For the CMBR

Michele Kaufman is a scientist in the Ohio State University departments of Physics and Astronomy. Her current research uses the Very Large Array of radio telescopes, the Hubble Space Telescope, and the Spitzer Space Telescope.

When I was an undergraduate, I heard Dr Tommy Gold say in a public lecture that the density and temperature of intergalactic gas were uncertain by factors of 1012. Later, as a graduate student at Harvard in 1964, I started research under David Layzer's supervision by calculating the expected radio-to-microwave background radiation produced by a combination of emission from discrete extragalactic radio sources and intergalactic free-free emission. The goal was to try to place limits on the amount of intergalactic ionized hydrogen. I included the effect of self-absorption. An earlier paper on the intergalactic free-free spectrum by Field and Henry (1964) had omitted self-absorption.

Before the Penzias and Wilson (1965a) result was widely announced, Arno Penzias visited Princeton, MIT, and Harvard, and at Harvard, he was directed to talk with me. Thus I learned that Penzias and Wilson had measured the background radiation at 4.08 GHz. This provided my model with an important constraint on the values of the intergalactic electron temperature and density, and in the summer of 1965 I published a paper in Nature on this with the conclusion that intergalactic free-free emission could account for the background measured by Penzias and Wilson (Kaufman 1965). This paper attracted some attention as the then only published alternative to fossil thermal radiation from a hot big bang. After the microwave background was measured at other frequencies, it was clear that intergalactic free-free emission was not the correct explanation for the CMBR. Reviews of the CMBR continued to reference my 1965 paper as a suggestion that did not pan out.

I later switched research areas from cosmology to galaxies, especially individual spiral galaxies. My research in the past 25 years has included detailed studies of spiral tracers in the grand-design spiral M81 and detailed multi-wavelength studies of galaxy pairs involved in grazing, prograde encounters (with Debra and Bruce Elmegreen). Our HST image of NGC 2207/IC 2163, part of the latter study, has appeared everywhere in the national news media, including the front page of The New York Times as well as scholarly journals (Elmegreen et al. 2006).

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