JWST is looking at the dark molecular clouds at the center of the Milky Way

There’s a strange object near the heart of the Milky Way that astronomers call “The Brick.” It is a large gas cloud called an infrared dark cloud (IDC). The brick is thick and crowded like others of its kind, but for some reason, it shows few signs of star formation.

Why?

The central molecular zone of the Milky Way (CMZ) can be a difficult region to study. Dark clouds of molecules settle there, giving birth to new stars. The CMZ is a large complex of molecular clouds that contain about 60 million times the solar gas. Brick is one of those clouds. Astronomers are keen to better understand this region, and JWST has the ability to see this dense region, revealing some of the details.

The brick is one of the most studied IDCs in the Milky Way. It shows much less star formation than other similar cloud layers. That creates mystery, and astronomers are drawn to mysteries.

A group of researchers hired JWST to study Brick, also known as G0.253 + 0.015. But it’s hard to see in a crowded place. Therefore, to study those gas clouds, astronomers resort to carbon monoxide. Hydrogen is abundant, but carbon monoxide is very bright and visible at certain wavelengths. Astronomers monitor it to track the movement and density of interstellar clouds.

The new study is titled “JWST reveals absorption of CO ice and gas in the central galactic cloud G0.253+0.015,” and is available at arXiv pre-print server. Lead author is Adam Ginsburg, Assistant Professor of Astronomy at the University of Florida.

There have been various proposed explanations for the lack of a Block in star formation. It may be small, it may be very turbulent, it may be magnetically forced, or it may actually be multiple clouds in a single line of sight. “Each of these explanations is likely to play a role in cloud formation and evolution,” the authors explain.

While the rate of star formation may lag behind other similar clouds, there are still more than 56,000 stars there.

Astronomers have devoted considerable effort to understanding the presence, distribution, and behavior of gas in the Milky Way, including the CMZ. But they haven’t investigated greenhouse gases like CO thoroughly. That’s because it takes powerful infrared energy to read it.

Enter JWST’s NIRCam and its powerful and flexible filters.

A team of researchers used NIRCam to study Brick in more detail. They found that the Brick contains more CO in the ice than they thought and while the CO in the Brick’s surface may be in the gas phase, it is trapped inside. What does that tell us about Bricks?

There is no firm decision yet regarding Bricks. In the denser regions of molecules within the Brick, CO is the primary coolant in the cloud. So at lower cloud densities, the cooling effect of CO should be stronger. Conversely, in the inner, denser regions of the cloud, CO may be completely frozen, and dust may be too small to replace carbon monoxide as the primary coolant.

Stars tend to form when the gas is cool, so finding this much CO should indicate a high rate of star formation. But the gas inside the brick is hotter than other clouds despite the presence of all that ice.

These results tell us something about the center of the galaxy as a whole. They change our understanding of both the average concentration of CO in GC and the gas-to-dust ratio in the same area. According to these results, both are very low.

If there is more CO in the Bricks and in the galactic center than previously thought, that has different implications for star formation models and may affect the rate of star formation in the Brick universe.

There are standard models for the distribution of CO in clouds, but like many things in astronomy and astrophysics, JWST gives astronomers more detailed information than they had before and overturns some established ideas. The team behind the research suggests that if the center of the Milky Way contains this much CO, other galaxies likely do too.

This is just the first group page based on their JWST Bricks configuration. While it shows new results for carbon monoxide, it doesn’t reach any conclusions. But it helps support Brick’s status as the most watched IDC.

A future paper will show the MIRI (Mid-Infrared Instrument) observation of Bricks, as well as MIRI and NIRCam observation of cloud C, another structure in the middle molecular area.

Further observations may provide an explanation, and astronomers may find their own explanation for the slow rate of Star formation.