Joel R. Primack & Brandon
Allgood talk with ScienceWatch.com and answer a
few questions about this month's Emerging Research Front
Paper in the field of Space Science.
Article: The shape of dark matter haloes:
dependence on mass, redshift, radius and
JR;Kravtsov, AV;Wechsler, RH;Faltenbacher,
Journal: MON NOTIC ROY ASTRON SOC, 367 (4): 1781-1796, APR
Addresses: Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA
Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064
Univ Missouri, Dept Phys & Astron, St Louis, MO 63121
(addresses have been truncated.)
Why do you think your paper is highly
Joel R. Primack: The article, led by my former grad student Brandon
Allgood, gets a lot of citations because it addresses a fundamental issue
in cosmology, i.e., the shape of dark matter halos of galaxies and galaxy
Brandon Allgood: As Joel points out, the paper addressed
both a fundamental question in cosmology and brought together and
reexamined the major previous works on the subject. Our attempt was to
create a foundation which all further works on the subject could use as a
base. It not only answered theoretical questions, but also put forth
predictions which we knew would be useful for upcoming surveys and, when
combined with these observations, would help to constrain the cosmological
Would you summarize the significance of your paper in
"My group has just finished a
new simulation on a new, much more powerful
supercomputer—the Pleiades machine at
NASA's Ames Research Center—that has
even higher resolution in a volume 1,000
times greater!" ~Joel R.
Joel R. Primack: The article also reconciled the apparent disagreements
between different papers in the literature by explaining that they had used
different methods of calculating the halo shapes. The article calculated
halo shapes by essentially every method that had previously been used. It
thus was a synthesis, as well as a major new contribution.
Brandon Allgood: Dark matter halos, as far as we can tell,
surround all observable galaxies. Based on the "double dark" cosmological
model (dark matter and dark energy), these halos and the galaxies within
them have formed via halo-halo merging.
How did you become involved in this research, and were
there any particular problems encountered along the way?
Joel R. Primack: In order to do this research, it was necessary to perform
supercomputer simulations that broke new ground. These were done at NASA's
Ames Research Center in Mountain View, California, on the Columbia
supercomputer, which was one of the fastest supercomputers in the world
three years ago.
Brandon Allgood: Joel's group had, and continues to have,
a large impact on cosmology. I personally saw that and was drawn to working
with him on fundamental problems in cosmology. As Joel points out, the
simulations used in the publication were pushing the envelope at the time.
Data handling and simulation design and execution were by far the hardest
Where do you see your research leading in the
Joel R. Primack: My group has just finished a new simulation on a new, much
more powerful supercomputer—the Pleiades machine at NASA's Ames
Research Center—that has even higher resolution in a volume 1,000
times greater! Pleiades is now the fastest unclassified supercomputer in
the world. This "Bolshoi" simulation, led by Professor Anatoly Klypin of
New Mexico State University, is the most ambitious cosmological simulation
yet, and it will be the basis for a great deal of new research.
Brandon Allgood: I have left academia for an
entrepreneurial career. I am currently focusing on pharmaceuticals at a
company I helped found, Numerate, Inc.
Do you foresee any social or political implications for
Joel R. Primack: I don't expect any social or political implications of
this fundamental astronomy research, except perhaps for public inspiration.
Professor Joel R. Primack
University of California
Santa Cruz, CA, USA Web
Brandon Allgood, Ph.D.
Senior Research Scientist
San Bruno, CA, USA Web