Far from being the rare, exotic "beasts" that inhabit only a tiny minority of galaxies, massive black holes (BHs), which range from a million to several billion times the mass of the Sun, are probably an integral component of most or all galaxies with a bulge. This past year has witnessed much frenzied activity in the search for these massive objects. Ho’s work has exploited the unique capabilities of the Hubble Space Telescope (HST) to measure BH masses in large samples of nearby galaxies. He has made use of both stellar and gas kinematical techniques, and applied them to both spiral and elliptical galaxies. The existing data reveal a remarkably tight correlation between the BH mass and the stellar velocity dispersion of the galactic bulge. This correlation may hold fundamental clues to the formation and fueling mechanisms of massive BHs.

The ubiquity of massive BHs lurking in our cosmic backyard offers an unprecedented opportunity to investigate accretion physics in these enigmatic objects. Ho has exploited this opportunity by continuing his efforts toward defining the poorly known broadband spectral properties of the nuclei of nearby galaxies. He has completed several studies in the hard x-ray band with the ASCA satellite, and new surveys are under way with the recently launched Chandra and XMM facilities. Hard x-rays are the best indicator of the accretion luminosity around massive BHs because they are relatively unaffected by absorption and are generated close to the central engine. In related efforts, observations are also being made at radio (VLA); mid-infrared (Keck); and near-infrared, optical, and ultraviolet (HST) wavelengths.

Lastly, Ho and collaborators (including OCIW postdoctoral associate Swara Ravindranath) are interested in characterizing the photometric structure of the central regions of nearby galaxies using high-resolution images obtained with the HST. They have developed novel techniques to analyze and fully exploit these data. The centers of nearby galaxies, especially the spirals, turn out to be extremely complex. The sharp images from HST reveal a bewildering assortment of fine structure, including nuclear spiral arms, dust lanes and disks, and compact star clusters. The luminosity distributions of the inner bulges often show significant departures from conventional forms. These details contain important clues about spiral galaxy formation and evolutionary history.