|The two forms of early-type galaxies, a lenticular/S0 (left) and an elliptical (left)|
After searching CO(1-0) (known to be a good tracer of H2, which is where all the cold gas mass is located), over 20% of early-type galaxies had molecular gas reservoirs. Not only did this study look at the presence and mass within these galaxies, but it picked out a very unusual galaxy, NGC 1266.
|CO(2-1) spectrum of NGC1266 taken using the IRAM 30m|
|Imaging of the CO emission overlaid atop Hα|
But what force is capable of driving molecular gas out of the system? And what type of physical phenomenon can control that force? In order to answer this question, we turned to the imaging data to figure this out. First, we used two interferometers: the Combined Array for Research in Millimeter Astronomy (CARMA) and the Submillimeter Array (SMA). By looking at the extremes of the velocities seen in the CO emission, we were able to get size details about the molecular gas. With these, we could derive energies and timescales associated with the outflow. This was able to tell us that star formation was unable to drive the extreme velocities (≈200 km/s) and the large mass fluxes (≈13 M⊙) associated with the outflow. If it was not star formation, there was one other possibility. It was possible that an accreting supermassive black hole in the center of NGC 1266 is the driver of the outflow.
How does one go about proving the presence of an active galactic nucleus (AGN)? We turned to the X-rays. Although not always associated with an AGN, often times they are. We were able to get time from the Chandra X-ray telescope to look at the X-ray details of NGC 1266. This hinted strongly at the presence of an AGN (and shocks too!), with hard X-rays originating at the same location as a radio source, and sitting underneath the densest part of the non-outflowing molecular gas. The AGN energetics also proved to be up to the challenge of driving the molecular gas out of the galaxy. In this paper, we even suspected that given the rate of the outflow, all of the starforming fuel will be depleted from the system in less than 100 million years.
|NGC1266 X-ray (blue), radio (green) and Hα (red) emission|
The official published version can be found on NASA ADS.
To get a PDF version made by me, you can download it here