Galaxies Collide, Pasadena's Jet Propulsion Laboratory Observes

Published : Monday, March 18, 2019 | 4:52 AM

This image shows two merging galaxies known as Arp 302, also called VV 340. In these images, different colors correspond to different wavelengths of infrared light. Blue and green are wavelengths both strongly emitted by stars. Red is a wavelength mostly emitted by dust. Credit: NASA/JPL-Caltech

Somewhere out there, a giant black hole is gorging itself on nascent stars while, closer to home Jet Propulsion Laboratory (JPL) researchers are watching to see if the collision of galaxies birth stars or kills them.

For more than 10 years, scientists working on the Great Observatories All-sky LIRG Survey, or GOALS, based at JPL in Pasadena, have observed the merging of nearby galaxies.

These they utilize as laboratories, of a sort, that echo an earlier period in the universe’s history — six to 10 billion years ago — when nearby galaxies merging.

The survey has focused on 200 nearby objects, including many galaxies in various stages of merging.

New images from NASA’s Spitzer Space Telescope show pairs of galaxies on the cusp of cosmic consolidation. Though the galaxies appear separate, gravity is pulling them into a merge that will yield a new galaxy.

Some will experience billions of years of growth. For others, however, the merger will kick off processes that eventually halt star formation, dooming the galaxies to a premature withering, JPL said in a news release.

One of the primary processes thought to be responsible for a sudden halt in star formation inside a merged galaxy is an overfed black hole, the statement said.

During a galactic merger, gas and dust are driven into the center of the galaxy, where they help make young stars and also feed a massive black hole found at the center. The sudden burst of activity can also create an unstable environment hindering the galaxies’ ability to make new stars.

Scientists are still working to fully understand the complex relationship between mergers, bursts of star formation, and black hole activity.

One of the newly merged galaxies is the subject of a detailed study with the W.M. Keck Observatory in Hawaii. There, GOALS scientists searched for galactic shockwaves driven by the central active galactic nucleus, an extremely bright object that is powered by a black hole feeding on material around it.

They say the lack of shock signatures suggests that the role of active galactic nuclei in shaping galaxy growth during a merger may not be straightforward.

JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena.

To learn more about GOALS, visit www.goals.ipac.caltech.edu.

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