What is AEGIS?


The story of galaxies is the first and grandest chapter in human history.

The building blocks of the Universe

Galaxies are the basic building blocks of the Universe. Their tiny points of light illuminate the vast cosmic architecture studded with giant superclusters surrounded by huge voids of nearly empty space. Each galaxy is a "star city" harboring up to a trillion stars. The gravity of a galaxy draws in fresh gas from its surroundings, which spawns new generations of stars. Supernova explosions over billions of years enrich the gas with oxygen, carbon, iron and other heavy elements, which are "cooked" only in massive stars. These heavy elements are the essential building blocks of planets such as Earth.

By these cycles of stellar birth and death, galaxies become fertile, self-sustaining ecosystems that evolve to become more and more suited for planets...and life. In essence, galaxies are the key agents by which the Universe builds complexity. Without them, the expanding cosmic soup would have diffused away into a sterile, featureless, and boring sea of gas.

Click here for an interactive image of the EGS!
HST/ ACS galaxy images
What can we learn from different wavelengths?
field_coverage_imgExtended Groth Strip, as covered by various observations - full moon shown for scale

Galaxy evolution is typified by long periods of calm punctuated by violent events such as the explosive growth of massive central black holes and disruptive collisions with other galaxies. These essential aspects of galactic history can be followed separately using the different telescopes of the multi-wavelength AEGIS database.

For example, images with the Hubble Space Telescope reveal the "morphological state" of a galaxy, whether quiescent and stable or disrupted by collisions with neighboring galaxies. The Chandra X-ray satellite and VLA radio data locate black holes buried in clouds of gas and dust clouds that Hubble cannot see. The GALEX and Spitzer satellites measure the rate of new star formation, including starbursts hidden by dust. Near-infrared images from the Palomar observatory enable AEGIS to measure the total stellar mass of galaxies. Optical spectra from the DEEP2 spectroscopic survey yield redshifts, distances, and look-back times, while CFHT photometry produces approximate redshifts and distances for galaxies too faint to be observed by DEEP2.

Details of the AEGIS survey
AEGIS is an international collaboration which involves nearly 100 scientists from 16 institutions in Europe, North America, and Asia. Using some of the world's most powerful telescopes, these astronomers have observed an area of the sky known as the Extended Groth Strip (EGS) in wavelengths ranging from X-rays through ultraviolet and visible light, down to infrared and radio wavelengths. Each data set covers an area of sky that is similar to or larger than the size of the moon and extends down to very faint objects. The large size of the survey makes it possible to observe statistically meaningful samples of relatively rare objects, such as massive accreting black holes, powerful starbursting galaxies, and merging galaxies. The depth of the survey allows astronomers to view very faint and distant objects, looking back through the last two-thirds of cosmic time at galaxies in their youth. aegis_logo
Ultimately, the goal is to understand how galaxies and large-scale structures form and evolve from early times into the universe we see around us today.