Little Dots: the ULX Analogy
Abstract
I consider recent observations of the Little Dots (LDs) observed in high--redshift (z∼ 7) galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super--Eddington (factors ∼ 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.
Related
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BibTeX
@misc{king2026little,
title = {{Little Dots: the ULX Analogy}},
author = {Andrew King},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09302},
eprint = {2609.09302},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09302},
note = {CC BY-SA 4.0},
}
RIS
TY - UNPB
TI - Little Dots: the ULX Analogy
AU - Andrew King
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09302
UR - https://arxiv.org/abs/2609.09302
AB - I consider recent observations of the Little Dots (LDs) observed in high--redshift (z∼ 7) galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super--Eddington (factors ∼ 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.
ER -