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Little Red Dots (LRDs), candidate high-redshift supermassive black holes accreting in dense gas, remain undetected in X-rays. In previous work, we provided the first quantitative models that reproduce the optical and near-infrared spectra…

Astrophysics of Galaxies · Physics 2026-05-18 Albert Sneppen , Darach Watson , James H. Matthews , Stuart A. Sim

The James Webb Space Telescope (JWST) has uncovered a population of compact, high-redshift sources, the Little Red Dots (LRDs), which may host supermassive black holes (BHs) significantly heavier than their stellar content compared with…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-23 Valerio De Luca , Loris Del Grosso , Gabriele Franciolini , Konstantinos Kritos , Emanuele Berti , Daniel D'Orazio , Joseph Silk

Using a sample of optically-selected quasars from the Sloan Digital Sky Survey, we have determined the radio-loud fraction (RLF) of quasars as a function of redshift and optical luminosity. The sample contains more than 30,000 objects and…

Recently, the James Webb Space Telescope (JWST) has revealed a new class of high redshift (high-$z$, $z>4$) compact galaxies which are red in the rest-frame optical and blue in the rest-frame UV as V-shaped spectral energy distributions…

To investigate the radio properties of the recently found high-redshift population, we collected a sample of $919$ little red dots (LRDs) from the literature. By cross-matching their coordinates with the radio catalogues based on the first-…

Astrophysics of Galaxies · Physics 2024-12-25 K. Perger , J. Fogasy , S. Frey , K. É. Gabányi

Little red dots (LRDs) draw extensive attention because of their unique observational characteristics and apparent overabundance in the early Universe, raising new insights into early black hole formation and growth. Early studies show that…

We present the radio luminosity function (RLF) of optically-selected quasars below 1~mJy, constructed by applying a Bayesian-fitting stacking technique to objects well below the nominal radio flux-density limit. We test the technique using…

Astrophysics of Galaxies · Physics 2020-01-22 Eliab Malefahlo , Mario G. Santos , Matt J. Jarvis , Sarah V. White , Jonathan T. L. Zwart

The X-ray luminosity function of distant (3<z<5.1) unabsorbed quasars has been measured. A sample of distant high-luminosity quasars ($10^{45} \leq L_{{\rm X},2-10} < 7.5 \times 10^{45}$ erg/s in the 2--10 keV energy band) from the catalog…

High Energy Astrophysical Phenomena · Physics 2019-06-21 G. A. Khorunzhev , S. Yu. Sazonov , R. A. Burenin

Little red dots (LRDs), a population of active galactic nuclei (AGNs) recently identified by JWST, are characterized by their compact morphology and red optical continuum emission, which is often interpreted as evidence for significant dust…

Astrophysics of Galaxies · Physics 2025-12-01 Kejian Chen , Zhengrong Li , Kohei Inayoshi , Luis C. Ho

JWST observations have uncovered a new population of red, compact objects at high redshifts dubbed `Little Red Dots' (LRDs), which typically show broad emission lines and are thought to be dusty Active Galactic Nuclei (AGN). Some of their…

Little red dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this {work}, we performed a comprehensive stacking analysis of NIRCam, MIRI, and ALMA images of a large and homogeneously selected…

We present the discovery of a gravitationally lensed dust-reddened QSO at $z=2.517$ discovered in a survey for red QSOs by infrared selection. $Hubble~Space~Telescope$ imaging in the WFC3/IR F160W and F125W filters reveals a quadruply…

Astrophysics of Galaxies · Physics 2018-07-17 E. Glikman , C. E. Rusu , S. G. Djorgovski , M. J. Graham , D. Stern , T. Urrutia , M. Lacy , J. M. O'Meara

The advent of the James Webb Space Telescope has revolutionised our understanding of the high-redshift Universe through its detection of bright, massive galaxies up to $z\gtrsim 10$ and its identification of peculiar sources called `little…

Astrophysics of Galaxies · Physics 2026-01-14 Giada Quadri , Alessandro Trinca , Alessandro Lupi , Monica Colpi , Marta Volonteri

Early JWST studies found an apparent population of massive, compact galaxies at redshifts $z\gtrsim7$. Recently three of these galaxies were shown to have prominent Balmer breaks, demonstrating that their light at $\lambda_{\rm rest} \sim…

JWST surveys have uncovered a population of compact, red sources ("Little Red Dots," LRDs) at $z \ge 5$ that exhibit broad Balmer emission yet remain X-ray faint, implying heavy obscuration with $N_H \ge 10^{24}$ cm$^{-2}$. We propose that…

Astrophysics of Galaxies · Physics 2026-05-29 Tak-Pong Woo

We present short \chandra observations of twelve bright (i<18) z_em~1.5 quasars from the Sloan Digital Sky Survey chosen to have significantly redder optical colors than most quasars at the same redshift. Of the five quasars with optical…

Over the past decades, nearly a million quasars have been explored to shed light on the evolution of supermassive black holes and galaxies. The ultraviolet-to-optical spectra of type-1 quasars particularly offer insights into their black…

Astrophysics of Galaxies · Physics 2024-08-09 Yongjung Kim , Dohyeong Kim , Myungshin Im , Minjin Kim

The high redshift 'little red dots' (LRDs) detected with the James Webb Space Telescope are considered to be the cores of emerging galaxies that host active galactic nuclei (AGN). For the first time, we compare LRDs with local compact…

Astrophysics of Galaxies · Physics 2025-05-07 Alister W. Graham , Igor V. Chilingarian , Dieu D. Nguyen , Roberto Soria , Mark Durre , Duncan A. Forbes

This is the fourth paper in a series aimed at finding high-redshift quasars from five-color imaging data taken along the Celestial Equator by the SDSS. during its commissioning phase. In this paper, we use the color-selected sample of 39…

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