Imaging and nulling with the Space Interferometer Mission

We present numerical simulations for a possible synthesis imaging mode of the Space Interferometer Mission (SIM). We summarize the general techniques SIM offers to perform imaging of high surface brightness sources and discuss their strengths and weaknesses. We describe an interactive software package that is used to provide realistic, photometrically correct estimates of SIM performance for various classes of astronomical objects. In particular, we simulate the cases of gaseous disks around black holes in the nuclei of galaxies and zodiacal dust disks around young stellar objects. Regarding the first, we show that a Keplerian velocity gradient of the line-emitting gaseous disk-and thus the mass of the putative black hole-can be determined with SIM to unprecedented accuracy in about 5 hr of integration time for objects with H alpha surface brightness comparable to the prototype M87. Detections and observations of exozodiacal dust disks depend critically on the disk properties and the nulling capabilities of SIM. Systems with similar disk size and at least 1/10 of the dust content of beta Pic can be detected by SIM at distances between 100 pc and a few kiloparsecs, if a nulling efficiency of 10(-4) is achieved. Possible inner clear regions indicative of the presence of massive planets also can be detected and imaged. On the other hand, exozodiacal disks with properties more similar to the solar system will not be found in reasonable integration times with SIM.