Centaurus A, the nearest galaxy to Earth with an active core, has undergone much scrutiny since the discovery of its peculiar shape in 1826. So, it’s pretty amazing when a new telescope comes online and shows us a whole new view of the workings of this complicated galaxy mess.
The most obvious feature in an optical picture of Cen A (or NGC 5128) is the thick, cloudy dust lane that runs through the center of this massive elliptical collection of stars. This dust lane hints that more interesting activity is going on inside while blocking our view of whatever that is.
Since the visible light is blocked, astronomers use other types of light to see the activity in the center. Infrared telescopes show a starburst of star formation, and radio and x-ray telescopes pinpoint the activity coming from the supermassive black hole in the center.
The image above adds in data from the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile. This telescope is only half built at the Chajnator site 16,000 feet above sea level. But astronomers have already jumped on the “Early Science” period to finally study the targets that they have been hoping to see for decades.
The “rainbow” of emission seen by ALMA is light with a wavelength of 1.3 millimeters and comes from carbon monoxide gas embedded in the dust lane. The colors indicate velocity, such that the blue is gas coming towards us and purple is gas moving away. This shows a classic rotating disk of material that is encircling the central engine of the active galaxy.
The ALMA data, re-colored so that orange is approaching and green is receding, and overlaid on a near-infrared image.
Cen A appears to be in the middle of a galaxy collision between the large elliptical and a smaller spiral galaxy. This collision has sparked the intense star formation and active supermassive back hole in the center as gas falls to the center of the system. This is the closest example of a process that occurs all over the universe, so astronomers use it as a detailed laboratory in order to extrapolate to more distant systems.
Previous views of Cen A in different wavelengths.
Centaurus A got its name as the first bright radio source discovered in the constellation of Centaurus. This is typically only observable from Southern Hemisphere sites, and the blazing radio light comes from the jets of relativistic material spewing forth in large jets see in the image above in green. Though this galaxy has made itself known for a long time, it’s really cool to see astronomers using a new telescope to peer further into its inner workings and detect something far more ephemeral and ghostly-looking as this carbon monoxide gas.
Top Image: ALMA Data overlaid on an optical image by the 2.2-meter telescope at ESO’s La Silla Observatory in Chile. Credits: ALMA (ESO/NAOJ/NRAO), T.A. Rector (University of Alaska Anchorage). Visible-light image: ESO. Middle Image Credits: ALMA (ESO/NAOJ/NRAO); ESO/Y. Beletsky. Bottom Image Credits: NASA, NRAO/AUI, DSS