NEAR-INFRARED SURFACE PHOTOMETRY OF SPIRAL GALAXIES .2. DERIVATION OFMASS MODELS

Near-infrared surface photometry of six spiral galaxies is used to sep arate the main stellar components and derive mass models whose predict ed rotation curves are compared to observed gas kinematics. For three of the galaxies, central stellar velocity dispersions are also used. F or these intrinsically bright objects, the mass-to-light ratio of the disk, in the K band, is found to be similar or equal to 1, as expected . In four Sb-Sc galaxies, there is some evidence that the mass-to-ligh t ratio of the bulge may be on average similar or equal to 20 % smalle r, but the a priori assumption that these ratios are identical does no t significantly bias the disk masses. Early-type spirals with a promin ent bulge, in which the apparent central mass-to-light ratio is known to be often low, can need a significant correction to the bulge mass.