Magnetic Fields May Be Key to Star Formation in Merging Galaxies

Astronomers have observed magnetic fields for the first time in the merging galaxies Arp220, providing new insight into the conditions necessary for star formation. The discovery, made by an international team led by Dr. David Clements from Imperial College, suggests that magnetic fields could play a crucial role in facilitating the creation of stars in galaxy mergers, acting similarly to a pressure cooker that prevents overheating and dispersion.

In this study, the researchers found magnetic fields linked to a disk of gas and dust, spanning a few hundred light-years, at the core of Arp220, a system where two galaxies are colliding. These magnetic fields might help regulate the intense bursts of star formation, preventing the process from becoming too chaotic. Just as a pressure cooker creates the perfect environment for cooking by sealing in pressure, magnetic fields could help keep the star-forming gas from being disrupted by the heat generated by young stars.

"This is the first time we've found evidence of magnetic fields in the core of a merger," said Dr. Clements. "But this discovery is just the beginning. We now need better models and to examine other galaxy mergers."

Dr. Clements used a cooking analogy to explain the role of magnetic fields: "If you want to cook up a lot of stars quickly, you need to compress a lot of gas. But as the heat from young stars builds up, things can boil over. A magnetic field acts like a pressure cooker lid, holding everything together."

Galaxy mergers often lead to starbursts, where stars are formed at an unusually fast rate. This efficiency in star formation has puzzled astronomers, who have long sought to understand the underlying mechanisms. One theory is that magnetic fields could provide an additional 'binding force' that helps keep the gas together, resisting the tendency for it to dissipate when heated by young stars or supernovae.

Previously, theoretical models suggested that magnetic fields might play a role, but these new observations are the first to show their presence in a real-world galaxy merger.

The team used the Submillimeter Array (SMA) on Maunakea, Hawaii, to study Arp220. The SMA captures light in wavelengths about a millimeter long, offering a view into a range of cosmic phenomena, including the formation of stars and black holes.

Arp220 is a luminous infrared galaxy formed by the merger of two gas-rich spiral galaxies, triggering rapid star formation. This galaxy is among the brightest objects in the far-infrared sky, where about half of all starlight is emitted.

The researchers plan to continue their study using the Atacama Large Millimeter/submillimeter Array (ALMA), the most powerful tool for observing molecular gas and dust, to explore magnetic fields in other ultraluminous infrared galaxies. This could shed further light on the role of magnetic fields in these energetic systems.

With this breakthrough, the team hopes to clarify how magnetic fields contribute to the dynamics of some of the most luminous galaxies in the local universe.