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arXiv · 1110.4118

No evidence of obscured, accreting black holes in most z=6 star-forming galaxies

Chris J. Willott
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Abstract

It has been claimed that there is a large population of obscured, accreting black holes at high-redshift and that the integrated black hole density at z=6 as inferred from X-ray observations is ~100 times greater than inferred from optical quasars. I have performed a stacking analysis of very deep Chandra X-ray data at the positions of photometrically-selected z=6 galaxy candidates. It is found that there is no evidence for a stacked X-ray signal in either the soft (0.5-2 keV) or hard (2-8 keV) X-ray bands. Previous work which reported a significant signal is affected by an incorrect method of background subtraction which underestimates the true background within the target aperture. The puzzle remains of why the z=6 black hole mass function has such a flat slope and a low normalization compared to the stellar mass function.

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Chris J. Willott. 2011-10-18. No evidence of obscured, accreting black holes in most z=6 star-forming galaxies. https://doi.org/10.1088/2041-8205%2F742%2F1%2Fl8

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