Anisotropic quenching is detected at the highest redshift yet and linked to preprocessing dominating over intrahalo effects by ~20% along the major axis in a delay-then-rapid quenching model informed by cluster accretion histories.
Evidence of violation of Case B recombination in Little Red Dots
9 Pith papers cite this work. Polarity classification is still indexing.
9
Pith papers citing it
abstract
Little Red Dots (LRDs) are a new class of compact extragalactic objects, with a v-shaped optical spectral energy distribution breaking close to the Balmer break wavelength, and broad, typically exponentially-shaped lines. They are believed to be supermassive black holes surrounded by very dense, ionized gas, leading us to explore for any departures from Case B recombination by examining the ratios of multiple hydrogen Balmer lines: $H\alpha$, $H\beta$, $H\gamma$, and $H\delta$. We analyze a dozen high-S/N LRDs with JWST/NIRSpec, measuring Balmer ratios in the seven objects with coverage of at least three lines. We decompose the line ratios into their respective broad and narrow components. Broad line ratios are consistent with Case B plus dust extinction in all objects but one, RUBIES EGS-49140, which departs from Case B expectations by more than $5\sigma$. The narrow components are consistent with minimal dust attenuation, while two objects exhibit narrow $H\alpha$/$H\beta \approx 1.8$. Such low decrements are observed in highly ionized density bounded nebulae, associated with starburst environments. Nevertheless, both flat decrement cases can be reconciled assuming an unresolved absorption feature. RUBIES EGS-49140, shows a high broad $H\alpha$/$H\beta$, but $H\gamma$/$H\alpha$ and $H\delta$/$H\alpha$ ratios are lower than expected for extinction-modified Case B, hinting at an unphysically steep dust law. These line ratios may be due to increased optical depth in the Balmer lines, as a direct effect of high density (log$n_e$ > 9) gas surrounding the black hole. If Case B recombination does hold in most LRDs, they must be moderate-to-heavily dust obscured ($A_V\simeq1-8$) while the host-galaxy should be dust-free, suggesting that the extinction in the broad lines is local to the LRD and not due to the general ISM of the host galaxy.
years
2026 9representative citing papers
Lyα observations of Little Red Dots show luminosities and equivalent widths like normal star-forming galaxies but lower Lyα/Hα ratios and extended asymmetric emission, supporting a two-component model with host-scale gas.
Eight low-redshift Little Red Dots identified in DESI DR1 exhibit broad Balmer lines, steep decrements, compact shapes, and negligible variability, with a number density roughly 10,000 times lower than at z>4.
Medium-band imaging reveals red emission-line galaxies at z>5 including compact objects likely missed by classic Little Red Dot selection criteria.
Analysis of ~100 JWST LRDs finds redder, compact UV emission with Fe II/Mg II ~8-10 and correlations suggesting central red continuum (β_UV~0) beyond host galaxy contribution.
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.
JWST observations of high-redshift galaxies show no evolution in dust geometry to z~2.4 and yield an empirical calibration linking resolved differential reddening to SFR surface density.
LRDs require Compton-thick gas at moderate metallicity plus high accretion rates producing weak X-rays to explain their non-detection, implying they are not chemically pristine.
A bias-controlled quasar sample of ~2000 objects demonstrates that the X-ray-to-UV luminosity relation remains constant from redshift 0.7 to 5.
citing papers explorer
-
A new sample of Little Red Dots at $z<0.45$ in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability
Eight low-redshift Little Red Dots identified in DESI DR1 exhibit broad Balmer lines, steep decrements, compact shapes, and negligible variability, with a number density roughly 10,000 times lower than at z>4.