University of
Notre Dame
College of
Science
Department of
Physics

 

Astrophysics Seminar

 

On the Importance of Outflows and Infall in Spiral Galaxies: Interstellar Dust as a Probe of Galaxy Assembly

 

Prof. J. Christopher Howk
Department of Physics
University of Notre Dame

 

Tuesday, September 16, 2008 - 12:30 p.m.   NSH 184

 

Dust is a minor constituent of the interstellar medium by mass, but has disproportionate effects on the thermal balance of the ISM, on the distribution of relative abundances of metals, and on the propagation of UV photons. A decade and more of observations have demonstrated that dust is an important tracer of extraplanar material in spiral galaxies. Most theories for the origin of the extraplanar dust argue for its expulsion from the disk, requiring the dust to be relatively robust to destruction during this process. However, all modern models of galaxy evolution require on-going infall of pristine gas to explain the metallicity distribution of stars in the Milky Way and, more fundamentally, the fact that galaxies have formed stars over many Gigayears even though their gas consumption times should be much shorter. I will discuss how multiwavelength observations of extraplanar dust may weigh on the mixture of "outflow versus infall" sources for thick disk and halo in nearby galaxies. I will discuss observational probes of extraplanar dust and will comment on the physical conditions of the material implied by the observations. I will discuss the origins of such dust and the implications for the origins of thick disk and halo gas.

 

 

 

 

All interested persons are cordially invited to attend.