Early Release Science from Hubble WFC3 at AAS Conference

The image above is a newly released image from the Hubble Space Telescope. The image shows a mosaic of a portion of the Great Observatories Origins Deep Survey (GOODS) South Field nearly 1/3 the size of the full moon taken in September and October of 2009. It combines data taken in 10 filters that span the infrared to near ultraviolet. It made use of the newly installed Wide Field Camera 3 (WCF3) and the Advanced Camera for Surveys (ACS). The survey used 100 Hubble orbits for images from the ACS and 104 for the WCF3 images. Galaxies in the image are as faint as 26.5th to 27th magnitude which is several thousand times fainter than can be viewed with the naked eye and shows 7,500 galaxies.

Some of the first science results from this image were discussed this morning at the AAS conference in Washington.

The nearest galaxy in this image is an estimated 1 billion light years distant. The furthest are nothing more than faint red specks that are 13 billion light years away meaning their light left them just a half billion years after the Big Bang. This dynamic range adds to the large volume of images of galaxies over the history of the universe that allows them to understand how galaxies have formed and evolved.

It reveals that galaxy life in the early universe was especially chaotic. There is an increased number of galaxy mergers. Furthermore, many galaxies are so active with star formation they were blowing themselves apart into unusual shapes (similar to M 82). Although this has been seen in other surveys, this new image confirms the irregularity of shape in all wavelengths. Many of the most distant galaxies appear to be ellipticals although some show traces of faint spiral arms.

The image also shows that galaxies continue to build in mass from this chaotic past but the rate of growth slows around eight to ten billion years ago.

One surprise was that a type of galaxies that were uncharacteristically red (indicative of old stars and a lack of star formation) was discovered to have more star formation that previously expected. Astronomers had called these galaxies “red and dead” but ultraviolet detectors found traces of ongoing star formation in the cores and in weak spiral arms in these galaxies leading them to suspect the galaxies aren’t as dead as previously thought.

The full spectrum coverage also allows for estimates of redshift (an indicator of distance) for galaxies too faint to have their redshift taken spectroscopically. By combining observations in numerous filters Hubble can now give redshift measurements with as little as a 4% error.

Although the results posted at the A A S meeting are very preliminary there are many teams working on this newest data release. In the 2-3 months since the images were taken, 4 papers have been submitted for publication.

See a zoomable version of the image here.