Supermassive black holes of hundred millions of solar masses are commonly found in galaxies. These black holes can gravitationally attract interstellar matter within dozens of light years. Subsequently, the accretion of matter onto these objects leads to a mechanism that can expel gas at 1000 times greater distances : jets. Jets are collimated streams of charged particles (called plasma), which emerge from a rotating accretion disk as a result of magnetic fields. The accretion disk is formed from infalling gas, heated as it approaches the black hole.
Black-hole jets may transport an energy at a rate 10 orders of magnitude higher than that radiated by the sun. By injecting energy onto the interstellar medium, jets can prevent the collapse of gas that leads to the formation of new stars, and thus affect the fate of galaxies. Models indicated that this process can take place over full-galaxy scales because bow shocks sweep the interstellar gas as the jet propagates through it - in the same way that bow shocks occur in the Earth’s atmosphere when an airplane travels supersonically.
To date, one of the most direct evidence that black-hole jets accelerate the interstellar medium comes from observations of the galaxy IC5063, 160 million light years away from us. IC5063 has a rare feature : its jet is spatially extended and nearly aligned with its gas disk. A group of scientists consisting of Dr Kalliopi Dasyra (University of Athens), Prof. Francoise Combes (Observatoire de Paris), Ms Allison Bostrom (University of Maryland), and Prof. Nektarios Vlahakis (University of Athens) discovered that the jet initiates winds in multiple regions of this galaxy. The winds are caused either by the direct encounter of the jet with several dense gas clouds on its path, or by the passage of the associated bow shocks by these clouds.
The winds carry molecular hydrogen and iron ions with high line-of-sight velocities (of 600-1200 km/s with respect to the regular gas motions). Four discrete wind starting points are observed along the radio jet (Figure 1). The gas temperatures in regions close to the jet exceed those in the surrounding medium. The increase in the molecular gas turbulence and temperature can affect star formation in an impressively large area corresponding to 1/5th of the total dense gas disk area.
Reference
K. M. Dasyra, A. C. Bostrom, F. Combes, N. Vlahakis : 2015, “A radio jet drives a molecular and atomic gas outflow in multiple regions within one square kiloparsec of the nucleus of the nearby galaxy IC5063”, The Astrophysical Journal, in press,