July 18, 2012
Ancient Spiral Galaxy Observed By Astronomers
Lee Rannals for redOrbit.com - Your Universe Online
A new discovery may help astronomers peer back in time to when spiral galaxies first began to take their shape.Scientists wrote in the journal Nature that they had found a surprising ancient spiral galaxy known as BX442.
The galaxy was found by astronomers who first surveyed 300 distant galaxies using the Hubble Space Telescope. They followed up and confirmed it using detailed observations and analyzes from the W.M. Keck Observatory in Hawaii.
“As you go back in time to the early universe -- about three billion years after the Big Bang; the light from this galaxy has been traveling to us for about 10.7 billion years -- galaxies look really strange, clumpy and irregular, not symmetric” astronomer Alice Shapley of UCLA said in a prepared statement. “The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?”
Using Keck's OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) instrument, astronomers were able to study different parts of BX442 and determine that it is rotating and is not just two unrelated disk galaxies.
“We first thought this could just be an illusion and that perhaps we were being led astray by the picture,” Shapley, a coauthor on the Nature paper, said. “What we found when we took spectra of this galaxy is that the spiral arms do belong to this galaxy; it wasn´t an illusion. Not only does it look like a rotating spiral disk galaxy; it really is. We were blown away.”
The Keck II Telescope was able to get equal or better resolution than the Hubble Space Telescope by using laser adaptive optics, which the lead author, astronomer David Law, said was critical for the study.
“Galaxies at this distance appear super, super faint and super, super tiny,” Law said. “We needed every inch of Keck´s light collecting area, exquisite image quality from the AO system, and a sensitive instrument to not only detect the galaxy but chop up its light into 3,600 pieces to analyze. OSIRIS is really one of the only instruments in the world that could do what we needed, and everything came together beautifully.”
It took the astronomers 13 hours over three nights with the Keck II Telescope to gather the spectra from BX422 needed to confirm the nature of the distant and early spiral.
“We got a beautiful map that told us this thing is a rotating disk,” Shapley said.
The spiral galaxy is also different than other similar galaxies because it appears to be in the process of merging with another galaxy.
“Indeed, many of the most well-known grand design spiral galaxies in the nearby universe (e.g., M51, M81, M101) are observed to have nearby companions, and small satellites such as the Sagittarius dwarf galaxy may even be partly responsible for producing spiral patterns in our own Milky Way galaxy,” the researchers wrote in their paper.
The team found through a simulation that the spiral pattern could be formed by merging with another galaxy.
“BX442 represents a link between early galaxies that are much more turbulent and the rotating spiral galaxies that we see around us,” Shapley said. “Indeed, this galaxy may highlight the importance of merger interactions at any cosmic epoch in creating grand design spiral structure.”