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Herschel reveals details of distant galaxies and quasars

Astronomers gain new insights into the different types of galaxies in the distant universe, which will allow them to explore part of the universe as it was some 11 billion years ago.
Provided by UK Space Agency, Swindon, England
Abell 2218
This image shows the region of sky around the massive galaxy cluster Abell 2218, as seen by Herschel and Hubble. On the left, the images at the three SPIRE wavelength bands are shown, while the center image is a false-color composite. The center of the galaxy cluster is shown as a white cross-hair, while the large yellow blob just below it is a more distant galaxy. The light from this distant galaxy is being bent and magnified by the immense mass of the Abell 2218 cluster, allowing astronomers to see it in more detail than would otherwise be possible without this chance alignment. It is seen as it was around 2.6 billion years after the Big Bang. The other structures in the image are largely due to closer, fainter galaxies which are observed by optical observatories such as the Hubble Space Telescope, as shown on the right.
ESA/SPIRE and HerMES Consortia (left); ESA/NASA/STScI (right)
July 2, 2010
Amazing new data captured by the European Space Agency's (ESA) Herschel Space Observatory has just been publicly released, allowing the world's astronomers to share in the Herschel Spectral and Photometric Imaging Receiver (SPIRE) instrument's observations of distant galaxies. From its vantage point nearly 1 million miles (1.5 million kilometers) from Earth, the Herschel spacecraft has given astronomers new insights into the different types of galaxies in the distant universe, which will allow them to explore part of the universe as it was some 11 billion years ago — just 3 billion years after the Big Bang.

"We're very proud to be supporting this groundbreaking mission," said David Parker, director of space science and exploration for the United Kingdom Space Agency. "Herschel is a key part of the United Kingdoms Space Agency's program to explore the ancient universe and understand how galaxies, stars, and planets form. Herschel can see back in time because the light left the stars making up the distant galaxies billions of years before our planet was formed and has been traveling through space ever since, only now to be captured by the spacecraft's sensitive eyes."

The new data is part of the Herschel Multi-tiered Extragalactic Survey (HerMES), led by Seb Oliver at the University of Sussex, United Kingdom, and Jamie Bock at the NASA Jet Propulsion Laboratory and California Institute of Technology.

The HerMES project is providing a view of the distant universe at wavelengths that can only be observed from space. Because the SPIRE camera onboard Herschel "sees" images in three submillimeter wavelength bands, or colors, it shows a different aspect of galaxies, and the camera is able to view cool objects previously invisible to astronomers. The appearance of an object in these three colors provides information on its temperature, distance, and luminosity.

Some of the data being released focus on a massive cluster of galaxies called Abell 2218. At a distance of over 2 billion light- years from Earth, the huge mass of the cluster warps the surrounding space, bending and magnifying light from background galaxies in a manner similar to light being magnified by a normal glass lens.

Abell 2218 is famous for being one of the best-known examples of this "gravitational lensing." The effect means that the background galaxies are magnified, allowing a much clearer view of objects as they were over 11 billion years ago, less than 3 billion years after the Big Bang. Without the gravitational lensing, these galaxies would be fainter and confused by the presence of the foreground galaxies, but this chance alignment provides the opportunity to explore a tiny part of the early universe in more detail. The Herschel observations of these distant galaxies tell astronomers how fast they were forming stars at these early times and help build a picture of how galaxies have evolved over the course of billions of years.

This image shows the Abell 2218 cluster as seen by the SPIRE instrument on Herschel in relation to an iconic image from the Hubble Space Telescope. The three wavelength bands are first shown as individual red, green, and blue images and then combined into a color image. The center of the cluster is marked as a white cross-hair, and the bright yellow object just below is the lensed galaxy. Most of the other galaxies shown are bluer and are in the foreground cluster.

The properties of the cluster are also of great interest to other astronomers, such as those using the Hubble Space Telescope. Observing at many wavelengths not only helps work out the precise effect of the lensing, but also shows the nature and behavior of galaxies within large clusters.

Using these new data, scientists can employ other telescopes to search for galaxies at a range of distances, shedding light on the way they have formed and evolved from soon after the Big Bang right up to the present day.

"Images like this show that SPIRE has opened up the possibility of observing at submillimeter wavelengths in a way that was just not possible before; this kind of clarity is unprecedented at these wavelengths," said Michael Zemcov of the California Institute of Technology. "Now that these data are available to the entire astronomical community, we will really be able to test our understanding of objects like galaxy clusters and, more profoundly, the formation of structure in the universe."

Evanthia Hatziminaoglou, at the European Southern Observatory, has been using the HerMES data to study the connection between galaxies and the supermassive black holes that lie at their center. These supermassive black holes grow by accreting gas, with some radiating vast quantities of power as quasars or "active galactic nuclei" (AGN). Looking at these objects with Herschel, Hatziminaoglou discovered that their submillimeter emission comes almost entirely from star formation and their properties, in these wavelengths, are indistinguishable from those of non-active galaxies. The results of her research confirm independently that supermassive black holes grow in size along with the galaxies in which they reside. "It is surprising to see that these two highly energetic astrophysical phenomena coexist in such harmony," said Hatziminaoglou.

The HerMES team hopes that by releasing catalogs of their galaxies to the astronomical community, telescopes around the world will be trained on these kinds of exotic, distant galaxies to help our understanding of how galaxies and AGN have evolved over the lifetime of the universe. Ian Smail, an astronomer at Durham University in the United Kingdom, is not a member of the HerMES team, but uses surveys of galaxies at different wavelengths to study their formation and evolution. Discussing the release of the HerMES catalogs, Smail said, "These first submillimeter views of young galaxies in the distant universe clearly show that huge numbers of new stars are being formed, but cloaked by dust, and so missed by optical observatories such as the Hubble Space Telescope. It is already clear that we live in a changing universe and, thanks to Herschel and SPIRE, few things are changing faster than our perception of it."

"We have made these images and lists of galaxies available to all astronomers sooner than we were obliged to because Herschel is a fantastic mission but has a limited lifetime, and it is vital that it is used for the best science," said Seb Oliver from Sussex University. "We hope that other astronomers will want to use Herschel and many other telescopes to study the galaxies we have discovered."
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