How normal galaxy in early universe actually looked like

An astronomer from University of Hawaii at Manoa has obtained the first image that shows the structure of a normal galaxy in the early universe.

The galaxy, called DLA 2222-0946, is so faint that it is virtually invisible at all but a few specific wavelengths. It is a member of a class of galaxies thought to be the progenitors of spiral galaxies like our own Milky Way.

These galaxies are known to contain most of the neutral gas that is the fuel for star formation, so they are an important tool for understanding star and galaxy formation and evolution. Discovered and classified over 30 years ago, they have been notoriously difficult to see directly.

Dr. Regina Jorgenson, an NSF Astronomy and Astrophysics Postdoctoral Fellow at the UHM's Institute for Astronomy, worked with Dr. Arthur Wolfe of the University of California, San Diego.

They used the advanced technologies of the W. M. Keck Observatory on Mauna Kea to obtain the first-ever spatially resolved images of a galaxy of this type.

DLA 2222-0946 was initially detected not by its own light, but by absorbing some of the light of an even more distant quasar. Galaxies detected in this way are called damped Lyman-alpha systems, or DLAs, based on the specific color of light they absorb due to their copious reservoirs of hydrogen gas.

While thousands of DLAs are now known thanks to the large Sloan Digitized Sky Survey (SDSS), their detection in absorption tells us only about the small part of the galaxy pierced by the background quasar's light. This is akin to trying to map a fog bank from a single headlight shining through it.

The results were presented at the winter American Astronomical Society meeting held near Washington, DC.