
- 1968AJS....73Q.161A