The ALPINE–CRISTAL– <i>JWST</i> survey: revealing less massive black holes in high-redshift galaxies

ABSTRACT We present a systematic search for broad-line active galactic nuclei (AGNs) in the ALPINE–CRISTAL–JWST sample of 18 star-forming galaxies ($M_\star &amp;gt;10^{9.5}~{\rm M}_{\odot }$) at redshifts $z=4.4\!-\!5.7$. Using James Webb Space Telescope (JWST)/NIRSpec IFU, we identify seven AGN candidates through the detection of broad H $\alpha$ emission lines from 33 aperture spectra centred on photometric peaks. These candidates include one highly robust AGN detection with full width at half-maximum (FWHM) $\sim$2800 km s$^{-1}$ and six showing broad components with FWHM $\sim 600\!-\!1600$ km s$^{-1}$, with two in a merger system. We highlight that only broad-line detection is effective since these candidates uniformly lie within narrow emission-line ratio diagnostic diagrams where star-forming galaxies and AGNs overlap. The broad-line AGN fraction ranges from 5.9 per cent to 33 per cent, depending on the robustness of the candidates. Assuming that the majority are AGNs, the relatively high AGN fraction is likely due to targeting high-mass galaxies, where simulations demonstrate that broad-line detection is more feasible. Their black hole masses range from $10^6$ to $10^{7.5}~{\rm M}_{\odot }$ with $0.1 \lesssim L_{\rm bol}/L_{\rm Edd}\lesssim 1$. Counter to previous JWST studies at high redshift that found overmassive black holes relative to their host galaxies, our candidates lie close to or below the local $M_{\rm BH}\!-\!M_\star$ scaling relations, thus demonstrating the effect of selection biases. This study provides new insights into AGN–host galaxy co-evolution at high redshift by identifying faint broad-line AGNs in galaxy samples, highlighting the importance of considering mass-dependent selection biases and the likelihood of a large population of AGNs being undermassive and just now being tapped by JWST.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-10-24
DOI
https://doi.org/10.1093/mnras/staf1709
Citations
3
Primary Topic
Astrophysical Phenomena and Observations
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article
Field-Weighted Citation Impact
3.46
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article

The ALPINE–CRISTAL– JWST survey: revealing less massive black holes in high-redshift galaxies

Juan Molina, Seiji Fujimoto, Zhaoxuan Liu, Akiyoshi Tsujita et al.
3 citations
Monthly Notices of the Royal Astronomical Society
Astrophysical Phenomena and Observations
3.46
article

The ALPINE–CRISTAL– JWST survey: revealing less massive black holes in high-redshift galaxies

Juan Molina, Seiji Fujimoto, Zhaoxuan Liu, Akiyoshi Tsujita, D. B. Sanders, Ilse De Looze, M. Relaño, J. D. Silverman, Wenke Ren, Michael Romano, Yu-Heng Lin, Vicente Villanueva, G. Zamorani, Anton M. Koekemoer, Rodrigo Herrera-Camus, Gareth C. Jones, A. Nanni, Ikki Mitsuhashi, M. Dessauges‐Zavadsky, Lin Yan, Manuel Solimano, Wuji Wang, R. L. Davies, Manuel Aravena, Jeyhan S. Kartaltepe, Andreas L. Faisst, E. Ibar, E. Veraldi
article en
3 citations

Abstract

ABSTRACT We present a systematic search for broad-line active galactic nuclei (AGNs) in the ALPINE–CRISTAL–JWST sample of 18 star-forming galaxies ($M_\star &amp;gt;10^{9.5}~{\rm M}_{\odot }$) at redshifts $z=4.4\!-\!5.7$. Using James Webb Space Telescope (JWST)/NIRSpec IFU, we identify seven AGN candidates through the detection of broad H $\alpha$ emission lines from 33 aperture spectra centred on photometric peaks. These candidates include one highly robust AGN detection with full width at half-maximum (FWHM) $\sim$2800 km s$^{-1}$ and six showing broad components with FWHM $\sim 600\!-\!1600$ km s$^{-1}$, with two in a merger system. We highlight that only broad-line detection is effective since these candidates uniformly lie within narrow emission-line ratio diagnostic diagrams where star-forming galaxies and AGNs overlap. The broad-line AGN fraction ranges from 5.9 per cent to 33 per cent, depending on the robustness of the candidates. Assuming that the majority are AGNs, the relatively high AGN fraction is likely due to targeting high-mass galaxies, where simulations demonstrate that broad-line detection is more feasible. Their black hole masses range from $10^6$ to $10^{7.5}~{\rm M}_{\odot }$ with $0.1 \lesssim L_{\rm bol}/L_{\rm Edd}\lesssim 1$. Counter to previous JWST studies at high redshift that found overmassive black holes relative to their host galaxies, our candidates lie close to or below the local $M_{\rm BH}\!-\!M_\star$ scaling relations, thus demonstrating the effect of selection biases. This study provides new insights into AGN–host galaxy co-evolution at high redshift by identifying faint broad-line AGNs in galaxy samples, highlighting the importance of considering mass-dependent selection biases and the likelihood of a large population of AGNs being undermassive and just now being tapped by JWST.

Monthly Notices of the Royal Astronomical SocietyVol. 544(1)
University of Geneva (CH), California Institute of Technology (US), University of Science and Technology of China (CN), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Planetary Science Institute (US), University of Hawaii System (US), Joint Institute for Laboratory Astrophysics (US), Scuola Internazionale Superiore di Studi Avanzati (IT), Johns Hopkins University (US), Rochester Institute of Technology (US), University of Concepción (CL), Universidad de Granada (ES), Université Paris Cité (FR), University of Cambridge (GB), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Ghent University (BE), Astrophysique, Instrumentation et Modélisation (FR), Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT), National Centre for Nuclear Research (PL), Kavli Institute for the Physics and Mathematics of the Universe (JP), Université Bourgogne Franche-Comté (FR), Institute of Astronomy (RU), Collurania Teramo Observatory (IT), CEA Paris-Saclay (FR), Millenium Nucleus for Planet Formation (CL), Max Planck Institute for Radio Astronomy (DE), Osservatorio Astronomico di Padova (IT), National Astronomical Observatory of Japan (JP), Infrared Processing and Analysis Center (US), Osservatorio di Astrofisica e Scienza dello Spazio, University of Warsaw (PL), Swinburne University of Technology (AU), University of Baltimore (US), The University of Tokyo (JP), University of Valparaíso (CL), The University of Texas at Austin (US), Universidad Diego Portales (CL)
Openalex Percentile: Top 7%
Astrophysical Phenomena and Observations
3.46
DOIOpen Access PDFOpenAlex
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