"What Can the Occult Do for You? Using Overlapping Galaxies to Probe Dust Properties in Galaxies" is the title of the talk to be presented by Benne Holwerda, associate professor of physics at the Unversity of Louisville.
Interstellar dust is still a dominant uncertainty in astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is reprocessed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy.
Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy.
The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.
A reception for Professor Holwerda begins at 4:10 p.m. in the Anderson Lounge, Wright Lab, second floor.