M106 Is Burstin’ Out All Over

I love pictures like this! It’s a view of the distant galaxy M106 in x-ray, optical, radio, and infrared light. Combined together, they tell a story of explosive action at the heart of this fascinating spiral. And, in astronomy, multi-wavelength views are where it’s at when it comes to getting the whole story about an object and its activities.

So, why the fireworks? M106 is similar to the Milky Way Galaxy, except that it has an extra pair of spiral arms. When you look at them at different wavelengths of light, something interesting shows up. The two extra arms aren’t in the plane of the galaxy like the ones in the Milky Way. Instead, they seem to be intersecting with M106 at an angle. Shock waves are reverberating through the galaxy and heating enough gas to form ten million Suns. That causes the gas to glow and we see it in the colored arms poking out from the galaxy.

The shock waves are being produced by the action of tremendously strong superheated jets of high-energy particles streaming out from the core of the galaxy. They’re bright in radio wavelengths of light. What’s likely happening is that the jets are whacking into the disk of the galaxy, and that in turn generates shock waves that heat the gas to thousands of degrees.

The Chandra X-ray Observatory part of this image reveals huge bubbles of hot gas above and below the plane of the galaxy. They tell astronomers that much of the gas that was once in the disk of the galaxy has been heated to millions of degrees and ejected into the outer regions by the jets from the black hole.

This tremendous amount of “mass loss” doesn’t bode well for M106. If the action of the jets keeps up, most of the galaxy’s remaining gas will be gone in the next 300 million years. That’s like next month in cosmic time scales, where the life of a galaxy can be measured in billions and billions of years.

This means that gas needed to form new stars is going to be very hard to come by in the galaxy, and thus in a few hundred million years, M106 will lose most of its star-making regions. Its stars will get older and older, and fewer new ones will replace them. Researchers used Spitzer Space Telescope data to estimate that stars are forming in the central regions of NGC 4258, at a rate which is about ten times less than in the Milky Way Galaxy.

The European Space Agency’s Herschel Space Observatory was used to confirm the estimate from Spitzer data of the low star formation rate in the central regions of NGC 4258. Herschel was also used to make an independent estimate of how much gas remains in the center of the galaxy. After allowing for the large boost in infrared emission caused by the shocks, the researchers found that the gas mass is ten times smaller than had been previously estimated.

Because M106 is relatively close to Earth, astronomers can study how its black hole is affecting the galaxy in great detail. The supermassive black hole is about ten times larger than the one in the Milky Way, and is also consuming material at a faster rate, potentially increasing its impact on the evolution of its host galaxy.

Of course, all galaxies slow down their star-making machinery as gas is used up, but in the case of M106, this appears to be a case of arrested development on a large scale, caused by the hungry appetite of a black hole.