Extending the Little Red Dot population at intermediate redshift with VIPERS

Krzysztof Lisiecki, Krzysztof Hryniewicz, Francesco Pistis, Michał J. Michałowski, Aidan P. Cotter, Maciej Koprowski, Miguel Figueira, Agnieszka Pollo, Katarzyna Małek, Olga Cucciati

First listed 2026-09-10 | Last updated 2026-09-09

Abstract

Little red dots (LRDs) are a recently identified population of compact, red sources characterised by a distinctive V-shaped UV-to-optical continuum and broad emission lines. Their physical structure and evolution remain uncertain, while their properties at intermediate redshifts are largely unexplored. We identify and characterise LRD-like sources at 0.5<z<1.75 using the VIMOS Public Extragalactic Redshift Survey (VIPERS), extending observational studies to a previously poorly explored cosmic epoch. We select candidates from their UV and optical slopes measured from broadband photometry and refine the sample using broad emission lines in VIPERS spectroscopy. We investigate their photometric, spectroscopic, and morphological properties, constrain their physical sizes with HSC imaging, measure their comoving number density and evolution, and characterise their local environments using the VIPERS galaxy density field. We also model the multi-wavelength emission of the unique X-ray-detected source with CIGALE, including X-ray and AGN emission. We identify 14 LRD-like sources, including one X-ray-detected object, whose HSC morphology remains unresolved. We measure their number density in two redshift bins, 0.5<z<1 and 1<z<1.75, and combine our results with literature measurements. We find a rapid decline in number density after cosmic noon. The two sources with sufficiently constrained environments are located in underdense regions. The SED of the X-ray-detected source is best reproduced by a radiatively efficient accretion disk viewed at low inclination. Our results demonstrate that LRD-like sources are present at z>0.5, bridging local and high-redshift studies. Their abundance, compact morphology, environmental properties, and multi-wavelength emission provide new constraints on the evolution and physical origin of this population.

Short digest

Lisiecki et al. search the 0.5<z<1.75 VIPERS survey for little-red-dot analogues, selecting V-shaped UV-to-optical continua from broadband slopes and retaining sources with broad spectral lines. They identify 14 compact V-LRDs, including one unresolved X-ray detection, and find that their comoving abundance drops rapidly after cosmic noon when placed alongside literature samples. The two objects with usable density-field measurements lie in underdense regions, while CIGALE modeling of the X-ray source favors a low-inclination, radiatively efficient accretion disk, extending empirical LRD constraints into the intermediate-redshift gap between local and JWST-era populations.

Key figures to inspect

• Figure 1. This figure establishes the sample visually and spectroscopically: it shows the V-shaped rest-frame SEDs, the UV and optical slope measurements used for selection, the broad-line identifications, and compact imaging cutouts across the redshift range.
• Figure 4. This is the paper's central evolutionary result, placing the two VIPERS number-density measurements against literature samples and showing the inferred rapid decline in LRD abundance after cosmic noon.
• Figure 5. This figure presents the direct environmental test, comparing the two measurable V-LRD local densities with the VIPERS field and matched control distributions to show that both occupy underdense regions.
• Figure 6. This figure gives the physical interpretation of the unique X-ray-detected V-LRD by comparing full UV-to-X-ray CIGALE fits and their residuals, highlighting why the preferred solution contains a radiatively efficient AGN disk viewed at low inclination.