[Paper Review] JADES. The diverse population of infant Black Holes at 4

R. Maiolino, Jan Scholtz+26 more|arXiv (Cornell University)|Aug 2, 2023

Galaxies: Formation, Evolution, Phenomena70 citations

TL;DR

The paper reports 12 new broad-line AGN at z>4 discovered in the JADES survey via NIRSpec, highlighting a population of moderate-luminosity black holes and evidence for possible dual AGN in merging systems, with implications for early BH-galaxy co-evolution.

ABSTRACT

We present 12 new AGN at 4 10^44 erg/s, among galaxies in the redshift range 4 10%.

Motivation & Objective

• Motivate study of accreting black holes at high redshift beyond the luminous quasars era.
• Characterise a population of moderate-luminosity AGN at z>4 using JWST/NIRSpec data.
• Investigate black hole masses, accretion rates, and host galaxy relations in the infant BH population.
• Explore evidence for BH mergers and the role of AGN in early galaxy evolution.

Proposed method

• Use NIRSpec MSA spectroscopy from the JADES survey across Deep/HST, Medium/JWST, and Medium/HST tiers to detect broad Balmer emission lines.
• Identify broad line regions (BLRs) via a broad component in H-alpha (and H-beta at z>7) with two-Gaussian fits to Balmer lines.
• Constrain black hole masses from broad line widths and luminosities, and derive bolometric luminosities to estimate Eddington ratios.
• Rule out outflows by checking the absence of broad components in [OIII] and analyzing line profiles across multiple resolutions.
• Decompose AGN and host galaxy light in NIRCam imaging to assess host properties and dynamical masses.
• Investigate possible dual BLR signatures to identify candidate merging black hole systems.

Experimental results

Research questions

• RQ1 What is the population of moderate-luminosity, high-redshift AGN accessible with JWST/NIRSpec?
• RQ2 What are the black hole masses and accretion properties of these AGN at 4 < z < 11?
• RQ3 Do early BHs show evidence of mergers or multiple BHs within a single system?
• RQ4 How do these BHs relate to their host galaxies, and do they align with local black hole–host scaling relations?

Key findings

• Detected 12 new broad-line AGN at z>4 in the JADES Deep/HST and Medium/JWST tiers (in addition to GN-z11).
• Inferred BH masses span roughly from 4×10^5 to 8×10^7 solar masses, probing the direct-collapse mass regime.
• Bolometric AGN luminosities are around 10^44–10^45 erg s^-1, with accretion rates typically below 0.5 times the Eddington rate, while smaller BHs (~10^6 M⊙) tend to accrete at Eddington or super-Eddington rates.
• The high-z AGN are over-massive relative to their host stellar masses when compared to the local M_BH–M_star relation, but align better with the local M_BH–velocity dispersion and M_BH–dynamical mass relations.
• Many AGN would occupy the star-forming region of the BPT diagram if only narrow lines were considered, indicating true AGN activity can be missed without broad lines.
• The broad-line AGN hosts are typically compact, with NIRCam imaging often showing central point sources; some hosts show detectable extended components with disk-like Sérsic profiles (n~1).
• Evidence for candidate dual BLRs in a subset of objects (e.g., ID 10013704 and 73488) suggests possible merging BHs in the early universe.
• The broad H-alpha profiles are not accompanied by broad [OIII], supporting a BLR origin rather than outflows or star-formation-driven features.