Inferring Obscured Cosmic Black Hole Accretion History from AGN Found by JWST/MIRI CEERS Survey

Cheng-An Hsieh, Tomotsugu Goto, Chih-Teng Ling, Seong Jin Kim, Tetsuya Hashimoto, Tom C. -C. Chien, Amos Y. -A. Chen

First listed 2025-05-30 | Last updated 2025-06-12

Abstract

This study presents the black hole accretion history (BHAH) of obscured active galactic nuclei (AGNs) identified from the JWST CEERS survey by Chien et al. (2024) using mid-infrared (MIR) SED fitting. We compute black hole accretion rates (BHARs) to estimate the black hole accretion density (BHAD), $ρ_{L_{\mathrm{disk}}}$, across $0 < z < 4.25$. MIR luminosity functions (LFs) are also constructed for these sources, modeled with modified Schechter and double power law forms, and corresponding BHAD, $ρ_{\mathrm{LF}}$, is derived by integrating the LFs and multiplying by the luminosity. Both $ρ_{\mathrm{LF}}$ extend to luminosities as low as $10^7 \, L_{\odot}$, two orders of magnitude fainter than pre-JWST studies. Our results show that BHAD peaks between redshifts 1 and 3, with the peak varying by method and model, $z \approx 1$--2 for $ρ_{L_{\mathrm{disk}}}$ and the double power law, and $z \approx 2$--3 for the modified Schechter function. A scenario where AGN activity peaks before cosmic star formation would challenge existing black hole formation theories, but our present study, based on early JWST observations, provides an initial exploration of this possibility. At $z \sim 3$, $ρ_{\mathrm{LF}}$ appears higher than X-ray estimates, suggesting that MIR observations are more effective in detecting obscured AGNs missed by X-ray observations. However, given the overlapping error bars, this difference remains within the uncertainties and requires confirmation with larger samples. These findings highlight the potential of JWST surveys to enhance the understanding of co-evolution between galaxies and AGNs.

Short digest

Builds the obscured black hole accretion history from CEERS MIRI sources whose AGN components are identified via CIGALE SED fitting, then converts accretion power and MIR luminosity functions into BHAD across 0<z<4.25. By summing BHARs for composites+AGNs and by integrating LFs (modified Schechter and double power law) down to 1e7 L_sun—two orders fainter than pre-JWST—the authors find BHAD peaking at z≈1–2 (ρ_Ldisk, DPL) or z≈2–3 (modified Schechter). At z≈3 their MIR-inferred BHAD lies above X-ray estimates, hinting at obscured growth missed in X-rays. The new depth strengthens the census of faint, dusty accretion, though the z≈3 excess is within current uncertainties and awaits larger samples.

Key figures to inspect

• Figure 2 (BHAD vs. redshift): Compare ρ_Ldisk and ρ_LF tracks from the modified Schechter and DPL fits; note where the peak lands (z≈1–2 vs. z≈2–3) and the z≈3 offset from X-ray BHAD curves and the scaled SFRD line.
• Figure 3 (LF + corner plot, lower-z bin): Inspect how the modified Schechter (with/without fixed parameters) and DPL reproduce the rest-frame TIR AGN LF, the achieved faint limit (~10^7 L_sun), and how posterior covariances among L*, φ*, and slopes propagate into BHAD.
• Figure 4 (LF + corner plot, higher-z bin): Track the evolution of LF shape and normalization with redshift, the applied luminosity cut, and how model choice shifts the integrated luminosity density that drives the higher-z BHAD peak.
• Figure 1 (Luminosity histograms by z): Verify the depth and distribution of composites vs. AGNs in each redshift bin, illustrating the 1–2 dex gain in faint-end coverage that underpins the LF integration.