Researchers have recently discovered magnetic fields linked to a disc of gas and dust spanning a few hundred light-years in a pair of merging galaxies known as Arp220. They believe these areas could be crucial for creating the perfect environment for transforming hydrogen gas into young stars.
Astronomers have discovered for the first time what could be the essential component for star formation, akin to the way steam cooks a Christmas pudding.
Much like a pressure cooker relies on a weight to maintain the necessary pressure for cooking, merging galaxies might require magnetic fields to establish ideal star formation conditions.
Up until this point, the actual presence of such magnetic forces had only been hypothesized and not confirmed.
A global team of scientists, led by astrophysicist Dr. David Clements from Imperial College, found signs of magnetic fields associated with a vast disc of gas and dust inside the system of merging galaxies named Arp220.
According to the researchers, these magnetic fields might help balance the environment in the cores of interacting galaxies, allowing for the conversion of substantial amounts of hydrogen gas into young stars without excessive star formation, which could cause instability.
This significant finding has been detailed in a new paper published in Monthly Notices of the Royal Astronomical Society.
“This marks the first time we have detected magnetic fields in a merger’s core,” stated Dr. Clements. “However, this is just the beginning; we need more advanced models and observations of other galaxy mergers.”
Dr. Clements used a cooking analogy to describe the role of magnetic fields in star production.
“To create many stars (like making Christmas puddings) quickly, a lot of gas (or ingredients) needs to be compressed together. This is what occurs in merger cores. However, as the heat from newly formed stars builds up (similar to cooking), things may overflow, causing the gas (or pudding mixture) to disperse,” he explained.
“To prevent this overflow, something needs to hold it all together—whether it’s a magnetic field in a galaxy or the lid and weight of a pressure cooker.”
Astronomers have long been on the lookout for the key factor that enables certain galaxies to form stars more effectively than average.
Galaxy mergers can produce stars at an extremely fast rate, a phenomenon known as a starburst. This behavior is distinct from other star-forming galaxies regarding the correlation between the rate of star formation and the total mass of stars—starburst galaxies appear to convert gas into stars more efficiently than others. The reason behind this remains a mystery for astronomers.
One theory suggests that magnetic fields could serve as an additional ‘binding force’ that keeps star-forming gas together longer, countering its tendency to spread out due to the heat generated by young, massive stars, or by supernovae from dying stars.
While past theoretical models proposed this idea, these new observations are the first to confirm the existence of magnetic fields in at least one specific galaxy.
The research team utilized the Submillimeter Array (SMA) located on Maunakea in Hawaii to investigate the innermost regions of the ultraluminous infrared galaxy Arp220.
The SMA is adept at capturing images in millimeter wavelengths, which bridge infrared and radio light, allowing astronomers to probe a variety of cosmic events, such as the activity surrounding supermassive black holes and the formation of stars and planets.
Arp220 is among the most luminous objects in the extragalactic far-infrared sky and results from the merger of two gas-rich spiral galaxies, which has sparked intense starburst activity within the regions surrounding the merger’s nucleus.
The extragalactic far-infrared sky represents a cosmic background composed of the combined light from distant galaxies’ dust emissions, with approximately 50% of all starlight emerging at these wavelengths.
Moving forward, the research team plans to employ the Atacama Large Millimeter/submillimeter Array (ALMA) to search for magnetic fields in other ultraluminous infrared galaxies.
This is particularly important as the next brightest local ultraluminous infrared galaxy compared to Arp220 is significantly fainter, by a factor of four or more.
With their current findings and ongoing observations, the researchers hope to gain a better understanding of the role magnetic fields play in some of the most luminous galaxies within the local universe.
