Students interested in astronomy as a career - you can read about How I became an Astronomer.

Education/Employment:

• BS - Caltech 1969
• PhD - UC Berkeley 1974
• Postdoctoral Fellow - UCSD 1974-77
• UCSD Faculty - 1977-Present.
• Also Visiting Research Scientist,Infrared Processing and Analysis Center, Caltech (IPAC), Caltech/JPL. ,

Recent Work:

Recently we have been studying the connection between AGN and Starburst Galaxies by observations of Luminous Infrared Galaxies at Optical, Infrared and Radio wavelengths. We have used VLBI techniques to show that high brightness temperature, radio cores are common in Luminous infrared Galaxies and that there is a common relation between Radio Power and Bolometric Luminosity for Luminous Infrared Galaxies and Quasars. A plausible case may also be made that these galaxies are Starbursts with activity on immense scales. We are attempting to determine which objects may be bona-fide AGN and which are Starbursts and whether there may be an evolutionary connection between the two. This is a family project with Dr. Carol J. Lonsdale, IPAC, Caltech, and Dr. Colin J. Lonsdale, Haystack Observatory, MIT (who also happen to be my wife & brother-in-law) and Dr. Philip J. Diamond of the NRAO.

The Intense Starburst in Arp 220

The image above is a false color r-band image of the Luminous Infrared Galaxy - Arp 220 (Courtesy D. Sanders & D.C. Kim, MaunaKea). This galaxy has a quasar-like luminosity coming from a dust-enshrouded central core which represents the strongly interacting nuclei of a pair of merging galaxies. We have demonstrated that Arp 220 has a compact radio emission and OH maser emission from a surrounding molecular cloud which must be smaller than a few pc in size. The compact radio emission comes from luminous radio supernovae (See our VLBI Radio Map of the NW nucleus) indicating that Arp 220 is forming stars at a rate of about 100 solar masses per year.

New work involves mid-infrared imaging and spectroscopy of Luminous Infrared Galaxies with UCSD's Long Wavelength Imaging Spectrometer (LWS) on the Keck Telescope as well as further VLBI studies of Luminous Infrared Galaxies in the continuum and OH maser emission. Click on the image above to view a larger scale image, or you can view a composite HST image (nearly 1Mbyte).

The Birth of A Quasar in Markarian 231

New radio images of the Luminous IR Galaxy Mrk 231 show a compact quasar-like radio core surrounded by a disk of molecular gas. The molecular disk, shown in our OH maser image, is a ring of intense star formation. Our high-resolution radio image shows the quasar core plus a bright radio lobe where a jet of rapidly streaming particles is plowing into clouds of molecular gas. The jet itself is invisible in this image, but you can observe what's happening here in an MPEG animation produced by IPAC's Robert Hurt. The timescale for "ram pressure" to move outward from the central core suggests that the quasar is quite young, less than a million years old. Although a quasar has "turned-on: in Mrk 231, about 2/3 of its energy still comes from star-formation. We believe that Mrk 231 is an example of a system in which the merger of two gas-rich spiral galaxies, shown in this simulation from the IMAX Movie Cosmic Voyage , stimulates an intense Starburst, which in turn feeds the coalescing black hole in the galaxy's center. As this black hole accretes material, the gravitational energy which is released powers a newly-formed quasar which will eventually blow the dust and gas away from the nucleus, revealing itself at wavelengths from gamma-rays to radio..

• The evolution of both actively star-forming and passively-evolving galaxies to determine the history of galaxy formation (including the global Star Formation History - SFH), in the context of cosmic structure formation and galaxy environment.
• The spatial distribution and clustering of evolved galaxies, starbursts, and AGN, and the evolution of their clustering in the key redshift range from 0.5 < z < 3 over which much of cosmic evolution has occurred.
• The evolutionary relationship between galaxies and AGN, and the contribution of AGN accretion energy to the cosmic backgrounds, relative to that from nucleosynthesis.

The satellite data will be complemented by an extensive program of ground-based optical, near-infrared and radio observations, providing identifications, photometric-redshifts, spectral energy distributions and other physical information. All of the survey data will be available to the Astronomical Community through the NASA/IPAC Infrared Science Archive.

Physics/Astronomy Education:

Last Updated March, 2001

You may also contact me at
CASS 0424, UCSD
9500 Gilman Drive
La Jolla, CA     92093-0424
(858) 534-4558

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