Research
I worked with Dr. Chris Churchill as a member of NMSU's Quasar
Absorption Line Group. For my Ph.D. thesis, I studied the abundance of
deuterium in the anti-center of the Milky Way Galaxy. This was a follow up
study to the work I describe below.
For past several years, I have been a senior scientist at the American
Institute of Physics. I was a leading member of the team that detected
radiation from the deuterium using the 12-meter (40-foot) radio telescope at
the US National Radio Astronomy Observatory site on Kitt Peak, Arizona (shown
above). This study concerned a gas cloud only 30 light years from the center
of the Milky Way (25,000 light years from Earth). We found only one part per
million of deuterium compared with hydrogen, a million times more
deuterium than had been predicted!
These observations confirm theoretical models that most deuterium, the heavy
isotope of hydrogen containing one proton and one neutron, is primordial (made
at the time of the Big Bang) and was not subsequently created in galaxies or
stars. In general, stars are expected to be net consumers (not producers) of
deuterium: they convert it into helium. The galactic center, however, is the
Big Apple of the Milky Way. It is the scene of jets, bursts, x-ray and gamma
sources, a massive black hole, filaments, arcs, and other material-processing
objects.
We deduced the following from our observations. First, the D/H ratio is
higher than one would expect in the absence of a source of virginal
unprocessed material (high in deuterium, low in heavier elements). This
demonstrates that matter comparatively rich in deuterium is raining down with
the cloud onto the plane of our galaxy. Second, the D/H ratio at the galactic
center is lower than in all other places in the galaxy. This is important
evidence confirming that dueterium is not made in stars and that what
deuterium we see is made by the Big Bang. Third, from models of deuterium
production in quasars, the observed D/H ratio suggests that the Milky Way
could not have harbored a quasar for at least a billion years, and probably
not for four billion years.
My work is discussed in the following popular science articles.
Meetings
I presented work at the IAU 231 Colloquium "Astrochemistry" in September 2005,
entitled
Metal-poor Molecular Gas beyond the Optical Disk of the
Galaxy
Publications
Deuterium in the Galactic Centre as a Result of Recent Infall of Low-metallicity Gas
D. A. Lubowich, J. M. Pasachoff, T. J. Balonek, T. J. Millar, C. Tremonti,
H. Roberts, & R. P. Galloway 2000, Nature, 405, 1025
Constraints on Galactic Center Activity: A Search for
Enhanced Galactic Center Lithium and Boron
D. A. Lubowich, B. E. Turner, & L. M. Hobbs 1998, ApJ, 508, 729L
A Search for Localized Sources of Noncosmological Deuterium
near the Galactic Center
D. A. Lubowich, K. R. Anantharamaiah, & J. M. Pasachoff 1989, ApJ, 345, 770L
Future Work
I successfully defended my Ph.D. thesis on The Galactic Deuterium
Distribution, on June 22, 2006. I hold a position as an Associate
Professor of Physics and Astronomy at Hofstra University.
