Comparing Hubble Space Telescope and millimeter interferometer images of young stellar object disks

With angular sizes of just a few arcseconds, circumstellar disks in nearby star formation regions require subarcsecond imaging to study in detail. The best-resolved disk images currently available are those made in optical and near-infrared reflected light using the Hubble Space Telescope. Millimeterwave imaging provides crucial comparative information on these disks, but at somewhat lower spatial resolution. We illustrate this through a comparison of OVRO Millimeter Array maps and HST images for two edge-on young disks, IRAS 04302+2247 and HH 30. Dense, rotating molecular gas structures are found along their visible dust lanes. Somewhat unexpectedly, the scattered light and millimeterwave data lead us to derive similar values for the size and mass of these disks. By providing millimeter maps with resolutions equal to or exceeding that of HST, ALMA will increase nearly one hundredfold the number of young disks that can be imaged at 10 AU resolution, thereby enabling huge gains in our understanding of how planetary systems form and evolve.