Little Dots: the ULX Analogy

RESUMO

I consider recent observations of the Little Dots (LDs) observed in high--redshift ($z\sim 7$) galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super--Eddington (factors $\sim 50$) rates. In physical terms, this idea makes them supermassive analogues of the (stellar--mass) ultraluminous X--ray sources (ULXs), whose hard X--ray emission is strongly anisotropic (`beamed'). In this paper I argue that the recent discovery of extended rest--frame hard X--ray ionization cones from an LD gives strong quantitative support to this view, as its geometry is what one would expect from a ULX--like object viewed not along one of its X--ray beams, but instead `from the side', very similar to the extreme Galactic system SS433. This in turn agrees in quantitative terms with recent suggestions that LDs resemble supermassive versions of SS433--like systems. I emphasize that in contrast, the rest--frame {\it soft} X--ray emission from LDs must be roughly {\it isotropic}, and presumably power the torus emission observed from these galaxies.