The X-ray weakness of Little Red Dots and JWST-selected AGN: comparison with local AGN in different accretion regimes

Abstract

We investigate the origin of the observed X-ray weakness in high z LRDs and other JWST-selected broad line AGN by comparing their X-ray and optical properties with those of a diverse sample of low z AGN, including super-Eddington accreting massive black holes (SEAMBHs), NLS1s, and type I AGN from large surveys. We examine the relations between X-ray luminosity, broad Hα line luminosity, Eddington ratio, bolometric luminosity and X-ray-to-bolometric luminosity correction, and explore whether high z sources may represent analogues of local highly accreting systems. While a few LRDs and JWST-selected AGN are consistent with the SEAMBHs population in the $L_x/L_{H\alpha }$ versus ${\lambda }_{Edd}$ plane, most lie below it, suggesting either more extreme accretion conditions, suppressed coronal emission or heavy obscuration. We identify an anti-correlation between $L_x/L_{H\alpha }$ and ${\lambda }_{Edd}$ in the low z, high accreting subsample, consistent with theoretical expectations of slim-disc accretion. We further show that, for SEAMBHs, $H\alpha$-based bolometric luminosities underestimate SED-based values even after dust correction. We find that SEAMBHs, LRDs, and JWST-selected AGN occupy a similar high-${\kappa }_{bol,x}$ regime, indicating that the relative deficit of X-ray emission compared to the bolometric output could potentially support the view that soft X-ray spectra arising from relatively cold coronae is a common feature of highly accreting systems across cosmic time. Our results are consistent with the idea that the observed X-ray weakness of LRDs and JWST-selected AGN may be linked to the physics of highly accreting SMBHs. Moreover, observational limitations at high z, including instrumental sensitivity and the steep X-ray spectra expected for highly accreting systems, likely further suppress the detected X-ray signal.

Accepted for publication in Astronomy and Astrophysics

References in corpus (41)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• A Global Three Dimensional Radiation Magneto-hydrodynamic Simulation of Super-Eddington Accretion Disks
• The XMM-Newton serendipitous survey IX. The fourth XMM-Newton serendipitous source catalogue
• On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies
• The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
• CAIXA: a Catalogue of AGN In the XMM-Newton Archive I. Spectral analysis
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H$\beta$ Time Lags and Implications for Super-Eddington Accretion
• A Catalog of Quasar Properties from Sloan Digital Sky Survey Data Release 16
• The Radius-Luminosity Relationship Depends on Optical Spectra in Active Galactic Nuclei
• Mean Spectral Energy Distributions and Bolometric Corrections for Luminous Quasars
• Supermassive black holes with high accretion rates in active galactic nuclei: II. the most luminous standard candles in the Universe
• Properties of AGN coronae in the NuSTAR era II: hybrid plasma
• Active galactic nuclei at z ~ 1.5: I. Spectral energy distribution and accretion discs
• Self-shadowing Effects of Slim Accretion Disks in Active Galactic Nuclei: Diverse Appearance of the Broad-line Region
• Chasing obscuration in type-I AGN: discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783
• Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots
• A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE): A First Look at the Rest-frame Optical Spectra of $z>6.5$ Quasars Using JWST
• A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
• BASS XXV: DR2 Broad-line Based Black Hole Mass Estimates and Biases from Obscuration
• On the Observational Difference Between the Accretion Disk-Corona Connections among Super- and Sub-Eddington Accreting Active Galactic Nuclei
• Little red dots as young supermassive black holes in dense ionized cocoons
• State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations
• Mock catalogs for the extragalactic X-ray sky: simulating AGN surveys with Athena and with the AXIS probe
• Surface Structure in an Accretion Disk Annulus with Comparable Radiation and Gas Pressure
• Super-Eddington QSO RX J0439.6-5311. II. Multi-wavelength Constraints on the Global Structure of the Accretion Flow
• RUBIES: A Spectroscopic Census of Little Red Dots; All V-Shaped Point Sources Have Broad Lines
• X-ray spectroscopic survey of highly-accreting AGN
• HYPerluminous quasars at the Epoch of ReionizatION (HYPERION). A new regime for the X-ray nuclear properties of the first quasars
• Theoretical modeling of Comptonized X-ray spectra of super-Eddington accretion flow: origin of hard excess in Ultraluminous X-Ray Sources
• Narrow line AGN selection in CEERS: spectroscopic selection, physical properties, X-ray and radio analysis
• Systematic Broad-band X-ray Study of super-Eddington Accretion onto Supermassive Black Holes. I. X-ray Continuum
• The warm outer layer of a Little Red Dot as the source of [Fe II] and collisional Balmer lines with scattering wings
• Investigating the nuclear properties of highly accreting active galactic nuclei with XMM-Newton
• Chasing the light: Shadowing, collimation, and the super-Eddington growth of infant black holes in JWST broad-line AGNs
• Modeling Multiple X-Ray Reflection in Super-Eddington Winds
• HYPERION: broad-band X-ray-to-near-infrared emission of Quasars in the first billion years of the Universe
• HYPERION. Shedding light on the first luminous quasars: A correlation between UV disc winds and X-ray continuum
• Radiative Shocks around Super-Eddington Accreting Black Holes
• JWST-discovered AGN: evidence for heavy obscuration in the type-2 sample from the first stacked X-ray detection