Dynamics of early type galaxies. I. The rotation curve of the elliptical galaxy NGC 4697.

The rotation curve, up to O'.6 from the center, has been derived from Ca ii H and K lines for the elliptical galaxy NGC 4697. A maximum seems to be reached at 15" with 65 km s '. The same galaxy has been investigated by means of photographic photometry in the B system. The luminosity profile follows the r114 law, and the mean ellipticity is 0.4. The total apparent magnitude is B = 10.30 mag, and the corresponding absolute magnitude reaches MB = - 20.5 mag, assuming a distance of 14.8 Mpc. The spatial velocity curve and the light density profile are derived. Mass and angular momentum have been computed on the hypothesis that the mass-to-light ratio is constant through the galaxy, leaving it as a free parameter. Under several assumptions it is found that the angular momentum of the elliptical NGC 4697 is lower than that of a spiral of comparable mass by a factor 5 to a factor 30, when the mass-to-light ratio varies from 5 to 50. Subject headings: galaxies, individual galaxies, motion in