Big Island Telescopes Provide Insight on Cosmic Food Chain

Powerful telescopes atop Mauna Kea are giving astronomers new insights in the way galaxies grow.

A study using the Subaru Observatory and the twin telescopes of the W.M. Keck Observatory has allowed scientists to observe a galaxy similar to our own Milky Way absorbing a smaller one.

Such gobbling of small galaxies by bigger neighbors is common throughout the universe, Keck spokesman Steve Jefferson said, but the shredded galaxies are so faint they are difficult to observe.

But a project spearheaded by Caroline Foster of the Australian Astronomical Observatory has used the Mauna Kea instruments to collect enough data to provide a detailed model of how and when it occurred.

Foster’s focus has been on the Umbrella galaxy, so-called because of its “parasol” which is composed of a stellar stream thought to be the remnants of a galaxy pulled apart by Umbrella’s powerful gravity field.

Astronomers first took wide images of Umbrella (technically known as NGC 4651) using the Subprime-Cam on Subaru, then used the DEIMOS spectrograph on Keck II to map out motions of the stream.

“This is important because our whole concept about what galaxies are and how they grow has not been fully verified,” co-author Aaron Romanowsky, an astronomer at several University of California universities said in a statement.

“We think they are constantly consuming smaller galaxies as part of a cosmic food chain, all pulled together by a mysterious form of invisible ‘dark matter,’” he said. “When a galaxy is torn apart, we sometimes get a glimpse of the hidden vista because the stripping process lights it up. That’s what occurred here.”

The project is a follow-up to a 2010 story by David Martinez-Delgado of the University of Heidelberg. When his team used small robotic telescopes to image eight isolated spiral galaxies, it found signs of mergers – shells, clouds and arcs of tidal debris – in six of them.

The Umbrella galaxy lies 62 million light-years away, the northern constellation of Coma Berenecies.