[meteorite-list] New Arecibo Receiver Triggers Quiet Revolution

[Ron Baalke]

http://www.news.cornell.edu/stories/March06/Arecibo.ALFA.lg.html

New Arecibo receiver triggers quiet revolution that could discover 
20,000 galaxies and 1,000 pulsars

By Lauren Gold (lg34 at cornell.edu)
Cornell University News Service
March 8, 2006

When the Arecibo L-Band Feed Array (ALFA) was installed on a misty 
April morning two years ago, it promised to bring phenomenal new 
sensitivity to the Arecibo Observatory.

Now, well into an ambitious series of comprehensive sky surveys using 
the receiver, astronomers say ALFA is delivering spectacularly: both 
by fulfilling the potential of the observatory's 1990s Gregorian 
upgrade and ultimately by changing business as usual for researchers 
worldwide.

The ALFA system of detectors and associated electronics, jointly 
built by National Astronomy and Ionosphere Center (NAIC) and 
Australian engineers, is slightly bigger than a washing machine and 
has seven feeds -- making it essentially a giant seven-pixel radio 
camera that allows researchers to image large swaths of sky and 
search for such time-variable phenomena as pulsars seven times more 
efficiently than in the past.

In just two years, ALFA has provided a wealth of new data, from 
comets passing near the Earth and giant clouds of gas in our own 
galaxy, to some of the most distant objects ever detected. It's a 
quiet revolution -- but Jim Cordes, Cornell professor of astronomy 
and one of the principal scientists behind ALFA's conception, says 
the improvements are unparalleled.

"You could very well say it's a new phase for Arecibo," Cordes said. 
"We're doing things that are pretty unique to what Arecibo can do -- 
playing on its strengths."

Cordes uses ALFA to find and observe pulsars, massive rapidly 
spinning neutron stars that are ejected in stellar explosions, or 
supernovae. The pulsar search could lead to a deeper understanding of 
Einstein's theory of relativity.

"ALFA is going to discover probably 1,000 new pulsars that we haven't 
seen yet," said former ALFA project manager Stephen Torchinsky. "The 
expectation is that we're going to find some exotic objects. We could 
use these systems to test the limits of the theory of relativity -- 
and at the most extreme cases, to find gravitational waves."

ALFA science is divided into three overarching surveys: the pulsar 
survey, a survey for sources of neutral hydrogen in the Milky Way and 
an extragalactic survey. In terms of sheer quantity of data, it is 
providing an abundance, spurring scientists to come up with new ways 
of sorting through and managing the constant torrent of information.

"It's like you have seven fire hoses of data coming at you," Cordes 
said. "It's really a challenge to deal with."

That challenge is being met in part by scientists at the Cornell 
Theory Center, who are creating a computer system to manage vast 
amounts of data from such surveys as the Arecibo Legacy Fast ALFA 
survey (ALFALFA), a broad extragalactic search for faint cosmic radio 
signals from hydrogen clouds.

ALFALFA is expected to detect some 20,000 galaxies from as far away 
as 750 million light years over the next six years. Astronomers hope 
the survey will lead to the discovery of dark galaxies: 
never-before-observed galaxies composed largely of dark matter and 
hydrogen gas that could offer valuable information about the way 
galaxies form and evolve.

"Without ALFA, a project like this could not have been done," said 
Riccardo Giovanelli, Cornell professor of astronomy and ALFALFA 
project leader. "It would have been too demanding on a few people."

But part of ALFA's value, say its users, is in the collaborative 
style of research it invites. In the receiver's two years of 
operation, the number of annual users at Arecibo has jumped by nearly 
50 percent -- to 335 users in 2005 from 215 users in 2003. (Other 
factors have been involved, but ALFA is credited with the majority of 
the increase.) "We're bringing new users to Arecibo," said Martha 
Haynes, Goldwin Smith Professor of Astronomy at Cornell and a member 
of the ALFALFA team. Many are undergraduates -- evidence that the 
receiver is energizing the next generation of astronomers.

Torchinsky, however, worries that ALFA's success could overpower 
other research. "It's changed the culture a lot," he said, "but I 
don't think it's entirely for the best. ALFA has begun to dominate 
astronomy work being done at Arecibo ... making it more difficult for 
individual proposals in general. Some good ideas have not been 
developed because of this."

But others say the increase in users -- especially young ones -- 
makes it clear that the change is a good one. And they add that the 
receiver's science will benefit researchers well beyond those 
currently involved.

"The goal of the major surveys is to produce archival databases that 
are accessible to all researchers and will be valuable resources for 
many decades to come," said Robert Brown, director of the 
Cornell-based NAIC, which manages the Arecibo Observatory for the 
National Science Foundation.

It's part of a welcome trend, said Haynes.

"ALFA and the big surveys have changed the way science is being done 
at Arecibo," she said. "It's exciting. It's challenging. This is the 
modern way of doing astronomy."

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