First detailed look at a normal galaxy in the very early universe

Jan 09, 2014
First detailed look at a normal galaxy in the very early universe
Top: A map of the hydrogen emission from DLA2222-0946. The mapped region, which covers only a portion of the galaxy, is about 5,000 parsecs (or 16,300 light-years) across. The position of the background quasar is marked by a "Q". Bottom: The corresponding map of the movement of the gas in the galaxy. Red means moving away from us; blue is moving towards us. Credit: R. Jorgenson

(Phys.org) —University of Hawaii at Manoa astronomer Regina Jorgenson has obtained the first image that shows the structure of a normal galaxy in the early universe. The results were presented at the winter American Astronomical Society meeting being held this week near Washington, DC.

The galaxy, called DLA2222-0946, is so faint that it is virtually invisible at all but a few specific wavelengths. It is a member of a class of 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. 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.

DLA2222-0946 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.

A full understanding of the requires a direct detection, which had eluded astronomers until now.

"These galaxies are extraordinary for being ordinary—they represent normal types of galaxies, rather than the brightest, extreme, and most rapidly star-forming galaxies that are typically observed at these redshifts," Dr. Jorgenson explained. "But this normalcy makes them nearly impossible to detect directly from the light they give off because first, that emission is relatively weak, and second, the bright background quasar used to find the galaxy hampers the detection of fainter foreground emission from the galaxy itself."

The galaxy is located at a redshift of 2.354, which corresponds to a time when the universe was about 20 percent of its current age, about 10.8 billion years ago. This time in the universe's history was a key period of galaxy formation, and hence observing typical galaxies from this time will potentially provide great insight into the relevant physical processes.

Determining exactly how galaxies such as these, which are essentially massive reservoirs of neutral gas, turn that gas into stars is a key missing piece of the star and puzzle.

A preprint of the paper, which will be published in the Astrophysical Journal, can be found at the arXiv website at arxiv.org/abs/1311.0045.

Explore further: Hubble unveils a deep sea of small and faint early galaxies

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GuruShabu
1 / 5 (2) Jan 09, 2014
All galaxies are "normal".
Hopefully, JWST (James Webb Space Telescope) will show once and for all that there is no beginning of time or space. There was no Big Bang and all galaxies as far as we are able to detect will not show any sign of the ageing so desired by the standard cosmology.
Fred Hoyle cosmology was defeated for a while but not for ever.
GuruShabu
1 / 5 (2) Jan 10, 2014
I have to re-phrase a little bit.
For sure galaxies "age" (the proportion of young giant blue stars and old small red stars varies and the amount of "metal" content over hydrogen does as well).
However, what I was trying to say and I did not say properly is that we will not find any different number of "young" galaxies on the theoretical "13.7 billion years edge" of the universe. Because the universe did not begin at any particular time. It is eternal in time and infinite in space.
Hopefully, the JWST will show clearer than HST shows today (in spite of all tentatives to show the opposite) that the universe is NOT homogeneous and the galaxies at that distance have the same characteristics (age, shapes and sizes) as they have in anywhere else.
Fleetfoot
5 / 5 (1) Jan 13, 2014
It's nice to have hope but the Hubble Law and the existence of the CMBR alone rule out Hoyle's cosmology. There are dozens of other measures too, for example the prevalence of quasars.