Photoelectric Photometry of the e0 Galaxy NGC 3379.

Abstract

Detailed photometric maps of the E0 galaxy NGC 3379 were made by means of photoelectric techniques. Approximately 400 points were measured in each of two colors. The galaxy is of quite uniform color except for a small region within about 20 seconds of arc of the center, which is a little redder- A(B - V) 0 06. The three-dimensional volume emissivity was calculated from the photometric results by a X2-minimum process. Two independent methods are proposed for calculating the three-dimensional mass density and gravitational potential fields from the volume emissivity. The gravitational potential fields calculated according to each of these methods are compared for the case in which the symmetry axis is assumed to be perpendicular to the line of sight with satisfactory agreement out to a radius within which half of the mass is presumed to reside. The departure beyond this point is discussed. A very preliminary discussion of the implications of this work concerning the structure of the galaxy is given. Under certain assumptions which may be of doubtful validity, we find that the mass of this galaxy is about 1011 solar masses and the mass-to-light ratio is about 9.