The missing FeII bump in faint JWST AGN: possible evidence for metal-poor broad-line regions at early cosmic times

Abstract

Recent JWST observations have revealed a large population of intermediate/low-luminosity AGN at early times with peculiar properties, different from local AGN or luminous quasars. To better understand the physical conditions in the BLRs of these early AGN, we used the optical FeII (4434--4684 Å) and the broad $\mathrm{H}\beta$ emission, and the ratio between their equivalent widths $R_{Fe}$, as a probe on a purposefully assembled sample. Specifically, we gathered a sample of 26 high redshift ($⟨z⟩$=6.4) AGN, observed by JWST, with broad $\mathrm{H}\beta$ detection both in the high and low luminosity regimes (respectively 14 faint AGN and 12 quasars), to investigate their optical FeII emission properties. In addition, we carefully selected control samples at lower $z$. We found that the population of faint AGN ($\log ({\mathrm{L}}_{\mathrm{H}\beta }/(\mathrm{erg}{\mathrm{s}}^{-1}))\lesssim 44$) exhibits a significantly lower FeII emission than their local counterparts ($R_{Fe}<$0.24 versus $R_{Fe}\simeq$0.85 in the control sample), while the quasars at the epoch of reionisation observed by JWST present a FeII emission profile that closely resembles that observed at $z<3$. We argue that the weakness of the FeII bump in the faint JWST AGN might be due to the reduced metallicity of their broad line region ($\lesssim 0.5Z_{\odot }$), while luminous quasars have already reached chemical maturity ($\sim Z{}_{\odot }$ or higher). Lastly, we highlight an intriguing similarity between the spectral properties of the high redshift population of faint AGN with those harboured in local metal poor dwarf galaxies.

Submitted to A&A, 27 pages, 13 figures

References in corpus (75)

• Array Programming with NumPy
• The James Webb Space Telescope
• A luminous quasar at a redshift of z = 7.085
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• A population of red candidate massive galaxies ~600 Myr after the Big Bang
• A Catalog of Broad Absorption Line Quasars in Sloan Digital Sky Survey Data Release 5
• The diversity of quasars unified by accretion and orientation
• A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z > 6 Quasars
• JADES. The diverse population of infant Black Holes at 4<z<11: merging, tiny, poor, but mighty
• Physical properties of 15 quasars at $z\gtrsim 6.5$
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• GA-NIFS: A massive black hole in a low-metallicity AGN at $z\sim 5.55$ revealed by JWST/NIRSpec IFS
• The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8
• Emission-line Diagnostics of Low Metallicity AGN
• A Catalog of Quasar Properties from Sloan Digital Sky Survey Data Release 16
• The destruction and recreation of the X-ray corona in a changing-look Active Galactic Nucleus
• The localized chemical pollution in NGC 5253 revisited: Results from deep echelle spectrophotometry
• EIGER I. a large sample of [OIII]-emitting galaxies at $5.3<z<6.9$ and direct evidence for local reionization by galaxies
• A First Look at the Abundance Pattern -- O/H, C/O, and Ne/O -- in $z>7$ Galaxies with JWST/NIRSpec
• RUBIES: Evolved Stellar Populations with Extended Formation Histories at $z\sim 7-8$ in Candidate Massive Galaxies Identified with JWST/NIRSpec
• The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-Epoch Spectroscopy
• A Candidate of a Least-Massive Black Hole at the First 1.1 Billion Years of the Universe
• Supermassive Black Holes at High Redshift are Expected to be Obscured by their Massive Host Galaxies' Inter Stellar Medium
• EIGER V. Characterizing the Host Galaxies of Luminous Quasars at $z\gtrsim 6$
• RUBIES: a complete census of the bright and red distant Universe with JWST/NIRSpec
• The low-end of the black hole mass function at cosmic dawn
• A dormant, overmassive black hole in the early Universe
• A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE): JWST Reveals a Filamentary Structure around a z=6.61 Quasar
• Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028
• Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots
• JADES: A large population of obscured, narrow line AGN at high redshift
• Fast cold gas in hot AGN outflows
• JADES -- The Rosetta Stone of JWST-discovered AGN: deciphering the intriguing nature of early AGN
• 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
• GA-NIFS: Black hole and host galaxy properties of two z$\simeq$6.8 quasars from the NIRSpec IFU
• New AGN diagnostic diagrams based on the [OIII]$\lambda 4363$ auroral line
• The most luminous blue quasars at $3.0<z<3.3$. I. A tale of two X-ray populations
• Chemical abundances of Seyfert 2 AGNs-III. Reducing the oxygen abundance discrepancy
• Dissecting the quasar main sequence: insight from host galaxy properties
• State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations
• Early Results from GLASS-JWST. XXI: Rapid assembly of a galaxy at z=6.23 revealed by its C/O abundance
• No Redshift Evolution in the Broad Line Region Metallicity up to z=7.54: Deep NIR Spectroscopy of ULAS J1342+0928
• High metal content of highly accreting quasars
• Super-Eddington QSO RX J0439.6-5311. II. Multi-wavelength Constraints on the Global Structure of the Accretion Flow
• Orientation effects on spectral emission features of quasars
• The web of the Giant: spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524
• The mass-metallicity relation of local active galaxies
• Improved Fe II emission line models for AGN using new atomic datasets
• Chemical abundances of Seyfert 2 AGNs I. Comparing oxygen abundances from distinct methods using SDSS
• CLOUDY view of the warm corona
• DESI z >~ 5 Quasar Survey. I. A First Sample of 400 New Quasars at z ~ 4.7-6.6
• Metallicity in Quasar Broad Line Regions at Redshift $\sim$ 6
• A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the H$\beta$ region
• GA-NIFS: Early-stage feedback in a heavily obscured AGN at $z=4.76$
• Do Some AGN Lack X-ray Emission?
• A quasar-galaxy merger at $z\sim 6.2$: black hole mass and quasar properties from the NIRSpec spectrum
• Chemical Abundance of z~6 Quasar Broad-Line Regions in the XQR-30 Sample
• The Impact of Star-Formation-Rate Surface Density on the Electron Density and Ionization Parameter of High-Redshift Galaxies
• HOMERUN a new approach to photoionization modelling. I -- reproducing observed emission lines with percent accuracy and obtaining accurate physical properties of the ionized gas
• High-ionization emission line ratios from quasar broad line regions: metallicity or density?
• Fe III emission in quasars: evidence for a dense turbulent medium
• On the AGN Nature of Broad Balmer Emission in Four Low-Redshift Metal-Poor Galaxies
• Placing High-Redshift Quasars in Perspective: a Catalog of Spectroscopic Properties from the Gemini Near Infrared Spectrograph -- Distant Quasar Survey
• High Eddington quasars as discovery tools: current state and challenges
• High-redshift quasars along the Main Sequence
• Chemical abundances along the quasar main sequence
• Mg II and Fe II fluxes of luminous quasars at z ~ 2.7 and evaluation of the Baldwin effect in the flux-to-abundance conversion method for quasars
• The mass-metallicity and fundamental metallicity relations in non-AGN and AGN-host galaxies
• Conditions for direct black hole seed collapse near a radio-loud quasar 1 Gyr after the Big Bang
• Electron temperature fluctuations in Seyfert galaxies
• No redshift evolution in the rest-frame UV emission line properties of quasars from z=1.5 to z=4.0
• Gemini Near Infrared Spectrograph -- Distant Quasar Survey: Augmented Spectroscopic Catalog and a Prescription for Correcting UV-Based Quasar Redshifts
• Quasars as standard candles VI: spectroscopic validation of the cosmological sample
• Probing the roles of orientation and multi-scale gas distributions in shaping the obscuration of Active Galactic Nuclei through cosmic time

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• The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z=3.55$
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