The astronomers who this spring announced that they had evidence of primordial gravitational waves jumped the gun because they did not take into proper account a confounding effect of galactic dust, two new analyses suggest.
A physicist at the California Institute of Technology in Pasadena and a co-leader of the BICEP2 experiment, says that although his group’s main paper “Has been revised based on many referee comments and resubmitted” for publication, the evidence for gravitational waves “Is certainly not being retracted”.
The critique comes on the heels of a presentation two weeks ago by Raphael Flauger, a theoretical physicist at New York University, who re-examined a map of dust polarization that the BICEP2 team had used in their analysis.
The difference between 3.5% and 8% may seem small, notes Spergel, but it becomes significant because the signal detected by BICEP2 depends on the square of the polarization fraction, he says.
“Dust could account for all or most of the signal” seen by BICEP2, says Paul Steinhardt, a cosmologist at Princeton University, who was not involved with any of the studies.
In assuming that the intensity of dust varies in the same way over all parts of the sky, including the South Pole, the researchers found no clear evidence that the BICEP2 signal should be attributed to gravitational waves.
The BICEP2 team argued that the intensity of the signal recorded at 150 gigahertz, when compared with data recorded by an older telescope, BICEP1, at 100 gigahertz, did not match the intensity pattern expected from dust.