Professor of Astronomy
Telephone No.: 610-896-1144
Most of my research activities have involved the use of radio astronomy to answer questions about the origin and evolution of large-scale structures in the Universe, structures such as galaxies and clusters of galaxies. A particular interest has been the cosmic microwave background radiation (CBR)--the "heat" left over from the Big Bang origin of the Universe. I was among the first to search for fluctuations in its intensity, fluctuations which provide information about the distribution of matter in the first few hundred thousand years of the history of the Universe. I am still engaged in such measurements, using the VLA for instance. Related work includes preparation for the Planck Surveyor, an ESA mission to map the CBR with unprecedented resolution and sensitivity. My major duties for Planck center on the extragalatic radio sources it will detect and characterize (see Planck Working Group 6).
In the past few years, my interests have shifted to more conventional radio, infrared and optical studies of galaxies, especially those in which star formation is proceeding rapidly. For instance, with colleagues from Arizona State University and the National Radio Astronomy Observatory, I have made the most sensitive radio maps of the sky ever constructed. One of these is the radio-frequency map of the Hubble Deep Field. We used these radio images to investigate the properties of star-forming galaxies very far from us, and hence seen much earlier in the history of the Universe. One such map is displayed here, in the form of radio contours overlaid on an optical Space Telescope photo of the same area. Note the overlap. The energy received from the fainter radio sources shown here is roughly equivalent to the energy that would be received from a flashlight at the distance of Saturn! I'm also interested in very young radio sources, those with spectra that rise with frequency.
For many of these observations I have used the
Very Large Array in New Mexico,
an array of 27 large radio telescopes. I have also used other radio, optical
and infrared telescopes in the U.S., Europe and Argentina.
Earlier research interests included optical pumping of He, pulsars, short time-scale phenomena in astronomy and the early stages of galaxy formation.
For further details see the list of publications in my curriculum vitae and also links I like to use.
I've taught a wide range of undergraduate courses in astronomy, ranging from an introductory survey course to upper-level, specialized courses in radio astronomy, cosmology and stellar structure. Astronomy 101 is an introductory course designed to cover all aspects of astronomy. Astronomy 112 is a course intended for nonscientists that focuses on cosmology; Astronomy 114 is a similar course on planetary science. Over the years, I have also taught several physics courses, both introductory and intermediate in level.
For astronomy majors, or potential majors, I teach Astronomy 206b (Introduction to Astrophysics--galaxies, cosmology and planetary science), Astronomy 320 (Cosmology), and Astronomy 322 (Non-Optical Astronomy).
Service to the Scientific Community
My role in national and international scientific societies (see curriculum vitae) has allowed me to become involved in activities such as strategic planning in physics and astronomy, and reform in American higher education (see listing of related publications in the curriculum vitae). I have recently served as the Education Officer of the American Astronomical Society, an elective post charged with advising the AAS on educational policies and practices at all levels. I also serve on advisory committees to departments and programs at Caltech and the Astronomical Society of the Pacific, and as a referee for a number of physics and astronomy journals.
In the past, I have served as president of one of the eight divisions of the International Astronomical Union, Division VIII, and on the Astronomy and Astrophysics Survey Committee.