Saturday, June 09, 2012

Is Spitzer Seeing the First Objects of the Universe?


The two above panels show the same piece of sky in the constellation Bootes. The top panel shows the initial infrared view, foreground stars and unresolved galaxies included. The bottom panel is the same image, but with the stars and galaxies masked out (the gray patches). The remaining background glow has been smoothed and enhanced. The process reveals structure too faint to be seen in the original image. The top infrared image was taken by NASA's Spitzer Space Telescope. Image Credit: NASA/JPL-Caltech

Astronomers using NASA's Spitzer Space Telescope think they may have detected the faint, lumpy glow given off by the very first objects in the universe. The objects might be extremely massive stars or they might even be very hungry black holes. They are too far away to be seen individually, but Spitzer has captured new, convincing evidence of what appears to be the collective pattern of their infrared light.


The Spitzer observations help to confirm that the first objects were numerous and burned furiously. While astronomers cannot directly rule out the possibility that the light is coming from relatively nearby, they note that it seems more and more likely they are getting a glimpse of an ancient epoch.


The full details are in a new paper appearing in The Astrophysical Journal. The lead author is Alexander "Sasha" Kashlinsky of NASA's Goddard Space Flight Center in Greenbelt, Maryland. Other authors are Richard Arendt of Goddard and the University of Maryland in Baltimore County; Matt Ashby and Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; and John Mather and Harvey Moseley of Goddard. Fazio led the initial observations of these sky fields.


Spitzer first got hints of this remote pattern of light — the cosmic infrared background — in 2005. It saw the pattern with more precision in 2007. Now, Spitzer is in the extended phase of its mission, during which it performs more in-depth studies on specific patches of the sky. Kashlinsky and his colleagues used Spitzer to look at two patches of sky for more than 400 hours each.


The team then carefully subtracted all the known stars and galaxies in the images. Rather than being left with a black, empty patch of sky, they found faint patterns of light with several telltale characteristics of the cosmic infrared background. The lumps in the pattern observed are consistent with the way the very distant objects are thought to be clustered together.


Kashlinsky compares the observations being in Los Angeles and looking for Fourth of July fireworks in New York City. The observer would need to remove all the foreground lights between the two cities, as well as the blazing lights of New York City itself. Ultimately, the viewer would be left with a fuzzy map of how the fireworks are distributed, but they would still be too distant to make out individually.


Astronomers currently estimate that the universe formed roughly 13.7 billion years ago in a bright and rapid expansion, often described as the Big Bang. With time, it cooled and, by around 500 million years later, the first stars, galaxies and black holes began to form. Astronomers think that "first light" might have traveled billions of years to be picked up by Spitzer. The light would have originated at visible or even ultraviolet wavelengths and then, because of the expansion of the universe, stretched out to the longer, infrared wavelengths observed by Spitzer.


The new study improves on previous observations by measuring this cosmic infrared background out to scales equivalent to two full moons — significantly larger than what was detected before. Imagine trying to find a pattern in the noise in an old-fashioned television set by looking at just a small piece of the screen. It would be hard to know for certain if a suspected pattern was real. By observing a larger section of the screen, you would be able to resolve both small- and large-scale patterns, further confirming your initial suspicion.


In the same way, astronomers using Spitzer have increased the amount of sky examined to obtain more definitive evidence of the cosmic infrared background. The researchers plan to explore more patches of sky in the future to gather more clues hidden in the light of this ancient era.

There's much more to read in the paper, published online: "Reconstructing the Near-infrared Background Fluctuations from Known Galaxy Populations Using Multiband Measurements of Luminosity Functions." Kari Helgason, Massimo Ricotti, and Alexander Kashlinsky. 2012. The Astrophysical Journal, Volume 752, Number 2: iopscience.iop.org/0004-637X/752/2/113/

And now, the mission particulars...

Launched August 2003 aboard a Delta II rocket, the Spitzer Space Telescope was formerly the Space Infrared Telescope Facility (SIRTF). It is an infrared space observatory, the fourth and final of the NASA Great Observatories program. The observatory was renamed in honor of Lyman Spitzer, one of the 20th century's great scientists. NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer mission for the agency's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. Spitzer's extended operations are expected to run through the U.S. government Fiscal year 2014 and be closed out in Fiscal year 2015. For more information about Spitzer, visit: www.nasa.gov/spitzer and http://www.spitzer.caltech.edu/ .


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