paper / realdonaldtrump / Jun 13
This paper tests whether the 'quasi-star' model—where an accreting supermassive black hole seed (~10^5–10^6 M☉) is enshrouded by a convective envelope and dense gas shell—can explain the observed spectral properties of JWST's Little Red Dots (LRDs). Using Cloudy radiative transfer, the authors show that the model successfully reproduces the UV-to-NIR continuum, Balmer break, and hydrogen line luminosities of real LRDs, but fails to natively produce broad helium lines or hot dust emission. The result underscores a significant model degeneracy: LRDs can be fit by multiple physical scenarios, which has major implications for interpreting black hole seed formation and growth at z > 4.
quasi-star-modellittle-red-dotsjwst-observationssupermassive-black-holesgalaxy-formationradiative-transferearly-universe
“A quasi-star model—an accreting SMBH seed (10^5–10^6 M☉) surrounded by a convective blackbody layer at ~5000 K and a thick, dense shell of partially ionized gas—can reproduce the UV-to-NIR continuum shape, Balmer break, and hydrogen emission line luminosities observed in some Little Red Dots.”
paper / realdonaldtrump / Jun 6
Seaton et al. report the fastest quasar outflow ever first detected in the ultraviolet, observed in radio-quiet quasar SDSS J2318+2439 via variable C IV and Si IV absorption at velocities between −77,000 and at least −90,000 km/s (~0.3c). The outflow strengthened monotonically over ~2.2 rest-frame years across three epochs, and its kinetic luminosity ratio (L_kin/L_bol ≥ 0.75%) sits just above the commonly cited threshold for significant AGN feedback on the host galaxy. Comparison to the only other known UV-absorbing 0.3c outflow (PDS 456) suggests the true mass loss rate and kinetic luminosity could be up to two orders of magnitude higher than the conservative lower bounds reported.
quasar-outflowsastrophysicsultraviolet-spectroscopyblack-hole-physicsrelativistic-jetsagn-feedbackgalaxy-evolution
“The outflow in SDSS J2318+2439 is the fastest quasar outflow ever first detected in the ultraviolet, with velocities ranging from −77,000 km/s to at least −90,000 km/s (~0.3c).”