Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Roberto Maiolino, Guido Risaliti, Matilde Signorini, Bartolomeo Trefoloni, Ignas Juodzbalis
| Summary:
We investigate the X-ray properties of a sample of 71 broad line and narrow
line AGN at 2$<$z$<$11 discovered by JWST in the GOODS fields, which have the
deepest Chandra observations ever obtained. Despite the widespread presence of
AGN signatures in their rest-optical and -UV spectra, the vast majority of them
is X-ray undetected. The stacked X-ray data of the non-detected sources also
results in a non-detection. The upper limit on the X-ray emission for many of
these AGN is one or even two orders of magnitude lower than expected from a
standard AGN SED. X-ray absorption by clouds with large (Compton-thick) column
density and low dust content, such as the Broad Line Region (BLR) clouds, can
explain the X-ray weakness. In this scenario the BLR covering factor should be
much larger than in low-z AGN or luminous quasars; this is supported by the
larger equivalent width of the broad component of H$alpha$ in JWST-selected
AGN. We also find that the JWST-discovered AGN lack prominent, fast outflows,
suggesting that, in JWST-selected AGN, dense gas lingers in the nuclear region,
resulting in large covering factors. We also note that a large fraction of
JWST-selected AGN matches the definition of NLSy1, typically accreting at high
rates and characterized by a steep X-ray spectrum — this can further
contribute to their observed weakness at high-z. Finally, we discuss that the
broad Balmer lines used to identify type 1 AGN cannot be ascribed to Very
Massive Stars or Supernovae, although we show that some of the faintest broad
lines could potentially be associated with superluminous SNe.
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