REVIEW 8 cited by
A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at z=3.5
Not yet reviewed by Pith; the record is open.
This paper has not been read by Pith yet. Machine review is queued; the pith claim, tier, and objections will appear here once it completes.
SPECIMEN: schema-true, not a live event
T0 review · schema-true
One-sentence machine reading of the paper's core claim.
pith:XXXXXXXX · record.json · timestamp
A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at z=3.5
read the original abstract
The origin of the rest-optical emission of compact, red, high-redshift sources known as `little red dots' (LRDs) poses a major puzzle. If interpreted as starlight, it would imply that LRDs would constitute the densest stellar systems in the Universe. However, alternative models suggest active galactic nuclei (AGN) may instead power the rest-optical continuum. Here, we present JWST/NIRSpec, NIRCam and MIRI observations from the RUBIES and PRIMER programs of The Cliff: a bright LRD at $z=3.55$ with an exceptional Balmer break, twice as strong as that of any high-redshift source previously observed. The spectra also reveal broad Hydrogen (H$\alpha\ \rm FWHM\sim1500$km/s) and He I emission, but no significant metal lines. We demonstrate that massive evolved stellar populations cannot explain the observed spectrum, even when considering unusually steep and strong dust attenuation, or reasonable variations in the initial mass function. Moreover, the formally best-fit stellar mass and compact size ($M_*\sim10^{10.5}\,M_\odot,\ r_{e}\sim40\,$pc) would imply densities at which near-monthly stellar collisions might lead to significant X-ray emission. We argue that the Balmer break, emission lines, and H$\alpha$ absorption line are instead most plausibly explained by a `black hole star' (BH*) scenario, in which dense gas surrounds a powerful ionising source. In contrast to recently proposed BH* models of dust-reddened AGN, we show that spectral fits in the rest UV to near-infrared favour an intrinsically redder continuum over strong dust reddening. This may point to a super-Eddington accreting massive black hole or, possibly, the presence of (super)massive stars in a nuclear star cluster. The Cliff is the clearest evidence to date that at least some LRDs are not ultra-dense, massive galaxies, and are instead powered by a central ionising source embedded in dense, absorbing gas.
Forward citations
Cited by 8 Pith papers
-
(LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample
The survey identifies 27 low-redshift LRDs with compact morphology, V-shaped continua, broad Balmer lines with extreme decrements, and ubiquitous outflows, matching high-z counterparts and yielding a number density lo...
-
Hidden Monsters with SPHEREx I: A goldmine for heavily reddened quasars at cosmic noon
Confirmation of 77 new heavily reddened quasars at 1.5 < z < 3.9 with high luminosities and extinctions, showing they are deficient in hot and warm dust relative to blue quasars and supporting a blow-out feedback phase.
-
Hidden Monsters with SPHEREx I: A goldmine for heavily reddened quasars at cosmic noon
SPHEREx data confirm 77 new luminous heavily reddened quasars at 1.5<z<3.9 that are hot-dust poor relative to unobscured quasars, supporting a blow-out feedback phase.
-
Spatial decomposition of Little Red Dots with JWST/NIRSpec IFU into broad-line red cores and narrow-line blue host galaxies
Spatially resolved JWST/NIRSpec IFU spectroscopy of five z~5 Little Red Dots shows blue continuum and narrow lines from extended hosts and red continuum plus broad Balmer features from compact cores.
-
JWST's Little Red Dots as collapsed Supermassive Dark Stars
Supermassive dark stars powered by dark matter annihilation can collapse into quasi-stars whose envelopes expand and cool to match the observed properties of many JWST Little Red Dots while bypassing the restrictive c...
-
Paschen Jumps in Little Red Dots: Evidence for Nebular Continua
Paschen jumps in Little Red Dots indicate their continua originate from free-bound recombination emission in low-temperature nebular gas rather than thermalized or AGN components.
-
The X-ray weakness of Little Red Dots and JWST-selected AGN: comparison with local AGN in different accretion regimes
High-z LRDs and JWST AGN exhibit X-ray weakness consistent with local super-Eddington accreting SMBHs, supporting a link to highly accreting systems across cosmic time.
-
No evolution in the number density of little red dots from cosmic dawn to cosmic noon
Number density of LRDs with L_bol ≳ 3×10^44 erg s^{-1} shows no evolution at z>2 and is ~350 times higher than model predictions at cosmic noon.
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.