Kavli Affiliate: Kohei Inayoshi
| First 5 Authors: Xiaojing Lin, Xiaojing Lin, , ,
| Summary:
JWST observations have revealed a population of high-redshift "little red
dots" (LRDs) that challenge conventional AGN models. We report the discovery of
three local LRDs at $z = 0.1-0.2$, initially selected from the SDSS database,
with follow-up optical/near-IR spectroscopy and photometry. They exhibit
properties fully consistent with those of high-redshift LRDs, including broad
hydrogen and helium emission lines, compact morphologies, V-shaped UV-optical
SED, declining near-IR continua, and no significant variability. Two sources
were targeted but not detected in X-rays with statistical significance. All
three sources show blue-shifted He I absorption, while two exhibit H$alpha$
and Na D absorption lines. We detect full Balmer and Paschen line series in all
three objects, along with abundant narrow [Fe II] emission in two. The emission
line analyses suggest narrow lines originate from AGN-powered metal-poor
regions with minimal dust; broad lines come from inner regions with
exceptionally high density or atypical dust properties; and [Fe II] emission
arises from dense gas between broad and narrow-line regions. One of our
objects, J1025+1402 (nicknamed "The Egg"), shows extremely high equivalent
width Na D, K I, Fe II, and Ca II triplet absorption lines, suggesting the
presence of a cool ($sim$5000 K), metal-enriched gas envelope. The
optical/near-IR continua of these LRDs are also consistent with theoretical
models featuring an atmosphere around black holes. The WISE-detected IR
emission is consistent with weak dust emission of $T sim 10^2-10^3$ K. We
propose a conceptual model consisting of a largely thermalized cool-gas
envelope surrounding the central black hole and an extended emission line
region with high-density outflowing gas to explain the observed properties of
these local LRDs.
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