Significance of a Luminosity Concentration Law in Elliptical Galaxies.

Abstract

view Abstract Citations (5) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Significance of a Luminosity Concentration Law in Elliptical Galaxies. Fish, Robert A. Abstract New photometry of elliptical galaxies in the Virgo Cluster and in the field based on Lick Observatory 120-in. plates, combined with the results of earlier workers, points to a correlation between the effective radius of a galaxy (as defined by de Vaucouleurs and measured along the minor axis) and the absolute luminosity. The laws L=are+b and L=cre312 fit a log-log plot of the 17 galaxies about equally well over a range in luminosity of a factor of 200 (M32-XGC 4472). The linear law is implicit in the purely radiative fragmentation model for the formation of galaxies proposed by Hoyle (Astrophys. J. 118, 513, 1953). The law L~re312 could result from fragmentation with nonradiative dissipations. In any case it implies that Lpcentrai is a constant, and that (L/re)1'2 is proportional to the velocity dispersion of the nucleus if all the galaxies possess the same mass spectrum and are constructed according to the same dynamical model. Either luminosity relation would provide a criterion of the absolute magnitude of a galaxy independent of the redshift. A number of elliptical members of double and triple systems were studied photometrically in this program, for it was felt that these systems might lead to information of evolutionary interest. Those associated with normal late-type spirals (Sc) are more condensed and those associated with early- type galaxies (E, SO, Sa) are less condensed than would correspond to either luminosity relation given above. The "late" and "early" populations of ellipticals may therefore be the result, respectively, of late and early formation of stars during the initial condensation of the galaxies. Alternatively, if Sc spirals are young galaxies, then the gradient of luminosity in an elliptical galaxy would seem to decrease with age. Population identifications are suggested for two ellipticals with peculiar spectra: XGC 3226 with the extreme "early" population, arid XCG 4486 with the "late" population. The former has weak (or absent) H and K lines and is paired with a Seyfert spiral; the latter has the well-known jet and broad emission lines. Publication: The Astronomical Journal Pub Date: September 1963 DOI: 10.1086/109075 Bibcode: 1963AJ.....68R..72F full text sources ADS | data products NED (1)