archiv~1.txt: SETI [ASTRO] UC Berkeley Team Challenges Cosmologists

SETI [ASTRO] UC Berkeley Team Challenges Cosmologists

Larry Klaes ( lklaes@bbn.com )
Fri, 19 Mar 1999 09:02:01 -0500

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>Date: Fri, 19 Mar 1999 5:03:58 GMT
>From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>To: astro@lists.mindspring.com
>Subject: [ASTRO] UC Berkeley Team Challenges Cosmologists
>Sender: owner-astro@brickbat12.mindspring.com
>Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>
>University of California-Berkeley
>
>Contact: Robert Sanders, (510) 643-6998
>
>FOR IMMEDIATE RELEASE: March 16, 1999
>
>UC Berkeley team challenges cosmologists to analyze simulation of cosmic
>microwave background -- and win a case of champagne
>
>Berkeley -- Scientists love a challenge, and now a group at the
>University of California, Berkeley, has one for the cosmologists: try to
>find the primordial seeds of the universe amidst simulated noise from
>the cosmos.
>
>The challenge, thrown down March 15, is designed to prepare scientists
>for the flood of data that will be sent back after the launch late next
>year of the Microwave Anisotropy Probe (MAP), a National Aeronautics and
>Space Administration satellite that will measure the microwave radiation
>left over from the big bang.
>
>The satellite will produce a microwave map of the universe much more
>detailed than its predecessor, the Cosmic Background Explorer (COBE)
>satellite, which gave scientists in 1992 their first evidence of clumps
>and wrinkles in the very early universe. These clumps of matter and
>energy presumably evolved into the clusters of galaxies we see today.
>
>The UC Berkeley group, which calls itself WOMBAT, for
>Wavelength-Oriented Microwave Background Analysis Team, has produced a
>detailed simulation of what MAP will see, complete with all the
>confounding contamination and noise of the universe.
>
>The teams that can pull the picture out of the noise will win a case of
>champagne or a toy stuffed animal -- a wombat.
>
>"We want to see if the analysis methods people have produced will really
>work," said Eric Gawiser, a graduate student in physics at UC Berkeley.
>"The idea is to get physicists to think about how they will deal with
>the uncertainties in the data."
>
>In fact, when the conclusion of the COBE team was first announced in
>1992, some scientists and statisticians attacked the data analysis as
>too weak to support their claims. Subsequent and more thorough analysis
>of the data convinced most scientists that the minute fluctuations seen
>in the cosmic microwave background are real.
>
>"We are trying to go through a process now that will create faith in the
>final results," Gawiser said.
>
>Joining Gawiser on the WOMBAT team are Doug Finkbeiner, also a graduate
>student in physics, Andrew Jaffe, a research physicist at UC Berkeley's
>Center for Particle Astrophysics, and a number of other UC Berkeley
>researchers working under the supervision of professors Joseph Silk,
>Marc Davis and George Smoot of the departments of physics and astronomy.
>
>Jaffe is deeply involved in analysis of data from a smaller
>balloon-borne experiment that is measuring the cosmic microwave
>background one small patch of sky at a time. Called the Millimeter
>Anisotropy eXperiment IMaging Array (MAXIMA), this NASA-funded UC
>Berkeley experiment first flew last summer out of Palestine, Texas, and
>will fly again this summer.
>
>WOMBAT's challenge also includes simulations of what MAXIMA will see,
>which is 50 times more detailed than what COBE measured, though in a
>piece of sky only 10 degrees on a side.
>
>The cosmic microwave background is the radiation that escaped from the
>fireball of the big bang about 300,000 years after the birth of the
>universe, when the growing cloud of matter and energy finally became
>transparent enough for light to wiggle out. In the 14 to 15 billion
>years since then, the radiation has cooled from several thousand degrees
>to a frigid 2.7 Kelvin, equivalent to 455 degrees below zero Fahrenheit.
>COBE was set up to look for structure in the apparently even glow of the
>microwave radiation and discovered fluctuations of about one part in
>100,000 -- that is, some areas were about 0.00002 degrees warmer or
>colder than others. Smoot, at the time a researcher at Lawrence Berkeley
>National Laboratory and now also a professor of physics at UC Berkeley,
>was the principal investigator on that experiment.
>
>The MAP satellite will scan the entire sky with 30 times greater
>resolution than COBE, yielding much finer detail about the early
>universe. Physicists and astronomers hope to glean from the structure of
>the microwave fluctuations some important details of the universe: its
>age and shape, how fast it is expanding, when and how the first galaxies
>formed, and whether it will expand forever.
>
>Though the COBE data were tough to analyze, the MAP data will be even
>tougher, according to the WOMBAT team. Microwave emission by distant
>galaxies will confuse the picture much more, as will microwave emission
>from the dust of our own galaxy.
>
>The WOMBAT simulation was constructed by Gawiser, Finkbeiner and Jaffe
>based on their estimates of foreground contamination by dust and
>galaxies and clusters of galaxies that emit microwave radiation in the
>same wavelength range (around 90 gigahertz) as the microwave background.
>
>In fact, Finkbeiner, Gawiser and Jaffe have put together the most
>realistic full-sky maps so far of all the major microwave foreground
>components, with estimated uncertainties. This is essential to any
>analysis of the microwave background.
>
>To create the simulation they also threw in instrument noise and a few
>other complications, including a recently proposed source -- microwave
>emission by spinning grains of dust.
>
>"The point of the challenge is to see if, given a signal screwed up with
>small sources and noise, physicists can reconstruct the signal that made
>it," Jaffe said.
>
>The UC Berkeley team expects perhaps six to eight groups around the
>world to take up the challenge. Among them, they hope, will be the large
>NASA team preparing for the MAP satellite mission and the team working
>on an even more advanced satellite called the Planck Surveyor. Planck is
>being built by the European Space Agency and will be launched in 2007.
>Distinguishing between the cosmic microwave background radiation and
>other foreground sources is possible because of their different
>microwave spectra, Gawiser said. The background radiation peaks at the
>center of the microwave band and is analogous to green in the visible
>light spectrum of the rainbow. Radio emission is low-frequency and
>analogous to red in the spectrum, while thermal dust emission is
>high-frequency, analogous to blue.
>
>All of these components are very noisy, however, and trying to subtract
>three forms of noise to get to the underlying noise of the density
>variations in the early universe should pose quite a challenge, he said,
>even for some of the world's most resourceful astrophysicists.
>
>While several methods for eliminating this foreground emission have been
>proposed by researchers around the world, the WOMBAT challenge provides
>the first chance to test those analysis techniques on realistic full-sky
>simulations.
>
>The WOMBAT group is offering two prizes to those who respond by July 15:
>a case of champagne for the team that most successfully determines the
>density, age and rate of expansion of each simulated universe from its
>cosmic microwave background radiation; and a stuffed toy wombat for the
>team that succeeds in the opposite task -- eliminating the microwave
>background to learn about the microwave emission of our own galaxy and
>other galaxies.
>
>The team is offering five simulations of the MAP sky, as well as five
>simulations of the small patches of sky that MAXIMA would see.
>Each MAP simulation covers the sky with 12 million pixels, each of which
>contains information on intensity and frequency. Though Gawiser and
>Finkbeiner simulated the sky maps on a desktop workstation, the best
>analysis will require a supercomputer, they said.
>
>"In all its glory, the problem is so hard that our largest dataset to
>date -- 400,000 pixels from the Boomerang balloon flight -- is already
>too big for supercomputers to handle," Jaffe said. "In the future, we
>will just have to become more clever."
>
>###
>
>For further information, contact Eric Gawiser or Doug Finkbeiner at
>(510) 642-5902 or gawiser@astron.berkeley.edu and
>dfink@astron.berkeley.edu, respectively; or Andrew Jaffe at (510)
>642-7570 or jaffe@cfpa.berkeley.edu.
>
>Examples of the WOMBAT simulation, both before and after foreground
>sources have been eliminated, can be found on the group's web page at
>http://astro.berkeley.edu/wombat .
>
>
>