Clever trick to cook stars like Christmas pudding detected for first time

Just like a pressure cooker with a weight on top of its lid to maintain pressure and keep your holiday dessert dense, moist, and edible, merging galaxies may need magnetic fields to create ideal conditions for star formation.

However, so far, the existence of such a force has only been theorized rather than observed.

An international team of researchers, led by Imperial College astrophysicist Dr David Clements, found evidence of magnetic fields associated with a disk of gas and dust hundreds of light-years deep within the galaxy of two merging galaxies, known as Arp220.

They say these regions may be key to making the centers of interacting galaxies suitable for converting large amounts of hydrogen gas into young stars. This is because when the heat is turned up too high, the magnetic field may be able to prevent intense bursts of star formation in the cores of merging galaxies, effectively “boiling” them.

A new paper revealing the discovery was published today in Royal Astronomical Society monthly notices.

Dr Clements said: “This is the first time we have found evidence of a magnetic field at the core of a merger, but this discovery is just a starting point. We now need better models to see what mergers are happening in other galaxies.”

When explaining the role of magnetic fields in star formation, he used a cooking metaphor.

“If you want to cook a lot of stars (Christmas pudding) in a short time, you need to squeeze a lot of gas (or raw materials) together. That’s what we see in the cores of mergers. But as young stars ( (or your cookware)) builds up, the substance boils, and the gas (or pudding mix) disperses,” says Dr. Clements.

“To stop this from happening, you need to add something to hold them together – the magnetic field in the galaxy, or the lid and weight of the pressure cooker.”

Astronomers have long searched for the magic ingredient that allows some galaxies to form stars more efficiently than normal.

One of the problems with galaxy mergers is that they can form stars very quickly, known as starbursts. This means they behave differently from other star-forming galaxies in terms of the relationship between star formation rate and the mass of stars in the galaxy – they appear to turn gas into stars more efficiently than non-starburst galaxies. Astronomers are puzzled as to why this happens.

One possibility is that the magnetic field could act as an additional “binding force,” holding the star-forming gas together longer, preventing the gas from expanding and dissipating as it is heated by young, hot stars or supernovae. Mass stars die.

Theoretical models have proposed this before, but the new observations are the first to show the presence of a magnetic field in at least one galaxy.

Researchers used the Submillimeter Array (SMA) on Mauna Kea, Hawaii, to probe the depths of the ultraluminous infrared galaxy Arp220.

The SMA is designed to image light at a wavelength of about 1 millimeter, which is on the border between infrared and radio wavelengths. This opens a window into a variety of astronomical phenomena, including supermassive black holes and the birth of stars and planets.

Arp220 is one of the brightest objects in the extragalactic far-infrared sky. It is the result of the merger of two gas-rich spiral galaxies, which triggers starburst activity in the merged core region.

The extragalactic far-infrared sky is the cosmic background radiation composed of the integrated light emitted by dust in distant galaxies. About half of starlight is emitted at far-infrared wavelengths.

The team’s next step will be to use the Atacama Large Millimeter/submillimeter Array (ALMA) – the most powerful telescope ever built to observe molecular gas and dust in the cold universe – to search for other ultra-bright infrared galaxies. magnetic field.

This is because the next brightest locally superluminous infrared galaxy is four times or more fainter than Arp220.

Through their results and further observations, the researchers hope that the role of magnetic fields in some of the brightest galaxies in the local universe will become clearer.