Pseudobulges in the Disk Galaxies NGC 7690 and NGC 4593

We present Ks-band surface photometry of NGC 7690 (Hubble type Sab) and NGC4593 (SBb). We find that, in both galaxies, a major part of the "bulge" is asflat as the disk and has approximately the same color as the inner disk. Inother words, the "bulges" of these galaxies have disk-like properties. Weconclude that these are examples of "pseudobulges" -- that is, products ofsecular dynamical evolution. Nonaxisymmetries such as bars and oval diskstransport disk gas toward the center. There, star formation builds densestellar components that look like -- and often are mistaken for -- merger-builtbulges but that were constructed slowly out of disk material. Thesepseudobulges can most easily be recognized when, as in the present galaxies,they retain disk-like properties. NGC 7690 and NGC 4593 therefore contribute tothe growing evidence that secular processes help to shape galaxies. NGC 4593 contains a nuclear ring of dust that is morphologically similar tonuclear rings of star formation that are seen in many barred and oval galaxies.The nuclear dust ring is connected to nearly radial dust lanes in the galaxy'sbar. Such dust lanes are a signature of gas inflow. We suggest that gas iscurrently accumulating in the dust ring and hypothesize that the gas ring willstarburst in the future. The observations of NGC 4593 therefore suggest thatmajor starburst events that contribute to pseudobulge growth can be episodic.