Haboobs in outer space: the when and where of dust storms in distant galaxies

Abstract

Dust grains are a minor component by mass of the interstellar medium of a galaxy. Yet they can be the dominant source of luminosity. At z ∼ 1, the luminosity density of the Universe in the IR is ∼ 10 times higher than it is at z ∼ 0; common high-redshift galaxies have IR luminosities and dust masses that surpass those of even rare low-redshift galaxies. Dusty galaxies must transition to dust-poor galaxies. In this thesis, we attempt to understand the When? and Where? of this transition. We examine the redshift distribution of the cosmic millimeter background and the spatial distributions of dust in high-redshift galaxies. The cosmic millimeter background is the flux surface density, across the entire sky, from dust emission from all galaxies in the Universe. We stack the 1.16mm flux densities of a sample of dusty galaxies to determine the evolution of their contribution to the background. We resolve ∼ 35% of the background at 1.16mm and ∼ 50% of the background at 850 μm. We make two unique predictions for the redshift origins of the total 1.16mm background. Dust is responsible for more than the IR emission from a galaxy. The existence of dust is a necessary but not sufficient condition for the attenuation of a galaxy's intrinsic UV emission; the IR- and emergent UV-emitting regions must be spatially coincident. We establish a relation between the ratio of infrared to UV luminosity and β for dusty galaxies at z ∼ 2, which implies that their regions are coincident. We also argue that the dust is spread on galactic scales. In dust-poor galaxies at low redshift, the amount of dust attenuating the emission from ionizing stars is greater than the amount attenuating the emission from massive but nonionizing stars. For dusty galaxies at z ∼ 1.3, the amounts may be unequal--though this result is subject to the assumption that high-redshift dusty galaxies have the same spatial and grain size distributions as low-redshift dust-poor galaxies. The dust properties of high-redshift galaxies may be more diverse than they are in low-redshift galaxies.