Digest
This paper uses JWST/NIRSpec IFU prism plus G395H data to spatially and spectrally decompose five broad-Hα-selected little red dots at z≈5 into continuum, narrow-line, broad-line, and absorption components. The key result is a clean spatial split: the blue continuum tracks the narrow-line region, while the red continuum is unresolved and coincident with the broad Balmer emission and absorption in a compact core. Radial profiles and [O III] equivalent-width maps show that the core is continuum-dominated, with a pronounced central [O III] EW dip and more extended narrow-line emission than the broad component. That directly strengthens the picture that LRDs are composite systems, with a red central engine embedded in a bluer host galaxy.
Key figures to inspect
- Figure 2. This figure is the best overview of the paper’s decomposition framework, showing how the PRISM spectra are split into blue and red continuum components and how the G395H data isolate narrow forbidden lines, broad Balmer emission, and Balmer absorption. It lets readers see exactly what observables are being mapped spatially in the rest of the paper and how the two-component interpretation is built from the spectroscopy.
- Figure 3. Use this representative IFU map to visualize the paper’s central claim in a single object. The contrast between spatially broader blue continuum and narrow-line emission versus the compact red continuum, broad Balmer emission, and absorption makes the red-core plus blue-host picture immediately tangible.
- Figure 4. This figure turns the continuum decomposition into a size measurement by comparing wavelength-dependent spatial profiles against the modeled JWST PSF. It is important because it quantitatively shows that the red continuum is unresolved while the blue continuum is extended, which is one of the paper’s cleanest tests of the central-engine-plus-host scenario.
- Figure 5. This is the line-emission counterpart to the continuum-size analysis, demonstrating that the broad Balmer component stays compact while the narrow-line emission, especially [O III], can be more extended. It matters because it ties the broad lines to the compact core and the narrow forbidden lines to the larger-scale host environment.
- Figure 6. The [O III] equivalent-width maps provide the sharpest physical diagnostic in the paper by revealing a central dip or plateau in EW where the red continuum is strongest. That non-monotonic structure is key evidence that the core is continuum-dominated rather than simply the brightest part of the narrow-line region, reinforcing the interpretation of a compact red central engine embedded in a blue host galaxy.