An international team, including researchers from the Center for Astrophysics | Harvard and Smithsonian (CfA), has detected magnetic fields within a gas and dust disk several hundred light-years across in Arp 220, a system formed by the merger of two galaxies.
Arp 220, one of the most infrared-luminous objects beyond the Milky Way, is believed to be the result of two colliding spiral galaxies rich in gas. This intense collision has triggered a surge in star formation, making it an ideal laboratory for studying conditions necessary for stars to emerge.
Astronomers have long sought to understand why some galaxies convert gas into stars more efficiently than others. The presence of magnetic fields may help explain this phenomenon by regulating star formation, akin to a pressure cooker managing heat and pressure.
David Clements of Imperial College, United Kingdom, who led the study, stated, "This is the first time we've found evidence of magnetic fields in the core of a merger. But this discovery is just a starting point. We now need better models and to see what's happening in other galaxy mergers."
The team utilized the Submillimeter Array (SMA), a collection of eight radio dishes located near the summit of Maunakea in Hawaii, to investigate Arp 220. The SMA is recognized for its high-resolution capabilities in studying celestial phenomena.
For a galaxy to form a significant number of stars in a short period, large quantities of gas must condense and collapse. However, as young stars heat their surroundings, this gas tends to disperse, hindering further star formation. Clements noted that a magnetic field can stabilize this process, similar to how a pressure cooker retains heat.
Galaxy mergers often experience rapid bursts of star formation, known as starbursts, which differentiate them from typical star-forming galaxies. In these starbursts, gas converts into stars at a significantly higher rate, prompting scientists to investigate the underlying mechanisms.
One hypothesis is that magnetic fields provide additional stabilization, preventing star-forming gas from expanding too quickly. These fields may sustain dense star-forming regions longer than expected, counteracting the disruptive effects of stellar heat and supernovae.
Theoretical models have predicted such magnetic influences, and the new observations offer concrete evidence of their existence in a merging galaxy.
Qizhou Zhang of the CfA, a co-author of the study, explained, "Another effect of the magnetic field is that it slows down the rotation of gas in the disks of merging galaxies, allowing gravity to pull the gas inward to fuel starbursts."
The research team plans to search for magnetic fields in other galaxies similar to Arp 220 to gain a clearer understanding of their role in some of the most luminous galaxies in the local universe.