Jet-accretion coupling in low/hard state Galactic black hole candidates

By means of quasi-simultaneous radio/X-ray observations of ten Galactic black hole binaries in the low/hard X-ray state, we have found evidence for a strong correlation between these two bands over more than three orders of magnitude in X-ray luminosity, from the 'quiescent' regime up to close to the soft state transition, where radio emission starts to decline, probably corresponding to the physical disappearance of the jet. We discuss three main consequences of this work: 1) Monte Carlo simulations show that the observed scatter to the relation is consistent with relatively low beaming (Gamma(radio) < 2) outflows in the low/hard state. 2) The X-ray luminosity at which the jet switches off seems to positively correlate with the black hole mass. 3) The non-linearity of the correlation implies that, below some X-ray luminosity, the power output of low/hard state black holes can be 'jet-dorninated'.