Little Dots: the ULX Analogy

arXiv:2609.09302 · astro-ph.GA · Submitted 2026-09-08 · Read on arXiv

astro-ph.GA

Submitted: 2026-09-08

Updated: 2026-09-08

Comments: MNRAS, accepted

License: http://creativecommons.org/licenses/by-sa/4.0/

The gist: I consider recent observations of the Little Dots (LDs) observed in high--redshift (z about 7) galaxies.

Abstract

I consider recent observations of the Little Dots (LDs) observed in high--redshift (z about 7) galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super--Eddington (factors about 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 soft X--ray emission from LDs must be roughly isotropic, and presumably power the torus emission observed from these galaxies.

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