Another astronomer with experience making background observations, Judd Bowman of the California Institute of Technology, concurs: "The authors have made a careful analysis, but at this early stage there may still be room for unanticipated effects to conspire."
Even if the signal is real, astrophysicist Doug Finkbeiner of Harvard University warns that it may not be a truly cosmic signal—that is, one that originates in the distant universe as opposed to our own Milky Way Galaxy. He says the team subtracted the galaxy's contribution to the signal using a highly idealized model. A slight infidelity in this model might mimic an extragalactic signal. Both galactic and extragalactic processes produce light in the same way—namely, by electrons spiraling around magnetic field lines—so the galactic subtraction is especially error-prone. "You're subtracting two things that are almost exactly the same across frequencies," Finkbeiner says.
If the signal is real, where might it come from? Kogut's team speculates it may be a curtain of light emitted by the earliest stars to form in the universe—so-called Population III stars. That would explain why the radio background does not match up with the infrared background, as it would if the radio sources were, like most celestial bodies, surrounded by dust. Dust is produced in stars and litters space only upon their demise, so the first stars lived in dust-free environs. But the team acknowledges that evidence is thin for this hypothesis. Astronomers have yet to do the calculations to verify whether these stars could indeed account for the emission.
"There's a lot of invoking of Population III sources for various observations that people make," says astronomer Michael Hauser of the Space Telescope Science Institute. "I think that's jumping to conclusions."
Another culprit might be active galactic nuclei (AGN), which are blazingly strong light sources powered by black holes. Kogut and his colleagues argue that there are not enough AGN to produce the signal they see. Others, though, are not ready to rule out this possibility.
"They're extrapolating from the known AGN sources, and there could be more," Spergel says. The infrared, visible and x-ray backgrounds turned out to come mostly from hidden populations of AGN.
Finkbeiner speculates the source may be electrons given off by dark matter in our galaxy or extraneous emission that accompanied the release of the microwave background in the primordial universe. Whatever the answer, astronomers are clearly relishing a brand new phenomenon to explore.
"This is a fascinating observation that will take some time to decipher properly," says Michael Vogeley of Drexel University in Philadelphia. Stay tuned, even if you have digital TV.
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Add Commentubiquitous bright blue 1-12 pixel sources on darker 3D fractal web in five 2007.09.06 IR and visible light HUDF images, Nor Pirzkal, Sangeeta Malhotra, James E Rhoads, Chun Xu, -- might be clusters of earliest hypernovae in recent cosmological simulations: Rich Murray 2008.08.17
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The 5 closeups are about 2.2x2.2 arc-seconds wide and high, about 70x70 pixels.
The HUDF is 315x315 arc-seconds, with N at top and E at left.
Each side has 10,500x10,500 pixels at 0.03 arc-second per pixel.
Click on All Sizes and select Original to view the highest resolution image of 3022x2496 pixels, which can be also be conveniently seen directly at their Zoomable image:
www.spacetelescope.org/images/html/zoomable/heic0714a.html
Notable in the deep background of the five closeups are ubiquitous bright blue sources, presumably extremely hot ultraviolet before redshifting, 1 to a dozen or so pixels, as single or short lines of spots, and a few irregular tiny blobs, probably, as predicted in many recent simulations, the earliest massive, short-lived hypernovae, GRBs with jets at various angles to our line of sight, expanding bubbles, earliest molecular and dust clouds with light echoes and bursts of star formation, and first small dwarf galaxies, always associated with a subtle darker 3D random fractal mesh of filaments of H and He atomic gases.
As a scientific layman, I am grateful for specific cogent, civil feedback, based on the details readily visible in images in the public domain.
www.spacetelescope.org/images/html/heic0714a.html
Hubble and Spitzer Uncover Smallest Galaxy Building Blocks
notable bright blue tiny sources on darker 3D fractal web in HUDF VLT ESO 28 images from 506 galaxies, z about 6 , RJ Bouwens, GD Illingworth,
JP Blakeslee, M Franx 2008.02.04 draft 36 page: Rich Murray 2008.08.17
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bright blue 1-4 pixel sources on darker 3D fractal web in IR and visible light
HUDF images -- might be the clusters of earliest hypernovae in the Naoki Yoshida and Lars Hernquist simulation: Rich Murray 2008.07.31
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Thursday, July 31, 2008
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Rich Murray, MA Room For All rmforall@comcast.net 505-501-229